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

package main

import (
	"bytes"
	"encoding/json"
	"errors"
	"go/parser"
	"go/token"
	"os"
	"path/filepath"
	"reflect"
	"strings"
	"testing"
	"time"

	"sourcedock.dev/petrbalvin/interpres/v2"
)

func TestRunParsesValidTOML(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := bytes.NewReader([]byte(`name = "x"
port = 8080
enabled = true
`))
	if code := Run(nil, in, &stdout, &stderr); code != 0 {
		t.Fatalf("Run returned %d, stderr = %q", code, stderr.String())
	}
	var got map[string]any
	if err := json.Unmarshal(stdout.Bytes(), &got); err != nil {
		t.Fatalf("invalid JSON output: %v\n%s", err, stdout.String())
	}
	if name := got["name"].(map[string]any); name["type"] != "string" || name["value"] != "x" {
		t.Errorf("name = %#v", got["name"])
	}
	if port := got["port"].(map[string]any); port["type"] != "integer" || port["value"] != "8080" {
		t.Errorf("port = %#v", got["port"])
	}
	if en := got["enabled"].(map[string]any); en["type"] != "bool" || en["value"] != "true" {
		t.Errorf("enabled = %#v", got["enabled"])
	}
}

func TestRunRejectsInvalidInput(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := bytes.NewReader([]byte("v = \n"))
	code := Run(nil, in, &stdout, &stderr)
	if code != 1 {
		t.Errorf("Run returned %d, want 1 (parse error); stderr = %q", code, stderr.String())
	}
	if stdout.Len() != 0 {
		t.Errorf("stdout should be empty on parse error, got %q", stdout.String())
	}
}

func TestRunReadErrorReturnsTwo(t *testing.T) {
	var stdout, stderr bytes.Buffer
	code := Run(nil, errorReader{}, &stdout, &stderr)
	if code != 2 {
		t.Errorf("Run returned %d, want 2 (read error); stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "read stdin") {
		t.Errorf("stderr = %q, want it to mention 'read stdin'", stderr.String())
	}
}

// errorReader is an io.Reader that always reports an error.
type errorReader struct{}

func (errorReader) Read(_ []byte) (int, error) { return 0, errors.New("boom") }

func TestRunEncodeErrorReturnsTwo(t *testing.T) {
	var stderr bytes.Buffer
	w := errorWriter{}
	in := bytes.NewReader([]byte(`k = "v"` + "\n"))
	code := Run(nil, in, w, &stderr)
	if code != 2 {
		t.Errorf("Run returned %d, want 2 (encode error); stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "encode") {
		t.Errorf("stderr = %q, want it to mention 'encode'", stderr.String())
	}
}

// errorWriter is an io.Writer that always reports an error.
type errorWriter struct{}

func (errorWriter) Write(_ []byte) (int, error) { return 0, errors.New("boom") }

func TestTagHandlesAllScalarTypes(t *testing.T) {
	now := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
	ldt := interpres.LocalDateTime{Time: now}
	ld := interpres.LocalDate{Time: time.Date(2026, 1, 2, 0, 0, 0, 0, time.UTC)}
	lt := interpres.LocalTime{Time: time.Date(0, 1, 1, 3, 4, 5, 0, time.UTC)}

	cases := []struct {
		name string
		in   any
		want map[string]string
	}{
		{"string", "x", map[string]string{"type": "string", "value": "x"}},
		{"bool", true, map[string]string{"type": "bool", "value": "true"}},
		{"bool-false", false, map[string]string{"type": "bool", "value": "false"}},
		{"int64", int64(42), map[string]string{"type": "integer", "value": "42"}},
		{"float", 1.5, map[string]string{"type": "float", "value": "1.5"}},
		{"time", now, map[string]string{"type": "datetime", "value": "2026-01-02T03:04:05Z"}},
		{"ldt", ldt, map[string]string{"type": "datetime-local", "value": "2026-01-02T03:04:05"}},
		{"ld", ld, map[string]string{"type": "date-local", "value": "2026-01-02"}},
		{"lt", lt, map[string]string{"type": "time-local", "value": "03:04:05"}},
	}
	for _, c := range cases {
		got, err := tag(c.in)
		if err != nil {
			t.Errorf("%s: tag returned error %v", c.name, err)
			continue
		}
		m, ok := got.(map[string]string)
		if !ok {
			t.Errorf("%s: tag returned %T, want map[string]string", c.name, got)
			continue
		}
		if m["type"] != c.want["type"] || m["value"] != c.want["value"] {
			t.Errorf("%s: tag = %#v, want %#v", c.name, m, c.want)
		}
	}
}

func TestTagRejectsUnsupportedType(t *testing.T) {
	// Channels are not produced by the parser; tag must reject them explicitly.
	var ch chan int
	got, err := tag(ch)
	if err == nil {
		t.Fatalf("expected error for chan int, got value %#v", got)
	}
	if !strings.Contains(err.Error(), "unsupported") {
		t.Errorf("err = %v, want substring 'unsupported'", err)
	}
	if got != nil {
		t.Errorf("got = %#v, want nil", got)
	}

	// The same applies when an unsupported type is nested inside a table.
	got, err = tag(map[string]any{"x": ch})
	if err == nil {
		t.Fatalf("expected error for nested chan int, got %#v", got)
	}
}

// Exercise the table, array-of-tables, and array shapes so all of tag's
// switch arms are visited.
func TestTagHandlesContainers(t *testing.T) {
	tbl := map[string]any{
		"name": "x",
		"items": []any{
			int64(1), int64(2),
		},
	}
	got, err := tag(tbl)
	if err != nil {
		t.Fatalf("tag(tbl) returned error: %v", err)
	}
	m, ok := got.(map[string]any)
	if !ok {
		t.Fatalf("tag returned %T, want map", got)
	}
	name, ok := m["name"].(map[string]string)
	if !ok || name["value"] != "x" {
		t.Errorf("name = %#v", m["name"])
	}
	items, ok := m["items"].([]any)
	if !ok {
		t.Fatalf("items = %T, want []any", m["items"])
	}
	if len(items) != 2 {
		t.Fatalf("len(items) = %d, want 2", len(items))
	}
	for _, raw := range items {
		if _, ok := raw.(map[string]string); !ok {
			t.Errorf("item = %T, want map[string]string", raw)
		}
	}

	// Direct tests of the array branches.
	if got, err := tag([]any{int64(1)}); err != nil {
		t.Errorf("tag([]any) returned error: %v", err)
	} else if len(got.([]any)) != 1 {
		t.Errorf("[]any tag = %#v", got)
	}
	if got, err := tag([]map[string]any{{"k": "v"}}); err != nil {
		t.Errorf("tag([]map) returned error: %v", err)
	} else if len(got.([]any)) != 1 {
		t.Errorf("[]map[string]any tag = %#v", got)
	}
}

func TestFormatFloatAllBranches(t *testing.T) {
	cases := map[float64]string{
		1.5:     "1.5",
		0:       "0",
		1e10:    "1e+10",
		-2.5e-3: "-0.0025",
	}
	for in, want := range cases {
		if got := formatFloat(in); got != want {
			t.Errorf("formatFloat(%v) = %q, want %q", in, got, want)
		}
	}
}

func TestTaggedHelper(t *testing.T) {
	got := tagged("string", "x")
	if got["type"] != "string" || got["value"] != "x" {
		t.Errorf("tagged = %#v", got)
	}
}

func TestValidateStdinAcceptsValidDocument(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := bytes.NewReader([]byte("title = \"ok\"\n"))
	if code := Run([]string{"--validate"}, in, &stdout, &stderr); code != 0 {
		t.Fatalf("Run returned %d, stderr = %q", code, stderr.String())
	}
	if stdout.Len() != 0 || stderr.Len() != 0 {
		t.Fatalf("validate should be quiet on success, stdout %q stderr %q", stdout.String(), stderr.String())
	}
}

func TestValidateStdinRejectsInvalidDocument(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := bytes.NewReader([]byte("title = \"unterminated\n"))
	if code := Run([]string{"--validate"}, in, &stdout, &stderr); code != 1 {
		t.Fatalf("Run returned %d, want 1; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "<stdin>") || !strings.Contains(stderr.String(), "line 1") {
		t.Fatalf("stderr = %q, want the name and the line", stderr.String())
	}
	if stdout.Len() != 0 {
		t.Fatalf("stdout should stay empty, got %q", stdout.String())
	}
}

func TestValidateFiles(t *testing.T) {
	dir := t.TempDir()
	good := dir + "/good.toml"
	bad := dir + "/bad.toml"
	if err := os.WriteFile(good, []byte("a = 1\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(bad, []byte("a =\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	if code := Run([]string{"--validate", good}, nil, &stdout, &stderr); code != 0 {
		t.Fatalf("one valid file: Run returned %d, stderr = %q", code, stderr.String())
	}
	if code := Run([]string{"--validate", good, bad}, nil, &stdout, &stderr); code != 1 {
		t.Fatalf("valid plus invalid: Run returned %d, want 1; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), bad) || !strings.Contains(stderr.String(), "line 1") {
		t.Fatalf("stderr = %q, want the file name and the line", stderr.String())
	}
}

func TestValidateMissingFileReturnsTwo(t *testing.T) {
	var stdout, stderr bytes.Buffer
	if code := Run([]string{"--validate", "no-such-file.toml"}, nil, &stdout, &stderr); code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
}

func TestAdapterModeRejectsPositionalArgument(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := bytes.NewReader([]byte("a = 1\n"))
	if code := Run([]string{"file.toml"}, in, &stdout, &stderr); code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "--validate") {
		t.Fatalf("stderr = %q, want it to point at --validate", stderr.String())
	}
}

func TestUnknownFlagReturnsTwo(t *testing.T) {
	var stdout, stderr bytes.Buffer
	if code := Run([]string{"--nope"}, nil, &stdout, &stderr); code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
}

// --- encoder mode ----------------------------------------------------------

func TestRunEncoderScalars(t *testing.T) {
	in := `{
    "s":   {"type": "string", "value": "quote \" and backslash \\"},
    "nl":  {"type": "string", "value": "line1\nline2"},
    "i":   {"type": "integer", "value": "-9223372036854775808"},
    "g":   {"type": "float", "value": "1.5"},
    "f":   {"type": "float", "value": "inf"},
    "b":   {"type": "bool", "value": "false"},
    "dt":  {"type": "datetime", "value": "1979-05-27T07:32:00-07:00"},
    "ldt": {"type": "datetime-local", "value": "1979-05-27T07:32:00"},
    "ld":  {"type": "date-local", "value": "1979-05-27"},
    "lt":  {"type": "time-local", "value": "07:32:00.999"}
}
`
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--encode"}, strings.NewReader(in), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, stderr = %q", code, stderr.String())
	}
	want := "b = false\n" +
		"dt = 1979-05-27T07:32-07:00\n" +
		"f = inf\n" +
		"g = 1.5\n" +
		"i = -9223372036854775808\n" +
		"ld = 1979-05-27\n" +
		"ldt = 1979-05-27T07:32\n" +
		"lt = 07:32:00.999\n" +
		"nl = \"line1\\nline2\"\n" +
		"s = \"quote \\\" and backslash \\\\\"\n"
	if stdout.String() != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", stdout.String(), want)
	}
}

func TestRunEncoderNested(t *testing.T) {
	in := `{
    "tbl": {"x": {"type": "bool", "value": "true"},
            "sub": {"y": {"type": "integer", "value": "1"}}},
    "items": [{"n": {"type": "string", "value": "a"}},
              {"n": {"type": "string", "value": "b"}}],
    "list": [{"type": "integer", "value": "1"}, {"type": "string", "value": "two"}],
    "emptyTbl": {},
    "emptyArr": []
}
`
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--encode"}, strings.NewReader(in), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, stderr = %q", code, stderr.String())
	}
	want := "emptyArr = []\n" +
		"list = [1, \"two\"]\n" +
		"\n[emptyTbl]\n" +
		"\n[tbl]\nx = true\n" +
		"\n[tbl.sub]\ny = 1\n" +
		"\n[[items]]\nn = \"a\"\n" +
		"\n[[items]]\nn = \"b\"\n"
	if stdout.String() != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", stdout.String(), want)
	}
}

func TestRunEncoderFloatTagDecides(t *testing.T) {
	// A float with no fraction is described by a bare integer literal, so the
	// tag decides the type; the output must stay a float.
	var stdout, stderr bytes.Buffer
	in := `{"whole": {"type": "float", "value": "1"}, "exp": {"type": "float", "value": "5e+22"}}`
	code := Run([]string{"--encode"}, strings.NewReader(in), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, stderr = %q", code, stderr.String())
	}
	if want := "exp = 5e+22\nwhole = 1.0\n"; stdout.String() != want {
		t.Errorf("output mismatch:\ngot:  %q\nwant: %q", stdout.String(), want)
	}
}

func TestRunEncoderRejectsBadInput(t *testing.T) {
	cases := []struct {
		name string
		in   string
		want string
	}{
		{"not-json", "not json", "decode JSON"},
		{"top-level-array", `[{"type": "integer", "value": "1"}]`, "must be a JSON object"},
		{"untagged-scalar", `{"x": 1}`, "unsupported JSON value"},
		{"literal-mismatch", `{"x": {"type": "integer", "value": "1.5"}}`, "parsed as float64"},
		{"offset-for-local", `{"x": {"type": "datetime-local", "value": "1979-05-27T07:32:00Z"}}`, "parsed as interpres.OffsetDateTime"},
		{"bad-literal", `{"x": {"type": "date-local", "value": "nope"}}`, "date-local"},
		{"smuggled-statement", `{"x": {"type": "integer", "value": "1\nx = 2"}}`, "not a single bare value"},
	}
	for _, c := range cases {
		var stdout, stderr bytes.Buffer
		code := Run([]string{"--encode"}, strings.NewReader(c.in), &stdout, &stderr)
		if code != 2 {
			t.Errorf("%s: Run returned %d, want 2; stderr = %q", c.name, code, stderr.String())
			continue
		}
		if !strings.Contains(stderr.String(), c.want) {
			t.Errorf("%s: stderr = %q, want it to mention %q", c.name, stderr.String(), c.want)
		}
		if stdout.Len() != 0 {
			t.Errorf("%s: stdout should be empty, got %q", c.name, stdout.String())
		}
	}
}

func TestRunEncoderFlagConflicts(t *testing.T) {
	var stdout, stderr bytes.Buffer
	if code := Run([]string{"--encode", "--validate"}, strings.NewReader(""), &stdout, &stderr); code != 2 {
		t.Errorf("Run returned %d, want 2 for the two modes together", code)
	}
	if !strings.Contains(stderr.String(), "cannot be combined") {
		t.Errorf("stderr = %q, want it to explain the conflict", stderr.String())
	}

	stdout.Reset()
	stderr.Reset()
	if code := Run([]string{"--encode", "file.json"}, strings.NewReader(""), &stdout, &stderr); code != 2 {
		t.Errorf("Run returned %d, want 2 for an argument", code)
	}
}

func TestEncodeAfterDecodeRoundTrip(t *testing.T) {
	doc := `title = "x"
flt = 1.5
whole = 7.0
big = 9223372036854775807
when = 1979-05-27T07:32:00-07:00
day = 1979-05-27
clock = 07:32:00.999
list = [1, "two"]
multi = "a\nb"

[tbl]
x = true

[[items]]
n = "a"
`
	var tagged, stderr bytes.Buffer
	if code := Run(nil, strings.NewReader(doc), &tagged, &stderr); code != 0 {
		t.Fatalf("decode returned %d, stderr = %q", code, stderr.String())
	}
	var out bytes.Buffer
	if code := Run([]string{"--encode"}, bytes.NewReader(tagged.Bytes()), &out, &stderr); code != 0 {
		t.Fatalf("encode returned %d, stderr = %q", code, stderr.String())
	}
	want, err := interpres.ParseMap([]byte(doc))
	if err != nil {
		t.Fatalf("parse of the original: %v", err)
	}
	got, err := interpres.ParseMap(out.Bytes())
	if err != nil {
		t.Fatalf("parse of the encoder output (%q): %v", out.String(), err)
	}
	if !reflect.DeepEqual(want, got) {
		t.Errorf("round trip changed the document:\noriginal: %#v\nencoded:  %#v\noutput: %q", want, got, out.String())
	}
}

func TestRunVersion(t *testing.T) {
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--version"}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	if !strings.HasPrefix(out, "interpres-decode ") {
		t.Errorf("output = %q, want the version prefix", out)
	}
}

func TestRunPlainJSON(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := strings.NewReader("host = \"db\"\nwhen = 1979-05-27T07:32:00-07:00\nitems = [1, 2]\n")
	code := Run([]string{"--json"}, in, &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	if !strings.Contains(out, "\"host\": \"db\"") {
		t.Errorf("output = %q, want plain JSON keys", out)
	}
	if strings.Contains(out, "\"type\"") {
		t.Errorf("output = %q, want no tags", out)
	}
	if !strings.Contains(out, "\n  \"") {
		t.Errorf("output = %q, want indentation", out)
	}
}

func TestValidateDirectorySummary(t *testing.T) {
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "good.toml"), []byte("a = 1\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(dir, "bad.toml"), []byte("a =\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	sub := filepath.Join(dir, "nested")
	if err := os.Mkdir(sub, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(sub, "deep.toml"), []byte("b = true\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	// A second invalid document, so the summary's invalid count is
	// exercised beyond the single failure the boolean tracked.
	if err := os.WriteFile(filepath.Join(sub, "worse.toml"), []byte("c =\n"), 0o644); err != nil {
		t.Fatal(err)
	}

	var stdout, stderr bytes.Buffer
	code := Run([]string{"--validate", dir}, strings.NewReader(""), &stdout, &stderr)
	if code != 1 {
		t.Fatalf("Run returned %d, want 1 for a directory with invalid files", code)
	}
	if !strings.Contains(stderr.String(), "checked 4 documents, 2 invalid") {
		t.Errorf("stderr = %q, want the summary", stderr.String())
	}
}

func TestInferStruct(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := strings.NewReader("host = \"db\"\nport = 5432\ntags = [\"a\"]\n\n[server]\nname = \"edge\"\n\n[[items]]\nn = 1\n")
	code := Run([]string{"--struct"}, in, &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{
		"type inferred struct {",
		"Host string `toml:\"host\"`",
		"Port int64 `toml:\"port\"`",
		"Tags []string `toml:\"tags\"`",
		"Server struct {",
		"Items []struct {",
	} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestRunSchemaTemplate(t *testing.T) {
	src := filepath.Join(t.TempDir(), "config.go")
	body := `package cfg

type Server struct {
	Host string ` + "`toml:\"host,comment=The host to dial,default=example.org\"`" + `
	Port int    ` + "`toml:\"port,default=8080\"`" + `
}

type Config struct {
	Name string  ` + "`toml:\"name\"`" + `
	Rate float64 ` + "`toml:\"rate,default=0.5\"`" + `
	On   bool    ` + "`toml:\"on\"`" + `
	Started time.Time ` + "`toml:\"started\"`" + `
	Server Server ` + "`toml:\"server,comment=The server section\"`" + `
	Items  []Item ` + "`toml:\"items\"`" + `
}

type Item struct {
	N int ` + "`toml:\"n\"`" + `
}
`
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Config", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{
		"# The server section",
		"[server]",
		"# The host to dial",
		"host = \"example.org\"",
		"port = 8080",
		"rate = 0.5",
		"on = false",
		"started = 1979-05-27T00:00:00Z",
		"[[items]]",
		"n = 0",
	} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestRunPlainJSONShapes(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := strings.NewReader("when = 1979-05-27T07:32:00-07:00\nd = 1979-05-27\nt = 07:32:00\nwall = 1979-05-27T07:32:00\n" +
		"items = [1, \"two\"]\n\n[[tables]]\nx = true\n")
	code := Run([]string{"--json"}, in, &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{
		"\"when\": \"1979-05-27T07:32-07:00\"",
		"\"d\": \"1979-05-27\"",
		"\"t\": \"07:32\"",
		"\"wall\": \"1979-05-27T07:32\"",
		"\"items\": [",
		"\"x\": true",
	} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestInferStructScalarShapes(t *testing.T) {
	var stdout, stderr bytes.Buffer
	in := strings.NewReader("f = 1.5\nb = true\nd = 1979-05-27\nldt = 1979-05-27T07:32:00\nlt = 07:32:00\nnums = [1, 2, 3]\nmixed = [1, \"a\"]\nempty = []\n")
	code := Run([]string{"--struct"}, in, &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{
		"F float64",
		"B bool",
		"D interpres.LocalDate",
		"Ldt interpres.LocalDateTime",
		"Lt interpres.LocalTime",
		"Nums []int64",
		"Mixed []any",
		"Empty []any",
	} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestRunHelpPrintsLongFlags(t *testing.T) {
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--help"}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, flag := range []string{"--encode", "--help", "--json", "--schema", "--struct", "--validate", "--version"} {
		if !strings.Contains(out, flag) {
			t.Errorf("usage output missing %q:\n%s", flag, out)
		}
	}
	// Every flag line of the list names its flag in the two-dash long form
	// only, so no line opens with a single dash.
	for line := range strings.SplitSeq(strings.TrimRight(out, "\n"), "\n") {
		if after, ok := strings.CutPrefix(line, "  -"); ok && !strings.HasPrefix(after, "-") {
			t.Errorf("usage line %q lists a flag with one dash", line)
		}
	}
}

func TestGoFieldName(t *testing.T) {
	cases := []struct{ key, want string }{
		{"host", "Host"},
		{"ab", "Ab"},
		{"http-host", "HttpHost"},
		{"3d", "Field3d"},
		{"", "Field"},
	}
	for _, c := range cases {
		if got := goFieldName(c.key, map[string]bool{}); got != c.want {
			t.Errorf("goFieldName(%q) = %q, want %q", c.key, got, c.want)
		}
	}
}

func TestGoFieldNameCollision(t *testing.T) {
	// Two keys that clean to the same name must not collide; the counter
	// keeps the fields apart and both stay exported.
	invented := map[string]bool{}
	cases := []struct{ key, want string }{
		{"a-b", "AB"},
		{"a b", "AB2"},
		{"a_b", "AB22"},
	}
	for _, c := range cases {
		if got := goFieldName(c.key, invented); got != c.want {
			t.Errorf("goFieldName(%q) = %q, want %q", c.key, got, c.want)
		}
	}
}

func TestInferStructDigitLeadingKey(t *testing.T) {
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--struct"}, strings.NewReader("3d = true\n"), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stdout.String(), "Field3d bool") {
		t.Errorf("output missing the exported Field3d field:\n%s", stdout.String())
	}
}

func TestInferStructBacktickKey(t *testing.T) {
	// A backtick in the key would end a raw string literal early, so the
	// tag has to be rendered as an interpreted literal instead.
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--struct"}, strings.NewReader("\"a`b\" = 1\n"), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	if !strings.Contains(out, "AB int64 \"toml:\\\"a`b\\\"\"") {
		t.Errorf("output missing the quoted tag:\n%s", out)
	}
	// The printed definition has to compile; parsing it as Go is the
	// syntax half of that proof.
	if _, err := parser.ParseFile(token.NewFileSet(), "inferred.go", "package p\n\n"+out, 0); err != nil {
		t.Errorf("the printed definition does not parse: %v\n%s", err, out)
	}
}

func TestInferStructMergesArrayElements(t *testing.T) {
	// The second element carries a key the first lacks, so the slice type
	// has to be inferred from both.
	var stdout, stderr bytes.Buffer
	in := strings.NewReader("[[items]]\nn = 1\n\n[[items]]\nextra = \"late\"\n")
	code := Run([]string{"--struct"}, in, &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{
		"Items []struct {",
		"N int64 `toml:\"n\"`",
		"Extra string `toml:\"extra\"`",
	} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestInferStructMixedArrayStaysValueArray(t *testing.T) {
	// One table element does not make the array an array of tables; a
	// struct slice would not decode the scalar element.
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--struct"}, strings.NewReader("arr = [1, {x = 1}]\n"), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	if !strings.Contains(out, "Arr []any") {
		t.Errorf("output = %q, want a value array typed []any", out)
	}
	if strings.Contains(out, "[]struct") {
		t.Errorf("output = %q, a mixed array must not become a struct slice", out)
	}
}

func TestRunStructParseError(t *testing.T) {
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--struct"}, strings.NewReader("a =\n"), &stdout, &stderr)
	if code != 1 {
		t.Fatalf("Run returned %d, want 1 (parse error); stderr = %q", code, stderr.String())
	}
	if stdout.Len() != 0 {
		t.Errorf("stdout should be empty on parse error, got %q", stdout.String())
	}
	if !strings.Contains(stderr.String(), "line 1") {
		t.Errorf("stderr = %q, want the library's line number", stderr.String())
	}
}

func TestRunStructWriteFailure(t *testing.T) {
	var stderr bytes.Buffer
	code := Run([]string{"--struct"}, strings.NewReader("a = 1\n"), errorWriter{}, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2 (write error); stderr = %q", code, stderr.String())
	}
}

func TestRunSchemaNeedsTypeAndExactlyOneFile(t *testing.T) {
	for _, args := range [][]string{{"--schema", "Config"}, {"--schema", "Config", "a.go", "b.go"}} {
		var stdout, stderr bytes.Buffer
		code := Run(args, strings.NewReader(""), &stdout, &stderr)
		if code != 2 {
			t.Errorf("Run(%v) returned %d, want 2", args, code)
		}
		if !strings.Contains(stderr.String(), "--schema") {
			t.Errorf("Run(%v) stderr = %q, want it to name --schema", args, stderr.String())
		}
	}
}

func TestRunSchemaUnparsableSource(t *testing.T) {
	src := filepath.Join(t.TempDir(), "broken.go")
	if err := os.WriteFile(src, []byte("this is not Go\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Config", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "broken.go") {
		t.Errorf("stderr = %q, want it to name the source file", stderr.String())
	}
}

func TestRunSchemaUnknownType(t *testing.T) {
	src := filepath.Join(t.TempDir(), "config.go")
	body := "package cfg\n\ntype Config struct {\n\tA int `toml:\"a\"`\n}\n"
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Missing", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), `no struct type "Missing"`) {
		t.Errorf("stderr = %q, want it to name the missing type", stderr.String())
	}
}

func TestRunSchemaRecursiveType(t *testing.T) {
	// A self-referential struct has no finite template; the generator has
	// to name the recursion instead of exhausting the stack.
	src := filepath.Join(t.TempDir(), "node.go")
	body := "package cfg\n\ntype Node struct {\n\tNext *Node `toml:\"next\"`\n}\n"
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Node", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2; stderr = %q", code, stderr.String())
	}
	for _, want := range []string{"recursive", "Node"} {
		if !strings.Contains(stderr.String(), want) {
			t.Errorf("stderr = %q, want it to mention %q", stderr.String(), want)
		}
	}
}

func TestRunSchemaMultiNameField(t *testing.T) {
	// A field list may name several fields of one type; each name is one
	// TOML key.
	src := filepath.Join(t.TempDir(), "range.go")
	if err := os.WriteFile(src, []byte("package cfg\n\ntype Range struct {\n\tMin, Max int\n}\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Range", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	for _, want := range []string{"min = 0", "max = 0"} {
		if !strings.Contains(out, want) {
			t.Errorf("output missing %q:\n%s", want, out)
		}
	}
}

func TestRunSchemaEmbeddedStructs(t *testing.T) {
	// The library inlines only untagged embedded structs; a tagged one
	// keeps its own section.
	src := filepath.Join(t.TempDir(), "embed.go")
	body := `package cfg

type Inner struct {
	X int ` + "`toml:\"x\"`" + `
}

type Tagged struct {
	Inner ` + "`toml:\"inner\"`" + `
	Y int  ` + "`toml:\"y\"`" + `
}

type Flat struct {
	Inner
	Z int ` + "`toml:\"z\"`" + `
}
`
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}

	var stdout, stderr bytes.Buffer
	code := Run([]string{"--schema", "Tagged", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Tagged: Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out := stdout.String()
	if !strings.Contains(out, "y = 0") || !strings.Contains(out, "[inner]") {
		t.Errorf("Tagged output = %q, want a y scalar and an [inner] section", out)
	}

	stdout.Reset()
	stderr.Reset()
	code = Run([]string{"--schema", "Flat", src}, strings.NewReader(""), &stdout, &stderr)
	if code != 0 {
		t.Fatalf("Flat: Run returned %d, want 0; stderr = %q", code, stderr.String())
	}
	out = stdout.String()
	if !strings.Contains(out, "x = 0") || !strings.Contains(out, "z = 0") {
		t.Errorf("Flat output = %q, want x and z flattened as scalars", out)
	}
	if strings.Contains(out, "[inner]") {
		t.Errorf("Flat output = %q, an untagged embedded struct must not become a section", out)
	}
}

func TestRunVersionWriteFailure(t *testing.T) {
	var stderr bytes.Buffer
	code := Run([]string{"--version"}, strings.NewReader(""), errorWriter{}, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2 (write error); stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "write stdout") {
		t.Errorf("stderr = %q, want it to mention the failed write", stderr.String())
	}
}

func TestRunSchemaWriteFailure(t *testing.T) {
	src := filepath.Join(t.TempDir(), "config.go")
	body := "package cfg\n\ntype Config struct {\n\tA int `toml:\"a\"`\n}\n"
	if err := os.WriteFile(src, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	var stderr bytes.Buffer
	code := Run([]string{"--schema", "Config", src}, strings.NewReader(""), errorWriter{}, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2 (write error); stderr = %q", code, stderr.String())
	}
}

func TestRunEncodeWriteFailure(t *testing.T) {
	var stderr bytes.Buffer
	in := `{"a": {"type": "integer", "value": "1"}}`
	code := Run([]string{"--encode"}, strings.NewReader(in), errorWriter{}, &stderr)
	if code != 2 {
		t.Fatalf("Run returned %d, want 2 (write error); stderr = %q", code, stderr.String())
	}
	if !strings.Contains(stderr.String(), "write stdout") {
		t.Errorf("stderr = %q, want it to mention the failed write", stderr.String())
	}
}

func TestRunEmptyInput(t *testing.T) {
	t.Run("default", func(t *testing.T) {
		var stdout, stderr bytes.Buffer
		code := Run(nil, strings.NewReader(""), &stdout, &stderr)
		if code != 0 {
			t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
		}
		if strings.TrimSpace(stdout.String()) != "{}" {
			t.Errorf("stdout = %q, want an empty table", stdout.String())
		}
	})
	t.Run("encode", func(t *testing.T) {
		var stdout, stderr bytes.Buffer
		code := Run([]string{"--encode"}, strings.NewReader(""), &stdout, &stderr)
		if code != 2 {
			t.Fatalf("Run returned %d, want 2, empty input is not JSON", code)
		}
	})
	t.Run("struct", func(t *testing.T) {
		var stdout, stderr bytes.Buffer
		code := Run([]string{"--struct"}, strings.NewReader(""), &stdout, &stderr)
		if code != 0 {
			t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
		}
		if !strings.Contains(stdout.String(), "type inferred struct {\n}") {
			t.Errorf("stdout = %q, want an empty struct", stdout.String())
		}
	})
	t.Run("validate", func(t *testing.T) {
		var stdout, stderr bytes.Buffer
		code := Run([]string{"--validate"}, strings.NewReader(""), &stdout, &stderr)
		if code != 0 {
			t.Fatalf("Run returned %d, want 0; stderr = %q", code, stderr.String())
		}
		if stdout.Len() != 0 || stderr.Len() != 0 {
			t.Errorf("validate should be quiet, stdout %q stderr %q", stdout.String(), stderr.String())
		}
	})
}

func TestRunJSONFlagConflicts(t *testing.T) {
	for _, args := range [][]string{
		{"--encode", "--json"},
		{"--struct", "--json"},
		{"--validate", "--json"},
		{"--json", "--schema", "Config", "config.go"},
	} {
		var stdout, stderr bytes.Buffer
		code := Run(args, strings.NewReader(""), &stdout, &stderr)
		if code != 2 {
			t.Errorf("Run(%v) returned %d, want 2", args, code)
		}
		if !strings.Contains(stderr.String(), "--json") {
			t.Errorf("Run(%v) stderr = %q, want it to explain the --json conflict", args, stderr.String())
		}
	}
}