interpres/decode_test.go

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

package interpres

import (
	"context"
	"errors"
	"fmt"
	"math"
	"net"
	"slices"
	"strings"
	"testing"
	"time"
)

func TestSyntaxErrorMessage(t *testing.T) {
	err := &SyntaxError{Line: 7, Msg: "expected '=' after key"}
	want := "interpres: line 7: expected '=' after key"
	if got := err.Error(); got != want {
		t.Errorf("Error() = %q, want %q", got, want)
	}
}

func TestParseRejectsInvalidUTF8(t *testing.T) {
	// The scan validates UTF-8 where it meets the byte, so the reported line
	// is the invalid byte's own, wherever in the document it sits.
	cases := []struct {
		name string
		doc  string
		line int
	}{
		{"in a basic string", "v = \"\xff\"\n", 1},
		{"in a literal string", "v = '\xff'\n", 1},
		{"in a multiline string", "v = \"\"\"\n\xff\"\"\"\n", 2},
		{"in a comment", "v = 1\n# caf\xe9\xff\n", 2},
		{"in a bare key", "va\xfflue = 1\n", 1},
		{"as a statement", "\xff = 1\n", 1},
		{"in a bare value", "v = \xff1\n", 1},
		{"after a value", "v = 1 \xff\n", 1},
		{"after the first line", "a = 1\nb = \"\xff\"\n", 2},
	}
	for _, c := range cases {
		_, err := ParseMap([]byte(c.doc))
		if err == nil {
			t.Fatalf("%s: expected a UTF-8 validation error", c.name)
		}
		se, ok := err.(*SyntaxError)
		if !ok {
			t.Fatalf("%s: err is %T, want *SyntaxError", c.name, err)
		}
		if !strings.Contains(se.Msg, "UTF-8") {
			t.Errorf("%s: Msg = %q, want it to mention UTF-8", c.name, se.Msg)
		}
		if se.Line != c.line {
			t.Errorf("%s: Line = %d, want %d", c.name, se.Line, c.line)
		}
	}
}

func TestUnmarshalIntoMap(t *testing.T) {
	var m map[string]any
	if err := Unmarshal([]byte(`name = "x"
count = 3
`), &m); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if m["name"] != "x" {
		t.Errorf("name = %#v", m["name"])
	}
	if m["count"] != int64(3) {
		t.Errorf("count = %#v (%T)", m["count"], m["count"])
	}
}

func TestUnmarshalIntoMapNested(t *testing.T) {
	var m map[string]any
	if err := Unmarshal([]byte("[a]\nb = 2\n"), &m); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	a, ok := m["a"].(map[string]any)
	if !ok {
		t.Fatalf("a = %T, want map[string]any", m["a"])
	}
	if a["b"] != int64(2) {
		t.Errorf("a.b = %#v", a["b"])
	}
}

func TestUnmarshalPrefilledMap(t *testing.T) {
	m := map[string]any{"keep": "yes"}
	if err := Unmarshal([]byte(`name = "x"`), &m); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if m["keep"] != "yes" {
		t.Errorf("keep = %#v", m["keep"])
	}
	if m["name"] != "x" {
		t.Errorf("name = %#v", m["name"])
	}
}

func TestUnmarshalTableToNonStructOrMap(t *testing.T) {
	var s string
	if err := Unmarshal([]byte("v = 1\n"), &s); err == nil {
		t.Fatal("expected an error for table-to-scalar")
	}
}

func TestUnmarshalIntoAny(t *testing.T) {
	// A non-nil any destination must accept the parsed tree.
	var x any
	if err := Unmarshal([]byte("[a]\nb = 2\n"), &x); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	tree, ok := x.(map[string]any)
	if !ok {
		t.Fatalf("x is %T, want map[string]any", x)
	}
	a, ok := tree["a"].(map[string]any)
	if !ok {
		t.Fatalf("a is %T, want map[string]any", tree["a"])
	}
	if a["b"] != int64(2) {
		t.Errorf("a.b = %#v", a["b"])
	}
}

func TestUnmarshalIntoNilAny(t *testing.T) {
	// A nil any target must still receive the parsed tree without
	// panicking.
	var x any
	if err := Unmarshal([]byte("v = 1\n"), &x); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if x == nil {
		t.Fatal("x is still nil after Unmarshal")
	}
	tree, ok := x.(map[string]any)
	if !ok {
		t.Fatalf("x is %T, want map[string]any", x)
	}
	if tree["v"] != int64(1) {
		t.Errorf("v = %#v", tree["v"])
	}
}

func TestParseContextHonoursCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	if _, err := ParseMapContext(ctx, []byte("a = 1\n")); !errors.Is(err, context.Canceled) {
		t.Fatalf("ParseContext returned %v, want context.Canceled", err)
	}
}

func TestUnmarshalContextHonoursCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	var cfg map[string]any
	if err := UnmarshalContext(ctx, []byte("a = 1\n"), &cfg); !errors.Is(err, context.Canceled) {
		t.Fatalf("UnmarshalContext returned %v, want context.Canceled", err)
	}
}

func TestDecoderDecodeContextHonoursCancellation(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	var cfg map[string]any
	err := NewDecoder().DecodeContext(ctx, []byte("a = 1\n"), &cfg)
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("DecodeContext returned %v, want context.Canceled", err)
	}
}

func TestContextRoundTrip(t *testing.T) {
	// The *Context variants with a Background context must produce the same
	// result as the non-context variants for ordinary inputs.
	in := []byte(`title = "x"
count = 3
`)
	if _, err := ParseMapContext(context.Background(), in); err != nil {
		t.Fatalf("ParseContext: %v", err)
	}
	var out struct {
		Title string `toml:"title"`
		Count int    `toml:"count"`
	}
	if err := UnmarshalContext(context.Background(), in, &out); err != nil {
		t.Fatalf("UnmarshalContext: %v", err)
	}
	if out.Title != "x" || out.Count != 3 {
		t.Errorf("out = %#v", out)
	}
	if err := NewDecoder().DecodeContext(context.Background(), in, &map[string]any{}); err != nil {
		t.Fatalf("Decoder.DecodeContext: %v", err)
	}
}

func TestUnmarshalIntToUintOverflow(t *testing.T) {
	type C struct {
		X uint8 `toml:"x"`
	}
	var c C
	err := Unmarshal([]byte("x = 300\n"), &c)
	if err == nil {
		t.Fatal("expected overflow error")
	}
	if !strings.Contains(err.Error(), "overflow") {
		t.Errorf("err = %v, want substring 'overflow'", err)
	}
}

func TestUnmarshalIntToUint16Boundary(t *testing.T) {
	type C struct {
		X uint16 `toml:"x"`
	}
	// Exactly 65535 fits, 65536 does not.
	var ok C
	if err := Unmarshal([]byte("x = 65535\n"), &ok); err != nil {
		t.Fatalf("65535 should fit uint16, got %v", err)
	}
	if ok.X != 65535 {
		t.Errorf("X = %d, want 65535", ok.X)
	}

	var bad C
	if err := Unmarshal([]byte("x = 65536\n"), &bad); err == nil {
		t.Fatal("65536 must not fit uint16")
	}
}

func TestUnmarshalIntToUint64FitsMaxInt64(t *testing.T) {
	type C struct {
		X uint64 `toml:"x"`
	}
	var c C
	tok := "x = 9223372036854775807\n" // math.MaxInt64
	if err := Unmarshal([]byte(tok), &c); err != nil {
		t.Fatalf("MaxInt64 should fit uint64, got %v", err)
	}
	if c.X != math.MaxInt64 {
		t.Errorf("X = %d, want %d", uint64(c.X), uint64(math.MaxInt64))
	}
}

func TestUnmarshalFloat32Overflow(t *testing.T) {
	// A finite float64 beyond the float32 range must not decode silently as
	// an infinity.
	type C struct {
		X float32 `toml:"x"`
	}
	var c C
	err := Unmarshal([]byte("x = 1e300\n"), &c)
	if err == nil {
		t.Fatal("expected overflow error for float32")
	}
	if !strings.Contains(err.Error(), "overflow") {
		t.Errorf("err = %v, want substring 'overflow'", err.Error())
	}
	// Infinities themselves pass through, and in-range values are untouched.
	var ok C
	if err := Unmarshal([]byte("x = inf\n"), &ok); err != nil {
		t.Fatalf("inf should decode into float32, got %v", err)
	}
	if !math.IsInf(float64(ok.X), 1) {
		t.Errorf("X = %v, want +Inf", ok.X)
	}
	if err := Unmarshal([]byte("x = 1.5\n"), &ok); err != nil || ok.X != 1.5 {
		t.Fatalf("1.5 should decode into float32, got %v (X=%v)", err, ok.X)
	}
}

func TestUnmarshalNegativeIntToUint(t *testing.T) {
	type C struct {
		X uint8 `toml:"x"`
	}
	var c C
	err := Unmarshal([]byte("x = -1\n"), &c)
	if err == nil {
		t.Fatal("expected negative-to-uint error")
	}
	if !strings.Contains(err.Error(), "negative") {
		t.Errorf("err = %v, want substring 'negative'", err)
	}
}

func TestUnmarshalIntToFloat(t *testing.T) {
	type C struct {
		X float64 `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte("x = 5\n"), &c); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if c.X != 5.0 {
		t.Errorf("X = %v, want 5.0", c.X)
	}
}

func TestUnmarshalIntToStringFails(t *testing.T) {
	type C struct {
		X string `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte(`x = 5`), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalStringToIntFails(t *testing.T) {
	type C struct {
		X int `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte(`x = "hello"`), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalArrayToScalarFails(t *testing.T) {
	type C struct {
		X int `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte("x = [1, 2]\n"), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalArrayOfTablesToScalarFails(t *testing.T) {
	type Item struct {
		Name string `toml:"name"`
	}
	type C struct {
		X Item `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte("[[x]]\nname = \"a\"\n"), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalFloatToIntFails(t *testing.T) {
	type C struct {
		X int `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte("x = 1.5\n"), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalBoolToIntFails(t *testing.T) {
	type C struct {
		X int `toml:"x"`
	}
	var c C
	if err := Unmarshal([]byte("x = true\n"), &c); err == nil {
		t.Fatal("expected type-mismatch error")
	}
}

func TestUnmarshalNonPointerRejected(t *testing.T) {
	var v int
	if err := Unmarshal([]byte("x = 1\n"), v); err == nil {
		t.Fatal("expected error for non-pointer target")
	}
}

func TestUnmarshalAssignErrorWrapped(t *testing.T) {
	// assignStruct wraps inner assignment errors with the key name.
	type C struct {
		Inner struct {
			X int `toml:"x"`
		} `toml:"inner"`
	}
	var c C
	err := Unmarshal([]byte("[inner]\nx = \"oops\"\n"), &c)
	if err == nil {
		t.Fatal("expected an assignment error")
	}
	if !strings.Contains(err.Error(), "x") {
		t.Errorf("err = %v, want it to mention key x", err)
	}
}

func TestUnmarshalAssignMapErrorWrapped(t *testing.T) {
	// assignMap wraps inner errors with the key of the bad element.
	m := map[string]int{}
	err := Unmarshal([]byte("[s]\nx = 1\n"), &m)
	if err == nil {
		t.Fatal("expected an assignment error")
	}
	if !strings.Contains(err.Error(), "s") {
		t.Errorf("err = %v, want it to mention key 's'", err)
	}
}

func TestUnmarshalAssignSliceErrorWrapped(t *testing.T) {
	// assignSlice wraps inner errors with the bad element's index.
	type C struct {
		Items []int `toml:"items"`
	}
	var c C
	err := Unmarshal([]byte(`items = [1, "oops"]`), &c)
	if err == nil {
		t.Fatal("expected an assignment error")
	}
	if !strings.Contains(err.Error(), "[1]") {
		t.Errorf("err = %v, want it to mention index [1]", err)
	}
}

func TestUnmarshalAssignTimeToWrongTypeFails(t *testing.T) {
	// assign maps time.Time to time.Time only.
	type C struct {
		T string `toml:"t"`
	}
	var c C
	err := Unmarshal([]byte("t = 2026-01-01T00:00:00Z\n"), &c)
	if err == nil {
		t.Fatal("expected time-to-string assignment to fail")
	}
}

func TestMarshalerUsesCustomEncoding(t *testing.T) {
	// A type that implements Marshaler can be encoded through a wrapping struct.
	val := inlineMarshaler(func() (any, error) {
		return map[string]any{"k": "v"}, nil
	})
	type wrap struct {
		Inner inlineMarshaler `toml:"inner"`
	}
	out, err := Marshal(wrap{Inner: val})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	got := string(out)
	if !strings.Contains(got, "[inner]") || !strings.Contains(got, "k = \"v\"") {
		t.Errorf("out = %q, want a [inner] table with k = \"v\"", got)
	}
}

type inlineMarshaler func() (any, error)

func (i inlineMarshaler) MarshalTOML() (any, error) { return i() }

// --- Unmarshaler -----------------------------------------------------------

// receiverSetter implements *Unmarshaler by reshaping a parsed table.
type receiverSetter struct {
	Field    string
	Received any
}

func (r *receiverSetter) UnmarshalTOML(data any) error {
	m, ok := data.(map[string]any)
	if !ok {
		return fmt.Errorf("interpres: receiverSetter expects table, got %T", data)
	}
	if v, ok := m["field"].(string); ok {
		r.Field = v
	}
	r.Received = data
	return nil
}

func TestUnmarshalerByPointer(t *testing.T) {
	type Cfg struct {
		R receiverSetter `toml:"r"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte(`[r]
field = "x"
`), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.R.Field != "x" {
		t.Errorf("Field = %q, want \"x\"", cfg.R.Field)
	}
	if cfg.R.Received == nil {
		t.Error("Receiver did not see parsed data")
	}
}

type scalarUnmarshaler struct{ val string }

func (s *scalarUnmarshaler) UnmarshalTOML(data any) error {
	str, ok := data.(string)
	if !ok {
		return fmt.Errorf("interpres: scalarUnmarshaler expects string, got %T", data)
	}
	s.val = str
	return nil
}

func TestUnmarshalerReceivesRawScalar(t *testing.T) {
	// Place the Unmarshaler-implementing field inside a wrapper struct so
	// the decoder dispatches the scalar value to its UnmarshalTOML.
	type Cfg struct {
		S scalarUnmarshaler `toml:"s"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte(`s = "hello"`), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.S.val != "hello" {
		t.Errorf("cfg.S.val = %q, want \"hello\"", cfg.S.val)
	}
}

type failingUnmarshaler struct{}

func (f *failingUnmarshaler) UnmarshalTOML(_ any) error { return errors.New("boom") }

func TestUnmarshalerErrorPropagates(t *testing.T) {
	type Cfg struct {
		F failingUnmarshaler `toml:"f"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte("f = 1"), &cfg); err == nil {
		t.Fatal("expected error from UnmarshalTOML")
	} else if !strings.Contains(err.Error(), "boom") {
		t.Errorf("err = %v, want substring \"boom\"", err)
	}
}

func TestUnmarshalerTakesPrecedenceOverDefault(t *testing.T) {
	// Even when the field is a scalar type and the value is a table,
	// UnmarshalTOML wins, because the receiver decides.
	type Cfg struct {
		R receiverSetter `toml:"r"`
	}
	var cfg Cfg
	in := []byte(`[r]
field = "y"
`)
	if err := Unmarshal(in, &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.R.Field != "y" {
		t.Errorf("Field = %q, want \"y\"", cfg.R.Field)
	}
}

// --- embedded field symmetry -----------------------------------------------

type RoundTripBase struct {
	ID   int    `toml:"id"`
	Name string `toml:"name"`
}

type RoundTripDerived struct {
	RoundTripBase
	X string `toml:"x"`
}

func TestUnmarshalEmbeddedStructRoundTrip(t *testing.T) {
	orig := RoundTripDerived{ID: 1, Name: "b", X: "x"}
	out, err := Marshal(orig)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var back RoundTripDerived
	if err := Unmarshal(out, &back); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if back != orig {
		t.Fatalf("round-trip mismatch:\nwas: %+v\nnow: %+v", orig, back)
	}
}

type RoundTripPtrCfg struct {
	*RoundTripBase
	X string `toml:"x"`
}

func TestUnmarshalEmbeddedPointerStruct(t *testing.T) {
	var cfg RoundTripPtrCfg
	if err := Unmarshal([]byte("id = 7\nname = \"n\"\nx = \"x\"\n"), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.RoundTripBase == nil || cfg.ID != 7 || cfg.Name != "n" || cfg.X != "x" {
		t.Fatalf("decoded: %+v", cfg)
	}
}

// A struct embedding a pointer to itself is legal Go; decoding into it must
// terminate. The schema walk used to recurse through the embedded type
// forever.
func TestUnmarshalSelfEmbeddedPointerStructTerminates(t *testing.T) {
	type SelfLink struct {
		*SelfLink
		X int    `toml:"x"`
		Y string `toml:"y"`
	}
	var n SelfLink
	if err := Unmarshal([]byte("x = 1\ny = \"s\"\n"), &n); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if n.X != 1 || n.Y != "s" {
		t.Fatalf("decoded: %+v", n)
	}

	// A nil self pointer on the encode side stays skippable, as any nil
	// embedded pointer is.
	out, err := Marshal(SelfLink{X: 2})
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	if want := "x = 2\ny = \"\"\n"; string(out) != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", out, want)
	}
}

type RoundTripExtra map[string]int

type RoundTripMapCfg struct {
	RoundTripExtra
	X string `toml:"x"`
}

func TestUnmarshalEmbeddedMap(t *testing.T) {
	var cfg RoundTripMapCfg
	if err := Unmarshal([]byte("alpha = 1\nx = \"x\"\n"), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.RoundTripExtra["alpha"] != 1 || cfg.X != "x" {
		t.Fatalf("decoded: %+v", cfg)
	}

	orig := RoundTripMapCfg{RoundTripExtra: RoundTripExtra{"a": 1}, X: "x"}
	out, err := Marshal(orig)
	if err != nil {
		t.Fatalf("marshal: %v", err)
	}
	var back RoundTripMapCfg
	if err := Unmarshal(out, &back); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if back.X != "x" || back.RoundTripExtra["a"] != 1 {
		t.Fatalf("round-trip mismatch: %+v", back)
	}
}

func TestUnmarshalEmbeddedNameClashShallowerWins(t *testing.T) {
	type Inner struct {
		Name string `toml:"name"`
		Deep string `toml:"deep"`
	}
	type Outer struct {
		Inner
		Name string `toml:"name"`
	}
	var v Outer
	if err := Unmarshal([]byte("name = \"outer\"\ndeep = \"d\"\n"), &v); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if v.Name != "outer" || v.Deep != "d" {
		t.Fatalf("decoded: %+v", v)
	}
}

func TestUnmarshalNameClashEqualDepthLaterWins(t *testing.T) {
	// At equal depth the field declared later resolves the name, matching the
	// documented rule.
	type C struct {
		First  string `toml:"v"`
		Second int    `toml:"v"`
	}
	var c C
	if err := Unmarshal([]byte("v = 1\n"), &c); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if c.Second != 1 {
		t.Fatalf("decoded: %+v, want the later field to take the value", c)
	}
}

func TestUnmarshalUnknownKeyWithoutEmbeddedMap(t *testing.T) {
	var cfg RoundTripDerived
	if err := Unmarshal([]byte("rogue = 1\n"), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.ID != 0 || cfg.X != "" {
		t.Fatalf("decoded: %+v", cfg)
	}
}

func TestUnmarshalStrictEmbeddedMapStaysStrict(t *testing.T) {
	type Cfg struct {
		RoundTripExtra
		Name string `toml:"name"`
	}
	dec := NewDecoder().DisallowUnknownFields()
	err := dec.Decode([]byte("name = \"n\"\nrogue = 1\n"), &Cfg{})
	if err == nil || !strings.Contains(err.Error(), "unknown field") {
		t.Fatalf("expected unknown field error, got: %v", err)
	}
}

func TestDecodeErrorCarriesPath(t *testing.T) {
	type Item struct {
		Name   string `toml:"name"`
		Weight uint8  `toml:"weight"`
	}
	type Cfg struct {
		Tags  []string `toml:"tags"`
		Items []Item   `toml:"items"`
	}
	var cfg Cfg
	err := Unmarshal([]byte("[[items]]\nname = \"a\"\nweight = 300\n"), &cfg)
	if err == nil {
		t.Fatal("expected an overflow error")
	}
	de, ok := errors.AsType[*DecodeError](err)
	if !ok {
		t.Fatalf("expected a *DecodeError, got %T: %v", err, err)
	}
	want := []string{"items", "[0]", "weight"}
	if !slices.Equal(de.Path, want) {
		t.Fatalf("Path = %v, want %v", de.Path, want)
	}
	if de.Err == nil || !strings.Contains(de.Err.Error(), "overflows uint8") {
		t.Fatalf("Err = %v", de.Err)
	}
	// The rendered message keeps its shape: segments joined with ": ".
	wantMsg := "items: [0]: weight: interpres: integer 300 overflows uint8"
	if err.Error() != wantMsg {
		t.Fatalf("message = %q, want %q", err.Error(), wantMsg)
	}
}

func TestDecodeErrorOnMapDestination(t *testing.T) {
	var m map[string]uint8
	err := Unmarshal([]byte("count = -1\n"), &m)
	if err == nil {
		t.Fatal("expected an error")
	}
	de, ok := errors.AsType[*DecodeError](err)
	if !ok {
		t.Fatalf("expected a *DecodeError, got %T: %v", err, err)
	}
	if !slices.Equal(de.Path, []string{"count"}) {
		t.Fatalf("Path = %v", de.Path)
	}
}

func TestUnmarshalIntoDefinedScalarTypes(t *testing.T) {
	// A defined type whose underlying kind is string or bool takes the value.
	// A bare reflect Set panics on such a type, because a string is not
	// assignable to a defined string type without a conversion.
	type Name string
	type Flag bool
	type Cfg struct {
		N Name `toml:"n"`
		F Flag `toml:"f"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte("n = \"x\"\nf = true\n"), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.N != "x" {
		t.Errorf("N = %q, want \"x\"", cfg.N)
	}
	if !cfg.F {
		t.Error("F = false, want true")
	}
}

// --- encoding.TextUnmarshaler and time.Duration ----------------------------

// textReceiver implements encoding.TextUnmarshaler on the pointer receiver.
type textReceiver struct{ Text string }

func (t *textReceiver) UnmarshalText(text []byte) error {
	t.Text = "got:" + string(text)
	return nil
}

// upperText is a defined string type whose UnmarshalText transforms the
// content, so a plain string assignment would leave the wrong value behind.
type upperText string

func (u *upperText) UnmarshalText(text []byte) error {
	*u = upperText(strings.ToUpper(string(text)))
	return nil
}

// failingTextUnmarshaler fails the decode from UnmarshalText.
type failingTextUnmarshaler struct{}

func (f *failingTextUnmarshaler) UnmarshalText(_ []byte) error { return errors.New("text boom") }

// textAndTOMLReceiver implements both decode interfaces; the TOML method wins.
type textAndTOMLReceiver struct{ From string }

func (t *textAndTOMLReceiver) UnmarshalTOML(any) error { t.From = "toml"; return nil }

func (t *textAndTOMLReceiver) UnmarshalText([]byte) error { t.From = "text"; return nil }

func TestTextUnmarshalerByPointer(t *testing.T) {
	type Cfg struct {
		R textReceiver `toml:"r"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte(`r = "hello"`), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.R.Text != "got:hello" {
		t.Errorf("Text = %q, want \"got:hello\"", cfg.R.Text)
	}
}

func TestTextUnmarshalerWinsOverKindAssignment(t *testing.T) {
	type Cfg struct {
		U upperText `toml:"u"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte(`u = "abc"`), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.U != "ABC" {
		t.Errorf("U = %q, want \"ABC\"", cfg.U)
	}
}

func TestTextUnmarshalerForNetIP(t *testing.T) {
	type Cfg struct {
		V4  net.IP   `toml:"v4"`
		V6  net.IP   `toml:"v6"`
		IPs []net.IP `toml:"ips"`
	}
	in := "v4 = \"192.0.2.1\"\nv6 = \"2001:db8::68\"\nips = [\"198.51.100.7\", \"203.0.113.9\"]\n"
	var cfg Cfg
	if err := Unmarshal([]byte(in), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if got := cfg.V4.String(); got != "192.0.2.1" {
		t.Errorf("V4 = %q, want \"192.0.2.1\"", got)
	}
	if got := cfg.V6.String(); got != "2001:db8::68" {
		t.Errorf("V6 = %q, want \"2001:db8::68\"", got)
	}
	if len(cfg.IPs) != 2 || cfg.IPs[0].String() != "198.51.100.7" || cfg.IPs[1].String() != "203.0.113.9" {
		t.Errorf("IPs = %v, want two addresses", cfg.IPs)
	}
}

func TestTextUnmarshalerSeesStringsOnly(t *testing.T) {
	// An integer keeps its own rule: the text method is not consulted, and the
	// value does not reach the receiver.
	type Cfg struct {
		R textReceiver `toml:"r"`
	}
	var cfg Cfg
	err := Unmarshal([]byte("r = 1\n"), &cfg)
	if err == nil {
		t.Fatal("expected an integer to be rejected for a text receiver")
	}
	if cfg.R.Text != "" {
		t.Errorf("Text = %q, want it untouched", cfg.R.Text)
	}
}

func TestUnmarshalTOMLWinsOverTextUnmarshaler(t *testing.T) {
	type Cfg struct {
		B textAndTOMLReceiver `toml:"b"`
	}
	var cfg Cfg
	if err := Unmarshal([]byte(`b = "x"`), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.B.From != "toml" {
		t.Errorf("From = %q, want \"toml\"", cfg.B.From)
	}
}

func TestTextUnmarshalerErrorCarriesPath(t *testing.T) {
	type Inner struct {
		F failingTextUnmarshaler `toml:"f"`
	}
	type Cfg struct {
		Inner Inner `toml:"inner"`
	}
	var cfg Cfg
	err := Unmarshal([]byte("[inner]\nf = \"x\"\n"), &cfg)
	if err == nil {
		t.Fatal("expected an error from UnmarshalText")
	}
	if !strings.Contains(err.Error(), "unmarshal text: text boom") {
		t.Errorf("err = %v, want the text error wrapped", err)
	}
	de, ok := errors.AsType[*DecodeError](err)
	if !ok {
		t.Fatalf("expected a *DecodeError, got %T: %v", err, err)
	}
	if !slices.Equal(de.Path, []string{"inner", "f"}) {
		t.Fatalf("Path = %v, want [inner f]", de.Path)
	}
}

func TestTextUnmarshalerReportsBadText(t *testing.T) {
	var cfg struct {
		IP net.IP `toml:"ip"`
	}
	err := Unmarshal([]byte(`ip = "not-an-ip"`), &cfg)
	if err == nil {
		t.Fatal("expected an error for a malformed address")
	}
	if !strings.Contains(err.Error(), "unmarshal text:") {
		t.Errorf("err = %v, want it wrapped as a text error", err)
	}
}

func TestUnmarshalDurations(t *testing.T) {
	type Cfg struct {
		FromText time.Duration `toml:"from_text"`
		FromInt  time.Duration `toml:"from_int"`
		Fraction time.Duration `toml:"fraction"`
	}
	in := "from_text = \"1h30m\"\nfrom_int = 5400000000000\nfraction = \"1.5s\"\n"
	var cfg Cfg
	if err := Unmarshal([]byte(in), &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.FromText != 90*time.Minute {
		t.Errorf("FromText = %v, want %v", cfg.FromText, 90*time.Minute)
	}
	if cfg.FromInt != 90*time.Minute {
		t.Errorf("FromInt = %v, want %v", cfg.FromInt, 90*time.Minute)
	}
	if cfg.Fraction != 1500*time.Millisecond {
		t.Errorf("Fraction = %v, want %v", cfg.Fraction, 1500*time.Millisecond)
	}
}

func TestUnmarshalDurationRejectsMalformedText(t *testing.T) {
	var cfg struct {
		D time.Duration `toml:"d"`
	}
	err := Unmarshal([]byte("d = \"90\"\n"), &cfg)
	if err == nil {
		t.Fatal("expected an error for a duration without a unit")
	}
	if !strings.Contains(err.Error(), "invalid duration") {
		t.Errorf("err = %v, want an invalid-duration message", err)
	}
}

func TestQuotedStringNeverBecomesDateTime(t *testing.T) {
	// The date-time types take a bare timestamp only, so the text path is
	// excluded for them and a quoted string stays a string.
	var stamp struct {
		S time.Time `toml:"s"`
	}
	err := Unmarshal([]byte("s = \"2026-06-26T10:00:00Z\"\n"), &stamp)
	if err == nil {
		t.Fatal("expected a quoted string to be rejected for time.Time")
	}
	if !strings.Contains(err.Error(), "cannot assign string") {
		t.Errorf("err = %v, want a cannot-assign message", err)
	}

	var day struct {
		D LocalDate `toml:"d"`
	}
	if err := Unmarshal([]byte("d = \"1979-05-27\"\n"), &day); err == nil {
		t.Fatal("expected a quoted string to be rejected for LocalDate")
	}
}

func TestDecoderMaxDepth(t *testing.T) {
	deep := func(n int) []byte {
		return []byte("v = " + strings.Repeat("[", n) + strings.Repeat("]", n) + "\n")
	}
	var cfg struct {
		V any `toml:"v"`
	}
	if err := NewDecoder().MaxDepth(4).Decode(deep(4), &cfg); err != nil {
		t.Fatalf("at the limit: %v", err)
	}
	err := NewDecoder().MaxDepth(4).Decode(deep(5), &cfg)
	if err == nil {
		t.Fatal("expected a nesting error")
	}
	if !strings.Contains(err.Error(), "limit of 4") {
		t.Errorf("err = %v, want it to name the limit", err)
	}
}

func TestDecoderMaxInputSize(t *testing.T) {
	doc := []byte("v = \"ab\"\n")
	var cfg struct {
		V string `toml:"v"`
	}
	if err := NewDecoder().MaxInputSize(len(doc)).Decode(doc, &cfg); err != nil {
		t.Fatalf("at the limit: %v", err)
	}
	err := NewDecoder().MaxInputSize(len(doc)-1).Decode(doc, &cfg)
	if err == nil {
		t.Fatal("expected a size error")
	}
	if !strings.Contains(err.Error(), "over the limit of 8") {
		t.Errorf("err = %v, want it to name the limit", err)
	}
	// Parse carries the nesting default and no size limit.
	if _, err := ParseMap(doc); err != nil {
		t.Fatalf("parse: %v", err)
	}
}

// --- OffsetDateTime --------------------------------------------------------

func TestOffsetDateTimeIsTheParsedType(t *testing.T) {
	// A document's offset date-time arrives as the wrapper, and a plain
	// time.Time destination still takes it, so a timestamp field needs no
	// change to keep working.
	in := []byte("stamp = 2026-06-26T10:00:00-07:00\n")
	want := time.Date(2026, 6, 26, 10, 0, 0, 0, time.FixedZone("", -7*3600))

	var plain struct {
		Stamp time.Time `toml:"stamp"`
	}
	if err := Unmarshal(in, &plain); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if !plain.Stamp.Equal(want) {
		t.Errorf("time.Time destination = %v, want %v", plain.Stamp, want)
	}

	var wrapped struct {
		Stamp OffsetDateTime `toml:"stamp"`
	}
	if err := Unmarshal(in, &wrapped); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if !wrapped.Stamp.Time.Equal(want) {
		t.Errorf("OffsetDateTime destination = %v, want %v", wrapped.Stamp.Time, want)
	}
	if got := wrapped.Stamp.String(); got != "2026-06-26T10:00-07:00" {
		t.Errorf("String() = %q, want 2026-06-26T10:00-07:00", got)
	}
}

func TestOffsetDateTimeFromHandBuiltTree(t *testing.T) {
	// A tree built by hand may carry a plain time.Time, which is the other
	// source of the offset kind; both date-time destinations take it.
	tree := map[string]any{"stamp": time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC)}
	want := time.Date(2026, 6, 26, 10, 0, 0, 0, time.UTC)

	var plain struct {
		Stamp time.Time `toml:"stamp"`
	}
	if err := newDecoder().decode(tree, &plain); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if !plain.Stamp.Equal(want) {
		t.Errorf("time.Time destination = %v, want %v", plain.Stamp, want)
	}

	var wrapped struct {
		Stamp OffsetDateTime `toml:"stamp"`
	}
	if err := newDecoder().decode(tree, &wrapped); err != nil {
		t.Fatalf("decode: %v", err)
	}
	if !wrapped.Stamp.Time.Equal(want) {
		t.Errorf("OffsetDateTime destination = %v, want %v", wrapped.Stamp.Time, want)
	}
}

// dateKindReceiver records the Go type UnmarshalTOML was handed.
type dateKindReceiver struct{ Kind string }

func (r *dateKindReceiver) UnmarshalTOML(data any) error {
	r.Kind = fmt.Sprintf("%T", data)
	return nil
}

func TestUnmarshalerReceivesOffsetDateTime(t *testing.T) {
	// The interface sees the wrapper, which names the date-time kind on its
	// own; the local kinds keep their own wrappers.
	var cfg struct {
		O dateKindReceiver `toml:"o"`
		L dateKindReceiver `toml:"l"`
	}
	in := []byte("o = 2026-06-26T10:00:00Z\nl = 2026-06-26T10:00:00\n")
	if err := Unmarshal(in, &cfg); err != nil {
		t.Fatalf("unmarshal: %v", err)
	}
	if cfg.O.Kind != "interpres.OffsetDateTime" {
		t.Errorf("offset kind = %q, want interpres.OffsetDateTime", cfg.O.Kind)
	}
	if cfg.L.Kind != "interpres.LocalDateTime" {
		t.Errorf("local kind = %q, want interpres.LocalDateTime", cfg.L.Kind)
	}
}

func TestDecoderUseNumber(t *testing.T) {
	data := []byte(`hex = 0x1f
sep = 1_000
signed = +1.0
exp = 1e6
posinf = inf
negzero = -0.0
plain = 42
frac = 2.5
`)
	t.Run("the tree keeps the literal", func(t *testing.T) {
		var tree map[string]any
		if err := NewDecoder().UseNumber().Decode(data, &tree); err != nil {
			t.Fatal(err)
		}
		for lit, key := range map[string]string{
			"0x1f": "hex", "1_000": "sep", "+1.0": "signed", "1e6": "exp",
			"inf": "posinf", "-0.0": "negzero", "42": "plain", "2.5": "frac",
		} {
			got, ok := tree[key].(Number)
			if !ok {
				t.Errorf("%s = %T, want Number", key, tree[key])
				continue
			}
			if string(got) != lit {
				t.Errorf("%s = %q, want %q", key, got, lit)
			}
		}
	})
	t.Run("typed fields take the evaluated value", func(t *testing.T) {
		var cfg struct {
			Hex   Number  `toml:"hex"`
			Plain int64   `toml:"plain"`
			Frac  float64 `toml:"frac"`
			Rate  time.Duration
		}
		dec := NewDecoder().UseNumber()
		if err := dec.Decode([]byte("hex = 0x1f\nplain = 42\nfrac = 2.5\nRate = 1_000\n"), &cfg); err != nil {
			t.Fatal(err)
		}
		if cfg.Hex != "0x1f" {
			t.Errorf("hex = %q, want 0x1f", cfg.Hex)
		}
		if cfg.Plain != 42 {
			t.Errorf("plain = %d, want 42", cfg.Plain)
		}
		if cfg.Frac != 2.5 {
			t.Errorf("frac = %g, want 2.5", cfg.Frac)
		}
		if cfg.Rate != 1000 {
			t.Errorf("rate = %s, want 1µs", cfg.Rate)
		}
	})
	t.Run("invalid numbers are still parse errors", func(t *testing.T) {
		for _, in := range []string{"a = 01\n", "a = 1__0\n", "a = 1x\n"} {
			var tree map[string]any
			if err := NewDecoder().UseNumber().Decode([]byte(in), &tree); err == nil {
				t.Errorf("%q decoded without an error", in)
			}
		}
	})
	t.Run("without UseNumber the tree holds the evaluated kinds", func(t *testing.T) {
		var tree map[string]any
		if err := NewDecoder().Decode([]byte("hex = 0x1f\nfrac = 2.5\n"), &tree); err != nil {
			t.Fatal(err)
		}
		if v, ok := tree["hex"].(int64); !ok || v != 31 {
			t.Errorf("hex = %#v, want int64 31", tree["hex"])
		}
		if v, ok := tree["frac"].(float64); !ok || v != 2.5 {
			t.Errorf("frac = %#v, want float64 2.5", tree["frac"])
		}
	})
}

func TestNumberMethods(t *testing.T) {
	tests := []struct {
		lit    Number
		wantI  int64
		wantF  float64
		intErr bool
	}{
		{lit: "42", wantI: 42, wantF: 42},
		{lit: "0x1f", wantI: 31, wantF: 31},
		{lit: "1_000", wantI: 1000, wantF: 1000},
		{lit: "+1.0", wantF: 1, intErr: true},
		{lit: "1e6", wantF: 1e6, intErr: true},
		{lit: "inf", wantF: math.Inf(1), intErr: true},
		{lit: "-2.5", wantF: -2.5, intErr: true},
	}
	for _, tt := range tests {
		i, err := tt.lit.Int64()
		if tt.intErr && err == nil {
			t.Errorf("%q.Int64() succeeded with %d, want an error", tt.lit, i)
		}
		if !tt.intErr {
			if err != nil {
				t.Errorf("%q.Int64() = %v", tt.lit, err)
				continue
			}
			if i != tt.wantI {
				t.Errorf("%q.Int64() = %d, want %d", tt.lit, i, tt.wantI)
			}
		}
		f, err := tt.lit.Float64()
		if err != nil {
			t.Errorf("%q.Float64() = %v", tt.lit, err)
			continue
		}
		if f != tt.wantF {
			t.Errorf("%q.Float64() = %g, want %g", tt.lit, f, tt.wantF)
		}
	}
	for _, lit := range []Number{"01", "1__0", "abc", ""} {
		if _, err := lit.Float64(); err == nil {
			t.Errorf("%q.Float64() succeeded, want an error", lit)
		}
		if _, err := lit.Int64(); err == nil {
			t.Errorf("%q.Int64() succeeded, want an error", lit)
		}
	}
}

func TestSyntaxErrorPosition(t *testing.T) {
	src := []byte("alpha = 1\nbeta x = 2\n")
	_, err := ParseMap(src)
	se, ok := errors.AsType[*SyntaxError](err)
	if !ok {
		t.Fatalf("err = %v, want a SyntaxError", err)
	}
	if se.Line != 2 {
		t.Errorf("Line = %d, want 2", se.Line)
	}
	if want := strings.Index(string(src), "x"); se.Offset != want {
		t.Errorf("Offset = %d, want %d", se.Offset, want)
	}
	if se.Column != 6 {
		t.Errorf("Column = %d, want 6", se.Column)
	}
	want := "beta x = 2\n     ^"
	if got := se.SourceLine(src); got != want {
		t.Errorf("SourceLine =\n%s\nwant:\n%s", got, want)
	}
}

func TestSyntaxErrorUTF8Offset(t *testing.T) {
	src := []byte("a = \"ok\"\nb = \"\xff\xfe\"\n")
	_, err := ParseMap(src)
	se, ok := errors.AsType[*SyntaxError](err)
	if !ok {
		t.Fatalf("err = %v, want a SyntaxError", err)
	}
	if !strings.Contains(se.Msg, "byte offset 14") {
		t.Errorf("Msg = %q, want it to name byte offset 14", se.Msg)
	}
	if se.Offset != 14 {
		t.Errorf("Offset = %d, want 14", se.Offset)
	}
	want := "b = \"\xff\xfe\"\n     ^"
	if got := se.SourceLine(src); got != want {
		t.Errorf("SourceLine =\n%q\nwant:\n%q", got, want)
	}
}

func TestSourceLineEdgePositions(t *testing.T) {
	src := []byte("a = 1\n")
	e := &SyntaxError{Line: 1, Msg: "no position"}
	if got, want := e.SourceLine(src), "a = 1\n^"; got != want {
		t.Errorf("SourceLine(zero offset) =\n%q\nwant:\n%q", got, want)
	}
	e = &SyntaxError{Line: 2, Offset: 100, Msg: "past the end"}
	if got, want := e.SourceLine(src), "\n^"; got != want {
		t.Errorf("SourceLine(offset past end) =\n%q\nwant:\n%q", got, want)
	}
}