package unstable

import (
	"errors"
	"fmt"
	"strconv"
	"strings"
	"testing"

	"github.com/pelletier/go-toml/v2/internal/assert"
)

func TestParser_AST_Numbers(t *testing.T) {
	examples := []struct {
		desc  string
		input string
		kind  Kind
		err   bool
	}{
		{
			desc:  "integer just digits",
			input: `1234`,
			kind:  Integer,
		},
		{
			desc:  "integer zero",
			input: `0`,
			kind:  Integer,
		},
		{
			desc:  "integer sign",
			input: `+99`,
			kind:  Integer,
		},
		{
			desc:  "integer hex uppercase",
			input: `0xDEADBEEF`,
			kind:  Integer,
		},
		{
			desc:  "integer hex lowercase",
			input: `0xdead_beef`,
			kind:  Integer,
		},
		{
			desc:  "integer octal",
			input: `0o01234567`,
			kind:  Integer,
		},
		{
			desc:  "integer binary",
			input: `0b11010110`,
			kind:  Integer,
		},
		{
			desc:  "float zero",
			input: `0.0`,
			kind:  Float,
		},
		{
			desc:  "float positive zero",
			input: `+0.0`,
			kind:  Float,
		},
		{
			desc:  "float negative zero",
			input: `-0.0`,
			kind:  Float,
		},
		{
			desc:  "float pi",
			input: `3.1415`,
			kind:  Float,
		},
		{
			desc:  "float negative",
			input: `-0.01`,
			kind:  Float,
		},
		{
			desc:  "float signed exponent",
			input: `5e+22`,
			kind:  Float,
		},
		{
			desc:  "float exponent lowercase",
			input: `1e06`,
			kind:  Float,
		},
		{
			desc:  "float exponent uppercase",
			input: `-2E-2`,
			kind:  Float,
		},
		{
			desc:  "float fractional with exponent",
			input: `6.626e-34`,
			kind:  Float,
		},
		{
			desc:  "float underscores",
			input: `224_617.445_991_228`,
			kind:  Float,
		},
		{
			desc:  "inf",
			input: `inf`,
			kind:  Float,
		},
		{
			desc:  "inf negative",
			input: `-inf`,
			kind:  Float,
		},
		{
			desc:  "inf positive",
			input: `+inf`,
			kind:  Float,
		},
		{
			desc:  "nan",
			input: `nan`,
			kind:  Float,
		},
		{
			desc:  "nan negative",
			input: `-nan`,
			kind:  Float,
		},
		{
			desc:  "nan positive",
			input: `+nan`,
			kind:  Float,
		},
	}

	for _, e := range examples {
		e := e
		t.Run(e.desc, func(t *testing.T) {
			p := Parser{}
			p.Reset([]byte(`A = ` + e.input))
			p.NextExpression()
			err := p.Error()
			if e.err {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)

				expected := astNode{
					Kind: KeyValue,
					Children: []astNode{
						{Kind: e.kind, Data: []byte(e.input)},
						{Kind: Key, Data: []byte(`A`)},
					},
				}
				compareNode(t, expected, p.Expression())
			}
		})
	}
}

type (
	astNode struct {
		Kind     Kind
		Data     []byte
		Children []astNode
	}
)

func compareNode(t *testing.T, e astNode, n *Node) {
	t.Helper()
	assert.Equal(t, e.Kind, n.Kind)
	assert.Equal(t, e.Data, n.Data)

	compareIterator(t, e.Children, n.Children())
}

func compareIterator(t *testing.T, expected []astNode, actual Iterator) {
	t.Helper()
	idx := 0

	for actual.Next() {
		n := actual.Node()

		if idx >= len(expected) {
			t.Fatal("extra child in actual tree")
		}
		e := expected[idx]

		compareNode(t, e, n)

		idx++
	}

	if idx < len(expected) {
		t.Fatal("missing children in actual", "idx =", idx, "expected =", len(expected))
	}
}

//nolint:funlen
func TestParser_AST(t *testing.T) {
	examples := []struct {
		desc  string
		input string
		ast   astNode
		err   bool
	}{
		{
			desc:  "simple string assignment",
			input: `A = "hello"`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: String,
						Data: []byte(`hello`),
					},
					{
						Kind: Key,
						Data: []byte(`A`),
					},
				},
			},
		},
		{
			desc:  "simple bool assignment",
			input: `A = true`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: Bool,
						Data: []byte(`true`),
					},
					{
						Kind: Key,
						Data: []byte(`A`),
					},
				},
			},
		},
		{
			desc:  "array of strings",
			input: `A = ["hello", ["world", "again"]]`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: Array,
						Children: []astNode{
							{
								Kind: String,
								Data: []byte(`hello`),
							},
							{
								Kind: Array,
								Children: []astNode{
									{
										Kind: String,
										Data: []byte(`world`),
									},
									{
										Kind: String,
										Data: []byte(`again`),
									},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`A`),
					},
				},
			},
		},
		{
			desc:  "array of arrays of strings",
			input: `A = ["hello", "world"]`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: Array,
						Children: []astNode{
							{
								Kind: String,
								Data: []byte(`hello`),
							},
							{
								Kind: String,
								Data: []byte(`world`),
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`A`),
					},
				},
			},
		},
		{
			desc:  "inline table",
			input: `name = { first = "Tom", last = "Preston-Werner" }`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Preston-Werner`)},
									{Kind: Key, Data: []byte(`last`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "multiline inline table",
			input: "name = {\n  first = \"Tom\",\n  last = \"Preston-Werner\"\n}",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Preston-Werner`)},
									{Kind: Key, Data: []byte(`last`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table with trailing comma",
			input: `name = { first = "Tom", last = "Preston-Werner", }`,
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Preston-Werner`)},
									{Kind: Key, Data: []byte(`last`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "empty inline table with newline",
			input: "name = {\n}",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind:     InlineTable,
						Children: nil,
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table with leading comma",
			input: "name = { first = \"Tom\"\n, last = \"Werner\" }",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Werner`)},
									{Kind: Key, Data: []byte(`last`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table with leading trailing comma",
			input: "name = { first = \"Tom\"\n, }",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table comma at start is error",
			input: "name = { , first = \"Tom\" }",
			err:   true,
		},
		{
			desc:  "inline table double comma across newline is error",
			input: "name = { first = \"Tom\",\n, last = \"Werner\" }",
			err:   true,
		},
	}

	for _, e := range examples {
		e := e
		t.Run(e.desc, func(t *testing.T) {
			p := Parser{}
			p.Reset([]byte(e.input))
			p.NextExpression()
			err := p.Error()
			if e.err {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)
				compareNode(t, e.ast, p.Expression())
			}
		})
	}
}

//nolint:funlen
func TestParser_AST_InlineTablesWithComments(t *testing.T) {
	examples := []struct {
		desc  string
		input string
		ast   astNode
		err   bool
	}{
		{
			desc:  "inline table with comment before first key-value",
			input: "name = { # comment\n first = \"Tom\" }",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: Comment,
								Data: []byte(`# comment`),
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table with comment after comma",
			input: "name = { first = \"Tom\", # comment\n last = \"Werner\" }",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: Comment,
								Data: []byte(`# comment`),
							},
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Werner`)},
									{Kind: Key, Data: []byte(`last`)},
								},
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "inline table with comment after key-value",
			input: "name = { first = \"Tom\" # comment\n }",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: InlineTable,
						Children: []astNode{
							{
								Kind: KeyValue,
								Children: []astNode{
									{Kind: String, Data: []byte(`Tom`)},
									{Kind: Key, Data: []byte(`first`)},
								},
							},
							{
								Kind: Comment,
								Data: []byte(`# comment`),
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`name`),
					},
				},
			},
		},
		{
			desc:  "array with comment after value",
			input: "a = [ 1 # comment\n ]",
			ast: astNode{
				Kind: KeyValue,
				Children: []astNode{
					{
						Kind: Array,
						Children: []astNode{
							{
								Kind: Integer,
								Data: []byte(`1`),
							},
							{
								Kind: Comment,
								Data: []byte(`# comment`),
							},
						},
					},
					{
						Kind: Key,
						Data: []byte(`a`),
					},
				},
			},
		},
		{
			desc:  "inline table with invalid comment before first key-value",
			input: "name = { # comment\r first = \"Tom\" }",
			err:   true,
		},
		{
			desc:  "inline table with invalid comment after comma",
			input: "name = { first = \"Tom\", # comment\r last = \"Werner\" }",
			err:   true,
		},
		{
			desc:  "inline table with invalid comment after key-value",
			input: "name = { first = \"Tom\" # comment\r }",
			err:   true,
		},
	}

	for _, e := range examples {
		e := e
		t.Run(e.desc, func(t *testing.T) {
			p := Parser{KeepComments: true}
			p.Reset([]byte(e.input))
			p.NextExpression()
			err := p.Error()
			if e.err {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)
				compareNode(t, e.ast, p.Expression())
			}
		})
	}
}

func BenchmarkParseBasicStringWithUnicode(b *testing.B) {
	p := &Parser{}
	b.Run("4", func(b *testing.B) {
		input := []byte(`"\u1234\u5678\u9ABC\u1234\u5678\u9ABC"`)
		b.ReportAllocs()
		b.SetBytes(int64(len(input)))

		for i := 0; i < b.N; i++ {
			_, _, _, _ = p.parseBasicString(input)
		}
	})
	b.Run("8", func(b *testing.B) {
		input := []byte(`"\u12345678\u9ABCDEF0\u12345678\u9ABCDEF0"`)
		b.ReportAllocs()
		b.SetBytes(int64(len(input)))

		for i := 0; i < b.N; i++ {
			_, _, _, _ = p.parseBasicString(input)
		}
	})
}

func BenchmarkParseBasicStringsEasy(b *testing.B) {
	p := &Parser{}

	for _, size := range []int{1, 4, 8, 16, 21} {
		b.Run(strconv.Itoa(size), func(b *testing.B) {
			input := []byte(`"` + strings.Repeat("A", size) + `"`)

			b.ReportAllocs()
			b.SetBytes(int64(len(input)))

			for i := 0; i < b.N; i++ {
				_, _, _, _ = p.parseBasicString(input)
			}
		})
	}
}

func TestParser_AST_DateTimes(t *testing.T) {
	examples := []struct {
		desc  string
		input string
		kind  Kind
		err   bool
	}{
		{
			desc:  "offset-date-time with delim 'T' and UTC offset",
			input: `2021-07-21T12:08:05Z`,
			kind:  DateTime,
		},
		{
			desc:  "offset-date-time with space delim and +8hours offset",
			input: `2021-07-21 12:08:05+08:00`,
			kind:  DateTime,
		},
		{
			desc:  "local-date-time with nano second",
			input: `2021-07-21T12:08:05.666666666`,
			kind:  LocalDateTime,
		},
		{
			desc:  "local-date-time",
			input: `2021-07-21T12:08:05`,
			kind:  LocalDateTime,
		},
		{
			desc:  "local-date",
			input: `2021-07-21`,
			kind:  LocalDate,
		},
	}

	for _, e := range examples {
		e := e
		t.Run(e.desc, func(t *testing.T) {
			p := Parser{}
			p.Reset([]byte(`A = ` + e.input))
			p.NextExpression()
			err := p.Error()
			if e.err {
				assert.Error(t, err)
			} else {
				assert.NoError(t, err)

				expected := astNode{
					Kind: KeyValue,
					Children: []astNode{
						{Kind: e.kind, Data: []byte(e.input)},
						{Kind: Key, Data: []byte(`A`)},
					},
				}
				compareNode(t, expected, p.Expression())
			}
		})
	}
}

// This example demonstrates how to parse a TOML document and preserving
// comments.  Comments are stored in the AST as Comment nodes. This example
// displays the structure of the full AST generated by the parser using the
// following structure:
//
//  1. Each root-level expression is separated by three dashes.
//  2. Bytes associated to a node are displayed in square brackets.
//  3. Siblings have the same indentation.
//  4. Children of a node are indented one level.
func ExampleParser_comments() {
	doc := `# Top of the document comment.
# Optional, any amount of lines.

# Above table.
[table] # Next to table.
# Above simple value.
key = "value" # Next to simple value.
# Below simple value.

# Some comment alone.

# Multiple comments, on multiple lines.

# Above inline table.
name = { first = "Tom", last = "Preston-Werner" } # Next to inline table.
# Below inline table.

# Above array.
array = [ 1, 2, 3 ] # Next to one-line array.
# Below array.

# Above multi-line array.
key5 = [ # Next to start of inline array.
  # Second line before array content.
  1, # Next to first element.
  # After first element.
  # Before second element.
  2,
  3, # Next to last element
  # After last element.
] # Next to end of array.
# Below multi-line array.

# Before array table.
[[products]] # Next to array table.
# After array table.
`

	var printGeneric func(*Parser, int, *Node)
	printGeneric = func(p *Parser, indent int, e *Node) {
		if e == nil {
			return
		}
		s := p.Shape(e.Raw)
		x := fmt.Sprintf("%d:%d->%d:%d (%d->%d)", s.Start.Line, s.Start.Column, s.End.Line, s.End.Column, s.Start.Offset, s.End.Offset)
		fmt.Printf("%-25s | %s%s [%s]\n", x, strings.Repeat("  ", indent), e.Kind, e.Data)
		printGeneric(p, indent+1, e.Child())
		printGeneric(p, indent, e.Next())
	}

	printTree := func(p *Parser) {
		for p.NextExpression() {
			e := p.Expression()
			fmt.Println("---")
			printGeneric(p, 0, e)
		}
		if err := p.Error(); err != nil {
			panic(err)
		}
	}

	p := &Parser{
		KeepComments: true,
	}
	p.Reset([]byte(doc))
	printTree(p)

	// Output:
	// ---
	// 1:1->1:31 (0->30)         | Comment [# Top of the document comment.]
	// ---
	// 2:1->2:33 (31->63)        | Comment [# Optional, any amount of lines.]
	// ---
	// 4:1->4:15 (65->79)        | Comment [# Above table.]
	// ---
	// 1:1->1:1 (0->0)           | Table []
	// 5:2->5:7 (81->86)         |   Key [table]
	// 5:9->5:25 (88->104)       | Comment [# Next to table.]
	// ---
	// 6:1->6:22 (105->126)      | Comment [# Above simple value.]
	// ---
	// 7:1->7:14 (127->140)      | KeyValue []
	// 7:7->7:14 (133->140)      |   String [value]
	// 7:1->7:4 (127->130)       |   Key [key]
	// 7:15->7:38 (141->164)     | Comment [# Next to simple value.]
	// ---
	// 8:1->8:22 (165->186)      | Comment [# Below simple value.]
	// ---
	// 10:1->10:22 (188->209)    | Comment [# Some comment alone.]
	// ---
	// 12:1->12:40 (211->250)    | Comment [# Multiple comments, on multiple lines.]
	// ---
	// 14:1->14:22 (252->273)    | Comment [# Above inline table.]
	// ---
	// 15:1->15:50 (274->323)    | KeyValue []
	// 15:8->15:9 (281->282)     |   InlineTable []
	// 15:10->15:23 (283->296)   |     KeyValue []
	// 15:18->15:23 (291->296)   |       String [Tom]
	// 15:10->15:15 (283->288)   |       Key [first]
	// 15:25->15:48 (298->321)   |     KeyValue []
	// 15:32->15:48 (305->321)   |       String [Preston-Werner]
	// 15:25->15:29 (298->302)   |       Key [last]
	// 15:1->15:5 (274->278)     |   Key [name]
	// 15:51->15:74 (324->347)   | Comment [# Next to inline table.]
	// ---
	// 16:1->16:22 (348->369)    | Comment [# Below inline table.]
	// ---
	// 18:1->18:15 (371->385)    | Comment [# Above array.]
	// ---
	// 19:1->19:20 (386->405)    | KeyValue []
	// 1:1->1:1 (0->0)           |   Array []
	// 19:11->19:12 (396->397)   |     Integer [1]
	// 19:14->19:15 (399->400)   |     Integer [2]
	// 19:17->19:18 (402->403)   |     Integer [3]
	// 19:1->19:6 (386->391)     |   Key [array]
	// 19:21->19:46 (406->431)   | Comment [# Next to one-line array.]
	// ---
	// 20:1->20:15 (432->446)    | Comment [# Below array.]
	// ---
	// 22:1->22:26 (448->473)    | Comment [# Above multi-line array.]
	// ---
	// 23:1->31:2 (474->694)     | KeyValue []
	// 1:1->1:1 (0->0)           |   Array []
	// 23:10->23:42 (483->515)   |     Comment [# Next to start of inline array.]
	// 24:3->24:38 (518->553)    |       Comment [# Second line before array content.]
	// 25:3->25:4 (556->557)     |     Integer [1]
	// 25:6->25:30 (559->583)    |     Comment [# Next to first element.]
	// 26:3->26:25 (586->608)    |       Comment [# After first element.]
	// 27:3->27:27 (611->635)    |       Comment [# Before second element.]
	// 28:3->28:4 (638->639)     |     Integer [2]
	// 29:3->29:4 (643->644)     |     Integer [3]
	// 29:6->29:28 (646->668)    |     Comment [# Next to last element]
	// 30:3->30:24 (671->692)    |       Comment [# After last element.]
	// 23:1->23:5 (474->478)     |   Key [key5]
	// 31:3->31:26 (695->718)    | Comment [# Next to end of array.]
	// ---
	// 32:1->32:26 (719->744)    | Comment [# Below multi-line array.]
	// ---
	// 34:1->34:22 (746->767)    | Comment [# Before array table.]
	// ---
	// 1:1->1:1 (0->0)           | ArrayTable []
	// 35:3->35:11 (770->778)    |   Key [products]
	// 35:14->35:36 (781->803)   | Comment [# Next to array table.]
	// ---
	// 36:1->36:21 (804->824)    | Comment [# After array table.]
}

func TestIterator_IsLast(t *testing.T) {
	// Test IsLast on an iterator with multiple elements using public Parser API
	doc := `array = [1, 2, 3]`
	p := Parser{}
	p.Reset([]byte(doc))
	p.NextExpression()

	e := p.Expression()
	arr := e.Value() // The array node

	it := arr.Children()
	count := 0
	lastCount := 0
	for it.Next() {
		count++
		if it.IsLast() {
			lastCount++
		}
	}

	assert.Equal(t, 3, count)
	assert.Equal(t, 1, lastCount)
}

func TestNodeChaining(t *testing.T) {
	// Test that sibling nodes are correctly chained via Next()
	// This exercises the internal PushAndChain functionality through public APIs
	doc := `a.b.c = 1`
	p := Parser{}
	p.Reset([]byte(doc))
	p.NextExpression()

	e := p.Expression()
	// KeyValue has children: value, then key parts (a, b, c)
	keyIt := e.Key()

	// Collect all key parts by following the iterator
	var keys []string
	for keyIt.Next() {
		keys = append(keys, string(keyIt.Node().Data))
	}

	assert.Equal(t, []string{"a", "b", "c"}, keys)
}

func TestMultipleExpressions(t *testing.T) {
	// Test parsing multiple top-level expressions
	// This exercises root iteration through public APIs
	doc := `
key1 = "value1"
key2 = "value2"
key3 = "value3"
`
	p := Parser{}
	p.Reset([]byte(doc))

	var keys []string
	for p.NextExpression() {
		e := p.Expression()
		keyIt := e.Key()
		keyIt.Next()
		keys = append(keys, string(keyIt.Node().Data))
	}

	assert.NoError(t, p.Error())
	assert.Equal(t, []string{"key1", "key2", "key3"}, keys)
}

func ExampleParser() {
	doc := `
	hello = "world"
	value = 42
	`
	p := Parser{}
	p.Reset([]byte(doc))
	for p.NextExpression() {
		e := p.Expression()
		fmt.Printf("Expression: %s\n", e.Kind)
		value := e.Value()
		it := e.Key()
		k := it.Node() // shortcut: we know there is no dotted key in the example
		fmt.Printf("%s -> (%s) %s\n", k.Data, value.Kind, value.Data)
	}

	// Output:
	// Expression: KeyValue
	// hello -> (String) world
	// Expression: KeyValue
	// value -> (Integer) 42
}

func TestParserErrorPosition(t *testing.T) {
	examples := []struct {
		name           string
		input          string
		expectedOffset int
		expectedLine   int
		expectedColumn int
	}{
		{
			name:           "comment then invalid key start",
			input:          "# comment\n= \"value\"",
			expectedOffset: 10,
			expectedLine:   2,
			expectedColumn: 1,
		},
		{
			name:           "no comment invalid key start",
			input:          "= \"value\"",
			expectedOffset: 0,
			expectedLine:   1,
			expectedColumn: 1,
		},
		{
			name:           "multiple comments then error",
			input:          "# c1\n# c2\n= \"val\"",
			expectedOffset: 10,
			expectedLine:   3,
			expectedColumn: 1,
		},
		{
			name:           "valid line then invalid key start",
			input:          "a = 1\n= \"val\"",
			expectedOffset: 6,
			expectedLine:   2,
			expectedColumn: 1,
		},
		{
			name:           "blank lines then error",
			input:          "\n\n= \"val\"",
			expectedOffset: 2,
			expectedLine:   3,
			expectedColumn: 1,
		},
		{
			name:           "expected newline but got invalid char",
			input:          "a = 1 b = 2",
			expectedOffset: 6,
			expectedLine:   1,
			expectedColumn: 7,
		},
	}

	for _, e := range examples {
		t.Run(e.name, func(t *testing.T) {
			p := Parser{}
			p.Reset([]byte(e.input))
			for p.NextExpression() {
			}
			err := p.Error()
			if err == nil {
				t.Fatal("expected an error")
			}

			var perr *ParserError
			if !errors.As(err, &perr) {
				t.Fatalf("expected *ParserError, got %T", err)
			}

			r := p.Range(perr.Highlight)
			shape := p.Shape(r)

			if int(r.Offset) != e.expectedOffset {
				t.Errorf("offset: got %d, want %d", r.Offset, e.expectedOffset)
			}
			if shape.Start.Line != e.expectedLine {
				t.Errorf("line: got %d, want %d", shape.Start.Line, e.expectedLine)
			}
			if shape.Start.Column != e.expectedColumn {
				t.Errorf("column: got %d, want %d", shape.Start.Column, e.expectedColumn)
			}
		})
	}
}

func TestParserErrorError(t *testing.T) {
	err := &ParserError{Message: "boom"}
	assert.Equal(t, "boom", err.Error())
}

func TestParserRangeNotSubslicePanics(t *testing.T) {
	p := &Parser{}
	p.Reset([]byte("a = 1"))
	// A slice with a capacity larger than the document cannot be one of its
	// subslices.
	other := make([]byte, 2, 64)
	assert.Panics(t, func() {
		_ = p.Range(other)
	})
}

func TestParserExpressionEmpty(t *testing.T) {
	p := &Parser{}
	p.Reset([]byte(""))
	assert.True(t, p.Expression() == nil)
}

func parseAll(doc string) error {
	p := &Parser{}
	p.Reset([]byte(doc))
	for p.NextExpression() {
	}
	return p.Error()
}

func TestParserScanErrors(t *testing.T) {
	invalid := []string{
		"a = [1\rx]",
		"# comment\rx",
		"# comment\x00",
		"a = '''\rx'''",
		"a = \"aaaaaaaaaaaaaaaaaaaaaaaa",
		"a = \"\\u0041\nx\"",
		"a = \"\\u0041\xffx\"",
		`a = """x""""""`,
		"a = \"\"\"\\\rx\"\"\"",
		"a = \"\"\"x\rz\"\"\"",
		"a = \"\"\"\xffx\"\"\"",
		"a = '\xc3\x28'",
		"a = '\xe0\x80\x80'",
		"a = '\xed\xa0\x80'",
		"a = '\xe1\x80\x28'",
		"a = '\xf0\x80\x80\x80'",
		"a = '\xf4\x90\x80\x80'",
		"a = '\xf1\x28\x80\x80'",
		"a = '\xf0\x9f'",
		"a = '\xc3'",
		"a = '\xfe'",
	}
	for _, doc := range invalid {
		t.Run(fmt.Sprintf("%q", doc), func(t *testing.T) {
			assert.Error(t, parseAll(doc))
		})
	}

	valid := []string{
		"a = \"\\e\"",   // TOML v1.1.0 escape (U+001B)
		"a = \"\\x1b\"", // TOML v1.1.0 hex escape
		"a = \"\"\"a\r\nb\"\"\"",
		"a = \"\"\"\\\n  \r\n  x\"\"\"",
		"a = '\xc3\xa9'",
		"a = '\xe2\x82\xac'",
		"a = '\xe0\xa4\x84'",
		"a = '\xed\x9f\xbf'",
		"a = '\xf0\x90\x80\x80'",
		"a = '\xf4\x8f\xbf\xbf'",
		"a = '\xf1\x80\x80\x80'",
		"# comment ends in unicode \xc3\xa9",
	}
	for _, doc := range valid {
		t.Run(fmt.Sprintf("%q", doc), func(t *testing.T) {
			assert.NoError(t, parseAll(doc))
		})
	}
}

func TestParserNextExpressionAfterError(t *testing.T) {
	p := &Parser{}
	p.Reset([]byte("a = \"\n\"\nb = 1"))
	for p.NextExpression() {
	}
	assert.Error(t, p.Error())
	assert.False(t, p.NextExpression())
}

func TestParserScanEdgeCases(t *testing.T) {
	invalid := []string{
		"a = {,}",
		"a = \"\"\"\\t a\rb\"\"\"",
		"a = \"\"\"\\t \xffx\"\"\"",
		"a = \"\"\"\\t x\"\"\"\"\"\"",
		"a = \"\"\"\\\n\r x\"\"\"",
		"a = '\xe1\x28\x80'",
	}
	for _, doc := range invalid {
		t.Run(fmt.Sprintf("%q", doc), func(t *testing.T) {
			assert.Error(t, parseAll(doc))
		})
	}

	valid := []string{
		"a = [1,\r\n2]",
		"# comment\r\nb = 1",
		"# comment\twith tab",
		"a = '''x\r\ny'''",
		"a = \"\\u0041\tb\"",
		"a = \"\"\"\\t a\r\nb\"\"\"",
		"a = \"\"\"\\t x\"\"\"\"",
		"a = \"\"\"\\t x\"\"\"\"\"",
	}
	for _, doc := range valid {
		t.Run(fmt.Sprintf("%q", doc), func(t *testing.T) {
			assert.NoError(t, parseAll(doc))
		})
	}
}

func TestUnquotedStringValueRequiresQuotes(t *testing.T) {
	p := Parser{}
	p.Reset([]byte(`timeout = 20s`))
	for p.NextExpression() {
	}

	err := p.Error()
	if err == nil {
		t.Fatal("expected parse error")
	}

	var perr *ParserError
	if !errors.As(err, &perr) {
		t.Fatalf("expected *ParserError, got %T", err)
	}

	if perr.Message != "strings must be quoted" {
		t.Fatalf("expected %q, got %q", "strings must be quoted", perr.Message)
	}
}