// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package interpres

import (
	"bytes"
	"context"
	"errors"
	"math"
	"net"
	"reflect"
	"strings"
	"testing"
	"time"
)

func TestMarshalScalars(t *testing.T) {
	type Cfg struct {
		Title    string  `toml:"title"`
		Count    int     `toml:"count"`
		Unsigned uint64  `toml:"unsigned"`
		Ratio    float64 `toml:"ratio"`
		Enabled  bool    `toml:"enabled"`
		Disabled bool    `toml:"disabled"`
	}
	out, err := Marshal(Cfg{
		Title:    "demo",
		Count:    42,
		Unsigned: 99,
		Ratio:    3.14,
		Enabled:  true,
		Disabled: false,
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "title = \"demo\"\ncount = 42\nunsigned = 99\nratio = 3.14\nenabled = true\ndisabled = false\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalFloatSpecials(t *testing.T) {
	type Cfg struct {
		PosInf float64 `toml:"pos_inf"`
		NegInf float64 `toml:"neg_inf"`
		NaN    float64 `toml:"nan"`
		Zero   float64 `toml:"zero"`
		IntVal float64 `toml:"int_val"`
		NegZ   float64 `toml:"neg_zero"`
	}
	out, err := Marshal(Cfg{
		PosInf: math.Inf(1),
		NegInf: math.Inf(-1),
		NaN:    math.NaN(),
		Zero:   0,
		IntVal: 7,
		NegZ:   math.Copysign(0, -1),
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "pos_inf = inf\nneg_inf = -inf\nnan = nan\nzero = 0.0\nint_val = 7.0\nneg_zero = 0.0\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalFloatNormalizesNegativeZero(t *testing.T) {
	// The output contract normalises negative zero to "0.0".
	type Cfg struct {
		Z float64 `toml:"z"`
	}
	out, err := Marshal(Cfg{Z: math.Copysign(0, -1)})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "z = 0.0\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalContextHonoursCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	type C struct {
		A int `toml:"a"`
	}
	if _, err := MarshalContext(ctx, C{A: 1}); !errors.Is(err, context.Canceled) {
		t.Fatalf("MarshalContext returned %v, want context.Canceled", err)
	}
}

func TestEncoderLayoutGroupedDefault(t *testing.T) {
	// NewEncoder must default to LayoutKindGrouped so legacy callers keep the
	// scalars-first ordering.
	type Cfg struct {
		Name string `toml:"name"`
		S    struct {
			Host string `toml:"host"`
		} `toml:"s"`
	}
	out, err := Marshal(Cfg{Name: "x", S: struct {
		Host string `toml:"host"`
	}{Host: "h"}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"x\"\n\n[s]\nhost = \"h\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderLayoutDeclarationPreservesOrder(t *testing.T) {
	type Inner struct {
		Host string `toml:"host"`
	}
	type Cfg struct {
		Name   string `toml:"name"`
		Server Inner  `toml:"server"`
		Debug  bool   `toml:"debug"`
	}
	in := Cfg{
		Name:   "x",
		Server: Inner{Host: "h"},
		Debug:  true,
	}
	out, err := Marshal(in, Layout(LayoutKindDeclaration))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// With Layout(LayoutKindDeclaration) the encoder walks entries in declaration order.
	// The output is still parseable, but a scalar that follows a header is
	// parsed as a sub-table key. That is the user's trade-off; see
	// docs/API.md.
	want := "name = \"x\"\n\n[server]\nhost = \"h\"\ndebug = true\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderLayoutGroupedDefaultOrder(t *testing.T) {
	// The default (LayoutKindGrouped) must lift the trailing scalar ahead of
	// the [server] block so the document round-trips losslessly.
	type Inner struct {
		Host string `toml:"host"`
	}
	type Cfg struct {
		Name   string `toml:"name"`
		Server Inner  `toml:"server"`
		Debug  bool   `toml:"debug"`
	}
	in := Cfg{
		Name:   "x",
		Server: Inner{Host: "h"},
		Debug:  true,
	}
	out, err := Marshal(in)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"x\"\ndebug = true\n\n[server]\nhost = \"h\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderOmitEmptyArrays(t *testing.T) {
	type Cfg struct {
		Tags    []string `toml:"tags"`
		Secrets []string `toml:"secrets"`
	}
	out, err := Marshal(Cfg{
		Tags:    []string{"a", "b"},
		Secrets: []string{},
	}, OmitEmptyArrays(true))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "tags = [\"a\", \"b\"]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderDefaultEmitsEmptyArray(t *testing.T) {
	type Cfg struct {
		Tags []string `toml:"tags"`
	}
	out, err := Marshal(Cfg{Tags: []string{}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "tags = []\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderOmitEmptyArrayOfTablesStillSkipped(t *testing.T) {
	type Item struct {
		Name string `toml:"name"`
	}
	type Cfg struct {
		Title string `toml:"title"`
		Items []Item `toml:"items"`
	}
	out, err := Marshal(Cfg{
		Title: "demo",
		Items: nil,
	}, OmitEmptyArrays(true))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "title = \"demo\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderLiteralMultiline(t *testing.T) {
	type Cfg struct {
		Long string `toml:"long"`
	}
	long := strings.Repeat("a", 50) + "\nline two\nline three"
	out, err := Marshal(Cfg{Long: long}, LiteralMultiline(20))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "long = '''\n" + long + "\n'''\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderLiteralMultilineBelowThreshold(t *testing.T) {
	// A multi-line value shorter than the threshold must remain escaped.
	type Cfg struct {
		Short string `toml:"short"`
	}
	out, err := Marshal(Cfg{Short: "one\ntwo"}, LiteralMultiline(1000))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "short = \"one\\ntwo\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderLiteralMultilineThresholdZero(t *testing.T) {
	// LiteralMultiline(0) disables the literal form entirely.
	type Cfg struct {
		S string `toml:"s"`
	}
	out, err := Marshal(Cfg{S: "a\nb\nc\nd"}, LiteralMultiline(0))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if !bytes.HasPrefix(out, []byte("s = \"")) {
		t.Errorf("output mismatch, expected basic quoted form:\ngot: %q", out)
	}
}

func TestEncoderLiteralMultilineFallsBackWhenUnsafe(t *testing.T) {
	// The literal form carries the value verbatim, so content it cannot
	// represent must fall back to the escaped basic string instead of
	// producing output that does not re-parse.
	cases := []struct {
		name string
		in   string
	}{
		{"embedded delimiter", "before ''' after\nsecond line"},
		{"control character", "a\x01b\nsecond"},
		{"delete character", "a\x7fb\nsecond"},
		{"lone carriage return", "first\rsecond\nthird"},
	}
	for _, c := range cases {
		out, err := Marshal(map[string]any{"s": c.in}, LiteralMultiline(5))
		if err != nil {
			t.Fatalf("%s: marshal: %v", c.name, err)
		}
		if !bytes.HasPrefix(out, []byte("s = \"")) {
			t.Errorf("%s: expected the basic quoted form, got:\n%s", c.name, out)
		}
		re, err := ParseMap(out)
		if err != nil {
			t.Errorf("%s: re-parse: %v\ndoc:\n%s", c.name, err, out)
			continue
		}
		if re["s"] != c.in {
			t.Errorf("%s: round-trip changed the value: %q", c.name, re["s"])
		}
	}
}

// marshalerFunc adapts a plain function value to the Marshaler interface.
// Tests use it to express "this field produces this TOML value" without a
// dedicated struct definition.
type marshalerFunc func() (any, error)

func (f marshalerFunc) MarshalTOML() (any, error) { return f() }

// failingMarshalerFunc invokes MarshalTOML to a fixed error; it lets us check
// that a MarshalTOML failure propagates back to Marshal.
type failingMarshalerFunc struct{}

func (failingMarshalerFunc) MarshalTOML() (any, error) {
	return nil, errors.New("oops")
}

func TestMarshalerReturningTime(t *testing.T) {
	// A Marshaler may return a date-time scalar; the encoder must emit it
	// using its canonical form.
	when := time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC)
	type Cfg struct {
		M marshalerFunc `toml:"m"`
	}
	out, err := Marshal(Cfg{M: marshalerFunc(func() (any, error) { return when, nil })})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "m = 2026-06-26T10:00Z\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerReturningDifferentStruct(t *testing.T) {
	// A Marshaler returning a struct (not a scalar) is treated as a sub-table
	// by the encoder.
	type Inner struct {
		V string `toml:"v"`
	}
	type Cfg struct {
		P marshalerFunc `toml:"p"`
	}
	out, err := Marshal(Cfg{P: marshalerFunc(func() (any, error) {
		return Inner{V: "x"}, nil
	})})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[p]\nv = \"x\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerReturningSliceOfMaps(t *testing.T) {
	// A Marshaler returning []map[string]any becomes an array of tables.
	type Cfg struct {
		Items marshalerFunc `toml:"items"`
	}
	out, err := Marshal(Cfg{Items: marshalerFunc(func() (any, error) {
		return []map[string]any{
			{"k": "a"},
			{"k": "b"},
		}, nil
	})})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[[items]]\nk = \"a\"\n\n[[items]]\nk = \"b\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerErrorPropagates(t *testing.T) {
	type Cfg struct {
		F failingMarshalerFunc `toml:"f"`
	}
	if _, err := Marshal(Cfg{F: failingMarshalerFunc{}}); err == nil {
		t.Fatal("expected an error from MarshalTOML")
	} else if !strings.Contains(err.Error(), "oops") {
		t.Errorf("err = %v, want substring \"oops\"", err)
	}
}

// nilMarshalerFunc is a Marshaler whose method returns nil with no error.
type nilMarshalerFunc struct{}

func (nilMarshalerFunc) MarshalTOML() (any, error) { return nil, nil }

func TestMarshalRejectsNilMarshalerResult(t *testing.T) {
	// nil has no TOML representation, so a MarshalTOML result of nil is an
	// error, not a silently dropped field.
	_, err := Marshal(struct {
		F nilMarshalerFunc `toml:"f"`
	}{})
	if err == nil {
		t.Fatal("expected an error for a nil MarshalTOML result")
	}
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "f" {
		t.Fatalf("Path = %v, want f", ee.Path)
	}

	// Inside a value array the nil result used to reach reflection as a zero
	// Value and panic.
	_, err = Marshal(map[string]any{"arr": []any{1, nilMarshalerFunc{}}})
	if err == nil {
		t.Fatal("expected an error for a nil MarshalTOML result in an array")
	}
	if !strings.Contains(err.Error(), "MarshalTOML returned a nil value") {
		t.Errorf("err = %v, want the nil-result message", err)
	}
}

// Two fields that resolve to one TOML key must marshal as one key, resolved
// the way the decoder resolves it, or the output would carry a duplicate key
// and never re-parse.
func TestMarshalDuplicateKeyResolvesToOneField(t *testing.T) {
	type SameLevel struct {
		First  int    `toml:"v"`
		Second string `toml:"v"`
	}
	out, err := Marshal(SameLevel{First: 1, Second: "s"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if want := "v = \"s\"\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	type Base struct {
		Name string `toml:"name"`
	}
	type Embedded struct {
		Base
		Name string `toml:"name"`
	}
	out, err = Marshal(Embedded{Base: Base{Name: "inner"}, Name: "outer"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// The shallower field wins, matching the decoder.
	if want := "name = \"outer\"\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
	if _, err := ParseMap(out); err != nil {
		t.Errorf("re-parse: %v\ndoc:\n%s", err, out)
	}
}

func TestMarshalEmbeddedScalarStruct(t *testing.T) {
	// A field declared directly as a scalar-struct type (here LocalDateTime)
	// must be encoded as a TOML scalar at the parent level, not rendered as
	// a sub-table.
	ldt := LocalDateTime{Time: time.Date(2026, 6, 26, 0, 0, 0, 0, time.UTC)}
	type Cfg struct {
		Name string        `toml:"name"`
		S    LocalDateTime `toml:"s"`
	}
	out, err := Marshal(Cfg{Name: "x", S: ldt})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"x\"\ns = 2026-06-26T00:00\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestEncoderChainedOptions(t *testing.T) {
	// All chainable options combined; verify they compose without errors.
	type Inner struct {
		V string `toml:"v"`
	}
	type Cfg struct {
		S string `toml:"s"`
		I Inner  `toml:"i"`
	}
	long := strings.Repeat("x", 200)
	out, err := Marshal(Cfg{S: "short", I: Inner{V: long}},
		Layout(LayoutKindDeclaration),
		OmitEmptyArrays(true),
		LiteralMultiline(50))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	_ = out // success path is enough; per-option correctness is exercised above.
}

func TestMarshalStringEscapes(t *testing.T) {
	cases := []struct {
		name string
		in   string
		want string // the TOML scalar value (without "s = " prefix)
	}{
		{"plain", "hello", `"hello"`},
		{"quote", `say "hi"`, `"say \"hi\""`},
		{"backslash", `a\b`, `"a\\b"`},
		{"newline", "line1\nline2", `"line1\nline2"`},
		{"tab", "col1\tcol2", `"col1\tcol2"`},
		{"cr", "line\rmore", `"line\rmore"`},
		{"control", "a\x01b", `"a\u0001b"`},
		{"unicode", "\u201csmart\u201d", `"“smart”"`}, // printable unicode; not escaped
		{"empty", "", `""`},
		{"slash_only", "a/b", `"a/b"`},
	}
	for _, c := range cases {
		out, err := Marshal(struct {
			S string `toml:"s"`
		}{S: c.in})
		if err != nil {
			t.Fatalf("%s: marshal: %v", c.name, err)
		}
		got := strings.TrimSuffix(string(out), "\n")
		want := "s = " + c.want
		if got != want {
			t.Errorf("%s:\ngot:  %s\nwant: %s", c.name, got, want)
		}
	}
}

func TestMarshalDateTime(t *testing.T) {
	type Cfg struct {
		Offset time.Time     `toml:"offset"`
		Local  LocalDateTime `toml:"local"`
		Day    LocalDate     `toml:"day"`
		Clock  LocalTime     `toml:"clock"`
	}
	out, err := Marshal(Cfg{
		Offset: time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC),
		Local:  LocalDateTime{Time: time.Date(2026, 6, 26, 7, 32, 0, 0, time.UTC)},
		Day:    LocalDate{Time: time.Date(2026, 6, 26, 0, 0, 0, 0, time.UTC)},
		Clock:  LocalTime{Time: time.Date(0, 1, 1, 7, 32, 0, 0, time.UTC)},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "offset = 2026-06-26T10:00Z\nlocal = 2026-06-26T07:32\nday = 2026-06-26\nclock = 07:32\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalDateTimeFractional(t *testing.T) {
	out, err := Marshal(struct {
		LDT LocalDateTime `toml:"ldt"`
		LT  LocalTime     `toml:"lt"`
	}{
		LDT: LocalDateTime{Time: time.Date(2026, 6, 26, 7, 32, 0, 123456789, time.UTC)},
		LT:  LocalTime{Time: time.Date(0, 1, 1, 7, 32, 0, 123, time.UTC)},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "ldt = 2026-06-26T07:32:00.123456789\nlt = 07:32:00.000000123\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalArraysOfScalars(t *testing.T) {
	type Cfg struct {
		Tags   []string `toml:"tags"`
		Ports  []int    `toml:"ports"`
		Mixed  []any    `toml:"mixed"`
		Empty  []int    `toml:"empty"`
		EmptyS []string `toml:"empty_s"`
	}
	out, err := Marshal(Cfg{
		Tags:   []string{"a", "b"},
		Ports:  []int{80, 443},
		Mixed:  []any{int64(1), "x", true},
		Empty:  nil,
		EmptyS: []string{},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "tags = [\"a\", \"b\"]\nports = [80, 443]\nmixed = [1, \"x\", true]\nempty_s = []\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalNestedArrays(t *testing.T) {
	type Cfg struct {
		Matrix [][]int    `toml:"matrix"`
		Words  [][]string `toml:"words"`
	}
	out, err := Marshal(Cfg{
		Matrix: [][]int{{1, 2}, {3, 4}},
		Words:  [][]string{{"a", "b"}, {"c"}},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "matrix = [[1, 2], [3, 4]]\nwords = [[\"a\", \"b\"], [\"c\"]]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalMixedArrayWithInlineTable(t *testing.T) {
	// Parse accepts a mixed array (TOML allows any value kinds in one array),
	// so Marshal of the parsed tree must re-emit it. The table element has no
	// header form inside a value array and renders inline.
	tree, err := ParseMap([]byte("arr = [1, {a = 2}, \"x\"]\n"))
	if err != nil {
		t.Fatalf("parse: %v", err)
	}
	out, err := Marshal(tree)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "arr = [1, {a = 2}, \"x\"]\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
	re, err := ParseMap(out)
	if err != nil {
		t.Fatalf("re-parse: %v", err)
	}
	if !reflect.DeepEqual(tree, re) {
		t.Fatalf("round-trip changed the tree:\nwas: %#v\nnow: %#v", tree, re)
	}
}

// A []any of tables is what Parse produces for a value array of inline
// tables; it must stay in the value-array form, or the output would re-parse
// as []map[string]any and the round-trip would change the value's type.
func TestMarshalValueArrayOfTablesStaysInline(t *testing.T) {
	for _, doc := range []string{
		"0=[{}]",
		"a = [{x = 1}, {x = 2}]\n",
		"b = [{x = 1}, 2, \"three\"]\n",
	} {
		tree, err := ParseMap([]byte(doc))
		if err != nil {
			t.Fatalf("%s: parse: %v", doc, err)
		}
		out, err := Marshal(tree)
		if err != nil {
			t.Fatalf("%s: marshal: %v", doc, err)
		}
		if bytes.HasPrefix(out, []byte("[[")) {
			t.Errorf("%s: emitted the [[header]] form for a value array:\n%s", doc, out)
		}
		re, err := ParseMap(out)
		if err != nil {
			t.Fatalf("%s: re-parse: %v\ndoc:\n%s", doc, err, out)
		}
		if !tomlEqual(tree, re) {
			t.Errorf("%s: round-trip changed the tree:\nwas: %#v\nnow: %#v\ndoc:\n%s", doc, tree, re, out)
		}
	}
}

func TestMarshalNestedInlineTables(t *testing.T) {
	tree := map[string]any{
		"mix": []any{
			int64(1),
			map[string]any{"deep": map[string]any{"n": int64(0)}, "list": []any{"a", true}},
			map[string]any{},
		},
	}
	out, err := Marshal(tree)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "mix = [1, {deep = {n = 0}, list = [\"a\", true]}, {}]\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalInlineTableWithDatetime(t *testing.T) {
	when := time.Date(1979, 5, 27, 7, 32, 0, 0, time.UTC)
	tree := map[string]any{
		"mix": []any{when, map[string]any{"t": LocalDateTime{when}}},
	}
	out, err := Marshal(tree)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "mix = [1979-05-27T07:32Z, {t = 1979-05-27T07:32}]\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalArrayOfTablesStaysHeaderForm(t *testing.T) {
	tree, err := ParseMap([]byte("[[items]]\nname = \"a\"\n\n[[items]]\nname = \"b\"\n"))
	if err != nil {
		t.Fatalf("parse: %v", err)
	}
	out, err := Marshal(tree)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[[items]]\nname = \"a\"\n\n[[items]]\nname = \"b\"\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalFloatExponentNoLeadingZero(t *testing.T) {
	// strconv.FormatFloat with 'g' would produce "1e+06" (leading zero in
	// exponent). The encoder must strip it so the output is "1e+6".
	type Cfg struct {
		Large float64 `toml:"large"`
		Small float64 `toml:"small"`
	}
	out, err := Marshal(Cfg{Large: 1e6, Small: 1e-5})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// Parse to check the output is valid TOML (for a strict parser that
	// rejects leading zeros in exponents).
	if _, err := ParseMap(out); err != nil {
		t.Fatalf("marshalled output is not valid TOML:\n%s\nerror: %v", out, err)
	}
	if string(out) != "large = 1e+6\nsmall = 1e-5\n" {
		t.Errorf("output mismatch:\ngot: %q", out)
	}
}

func TestMarshalStructAsTable(t *testing.T) {
	type Server struct {
		Host string `toml:"host"`
		Port int    `toml:"port"`
	}
	type Cfg struct {
		Title  string `toml:"title"`
		Server Server `toml:"server"`
	}
	out, err := Marshal(Cfg{
		Title:  "demo",
		Server: Server{Host: "127.0.0.1", Port: 9090},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "title = \"demo\"\n\n[server]\nhost = \"127.0.0.1\"\nport = 9090\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalArrayOfTables(t *testing.T) {
	type Item struct {
		Name string `toml:"name"`
		Qty  int    `toml:"qty"`
	}
	type Cfg struct {
		Items []Item `toml:"items"`
	}
	out, err := Marshal(Cfg{
		Items: []Item{
			{Name: "a", Qty: 1},
			{Name: "b", Qty: 2},
		},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[[items]]\nname = \"a\"\nqty = 1\n\n[[items]]\nname = \"b\"\nqty = 2\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalEmptyArrayOfTablesIsSkipped(t *testing.T) {
	type Item struct {
		Name string `toml:"name"`
	}
	type Cfg struct {
		Title string `toml:"title"`
		Items []Item `toml:"items"`
	}
	out, err := Marshal(Cfg{
		Title: "demo",
		Items: nil,
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "title = \"demo\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalNestedTablesAndArrays(t *testing.T) {
	type SMTP struct {
		Host string `toml:"host"`
		Port int    `toml:"port"`
	}
	type Form struct {
		Name string `toml:"name"`
		SMTP SMTP   `toml:"smtp"`
	}
	type Cfg struct {
		Port  int    `toml:"port"`
		Forms []Form `toml:"forms"`
	}
	out, err := Marshal(Cfg{
		Port: 8080,
		Forms: []Form{
			{Name: "contact", SMTP: SMTP{Host: "h1", Port: 587}},
			{Name: "feedback", SMTP: SMTP{Host: "h2", Port: 25}},
		},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "port = 8080\n\n[[forms]]\nname = \"contact\"\n\n[forms.smtp]\nhost = \"h1\"\nport = 587\n\n[[forms]]\nname = \"feedback\"\n\n[forms.smtp]\nhost = \"h2\"\nport = 25\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalStructTags(t *testing.T) {
	type Cfg struct {
		Keep     string `toml:"keep"`
		Rename   string `toml:"renamed"`
		Skip     string `toml:"-"`
		Untagged string
	}
	out, err := Marshal(Cfg{
		Keep: "k", Rename: "r", Skip: "s", Untagged: "u",
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "keep = \"k\"\nrenamed = \"r\"\nuntagged = \"u\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalEmbeddedStructPromoted(t *testing.T) {
	type Base struct {
		ID int `toml:"id"`
	}
	type Derived struct {
		Base
		Name string `toml:"name"`
	}
	out, err := Marshal(Derived{ID: 1, Name: "x"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "id = 1\nname = \"x\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalEmbeddedStructAsTable(t *testing.T) {
	type Inner struct {
		Host string `toml:"host"`
	}
	type Cfg struct {
		Inner Inner  `toml:"inner"`
		Name  string `toml:"name"`
	}
	out, err := Marshal(Cfg{Inner: Inner{Host: "h"}, Name: "n"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"n\"\n\n[inner]\nhost = \"h\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTagOptionOmitZero(t *testing.T) {
	type Server struct {
		Host string `toml:"host"`
	}
	type Cfg struct {
		Name   string    `toml:"name,omitzero"`
		Count  int       `toml:"count,omitzero"`
		Ratio  float64   `toml:"ratio,omitzero"`
		When   time.Time `toml:"when,omitzero"`
		Server Server    `toml:"server,omitzero"`
		Always string    `toml:"always"`
	}
	out, err := Marshal(Cfg{Always: "kept"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// Every omitzero field sits at its zero value, so only always is emitted.
	want := "always = \"kept\"\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	when := time.Date(2026, 9, 17, 12, 0, 0, 0, time.UTC)
	out, err = Marshal(Cfg{Name: "x", Count: 1, Ratio: 0.5, When: when, Server: Server{Host: "h"}, Always: "kept"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want = "name = \"x\"\ncount = 1\nratio = 0.5\nwhen = 2026-09-17T12:00Z\nalways = \"kept\"\n\n[server]\nhost = \"h\"\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTagOptionOmitEmpty(t *testing.T) {
	type Cfg struct {
		Tags   []string       `toml:"tags,omitempty"`
		Ports  []int          `toml:"ports,omitempty"`
		Matrix [][]int        `toml:"matrix,omitempty"`
		Extra  map[string]any `toml:"extra,omitempty"`
		Name   string         `toml:"name,omitempty"`
		Keep   []string       `toml:"keep"`
	}
	out, err := Marshal(Cfg{
		Ports:  []int{},
		Matrix: [][]int{{1}},
		Extra:  map[string]any{},
		Name:   "set",
		Keep:   []string{},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// tags is nil (omitted anyway), ports and extra are empty collections
	// dropped by omitempty, matrix is populated, name is a string the option
	// does not cover, keep is empty but carries no option so it emits [].
	want := "matrix = [[1]]\nname = \"set\"\nkeep = []\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTagOptionOnTaggedEmbeddedStruct(t *testing.T) {
	type Inner struct {
		N int `toml:"n"`
	}
	type Cfg struct {
		Inner Inner  `toml:"inner,omitzero"`
		Name  string `toml:"name"`
	}
	out, err := Marshal(Cfg{Name: "x"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"x\"\n"
	if string(out) != want {
		t.Fatalf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalMapKeysSorted(t *testing.T) {
	m := map[string]any{
		"zeta":  1,
		"alpha": 2,
		"mu":    3,
	}
	out, err := Marshal(m)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "alpha = 2\nmu = 3\nzeta = 1\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalMapWithSubMap(t *testing.T) {
	m := map[string]any{
		"meta": map[string]any{"x": 1, "y": 2},
		"a":    "z",
	}
	out, err := Marshal(m)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "a = \"z\"\n\n[meta]\nx = 1\ny = 2\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalMarshaler(t *testing.T) {
	type Port int
	type Cfg struct {
		P Port `toml:"p"`
	}
	out, err := Marshal(Cfg{P: 8080})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "p = 8080\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalMarshalerReturningScalar(t *testing.T) {
	type Wrapped struct {
		Value string `toml:"value"`
	}
	type Alias struct{}
	out, err := Marshal(struct {
		W Wrapped `toml:"w"`
	}{W: Wrapped{Value: "hello"}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[w]\nvalue = \"hello\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
	_ = Alias{}
}

func TestMarshalMarshalerReturningDifferentShape(t *testing.T) {
	out, err := Marshal(struct {
		C Custom `toml:"c"`
	}{C: Custom{tag: "x"}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	// Custom returns a string from MarshalTOML.
	want := "c = \"x\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalNilPointerFieldSkipped(t *testing.T) {
	type Cfg struct {
		Name   string  `toml:"name"`
		Hidden *string `toml:"hidden"`
	}
	out, err := Marshal(Cfg{Name: "x"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"x\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalNonNilPointerFollowed(t *testing.T) {
	v := "v"
	type Cfg struct {
		Name   string  `toml:"name"`
		Hidden *string `toml:"hidden"`
	}
	out, err := Marshal(Cfg{Name: "n", Hidden: &v})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "name = \"n\"\nhidden = \"v\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTopLevelMustBeStructOrMap(t *testing.T) {
	if _, err := Marshal(42); err == nil {
		t.Errorf("expected error marshalling int at top level")
	}
	if _, err := Marshal("hello"); err == nil {
		t.Errorf("expected error marshalling string at top level")
	}
	if _, err := Marshal(nil); err == nil {
		t.Errorf("expected error marshalling nil")
	}
}

func TestMarshalMapKeyMustBeString(t *testing.T) {
	m := map[int]any{1: "x"}
	if _, err := Marshal(m); err == nil {
		t.Errorf("expected error for non-string map key")
	}
}

func TestMarshalUnexportedFieldSkipped(t *testing.T) {
	type Cfg struct {
		Pub  string `toml:"pub"`
		priv string
	}
	out, err := Marshal(Cfg{Pub: "p", priv: "s"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "pub = \"p\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalBareAndQuotedKeys(t *testing.T) {
	type Cfg struct {
		Bare string `toml:"bare_key"`
		Dash string `toml:"with-dash"`
		Num  string `toml:"num123"`
		Q    string `toml:"needs space"`
		Dot  string `toml:"needs.dot"`
	}
	out, err := Marshal(Cfg{
		Bare: "a", Dash: "b", Num: "c", Q: "d", Dot: "e",
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "bare_key = \"a\"\nwith-dash = \"b\"\nnum123 = \"c\"\n\"needs space\" = \"d\"\n\"needs.dot\" = \"e\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalThenParseRoundTrip(t *testing.T) {
	type Server struct {
		Host    string   `toml:"host"`
		Port    int      `toml:"port"`
		Enabled bool     `toml:"enabled"`
		Tags    []string `toml:"tags"`
	}
	type Form struct {
		Name    string   `toml:"name"`
		Allowed []string `toml:"allowed"`
	}
	type Cfg struct {
		Title  string    `toml:"title"`
		Count  int       `toml:"count"`
		Ratio  float64   `toml:"ratio"`
		Server Server    `toml:"server"`
		Forms  []Form    `toml:"forms"`
		Due    time.Time `toml:"due"`
		Day    LocalDate `toml:"day"`
	}
	in := Cfg{
		Title: "demo",
		Count: 42,
		Ratio: 3.14,
		Server: Server{
			Host: "127.0.0.1", Port: 9090, Enabled: true,
			Tags: []string{"a", "b"},
		},
		Forms: []Form{
			{Name: "contact", Allowed: []string{"x"}},
			{Name: "feedback", Allowed: nil},
		},
		Due: time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC),
		Day: LocalDate{Time: time.Date(2026, 6, 26, 0, 0, 0, 0, time.UTC)},
	}
	out, err := Marshal(in)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	tree1, err := ParseMap(out)
	if err != nil {
		t.Fatalf("parse of marshalled: %v\noutput:\n%s", err, out)
	}
	// Decode back into the struct.
	var out2 Cfg
	if err := Unmarshal(out, &out2); err != nil {
		t.Fatalf("unmarshal of marshalled: %v", err)
	}
	if !reflect.DeepEqual(in, out2) {
		t.Errorf("round-trip mismatch:\nin:  %#v\nout: %#v", in, out2)
	}
	_ = tree1
}

func TestMarshalRoundTripFromUntypedTree(t *testing.T) {
	src := []byte(`title = "demo"
count = 42
ratio = 3.14
enabled = true

[server]
host = "127.0.0.1"
port = 9090

[[items]]
name = "a"
qty = 1

[[items]]
name = "b"
qty = 2

[meta]
created = 2026-06-26T10:00:00Z

mixed = [1, {n = 1, name = "a value long enough to push this line well past the one hundred column limit"}]
`)
	tree1, err := ParseMap(src)
	if err != nil {
		t.Fatalf("parse src: %v", err)
	}
	out, err := Marshal(tree1)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	tree2, err := ParseMap(out)
	if err != nil {
		t.Fatalf("re-parse marshalled: %v\noutput:\n%s", err, out)
	}
	if !reflect.DeepEqual(tree1, tree2) {
		t.Errorf("round-trip mismatch:\nbefore: %#v\nafter:  %#v", tree1, tree2)
	}
}

func TestMarshalUintOverflow(t *testing.T) {
	type Cfg struct {
		Big uint64 `toml:"big"`
	}
	if _, err := Marshal(Cfg{Big: 1<<63 + 1}); err == nil {
		t.Errorf("expected overflow error")
	}
}

func TestMarshalKeyRequiresUTF8(t *testing.T) {
	m := map[string]any{"\xff": "x"}
	if _, err := Marshal(m); err == nil {
		t.Errorf("expected error for invalid UTF-8 key")
	}
	// The check must reach the keys of table headers and of inline tables
	// nested inside value arrays, not only scalar keys: both write keys
	// through the same path.
	nested := map[string]any{"\xff": map[string]any{"k": "v"}}
	if _, err := Marshal(nested); err == nil {
		t.Errorf("expected error for invalid UTF-8 table header key")
	}
	inline := map[string]any{"mix": []any{1, map[string]any{"\xff": 1}}}
	if _, err := Marshal(inline); err == nil {
		t.Errorf("expected error for invalid UTF-8 inline table key")
	}
}

func TestMarshalStringRequiresUTF8(t *testing.T) {
	type Cfg struct {
		S string `toml:"s"`
	}
	if _, err := Marshal(Cfg{S: "abc\xff"}); err == nil {
		t.Errorf("expected error for invalid UTF-8 string")
	}
}

func TestLocalDateString(t *testing.T) {
	ld := LocalDate{Time: time.Date(1979, 5, 27, 0, 0, 0, 0, time.UTC)}
	if got := ld.String(); got != "1979-05-27" {
		t.Errorf("LocalDate.String() = %q, want 1979-05-27", got)
	}
}

func TestLocalDateTimeString(t *testing.T) {
	// The rendering drops zero seconds and the trailing zeros of a fraction,
	// which TOML 1.1 allows and which keeps a value written without seconds
	// written without them.
	ldt := LocalDateTime{Time: time.Date(1979, 5, 27, 7, 32, 0, 0, time.UTC)}
	if got := ldt.String(); got != "1979-05-27T07:32" {
		t.Errorf("LocalDateTime.String() = %q, want 1979-05-27T07:32", got)
	}
	ldt2 := LocalDateTime{Time: time.Date(1979, 5, 27, 7, 32, 0, 5, time.UTC)}
	if got := ldt2.String(); got != "1979-05-27T07:32:00.000000005" {
		t.Errorf("LocalDateTime.String() = %q, want 1979-05-27T07:32:00.000000005", got)
	}
	ldt3 := LocalDateTime{Time: time.Date(1979, 5, 27, 7, 32, 0, 500, time.UTC)}
	if got := ldt3.String(); got != "1979-05-27T07:32:00.0000005" {
		t.Errorf("LocalDateTime.String() = %q, want 1979-05-27T07:32:00.0000005", got)
	}
	ldt4 := LocalDateTime{Time: time.Date(1979, 5, 27, 7, 32, 30, 500000000, time.UTC)}
	if got := ldt4.String(); got != "1979-05-27T07:32:30.5" {
		t.Errorf("LocalDateTime.String() = %q, want 1979-05-27T07:32:30.5", got)
	}
}

func TestLocalTimeString(t *testing.T) {
	lt := LocalTime{Time: time.Date(0, 1, 1, 7, 32, 0, 0, time.UTC)}
	if got := lt.String(); got != "07:32" {
		t.Errorf("LocalTime.String() = %q, want 07:32", got)
	}
	lt2 := LocalTime{Time: time.Date(0, 1, 1, 7, 32, 15, 250000000, time.UTC)}
	if got := lt2.String(); got != "07:32:15.25" {
		t.Errorf("LocalTime.String() = %q, want 07:32:15.25", got)
	}
}

func TestEncoderEquivalenceToMarshal(t *testing.T) {
	type Cfg struct {
		Title string `toml:"title"`
		Count int    `toml:"count"`
	}
	in := Cfg{Title: "x", Count: 7}
	a, err := Marshal(in)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	b, err := Marshal(in)
	if err != nil {
		t.Fatalf("encoder marshal: %v", err)
	}
	if !reflect.DeepEqual(a, b) {
		t.Errorf("Marshal and Encoder disagree:\n%s\n%s", a, b)
	}
}

type Custom struct {
	tag string
}

func (c Custom) MarshalTOML() (any, error) { return c.tag, nil }

// encodeErrBad is a Marshaler whose MarshalTOML always fails.
type encodeErrBad struct {
	msg string
}

func (encodeErrBad) MarshalTOML() (any, error) { return nil, errors.New("bad timestamp") }

func TestEncodeErrorCarriesPath(t *testing.T) {
	type Inner struct {
		Port encodeErrBad `toml:"port"`
	}
	type Cfg struct {
		Server Inner `toml:"server"`
	}
	_, err := Marshal(Cfg{Server: Inner{Port: encodeErrBad{}}})
	if err == nil {
		t.Fatal("expected a marshal error")
	}
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "server.port" {
		t.Fatalf("Path = %v, want server.port", ee.Path)
	}
	if ee.Err == nil || ee.Err.Error() != "bad timestamp" {
		t.Fatalf("Err = %v", ee.Err)
	}
	if err.Error() != "interpres: server.port: bad timestamp" {
		t.Fatalf("message = %q", err.Error())
	}
}

func TestEncodeErrorTopLevelPathHasNoLeadingDot(t *testing.T) {
	type Cfg struct {
		Port encodeErrBad `toml:"port"`
	}
	_, err := Marshal(Cfg{})
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "port" {
		t.Fatalf("Path = %v, want port", ee.Path)
	}
	if err.Error() != "interpres: port: bad timestamp" {
		t.Fatalf("message = %q", err.Error())
	}
}

func TestEncodeErrorHeterogeneousArrayPath(t *testing.T) {
	type Item struct {
		N int `toml:"n"`
	}
	cfg := map[string]any{
		"items": []any{Item{}, 3},
	}
	_, err := Marshal(cfg)
	if err == nil {
		t.Fatal("expected a heterogeneous array error")
	}
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "items[0]" {
		t.Fatalf("Path = %v, want items[0]", ee.Path)
	}
}

// --- encoding.TextMarshaler and time.Duration ------------------------------

// textTag is a value-receiver encoding.TextMarshaler, so the encoder finds the
// method on the value itself.
type textTag string

func (t textTag) MarshalText() ([]byte, error) { return []byte("tag:" + string(t)), nil }

// textPointer carries MarshalText on the pointer receiver only, so the encoder
// has to look at the address of an addressable field.
type textPointer struct{ V string }

func (t *textPointer) MarshalText() ([]byte, error) { return []byte(strings.ToUpper(t.V)), nil }

// textAndTOML implements both encoding interfaces; the TOML method wins.
type textAndTOML struct{}

func (textAndTOML) MarshalTOML() (any, error)    { return "toml", nil }
func (textAndTOML) MarshalText() ([]byte, error) { return []byte("text"), nil }

// brokenText fails the marshal from MarshalText.
type brokenText struct{}

func (brokenText) MarshalText() ([]byte, error) { return nil, errors.New("text boom") }

// notUTF8 renders bytes that no TOML string can carry.
type notUTF8 struct{}

func (notUTF8) MarshalText() ([]byte, error) { return []byte{0xff, 0xfe}, nil }

// textTagBoth renders itself with a prefix and strips it again on decode, so
// the round trip through a TOML string is lossless.
type textTagBoth string

func (t textTagBoth) MarshalText() ([]byte, error) { return []byte("tag:" + string(t)), nil }

func (t *textTagBoth) UnmarshalText(text []byte) error {
	trimmed, ok := strings.CutPrefix(string(text), "tag:")
	if !ok {
		return errors.New("textTagBoth: missing the tag prefix")
	}
	*t = textTagBoth(trimmed)
	return nil
}

func TestMarshalTextValues(t *testing.T) {
	// The pointer receiver is reachable only through an addressable field, so
	// the whole value is marshalled through a pointer here.
	type Cfg struct {
		IP       net.IP        `toml:"ip"`
		Duration time.Duration `toml:"duration"`
		Tag      textTag       `toml:"tag"`
		Pointer  textPointer   `toml:"pointer"`
		Both     textAndTOML   `toml:"both"`
	}
	out, err := Marshal(&Cfg{
		IP:       net.IPv4(192, 0, 2, 1),
		Duration: 90 * time.Minute,
		Tag:      "x",
		Pointer:  textPointer{V: "abc"},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "ip = \"192.0.2.1\"\nduration = \"1h30m0s\"\ntag = \"tag:x\"\npointer = \"ABC\"\nboth = \"toml\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTextValuesInContainers(t *testing.T) {
	// Slice elements are addressable, so a pointer-receiver MarshalText is used
	// there too, and an array of such values stays a value array: each element's
	// TOML form is a string, so the [[header]] form cannot carry it.
	type Cfg struct {
		Map   map[string]net.IP `toml:"map"`
		Durs  []time.Duration   `toml:"durs"`
		Ptrs  []textPointer     `toml:"ptrs"`
		Empty []textPointer     `toml:"empty"`
	}
	out, err := Marshal(Cfg{
		Map:   map[string]net.IP{"a": net.IPv4(10, 0, 0, 1)},
		Durs:  []time.Duration{0, 250 * time.Millisecond},
		Ptrs:  []textPointer{{V: "a"}, {V: "b"}},
		Empty: []textPointer{},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "durs = [\"0s\", \"250ms\"]\nptrs = [\"A\", \"B\"]\nempty = []\n\n[map]\na = \"10.0.0.1\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTextLeavesDateTimesAlone(t *testing.T) {
	// The four date-time types carry time.Time's text methods through an
	// embedded field; their TOML form is a bare atom, never a quoted string.
	stamp := time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC)
	type Cfg struct {
		Stamp time.Time     `toml:"stamp"`
		Ptr   *time.Time    `toml:"ptr"`
		Day   LocalDate     `toml:"day"`
		At    LocalDateTime `toml:"at"`
		Clock LocalTime     `toml:"clock"`
	}
	out, err := Marshal(&Cfg{
		Stamp: stamp,
		Ptr:   &stamp,
		Day:   LocalDate{time.Date(1979, 5, 27, 0, 0, 0, 0, time.UTC)},
		At:    LocalDateTime{time.Date(1979, 5, 27, 7, 32, 0, 0, time.UTC)},
		Clock: LocalTime{time.Date(0, 1, 1, 7, 32, 0, 0, time.UTC)},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "stamp = 2026-06-26T10:00Z\nptr = 2026-06-26T10:00Z\nday = 1979-05-27\nat = 1979-05-27T07:32\nclock = 07:32\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTextNilPointerOmitted(t *testing.T) {
	type Cfg struct {
		P *textPointer `toml:"p"`
		K string       `toml:"k"`
	}
	out, err := Marshal(&Cfg{K: "x"})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if want := "k = \"x\"\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalTextErrorCarriesPath(t *testing.T) {
	type Inner struct {
		F brokenText `toml:"f"`
	}
	type Cfg struct {
		Inner Inner `toml:"inner"`
	}
	_, err := Marshal(Cfg{})
	if err == nil {
		t.Fatal("expected an error from MarshalText")
	}
	if !strings.Contains(err.Error(), "text boom") {
		t.Errorf("err = %v, want substring \"text boom\"", err)
	}
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "inner.f" {
		t.Fatalf("Path = %v, want inner.f", ee.Path)
	}
}

func TestMarshalTextRejectsInvalidUTF8(t *testing.T) {
	// A TOML string holds UTF-8 only, so text that is not gets an error rather
	// than replacement characters.
	_, err := Marshal(struct {
		V notUTF8 `toml:"v"`
	}{})
	if err == nil {
		t.Fatal("expected an error for text that is not valid UTF-8")
	}
	if !strings.Contains(err.Error(), "UTF-8") {
		t.Errorf("err = %v, want a UTF-8 message", err)
	}
}

func TestMarshalTextValuesRoundTrip(t *testing.T) {
	type Cfg struct {
		Duration time.Duration `toml:"duration"`
		IP       net.IP        `toml:"ip"`
		Tag      textTagBoth   `toml:"tag"`
	}
	in := Cfg{Duration: 90 * time.Minute, IP: net.IPv4(198, 51, 100, 7), Tag: "y"}
	out, err := Marshal(&in)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var back Cfg
	if err := Unmarshal(out, &back); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if back.Duration != in.Duration {
		t.Errorf("Duration = %v, want %v", back.Duration, in.Duration)
	}
	if !back.IP.Equal(in.IP) {
		t.Errorf("IP = %v, want %v", back.IP, in.IP)
	}
	if back.Tag != in.Tag {
		t.Errorf("Tag = %q, want %q", back.Tag, in.Tag)
	}
}

// --- TOML 1.1 output forms -------------------------------------------------

func TestMarshalDateTimeRendering(t *testing.T) {
	// The seconds are written only when the value carries them, and a fraction
	// drops its trailing zeros. Both are the same value either way; the shorter
	// form is the one TOML 1.1 allows.
	base := time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC)
	cases := []struct {
		name string
		val  any
		want string
	}{
		{"offset-zero-seconds", base, "v = 2026-06-26T10:00Z\n"},
		{"offset-wrapper", OffsetDateTime{Time: base}, "v = 2026-06-26T10:00Z\n"},
		{"offset-seconds", base.Add(30 * time.Second), "v = 2026-06-26T10:00:30Z\n"},
		{"offset-fraction", base.Add(500 * time.Millisecond), "v = 2026-06-26T10:00:00.5Z\n"},
		{"offset-zone", time.Date(2026, 6, 26, 10, 0, 0, 0, time.FixedZone("", -7*3600)), "v = 2026-06-26T10:00-07:00\n"},
		{"local-zero-seconds", LocalDateTime{Time: base}, "v = 2026-06-26T10:00\n"},
		{"local-fraction", LocalDateTime{Time: base.Add(2500 * time.Millisecond)}, "v = 2026-06-26T10:00:02.5\n"},
		{"date", LocalDate{Time: base}, "v = 2026-06-26\n"},
		{"time-zero-seconds", LocalTime{Time: base}, "v = 10:00\n"},
		{"time-seconds", LocalTime{Time: base.Add(15 * time.Second)}, "v = 10:00:15\n"},
		{"time-nanoseconds", LocalTime{Time: base.Add(123456789 * time.Nanosecond)}, "v = 10:00:00.123456789\n"},
	}
	for _, c := range cases {
		out, err := Marshal(map[string]any{"v": c.val})
		if err != nil {
			t.Errorf("%s: marshal: %v", c.name, err)
			continue
		}
		if string(out) != c.want {
			t.Errorf("%s: output mismatch:\ngot:  %q\nwant: %q", c.name, out, c.want)
		}
	}
}

func TestMarshalInlineTableBreaksWhenLong(t *testing.T) {
	// A table element of a value array is written inline; a long one carries
	// newlines and a trailing comma instead of running past the line limit,
	// which TOML 1.1 allows an inline table to do.
	const long = "a-very-long-value-that-pushes-the-line-well-past-the-one-hundred-column-limit"
	type Cfg struct {
		Arr []any `toml:"arr"`
	}
	out, err := Marshal(Cfg{Arr: []any{int64(1), map[string]any{"n": int64(1), "name": long}}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "arr = [1, {\n\tn = 1,\n\tname = \"" + long + "\",\n}]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	// The same values without the long string stay on one line.
	out, err = Marshal(Cfg{Arr: []any{int64(1), map[string]any{"n": int64(1), "name": "short"}}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if want := "arr = [1, {n = 1, name = \"short\"}]\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	// The broken form parses back to the same tree.
	tree, err := ParseMap(out)
	if err != nil {
		t.Fatalf("parse of the encoder output: %v", err)
	}
	if got := len(tree["arr"].([]any)); got != 2 {
		t.Fatalf("arr has %d elements, want 2", got)
	}
}

func TestMarshalNestedInlineTableBreaksIndependently(t *testing.T) {
	// A nested table breaks on its own measure, so a table whose entries stay
	// short keeps the one-line form inside a parent that broke.
	const long = "a-very-long-value-that-pushes-the-line-well-past-the-one-hundred-column-limit"
	type Cfg struct {
		Arr []any `toml:"arr"`
	}
	out, err := Marshal(Cfg{Arr: []any{int64(1), map[string]any{"n": int64(1), "sub": map[string]any{"name": long}}}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "arr = [1, {\n\tn = 1,\n\tsub = {name = \"" + long + "\"},\n}]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

type inlineTLS struct {
	On bool `toml:"on"`
}

type inlineServer struct {
	Host string    `toml:"host"`
	Port int       `toml:"port"`
	TLS  inlineTLS `toml:"tls"`
}

type inlineBig struct {
	A int `toml:"a"`
	B int `toml:"b"`
	C int `toml:"c"`
}

func TestEncoderInlineTables(t *testing.T) {
	type Cfg struct {
		Server inlineServer `toml:"server"`
		Big    inlineBig    `toml:"big"`
	}
	cfg := Cfg{Server: inlineServer{Host: "127.0.0.1", Port: 9090}, Big: inlineBig{A: 1, B: 2, C: 3}}

	// The default keeps every sub-table a header section.
	headerForm, err := Marshal(cfg)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[server]\nhost = \"127.0.0.1\"\nport = 9090\n\n[server.tls]\non = false\n\n[big]\na = 1\nb = 2\nc = 3\n"
	if string(headerForm) != want {
		t.Errorf("default output mismatch:\ngot:  %q\nwant: %q", headerForm, want)
	}

	// With the option both fit the threshold and become inline tables, nested
	// ones included.
	out, err := Marshal(cfg, InlineTables(60))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want = "server = {host = \"127.0.0.1\", port = 9090, tls = {on = false}}\nbig = {a = 1, b = 2, c = 3}\n"
	if string(out) != want {
		t.Errorf("compact output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	// A threshold below the rendering keeps the header form.
	out, err = Marshal(cfg, InlineTables(10))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if string(out) != string(headerForm) {
		t.Errorf("small threshold output mismatch:\ngot:  %q\nwant: %q", out, headerForm)
	}
}

func TestEncoderInlineTablesOrderAndRoundTrip(t *testing.T) {
	// An inlined sub-table is a value line, so it precedes every header of the
	// document; written after a header it would be read back as part of that
	// table. The compact form and the header form parse to the same tree.
	type Four struct {
		A int `toml:"a"`
		B int `toml:"b"`
		C int `toml:"c"`
		D int `toml:"d"`
	}
	type Cfg struct {
		Small inlineTLS `toml:"small"`
		Big   Four      `toml:"big"`
	}
	cfg := Cfg{Small: inlineTLS{On: true}, Big: Four{A: 1, B: 2, C: 3, D: 4}}

	headerForm, err := Marshal(cfg)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	compact, err := Marshal(cfg, InlineTables(20))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "small = {on = true}\n\n[big]\na = 1\nb = 2\nc = 3\nd = 4\n"
	if string(compact) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", compact, want)
	}

	got, err := ParseMap(compact)
	if err != nil {
		t.Fatalf("parse of the compact output: %v", err)
	}
	ref, err := ParseMap(headerForm)
	if err != nil {
		t.Fatalf("parse of the header output: %v", err)
	}
	if !reflect.DeepEqual(got, ref) {
		t.Errorf("the compact form changed the tree:\ncompact: %#v\nheaders: %#v", got, ref)
	}
	if _, ok := got["big"].(map[string]any); !ok {
		t.Errorf("big = %#v, want a table", got["big"])
	}
}

func TestEncoderInlineTablesKeepsArraysOfTables(t *testing.T) {
	// An array of tables has no inline form that keeps the value's type, so the
	// option leaves it alone and the tree keeps its []map[string]any shape.
	type Item struct {
		N int `toml:"n"`
	}
	type Cfg struct {
		Items []Item    `toml:"items"`
		Small inlineTLS `toml:"small"`
	}
	cfg := Cfg{Items: []Item{{N: 1}}, Small: inlineTLS{On: true}}
	out, err := Marshal(cfg, InlineTables(60))
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "small = {on = true}\n\n[[items]]\nn = 1\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
	tree, err := ParseMap(out)
	if err != nil {
		t.Fatalf("parse: %v", err)
	}
	if _, ok := tree["items"].([]map[string]any); !ok {
		t.Errorf("items = %#v, want []map[string]any", tree["items"])
	}
}

// --- Marshaler on array elements -------------------------------------------

// countingMarshaler reports how often its method ran, so a test can check that
// the encoder resolves an element once.
type countingMarshaler struct{ calls *int }

func (c countingMarshaler) MarshalTOML() (any, error) {
	*c.calls++
	return map[string]any{"n": int64(*c.calls)}, nil
}

// ptrMarshaler carries MarshalTOML on the pointer receiver only.
type ptrMarshaler struct{ V string }

func (p *ptrMarshaler) MarshalTOML() (any, error) { return map[string]any{"v": p.V}, nil }

func TestMarshalerElementOfArrayOfTables(t *testing.T) {
	// An element is classified by what MarshalTOML returns, so methods that
	// render tables keep the [[header]] form the Go kind would have given them.
	type Cfg struct {
		Items []marshalerFunc `toml:"items"`
	}
	out, err := Marshal(Cfg{Items: []marshalerFunc{
		func() (any, error) { return map[string]any{"k": "a"}, nil },
		func() (any, error) { return map[string]any{"k": "b"}, nil },
	}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[[items]]\nk = \"a\"\n\n[[items]]\nk = \"b\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerElementScalarResultMakesValueArray(t *testing.T) {
	// One element rendering itself as a scalar turns the whole array into a
	// value array, with the table elements written inline.
	type Cfg struct {
		Items []marshalerFunc `toml:"items"`
	}
	out, err := Marshal(Cfg{Items: []marshalerFunc{
		func() (any, error) { return map[string]any{"k": "a"}, nil },
		func() (any, error) { return "x", nil },
	}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "items = [{k = \"a\"}, \"x\"]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerElementRunsOnce(t *testing.T) {
	// Classification and emission share one result, so the method runs exactly
	// once per element even when it decides the array's form.
	calls := 0
	type Cfg struct {
		Items []countingMarshaler `toml:"items"`
	}
	out, err := Marshal(Cfg{Items: []countingMarshaler{{calls: &calls}, {calls: &calls}, {calls: &calls}}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if calls != 3 {
		t.Errorf("MarshalTOML ran %d times, want 3", calls)
	}
	want := "[[items]]\nn = 1\n\n[[items]]\nn = 2\n\n[[items]]\nn = 3\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerPointerReceiverOnElement(t *testing.T) {
	// A slice element is addressable, so a pointer-receiver MarshalTOML is
	// found there, and the method's table keeps the [[header]] form.
	type Cfg struct {
		Items []ptrMarshaler `toml:"items"`
	}
	out, err := Marshal(&Cfg{Items: []ptrMarshaler{{V: "a"}, {V: "b"}}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "[[items]]\nv = \"a\"\n\n[[items]]\nv = \"b\"\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}

	// The same method is found on an addressable struct field, whose result is
	// a table and so keeps a header section.
	type Field struct {
		F ptrMarshaler `toml:"f"`
	}
	out, err = Marshal(&Field{F: ptrMarshaler{V: "c"}})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if want := "[f]\nv = \"c\"\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalerElementErrorCarriesPath(t *testing.T) {
	type Cfg struct {
		Items []any `toml:"items"`
	}
	_, err := Marshal(Cfg{Items: []any{map[string]any{"k": "a"}, failingMarshalerFunc{}}})
	if err == nil {
		t.Fatal("expected an error from MarshalTOML")
	}
	if !strings.Contains(err.Error(), "oops") {
		t.Errorf("err = %v, want substring \"oops\"", err)
	}
	ee, ok := errors.AsType[*EncodeError](err)
	if !ok {
		t.Fatalf("expected an *EncodeError, got %T: %v", err, err)
	}
	if ee.Path.String() != "items[1]" {
		t.Fatalf("Path = %v, want items[1]", ee.Path)
	}
}

func TestMarshalerResultIsNormalised(t *testing.T) {
	// A result is normalised like any other value, so a method may return a
	// plain int or a duration where the Go kind alone would not encode.
	type Cfg struct {
		Plain    marshalerFunc `toml:"plain"`
		Duration marshalerFunc `toml:"duration"`
		Elements []any         `toml:"elements"`
	}
	out, err := Marshal(Cfg{
		Plain:    func() (any, error) { return 7, nil },
		Duration: func() (any, error) { return 90 * time.Minute, nil },
		Elements: []any{marshalerFunc(func() (any, error) { return 8, nil })},
	})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	want := "plain = 7\nduration = \"1h30m0s\"\nelements = [8]\n"
	if string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

func TestMarshalNumber(t *testing.T) {
	t.Run("the literal is written as it is", func(t *testing.T) {
		out, err := Marshal(map[string]any{
			"hex": Number("0x1f"), "sep": Number("1_000"),
			"signed": Number("+1.0"), "inf": Number("inf"),
		})
		if err != nil {
			t.Fatal(err)
		}
		want := "hex = 0x1f\ninf = inf\nsep = 1_000\nsigned = +1.0\n"
		if string(out) != want {
			t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
		}
	})
	t.Run("a Number field round-trips", func(t *testing.T) {
		type Cfg struct {
			Rate Number `toml:"rate"`
		}
		out, err := Marshal(Cfg{Rate: "1_000"})
		if err != nil {
			t.Fatal(err)
		}
		if string(out) != "rate = 1_000\n" {
			t.Fatalf("output %q", out)
		}
		var back map[string]any
		if err := Unmarshal(out, &back, NumbersAsLiterals(true)); err != nil {
			t.Fatal(err)
		}
		if got, ok := back["rate"].(Number); !ok || got != "1_000" {
			t.Errorf("round trip = %#v, want Number(\"1_000\")", back["rate"])
		}
	})
	t.Run("a Number inside a value array", func(t *testing.T) {
		out, err := Marshal(map[string]any{"vals": []any{Number("0x1f"), "s", int64(2)}})
		if err != nil {
			t.Fatal(err)
		}
		want := "vals = [0x1f, \"s\", 2]\n"
		if string(out) != want {
			t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
		}
	})
	t.Run("an invalid literal is an error", func(t *testing.T) {
		for _, lit := range []Number{"01", "1__0", "abc", "1.2.3"} {
			if _, err := Marshal(map[string]any{"n": lit}); err == nil {
				t.Errorf("Number(%q) encoded without an error", lit)
			}
		}
	})
}

func TestMarshalAppend(t *testing.T) {
	buf := []byte("preamble\n")
	out, err := MarshalAppend(buf, map[string]any{"a": int64(1)})
	if err != nil {
		t.Fatal(err)
	}
	want := "preamble\na = 1\n"
	if string(out) != want {
		t.Errorf("output %q, want %q", out, want)
	}
	if &out[0] != &buf[0] {
		t.Log("append reallocated; capacity differed")
	}
	out2, err := MarshalAppend(out, map[string]any{"b": true})
	if err != nil {
		t.Fatal(err)
	}
	if string(out2) != want+"b = true\n" {
		t.Errorf("second append %q", out2)
	}
	buf = []byte("keep\n")
	if out3, err := MarshalAppend(buf, Document{}); err == nil {
		t.Errorf("MarshalAppend with an unencodable value = %q, want an error", out3)
	}
}

func TestMarshalCyclicData(t *testing.T) {
	t.Run("a cyclic struct is an error, not a crash", func(t *testing.T) {
		type Node struct {
			Name string `toml:"name"`
			Next *Node  `toml:"next"`
		}
		a := &Node{Name: "a"}
		b := &Node{Name: "b"}
		a.Next = b
		b.Next = a
		_, err := Marshal(a)
		if err == nil {
			t.Fatal("Marshal(cyclic) succeeded, want an error")
		}
		if !strings.Contains(err.Error(), "may be cyclic") {
			t.Errorf("err = %v, want it to name the cycle", err)
		}
	})
	t.Run("a cyclic map is an error", func(t *testing.T) {
		m := map[string]any{}
		m["self"] = m
		if _, err := Marshal(m); err == nil {
			t.Fatal("Marshal(cyclic map) succeeded, want an error")
		}
	})
	t.Run("a cyclic value array is an error", func(t *testing.T) {
		m := map[string]any{}
		m["items"] = []any{int64(1), m}
		if _, err := Marshal(map[string]any{"outer": m}); err == nil {
			t.Fatal("Marshal(cyclic array) succeeded, want an error")
		}
	})
	t.Run("a deeply nested but finite value encodes", func(t *testing.T) {
		type Node struct {
			Next *Node `toml:"next"`
		}
		root := &Node{}
		cur := root
		for range 5000 {
			cur.Next = &Node{}
			cur = cur.Next
		}
		if _, err := Marshal(root); err != nil {
			t.Errorf("Marshal(deep) = %v, want nil", err)
		}
	})
}

func TestUnmarshalOptionsShape(t *testing.T) {
	data := []byte("host = \"db\"\nextra = 1\n")
	type Config struct {
		Host string `toml:"host,required"`
	}
	t.Run("the zero value takes the defaults", func(t *testing.T) {
		var cfg struct {
			Host  string `toml:"host"`
			Extra int    `toml:"extra"`
		}
		if err := Unmarshal(data, &cfg); err != nil {
			t.Fatal(err)
		}
		if cfg.Host != "db" || cfg.Extra != 1 {
			t.Errorf("decoded %+v", cfg)
		}
	})
	t.Run("strict and required work in one call", func(t *testing.T) {
		err := Unmarshal(data, &Config{}, RejectUnknownFields(true))
		want := `interpres: unknown field "extra" for interpres.Config`
		if err == nil || err.Error() != want {
			t.Errorf("err = %v, want %q", err, want)
		}
	})
	t.Run("UseNumber keeps the literal", func(t *testing.T) {
		var tree map[string]any
		in := []byte("n = 1_000\n")
		if err := Unmarshal(in, &tree, NumbersAsLiterals(true)); err != nil {
			t.Fatal(err)
		}
		if got, ok := tree["n"].(Number); !ok || got != "1_000" {
			t.Errorf("n = %#v, want Number(\"1_000\")", tree["n"])
		}
	})
	t.Run("the limits apply", func(t *testing.T) {
		var nested strings.Builder
		nested.WriteString("x = ")
		for range 20 {
			nested.WriteString("[")
		}
		nested.WriteString("1")
		for range 20 {
			nested.WriteString("]")
		}
		var tree map[string]any
		if err := Unmarshal([]byte(nested.String()), &tree, MaxNestingDepth(10)); err == nil {
			t.Error("a document over MaxDepth decoded, want an error")
		}
		if err := Unmarshal([]byte("a = 1\n"), &tree, MaxInputSize(2)); err == nil {
			t.Error("a document over MaxInputSize decoded, want an error")
		}
	})
}

func TestInlineTag(t *testing.T) {
	type Inner struct {
		A int `toml:"a"`
		B int `toml:"b"`
	}
	t.Run("a struct field writes inline", func(t *testing.T) {
		type Cfg struct {
			Inner Inner `toml:"inner,inline"`
		}
		out, err := Marshal(Cfg{Inner: Inner{1, 2}})
		if err != nil {
			t.Fatal(err)
		}
		if string(out) != "inner = {a = 1, b = 2}\n" {
			t.Errorf("output %q", out)
		}
	})
	t.Run("a map field writes inline", func(t *testing.T) {
		type Cfg struct {
			Opts map[string]int `toml:"opts,inline"`
		}
		out, err := Marshal(Cfg{Opts: map[string]int{"x": 1}})
		if err != nil {
			t.Fatal(err)
		}
		if string(out) != "opts = {x = 1}\n" {
			t.Errorf("output %q", out)
		}
	})
	t.Run("a named embedded struct writes inline", func(t *testing.T) {
		type Cfg struct {
			Inner `toml:"inner,inline"`
		}
		out, err := Marshal(Cfg{Inner: Inner{1, 2}})
		if err != nil {
			t.Fatal(err)
		}
		if string(out) != "inner = {a = 1, b = 2}\n" {
			t.Errorf("output %q", out)
		}
	})
	t.Run("an inline field decodes back", func(t *testing.T) {
		type Cfg struct {
			Inner Inner `toml:"inner,inline"`
		}
		var cfg Cfg
		if err := Unmarshal([]byte("inner = {a = 3, b = 4}\n"), &cfg); err != nil {
			t.Fatal(err)
		}
		if cfg.Inner != (Inner{3, 4}) {
			t.Errorf("decoded %+v", cfg.Inner)
		}
	})
	t.Run("a forced inline of an array of tables is an error", func(t *testing.T) {
		type Item struct {
			N int `toml:"n"`
		}
		type Cfg struct {
			Items []Item `toml:"items,inline"`
		}
		if _, err := Marshal(Cfg{Items: []Item{{1}}}); err == nil {
			t.Error("forced inline of an array of tables succeeded, want an error")
		}
	})
	t.Run("without the tag the header form stands", func(t *testing.T) {
		type Cfg struct {
			Inner Inner `toml:"inner"`
		}
		out, err := Marshal(Cfg{Inner: Inner{1, 2}})
		if err != nil {
			t.Fatal(err)
		}
		if string(out) != "[inner]\na = 1\nb = 2\n" {
			t.Errorf("output %q", out)
		}
	})
}

func TestOmitEmptyJSONSemantics(t *testing.T) {
	type Cfg struct {
		Empty   string            `toml:"empty,omitempty"`
		Full    string            `toml:"full,omitempty"`
		Zero    int               `toml:"zero,omitempty"`
		One     int               `toml:"one,omitempty"`
		Off     bool              `toml:"off,omitempty"`
		On      bool              `toml:"on,omitempty"`
		Nil     *string           `toml:"nil,omitempty"`
		Set     *string           `toml:"set,omitempty"`
		Nothing map[string]string `toml:"nothing,omitempty"`
		Somethg map[string]string `toml:"somethg,omitempty"`
	}
	s := "x"
	out, err := Marshal(Cfg{
		Full:    "y",
		One:     1,
		On:      true,
		Set:     &s,
		Somethg: map[string]string{"k": "v"},
	})
	if err != nil {
		t.Fatal(err)
	}
	want := "full = \"y\"\none = 1\non = true\nset = \"x\"\n\n[somethg]\nk = \"v\"\n"
	if string(out) != want {
		t.Errorf("output:\n%q\nwant:\n%q", out, want)
	}
}

func TestEmitFieldComments(t *testing.T) {
	type Cfg struct {
		Host string `toml:"host,comment=The host to dial"`
		Port int    `toml:"port,comment=The port to listen on.\nThe default is 8080."`
		User string `toml:"user"`
	}
	cfg := Cfg{Host: "db", Port: 5432, User: "admin"}
	t.Run("off by default", func(t *testing.T) {
		out, err := Marshal(cfg)
		if err != nil {
			t.Fatal(err)
		}
		want := "host = \"db\"\nport = 5432\nuser = \"admin\"\n"
		if string(out) != want {
			t.Errorf("output:\n%q", out)
		}
	})
	t.Run("on, the comments print above their lines", func(t *testing.T) {
		out, err := Marshal(cfg, EmitFieldComments(true))
		if err != nil {
			t.Fatal(err)
		}
		want := "# The host to dial\nhost = \"db\"\n" +
			"# The port to listen on.\n# The default is 8080.\nport = 5432\n" +
			"user = \"admin\"\n"
		if string(out) != want {
			t.Errorf("output:\n%q\nwant:\n%q", out, want)
		}
		var back Cfg
		if err := Unmarshal(out, &back); err != nil {
			t.Fatalf("the output does not re-parse: %v", err)
		}
		if back != cfg {
			t.Errorf("round trip = %+v", back)
		}
	})
	t.Run("a table header carries its comment", func(t *testing.T) {
		type Inner struct {
			A int `toml:"a,comment=The a"`
		}
		type Nested struct {
			Inner Inner `toml:"inner,comment=The inner table"`
		}
		out, err := Marshal(Nested{Inner: Inner{1}}, EmitFieldComments(true))
		if err != nil {
			t.Fatal(err)
		}
		want := "# The inner table\n[inner]\n# The a\na = 1\n"
		if string(out) != want {
			t.Errorf("output:\n%q\nwant:\n%q", out, want)
		}
	})
}