package parser_test

import (
	"fmt"
	"io"
	"reflect"
	"strconv"
	"strings"
	"testing"

	. "github.com/d5/tengo/v2/parser"
	"github.com/d5/tengo/v2/require"
	"github.com/d5/tengo/v2/token"
)

func TestParserError(t *testing.T) {
	err := &Error{Pos: SourceFilePos{
		Offset: 10, Line: 1, Column: 10,
	}, Msg: "test"}
	require.Equal(t, "Parse Error: test\n\tat 1:10", err.Error())
}

func TestParserErrorList(t *testing.T) {
	var list ErrorList
	list.Add(SourceFilePos{Offset: 20, Line: 2, Column: 10}, "error 2")
	list.Add(SourceFilePos{Offset: 30, Line: 3, Column: 10}, "error 3")
	list.Add(SourceFilePos{Offset: 10, Line: 1, Column: 10}, "error 1")
	list.Sort()
	require.Equal(t, "Parse Error: error 1\n\tat 1:10 (and 2 more errors)",
		list.Error())
}

func TestParseArray(t *testing.T) {
	expectParse(t, "[1, 2, 3]", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				arrayLit(p(1, 1), p(1, 9),
					intLit(1, p(1, 2)),
					intLit(2, p(1, 5)),
					intLit(3, p(1, 8)))))
	})

	expectParse(t, `
[
	1,
	2,
	3
]`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				arrayLit(p(2, 1), p(6, 1),
					intLit(1, p(3, 2)),
					intLit(2, p(4, 2)),
					intLit(3, p(5, 2)))))
	})
	expectParse(t, `
[
	1,
	2,
	3

]`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				arrayLit(p(2, 1), p(7, 1),
					intLit(1, p(3, 2)),
					intLit(2, p(4, 2)),
					intLit(3, p(5, 2)))))
	})

	expectParse(t, `[1, "foo", 12.34]`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				arrayLit(p(1, 1), p(1, 17),
					intLit(1, p(1, 2)),
					stringLit("foo", p(1, 5)),
					floatLit(12.34, p(1, 12)))))
	})

	expectParse(t, "a = [1, 2, 3]", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(arrayLit(p(1, 5), p(1, 13),
					intLit(1, p(1, 6)),
					intLit(2, p(1, 9)),
					intLit(3, p(1, 12)))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a = [1 + 2, b * 4, [4, c]]", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(arrayLit(p(1, 5), p(1, 26),
					binaryExpr(
						intLit(1, p(1, 6)),
						intLit(2, p(1, 10)),
						token.Add,
						p(1, 8)),
					binaryExpr(
						ident("b", p(1, 13)),
						intLit(4, p(1, 17)),
						token.Mul,
						p(1, 15)),
					arrayLit(p(1, 20), p(1, 25),
						intLit(4, p(1, 21)),
						ident("c", p(1, 24))))),
				token.Assign,
				p(1, 3)))
	})

	expectParseError(t, `[1, 2, 3,]`)
	expectParseError(t, `
[
	1,
	2,
	3,
]`)
	expectParseError(t, `
[
	1,
	2,
	3,

]`)
	expectParseError(t, `[1, 2, 3, ,]`)
}

func TestParseAssignment(t *testing.T) {
	expectParse(t, "a = 5", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(intLit(5, p(1, 5))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a := 5", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(intLit(5, p(1, 6))),
				token.Define,
				p(1, 3)))
	})

	expectParse(t, "a, b = 5, 10", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1)),
					ident("b", p(1, 4))),
				exprs(
					intLit(5, p(1, 8)),
					intLit(10, p(1, 11))),
				token.Assign,
				p(1, 6)))
	})

	expectParse(t, "a, b := 5, 10", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1)),
					ident("b", p(1, 4))),
				exprs(
					intLit(5, p(1, 9)),
					intLit(10, p(1, 12))),
				token.Define,
				p(1, 6)))
	})

	expectParse(t, "a, b = a + 2, b - 8", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1)),
					ident("b", p(1, 4))),
				exprs(
					binaryExpr(
						ident("a", p(1, 8)),
						intLit(2, p(1, 12)),
						token.Add,
						p(1, 10)),
					binaryExpr(
						ident("b", p(1, 15)),
						intLit(8, p(1, 19)),
						token.Sub,
						p(1, 17))),
				token.Assign,
				p(1, 6)))
	})

	expectParse(t, "a = [1, 2, 3]", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(arrayLit(p(1, 5), p(1, 13),
					intLit(1, p(1, 6)),
					intLit(2, p(1, 9)),
					intLit(3, p(1, 12)))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a = [1 + 2, b * 4, [4, c]]", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(arrayLit(p(1, 5), p(1, 26),
					binaryExpr(
						intLit(1, p(1, 6)),
						intLit(2, p(1, 10)),
						token.Add,
						p(1, 8)),
					binaryExpr(
						ident("b", p(1, 13)),
						intLit(4, p(1, 17)),
						token.Mul,
						p(1, 15)),
					arrayLit(p(1, 20), p(1, 25),
						intLit(4, p(1, 21)),
						ident("c", p(1, 24))))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a += 5", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(intLit(5, p(1, 6))),
				token.AddAssign,
				p(1, 3)))
	})

	expectParse(t, "a *= 5 + 10", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(
					binaryExpr(
						intLit(5, p(1, 6)),
						intLit(10, p(1, 10)),
						token.Add,
						p(1, 8))),
				token.MulAssign,
				p(1, 3)))
	})
}

func TestParseBoolean(t *testing.T) {
	expectParse(t, "true", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				boolLit(true, p(1, 1))))
	})

	expectParse(t, "false", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				boolLit(false, p(1, 1))))
	})

	expectParse(t, "true != false", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					boolLit(true, p(1, 1)),
					boolLit(false, p(1, 9)),
					token.NotEqual,
					p(1, 6))))
	})

	expectParse(t, "!false", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				unaryExpr(
					boolLit(false, p(1, 2)),
					token.Not,
					p(1, 1))))
	})
}

func TestParseCall(t *testing.T) {
	expectParse(t, "add(1, 2, 3)", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					ident("add", p(1, 1)),
					p(1, 4), p(1, 12), NoPos,
					intLit(1, p(1, 5)),
					intLit(2, p(1, 8)),
					intLit(3, p(1, 11)))))
	})

	expectParse(t, "add(1, 2, v...)", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					ident("add", p(1, 1)),
					p(1, 4), p(1, 15), p(1, 12),
					intLit(1, p(1, 5)),
					intLit(2, p(1, 8)),
					ident("v", p(1, 11)))))
	})

	expectParse(t, "a = add(1, 2, 3)", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1))),
				exprs(
					callExpr(
						ident("add", p(1, 5)),
						p(1, 8), p(1, 16), NoPos,
						intLit(1, p(1, 9)),
						intLit(2, p(1, 12)),
						intLit(3, p(1, 15)))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a, b = add(1, 2, 3)", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1)),
					ident("b", p(1, 4))),
				exprs(
					callExpr(
						ident("add", p(1, 8)),
						p(1, 11), p(1, 19), NoPos,
						intLit(1, p(1, 12)),
						intLit(2, p(1, 15)),
						intLit(3, p(1, 18)))),
				token.Assign,
				p(1, 6)))
	})

	expectParse(t, "add(a + 1, 2 * 1, (b + c))", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					ident("add", p(1, 1)),
					p(1, 4), p(1, 26), NoPos,
					binaryExpr(
						ident("a", p(1, 5)),
						intLit(1, p(1, 9)),
						token.Add,
						p(1, 7)),
					binaryExpr(
						intLit(2, p(1, 12)),
						intLit(1, p(1, 16)),
						token.Mul,
						p(1, 14)),
					parenExpr(
						binaryExpr(
							ident("b", p(1, 20)),
							ident("c", p(1, 24)),
							token.Add,
							p(1, 22)),
						p(1, 19), p(1, 25)))))
	})

	expectParseString(t, "a + add(b * c) + d", "((a + add((b * c))) + d)")
	expectParseString(t, "add(a, b, 1, 2 * 3, 4 + 5, add(6, 7 * 8))",
		"add(a, b, 1, (2 * 3), (4 + 5), add(6, (7 * 8)))")
	expectParseString(t, "f1(a) + f2(b) * f3(c)", "(f1(a) + (f2(b) * f3(c)))")
	expectParseString(t, "(f1(a) + f2(b)) * f3(c)",
		"(((f1(a) + f2(b))) * f3(c))")

	expectParse(t, "func(a, b) { a + b }(1, 2)", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					funcLit(
						funcType(
							identList(
								p(1, 5), p(1, 10),
								false,
								ident("a", p(1, 6)),
								ident("b", p(1, 9))),
							p(1, 1)),
						blockStmt(
							p(1, 12), p(1, 20),
							exprStmt(
								binaryExpr(
									ident("a", p(1, 14)),
									ident("b", p(1, 18)),
									token.Add,
									p(1, 16))))),
					p(1, 21), p(1, 26), NoPos,
					intLit(1, p(1, 22)),
					intLit(2, p(1, 25)))))
	})

	expectParse(t, `a.b()`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					selectorExpr(
						ident("a", p(1, 1)),
						stringLit("b", p(1, 3))),
					p(1, 4), p(1, 5), NoPos)))
	})

	expectParse(t, `a.b.c()`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					selectorExpr(
						selectorExpr(
							ident("a", p(1, 1)),
							stringLit("b", p(1, 3))),
						stringLit("c", p(1, 5))),
					p(1, 6), p(1, 7), NoPos)))
	})

	expectParse(t, `a["b"].c()`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					selectorExpr(
						indexExpr(
							ident("a", p(1, 1)),
							stringLit("b", p(1, 3)),
							p(1, 2), p(1, 6)),
						stringLit("c", p(1, 8))),
					p(1, 9), p(1, 10), NoPos)))
	})

	expectParseError(t, `add(...a, 1)`)
	expectParseError(t, `add(a..., 1)`)
	expectParseError(t, `add(a..., b...)`)
	expectParseError(t, `add(1, a..., b...)`)
	expectParseError(t, `add(...)`)
	expectParseError(t, `add(1, ...)`)
	expectParseError(t, `add(1, ..., )`)
	expectParseError(t, `add(...a)`)
}

func TestParseChar(t *testing.T) {
	expectParse(t, `'A'`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				charLit('A', 1)))
	})
	expectParse(t, `'九'`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				charLit('九', 1)))
	})

	expectParseError(t, `''`)
	expectParseError(t, `'AB'`)
	expectParseError(t, `'A九'`)
}

func TestParseCondExpr(t *testing.T) {
	expectParse(t, "a ? b : c", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				condExpr(
					ident("a", p(1, 1)),
					ident("b", p(1, 5)),
					ident("c", p(1, 9)),
					p(1, 3),
					p(1, 7))))
	})
	expectParse(t, `a ?
b :
c`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				condExpr(
					ident("a", p(1, 1)),
					ident("b", p(1, 5)),
					ident("c", p(1, 9)),
					p(1, 3),
					p(1, 7))))
	})

	expectParseString(t, `a ? b : c`, "(a ? b : c)")
	expectParseString(t, `a + b ? c - d : e * f`,
		"((a + b) ? (c - d) : (e * f))")
	expectParseString(t, `a == b ? c + (d / e) : f ? g : h + i`,
		"((a == b) ? (c + ((d / e))) : (f ? g : (h + i)))")
	expectParseString(t, `(a + b) ? (c - d) : (e * f)`,
		"(((a + b)) ? ((c - d)) : ((e * f)))")
	expectParseString(t, `a + (b ? c : d) - e`, "((a + ((b ? c : d))) - e)")
	expectParseString(t, `a ? b ? c : d : e`, "(a ? (b ? c : d) : e)")
	expectParseString(t, `a := b ? c : d`, "a := (b ? c : d)")
	expectParseString(t, `x := a ? b ? c : d : e`,
		"x := (a ? (b ? c : d) : e)")

	// ? : should be at the end of each line if it's multi-line
	expectParseError(t, `a
? b
: c`)
	expectParseError(t, `a ? (b : e)`)
	expectParseError(t, `(a ? b) : e`)
}

func TestParseError(t *testing.T) {
	expectParse(t, `error(1234)`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				errorExpr(p(1, 1), intLit(1234, p(1, 7)), p(1, 6), p(1, 11))))
	})

	expectParse(t, `err1 := error("some error")`, func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("err1", p(1, 1))),
				exprs(errorExpr(p(1, 9),
					stringLit("some error", p(1, 15)), p(1, 14), p(1, 27))),
				token.Define, p(1, 6)))
	})

	expectParse(t, `return error("some error")`, func(p pfn) []Stmt {
		return stmts(
			returnStmt(p(1, 1),
				errorExpr(p(1, 8),
					stringLit("some error", p(1, 14)), p(1, 13), p(1, 26))))
	})

	expectParse(t, `return error("some" + "error")`, func(p pfn) []Stmt {
		return stmts(
			returnStmt(p(1, 1),
				errorExpr(p(1, 8),
					binaryExpr(
						stringLit("some", p(1, 14)),
						stringLit("error", p(1, 23)),
						token.Add, p(1, 21)),
					p(1, 13), p(1, 30))))
	})

	expectParseError(t, `error()`) // must have a value
}

func TestParseForIn(t *testing.T) {
	expectParse(t, "for x in y {}", func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("_", p(1, 5)),
				ident("x", p(1, 5)),
				ident("y", p(1, 10)),
				blockStmt(p(1, 12), p(1, 13)),
				p(1, 1)))
	})

	expectParse(t, "for _ in y {}", func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("_", p(1, 5)),
				ident("_", p(1, 5)),
				ident("y", p(1, 10)),
				blockStmt(p(1, 12), p(1, 13)),
				p(1, 1)))
	})

	expectParse(t, "for x in [1, 2, 3] {}", func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("_", p(1, 5)),
				ident("x", p(1, 5)),
				arrayLit(
					p(1, 10), p(1, 18),
					intLit(1, p(1, 11)),
					intLit(2, p(1, 14)),
					intLit(3, p(1, 17))),
				blockStmt(p(1, 20), p(1, 21)),
				p(1, 1)))
	})

	expectParse(t, "for x, y in z {}", func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("x", p(1, 5)),
				ident("y", p(1, 8)),
				ident("z", p(1, 13)),
				blockStmt(p(1, 15), p(1, 16)),
				p(1, 1)))
	})

	expectParse(t, "for x, y in {k1: 1, k2: 2} {}", func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("x", p(1, 5)),
				ident("y", p(1, 8)),
				mapLit(
					p(1, 13), p(1, 26),
					mapElementLit(
						"k1", p(1, 14), p(1, 16), intLit(1, p(1, 18))),
					mapElementLit(
						"k2", p(1, 21), p(1, 23), intLit(2, p(1, 25)))),
				blockStmt(p(1, 28), p(1, 29)),
				p(1, 1)))
	})
}

func TestParseFor(t *testing.T) {
	expectParse(t, "for {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(nil, nil, nil, blockStmt(p(1, 5), p(1, 6)), p(1, 1)))
	})

	expectParse(t, "for a == 5 {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				nil,
				binaryExpr(
					ident("a", p(1, 5)),
					intLit(5, p(1, 10)),
					token.Equal,
					p(1, 7)),
				nil,
				blockStmt(p(1, 12), p(1, 13)),
				p(1, 1)))
	})

	expectParse(t, "for a := 0; a == 5;  {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				assignStmt(
					exprs(ident("a", p(1, 5))),
					exprs(intLit(0, p(1, 10))),
					token.Define, p(1, 7)),
				binaryExpr(
					ident("a", p(1, 13)),
					intLit(5, p(1, 18)),
					token.Equal,
					p(1, 15)),
				nil,
				blockStmt(p(1, 22), p(1, 23)),
				p(1, 1)))
	})

	expectParse(t, "for a := 0; a < 5; a++ {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				assignStmt(
					exprs(ident("a", p(1, 5))),
					exprs(intLit(0, p(1, 10))),
					token.Define, p(1, 7)),
				binaryExpr(
					ident("a", p(1, 13)),
					intLit(5, p(1, 17)),
					token.Less,
					p(1, 15)),
				incDecStmt(
					ident("a", p(1, 20)),
					token.Inc, p(1, 21)),
				blockStmt(p(1, 24), p(1, 25)),
				p(1, 1)))
	})

	expectParse(t, "for ; a < 5; a++ {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				nil,
				binaryExpr(
					ident("a", p(1, 7)),
					intLit(5, p(1, 11)),
					token.Less,
					p(1, 9)),
				incDecStmt(
					ident("a", p(1, 14)),
					token.Inc, p(1, 15)),
				blockStmt(p(1, 18), p(1, 19)),
				p(1, 1)))
	})

	expectParse(t, "for a := 0; ; a++ {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				assignStmt(
					exprs(ident("a", p(1, 5))),
					exprs(intLit(0, p(1, 10))),
					token.Define, p(1, 7)),
				nil,
				incDecStmt(
					ident("a", p(1, 15)),
					token.Inc, p(1, 16)),
				blockStmt(p(1, 19), p(1, 20)),
				p(1, 1)))
	})

	expectParse(t, "for a == 5 && b != 4 {}", func(p pfn) []Stmt {
		return stmts(
			forStmt(
				nil,
				binaryExpr(
					binaryExpr(
						ident("a", p(1, 5)),
						intLit(5, p(1, 10)),
						token.Equal,
						p(1, 7)),
					binaryExpr(
						ident("b", p(1, 15)),
						intLit(4, p(1, 20)),
						token.NotEqual,
						p(1, 17)),
					token.LAnd,
					p(1, 12)),
				nil,
				blockStmt(p(1, 22), p(1, 23)),
				p(1, 1)))
	})
}

func TestParseFunction(t *testing.T) {
	expectParse(t, "a = func(b, c, d) { return d }", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1))),
				exprs(
					funcLit(
						funcType(
							identList(p(1, 9), p(1, 17), false,
								ident("b", p(1, 10)),
								ident("c", p(1, 13)),
								ident("d", p(1, 16))),
							p(1, 5)),
						blockStmt(p(1, 19), p(1, 30),
							returnStmt(p(1, 21), ident("d", p(1, 28)))))),
				token.Assign,
				p(1, 3)))
	})
}

func TestParseVariadicFunction(t *testing.T) {
	expectParse(t, "a = func(...args) { return args }", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1))),
				exprs(
					funcLit(
						funcType(
							identList(
								p(1, 9), p(1, 17),
								true,
								ident("args", p(1, 13)),
							), p(1, 5)),
						blockStmt(p(1, 19), p(1, 33),
							returnStmt(p(1, 21),
								ident("args", p(1, 28)),
							),
						),
					),
				),
				token.Assign,
				p(1, 3)))
	})
}

func TestParseVariadicFunctionWithArgs(t *testing.T) {
	expectParse(t, "a = func(x, y, ...z) { return z }", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					ident("a", p(1, 1))),
				exprs(
					funcLit(
						funcType(
							identList(
								p(1, 9), p(1, 20),
								true,
								ident("x", p(1, 10)),
								ident("y", p(1, 13)),
								ident("z", p(1, 19)),
							), p(1, 5)),
						blockStmt(p(1, 22), p(1, 33),
							returnStmt(p(1, 24),
								ident("z", p(1, 31)),
							),
						),
					),
				),
				token.Assign,
				p(1, 3)))
	})

	expectParseError(t, "a = func(x, y, ...z, invalid) { return z }")
	expectParseError(t, "a = func(...args, invalid) { return args }")
}

func TestParseIf(t *testing.T) {
	expectParse(t, "if a == 5 {}", func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				nil,
				binaryExpr(
					ident("a", p(1, 4)),
					intLit(5, p(1, 9)),
					token.Equal,
					p(1, 6)),
				blockStmt(
					p(1, 11), p(1, 12)),
				nil,
				p(1, 1)))
	})

	expectParse(t, "if a == 5 && b != 3 {}", func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				nil,
				binaryExpr(
					binaryExpr(
						ident("a", p(1, 4)),
						intLit(5, p(1, 9)),
						token.Equal,
						p(1, 6)),
					binaryExpr(
						ident("b", p(1, 14)),
						intLit(3, p(1, 19)),
						token.NotEqual,
						p(1, 16)),
					token.LAnd,
					p(1, 11)),
				blockStmt(
					p(1, 21), p(1, 22)),
				nil,
				p(1, 1)))
	})

	expectParse(t, "if a == 5 { a = 3; a = 1 }", func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				nil,
				binaryExpr(
					ident("a", p(1, 4)),
					intLit(5, p(1, 9)),
					token.Equal,
					p(1, 6)),
				blockStmt(
					p(1, 11), p(1, 26),
					assignStmt(
						exprs(ident("a", p(1, 13))),
						exprs(intLit(3, p(1, 17))),
						token.Assign,
						p(1, 15)),
					assignStmt(
						exprs(ident("a", p(1, 20))),
						exprs(intLit(1, p(1, 24))),
						token.Assign,
						p(1, 22))),
				nil,
				p(1, 1)))
	})

	expectParse(t, "if a == 5 { a = 3; a = 1 } else { a = 2; a = 4 }",
		func(p pfn) []Stmt {
			return stmts(
				ifStmt(
					nil,
					binaryExpr(
						ident("a", p(1, 4)),
						intLit(5, p(1, 9)),
						token.Equal,
						p(1, 6)),
					blockStmt(
						p(1, 11), p(1, 26),
						assignStmt(
							exprs(ident("a", p(1, 13))),
							exprs(intLit(3, p(1, 17))),
							token.Assign,
							p(1, 15)),
						assignStmt(
							exprs(ident("a", p(1, 20))),
							exprs(intLit(1, p(1, 24))),
							token.Assign,
							p(1, 22))),
					blockStmt(
						p(1, 33), p(1, 48),
						assignStmt(
							exprs(ident("a", p(1, 35))),
							exprs(intLit(2, p(1, 39))),
							token.Assign,
							p(1, 37)),
						assignStmt(
							exprs(ident("a", p(1, 42))),
							exprs(intLit(4, p(1, 46))),
							token.Assign,
							p(1, 44))),
					p(1, 1)))
		})

	expectParse(t, `
if a == 5 {
	b = 3
	c = 1
} else if d == 3 {
	e = 8
	f = 3
} else {
	g = 2
	h = 4
}`, func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				nil,
				binaryExpr(
					ident("a", p(2, 4)),
					intLit(5, p(2, 9)),
					token.Equal,
					p(2, 6)),
				blockStmt(
					p(2, 11), p(5, 1),
					assignStmt(
						exprs(ident("b", p(3, 2))),
						exprs(intLit(3, p(3, 6))),
						token.Assign,
						p(3, 4)),
					assignStmt(
						exprs(ident("c", p(4, 2))),
						exprs(intLit(1, p(4, 6))),
						token.Assign,
						p(4, 4))),
				ifStmt(
					nil,
					binaryExpr(
						ident("d", p(5, 11)),
						intLit(3, p(5, 16)),
						token.Equal,
						p(5, 13)),
					blockStmt(
						p(5, 18), p(8, 1),
						assignStmt(
							exprs(ident("e", p(6, 2))),
							exprs(intLit(8, p(6, 6))),
							token.Assign,
							p(6, 4)),
						assignStmt(
							exprs(ident("f", p(7, 2))),
							exprs(intLit(3, p(7, 6))),
							token.Assign,
							p(7, 4))),
					blockStmt(
						p(8, 8), p(11, 1),
						assignStmt(
							exprs(ident("g", p(9, 2))),
							exprs(intLit(2, p(9, 6))),
							token.Assign,
							p(9, 4)),
						assignStmt(
							exprs(ident("h", p(10, 2))),
							exprs(intLit(4, p(10, 6))),
							token.Assign,
							p(10, 4))),
					p(5, 8)),
				p(2, 1)))
	})

	expectParse(t, "if a := 3; a < b {}", func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				assignStmt(
					exprs(ident("a", p(1, 4))),
					exprs(intLit(3, p(1, 9))),
					token.Define, p(1, 6)),
				binaryExpr(
					ident("a", p(1, 12)),
					ident("b", p(1, 16)),
					token.Less, p(1, 14)),
				blockStmt(
					p(1, 18), p(1, 19)),
				nil,
				p(1, 1)))
	})

	expectParse(t, "if a++; a < b {}", func(p pfn) []Stmt {
		return stmts(
			ifStmt(
				incDecStmt(ident("a", p(1, 4)), token.Inc, p(1, 5)),
				binaryExpr(
					ident("a", p(1, 9)),
					ident("b", p(1, 13)),
					token.Less, p(1, 11)),
				blockStmt(
					p(1, 15), p(1, 16)),
				nil,
				p(1, 1)))
	})

	expectParseError(t, `if {}`)
	expectParseError(t, `if a == b { } else a != b { }`)
	expectParseError(t, `if a == b { } else if { }`)
	expectParseError(t, `else { }`)
	expectParseError(t, `if ; {}`)
	expectParseError(t, `if a := 3; {}`)
	expectParseError(t, `if ; a < 3 {}`)
}

func TestParseImport(t *testing.T) {
	expectParse(t, `a := import("mod1")`, func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(importExpr("mod1", p(1, 6))),
				token.Define, p(1, 3)))
	})

	expectParse(t, `import("mod1").var1`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				selectorExpr(
					importExpr("mod1", p(1, 1)),
					stringLit("var1", p(1, 16)))))
	})

	expectParse(t, `import("mod1").func1()`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				callExpr(
					selectorExpr(
						importExpr("mod1", p(1, 1)),
						stringLit("func1", p(1, 16))),
					p(1, 21), p(1, 22), NoPos)))
	})

	expectParse(t, `for x, y in import("mod1") {}`, func(p pfn) []Stmt {
		return stmts(
			forInStmt(
				ident("x", p(1, 5)),
				ident("y", p(1, 8)),
				importExpr("mod1", p(1, 13)),
				blockStmt(p(1, 28), p(1, 29)),
				p(1, 1)))
	})
}

func TestParseIndex(t *testing.T) {
	expectParse(t, "[1, 2, 3][1]", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				indexExpr(
					arrayLit(p(1, 1), p(1, 9),
						intLit(1, p(1, 2)),
						intLit(2, p(1, 5)),
						intLit(3, p(1, 8))),
					intLit(1, p(1, 11)),
					p(1, 10), p(1, 12))))
	})

	expectParse(t, "[1, 2, 3][5 - a]", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				indexExpr(
					arrayLit(p(1, 1), p(1, 9),
						intLit(1, p(1, 2)),
						intLit(2, p(1, 5)),
						intLit(3, p(1, 8))),
					binaryExpr(
						intLit(5, p(1, 11)),
						ident("a", p(1, 15)),
						token.Sub,
						p(1, 13)),
					p(1, 10), p(1, 16))))
	})

	expectParse(t, "[1, 2, 3][5 : a]", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				sliceExpr(
					arrayLit(p(1, 1), p(1, 9),
						intLit(1, p(1, 2)),
						intLit(2, p(1, 5)),
						intLit(3, p(1, 8))),
					intLit(5, p(1, 11)),
					ident("a", p(1, 15)),
					p(1, 10), p(1, 16))))
	})

	expectParse(t, "[1, 2, 3][a + 3 : b - 8]", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				sliceExpr(
					arrayLit(p(1, 1), p(1, 9),
						intLit(1, p(1, 2)),
						intLit(2, p(1, 5)),
						intLit(3, p(1, 8))),
					binaryExpr(
						ident("a", p(1, 11)),
						intLit(3, p(1, 15)),
						token.Add,
						p(1, 13)),
					binaryExpr(
						ident("b", p(1, 19)),
						intLit(8, p(1, 23)),
						token.Sub,
						p(1, 21)),
					p(1, 10), p(1, 24))))
	})

	expectParse(t, `{a: 1, b: 2}["b"]`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				indexExpr(
					mapLit(p(1, 1), p(1, 12),
						mapElementLit(
							"a", p(1, 2), p(1, 3), intLit(1, p(1, 5))),
						mapElementLit(
							"b", p(1, 8), p(1, 9), intLit(2, p(1, 11)))),
					stringLit("b", p(1, 14)),
					p(1, 13), p(1, 17))))
	})

	expectParse(t, `{a: 1, b: 2}[a + b]`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				indexExpr(
					mapLit(p(1, 1), p(1, 12),
						mapElementLit(
							"a", p(1, 2), p(1, 3), intLit(1, p(1, 5))),
						mapElementLit(
							"b", p(1, 8), p(1, 9), intLit(2, p(1, 11)))),
					binaryExpr(
						ident("a", p(1, 14)),
						ident("b", p(1, 18)),
						token.Add,
						p(1, 16)),
					p(1, 13), p(1, 19))))
	})
}

func TestParseLogical(t *testing.T) {
	expectParse(t, "a && 5 || true", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					binaryExpr(
						ident("a", p(1, 1)),
						intLit(5, p(1, 6)),
						token.LAnd,
						p(1, 3)),
					boolLit(true, p(1, 11)),
					token.LOr,
					p(1, 8))))
	})

	expectParse(t, "a || 5 && true", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					ident("a", p(1, 1)),
					binaryExpr(
						intLit(5, p(1, 6)),
						boolLit(true, p(1, 11)),
						token.LAnd,
						p(1, 8)),
					token.LOr,
					p(1, 3))))
	})

	expectParse(t, "a && (5 || true)", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					ident("a", p(1, 1)),
					parenExpr(
						binaryExpr(
							intLit(5, p(1, 7)),
							boolLit(true, p(1, 12)),
							token.LOr,
							p(1, 9)),
						p(1, 6), p(1, 16)),
					token.LAnd,
					p(1, 3))))
	})
}

func TestParseMap(t *testing.T) {
	expectParse(t, "{ key1: 1, key2: \"2\", key3: true }", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				mapLit(p(1, 1), p(1, 34),
					mapElementLit(
						"key1", p(1, 3), p(1, 7), intLit(1, p(1, 9))),
					mapElementLit(
						"key2", p(1, 12), p(1, 16), stringLit("2", p(1, 18))),
					mapElementLit(
						"key3", p(1, 23), p(1, 27), boolLit(true, p(1, 29))))))
	})

	expectParse(t, "{ \"key1\": 1 }", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				mapLit(p(1, 1), p(1, 13),
					mapElementLit(
						"key1", p(1, 3), p(1, 9), intLit(1, p(1, 11))))))
	})

	expectParse(t, "a = { key1: 1, key2: \"2\", key3: true }",
		func(p pfn) []Stmt {
			return stmts(assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(mapLit(p(1, 5), p(1, 38),
					mapElementLit(
						"key1", p(1, 7), p(1, 11), intLit(1, p(1, 13))),
					mapElementLit(
						"key2", p(1, 16), p(1, 20), stringLit("2", p(1, 22))),
					mapElementLit(
						"key3", p(1, 27), p(1, 31), boolLit(true, p(1, 33))))),
				token.Assign,
				p(1, 3)))
		})

	expectParse(t, "a = { key1: 1, key2: \"2\", key3: { k1: `bar`, k2: 4 } }",
		func(p pfn) []Stmt {
			return stmts(assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(mapLit(p(1, 5), p(1, 54),
					mapElementLit(
						"key1", p(1, 7), p(1, 11), intLit(1, p(1, 13))),
					mapElementLit(
						"key2", p(1, 16), p(1, 20), stringLit("2", p(1, 22))),
					mapElementLit(
						"key3", p(1, 27), p(1, 31),
						mapLit(p(1, 33), p(1, 52),
							mapElementLit(
								"k1", p(1, 35),
								p(1, 37), stringLit("bar", p(1, 39))),
							mapElementLit(
								"k2", p(1, 46),
								p(1, 48), intLit(4, p(1, 50))))))),
				token.Assign,
				p(1, 3)))
		})

	expectParse(t, `
{
	key1: 1,
	key2: "2",
	key3: true
}`, func(p pfn) []Stmt {
		return stmts(exprStmt(
			mapLit(p(2, 1), p(6, 1),
				mapElementLit(
					"key1", p(3, 2), p(3, 6), intLit(1, p(3, 8))),
				mapElementLit(
					"key2", p(4, 2), p(4, 6), stringLit("2", p(4, 8))),
				mapElementLit(
					"key3", p(5, 2), p(5, 6), boolLit(true, p(5, 8))))))
	})

	expectParseError(t, `
{
	key1: 1,
	key2: "2",
	key3: true,
}`) // unlike Go, trailing comma for the last element is illegal

	expectParseError(t, `{ key1: 1, }`)
	expectParseError(t, `{
key1: 1,
key2: 2,
}`)
}

func TestParsePrecedence(t *testing.T) {
	expectParseString(t, `a + b + c`, `((a + b) + c)`)
	expectParseString(t, `a + b * c`, `(a + (b * c))`)
	expectParseString(t, `x = 2 * 1 + 3 / 4`, `x = ((2 * 1) + (3 / 4))`)
}

func TestParseSelector(t *testing.T) {
	expectParse(t, "a.b", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				selectorExpr(
					ident("a", p(1, 1)),
					stringLit("b", p(1, 3)))))
	})

	expectParse(t, "a.b.c", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				selectorExpr(
					selectorExpr(
						ident("a", p(1, 1)),
						stringLit("b", p(1, 3))),
					stringLit("c", p(1, 5)))))
	})

	expectParse(t, "{k1:1}.k1", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				selectorExpr(
					mapLit(
						p(1, 1), p(1, 6),
						mapElementLit(
							"k1", p(1, 2), p(1, 4), intLit(1, p(1, 5)))),
					stringLit("k1", p(1, 8)))))

	})
	expectParse(t, "{k1:{v1:1}}.k1.v1", func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				selectorExpr(
					selectorExpr(
						mapLit(
							p(1, 1), p(1, 11),
							mapElementLit("k1", p(1, 2), p(1, 4),
								mapLit(p(1, 5), p(1, 10),
									mapElementLit(
										"v1", p(1, 6),
										p(1, 8), intLit(1, p(1, 9)))))),
						stringLit("k1", p(1, 13))),
					stringLit("v1", p(1, 16)))))
	})

	expectParse(t, "a.b = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						ident("a", p(1, 1)),
						stringLit("b", p(1, 3)))),
				exprs(intLit(4, p(1, 7))),
				token.Assign, p(1, 5)))
	})

	expectParse(t, "a.b.c = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						selectorExpr(
							ident("a", p(1, 1)),
							stringLit("b", p(1, 3))),
						stringLit("c", p(1, 5)))),
				exprs(intLit(4, p(1, 9))),
				token.Assign, p(1, 7)))
	})

	expectParse(t, "a.b.c = 4 + 5", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						selectorExpr(
							ident("a", p(1, 1)),
							stringLit("b", p(1, 3))),
						stringLit("c", p(1, 5)))),
				exprs(
					binaryExpr(
						intLit(4, p(1, 9)),
						intLit(5, p(1, 13)),
						token.Add,
						p(1, 11))),
				token.Assign, p(1, 7)))
	})

	expectParse(t, "a[0].c = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						indexExpr(
							ident("a", p(1, 1)),
							intLit(0, p(1, 3)),
							p(1, 2), p(1, 4)),
						stringLit("c", p(1, 6)))),
				exprs(intLit(4, p(1, 10))),
				token.Assign, p(1, 8)))
	})

	expectParse(t, "a.b[0].c = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						indexExpr(
							selectorExpr(
								ident("a", p(1, 1)),
								stringLit("b", p(1, 3))),
							intLit(0, p(1, 5)),
							p(1, 4), p(1, 6)),
						stringLit("c", p(1, 8)))),
				exprs(intLit(4, p(1, 12))),
				token.Assign, p(1, 10)))
	})

	expectParse(t, "a.b[0][2].c = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						indexExpr(
							indexExpr(
								selectorExpr(
									ident("a", p(1, 1)),
									stringLit("b", p(1, 3))),
								intLit(0, p(1, 5)),
								p(1, 4), p(1, 6)),
							intLit(2, p(1, 8)),
							p(1, 7), p(1, 9)),
						stringLit("c", p(1, 11)))),
				exprs(intLit(4, p(1, 15))),
				token.Assign, p(1, 13)))
	})

	expectParse(t, `a.b["key1"][2].c = 4`, func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						indexExpr(
							indexExpr(
								selectorExpr(
									ident("a", p(1, 1)),
									stringLit("b", p(1, 3))),
								stringLit("key1", p(1, 5)),
								p(1, 4), p(1, 11)),
							intLit(2, p(1, 13)),
							p(1, 12), p(1, 14)),
						stringLit("c", p(1, 16)))),
				exprs(intLit(4, p(1, 20))),
				token.Assign, p(1, 18)))
	})

	expectParse(t, "a[0].b[2].c = 4", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(
					selectorExpr(
						indexExpr(
							selectorExpr(
								indexExpr(
									ident("a", p(1, 1)),
									intLit(0, p(1, 3)),
									p(1, 2), p(1, 4)),
								stringLit("b", p(1, 6))),
							intLit(2, p(1, 8)),
							p(1, 7), p(1, 9)),
						stringLit("c", p(1, 11)))),
				exprs(intLit(4, p(1, 15))),
				token.Assign, p(1, 13)))
	})

	expectParseError(t, `a.(b.c)`)
}

func TestParseSemicolon(t *testing.T) {
	expectParse(t, "1", func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))))
	})

	expectParse(t, "1;", func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))))
	})

	expectParse(t, "1;;", func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))),
			emptyStmt(false, p(1, 3)))
	})

	expectParse(t, `1
`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))))
	})

	expectParse(t, `1
;`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))),
			emptyStmt(false, p(2, 1)))
	})

	expectParse(t, `1;
;`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(intLit(1, p(1, 1))),
			emptyStmt(false, p(2, 1)))
	})
}

func TestParseString(t *testing.T) {
	expectParse(t, `a = "foo\nbar"`, func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(stringLit("foo\nbar", p(1, 5))),
				token.Assign,
				p(1, 3)))
	})

	expectParse(t, "a = `raw string`", func(p pfn) []Stmt {
		return stmts(
			assignStmt(
				exprs(ident("a", p(1, 1))),
				exprs(stringLit("raw string", p(1, 5))),
				token.Assign,
				p(1, 3)))
	})
}

func TestParseInt(t *testing.T) {
	testCases := []string{
		// All valid digits
		"1234567890",
		"0b10",
		"0o12345670",
		"0x123456789abcdef0",
		"0x123456789ABCDEF0",

		// Alternative base prefixes
		"010",
		"0B10",
		"0O10",
		"0X10",

		// Invalid digits
		"0b2",
		"08",
		"0o8",
		"1a",
		"0xg",

		// Range errors
		"9223372036854775807",
		"9223372036854775808", // invalid: range error

		// Examples from specification (https://go.dev/ref/spec#Integer_literals)
		"42",
		"4_2",
		"0600",
		"0_600",
		"0o600",
		"0O600", // second character is capital letter 'O'
		"0xBadFace",
		"0xBad_Face",
		"0x_67_7a_2f_cc_40_c6",
		"170141183460469231731687303715884105727",
		"170_141183_460469_231731_687303_715884_105727",
		"42_",        // invalid: _ must separate successive digits
		"4__2",       // invalid: only one _ at a time
		"0_xBadFace", // invalid: _ must separate successive digits
	}

	for _, num := range testCases {
		t.Run(num, func(t *testing.T) {
			expected, err := strconv.ParseInt(num, 0, 64)
			if err == nil {
				expectParse(t, num, func(p pfn) []Stmt {
					return stmts(exprStmt(intLit(expected, p(1, 1))))
				})
			} else {
				expectParseError(t, num)
			}
		})
	}
}

func TestParseFloat(t *testing.T) {
	testCases := []string{
		// Different placements of decimal point
		".0",
		"0.",
		"0.0",
		"00.0",
		"00.00",
		"0.0.0",
		"0..0",

		// Ignoring leading zeros
		"010.0",
		"00010.0",
		"08.0",
		"0a.0", // ivalid: hex character

		// Exponents
		"1e1",
		"1E1",
		"1e1.1",
		"1e+1",
		"1e-1",
		"1e+-1",
		"0x1p1",
		"0x10p1",

		// Examples from language specifcation (https://go.dev/ref/spec#Floating-point_literals)
		"0.",
		"72.40",
		"072.40", // == 72.40
		"2.71828",
		"1.e+0",
		"6.67428e-11",
		"1E6",
		".25",
		".12345E+5",
		"1_5.",        // == 15.0
		"0.15e+0_2",   // == 15.0
		"0x1p-2",      // == 0.25
		"0x2.p10",     // == 2048.0
		"0x1.Fp+0",    // == 1.9375
		"0X.8p-0",     // == 0.5
		"0X_1FFFP-16", // == 0.1249847412109375
		"0x.p1",       // invalid: mantissa has no digits
		"1p-2",        // invalid: p exponent requires hexadecimal mantissa
		"0x1.5e-2",    // invalid: hexadecimal mantissa requires p exponent
		"1_.5",        // invalid: _ must separate successive digits
		"1._5",        // invalid: _ must separate successive digits
		"1.5_e1",      // invalid: _ must separate successive digits
		"1.5e_1",      // invalid: _ must separate successive digits
		"1.5e1_",      // invalid: _ must separate successive digits
	}

	for _, num := range testCases {
		t.Run(num, func(t *testing.T) {
			expected, err := strconv.ParseFloat(num, 64)
			if err == nil {
				expectParse(t, num, func(p pfn) []Stmt {
					return stmts(exprStmt(floatLit(expected, p(1, 1))))
				})
			} else {
				expectParseError(t, num)
			}
		})
	}
}

func TestMismatchBrace(t *testing.T) {
	expectParseError(t, `
fmt := import("fmt")
out := 0
if 3 == 1 {
	out = 1
}
} else {
	out = 2
}
fmt.println(out)
	`)
}

func TestParseNumberExpressions(t *testing.T) {
	expectParse(t, `0x15e+2`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					intLit(0x15e, p(1, 1)),
					intLit(2, p(1, 7)),
					token.Add,
					p(1, 6))))
	})

	expectParse(t, `0-_42`, func(p pfn) []Stmt {
		return stmts(
			exprStmt(
				binaryExpr(
					intLit(0, p(1, 1)),
					ident("_42", p(1, 3)),
					token.Sub,
					p(1, 2))))
	})
}

type pfn func(int, int) Pos          // position conversion function
type expectedFn func(pos pfn) []Stmt // callback function to return expected results

type parseTracer struct {
	out []string
}

func (o *parseTracer) Write(p []byte) (n int, err error) {
	o.out = append(o.out, string(p))
	return len(p), nil
}

//type slowPrinter struct {
//}
//
//func (o *slowPrinter) Write(p []byte) (n int, err error) {
//	fmt.Print(string(p))
//	time.Sleep(25 * time.Millisecond)
//	return len(p), nil
//}

func expectParse(t *testing.T, input string, fn expectedFn) {
	testFileSet := NewFileSet()
	testFile := testFileSet.AddFile("test", -1, len(input))

	var ok bool
	defer func() {
		if !ok {
			// print trace
			tr := &parseTracer{}
			p := NewParser(testFile, []byte(input), tr)
			actual, _ := p.ParseFile()
			if actual != nil {
				t.Logf("Parsed:\n%s", actual.String())
			}
			t.Logf("Trace:\n%s", strings.Join(tr.out, ""))
		}
	}()

	p := NewParser(testFile, []byte(input), nil)
	actual, err := p.ParseFile()
	require.NoError(t, err)

	expected := fn(func(line, column int) Pos {
		return Pos(int(testFile.LineStart(line)) + (column - 1))
	})
	require.Equal(t, len(expected), len(actual.Stmts))

	for i := 0; i < len(expected); i++ {
		equalStmt(t, expected[i], actual.Stmts[i])
	}

	ok = true
}

func expectParseError(t *testing.T, input string) {
	testFileSet := NewFileSet()
	testFile := testFileSet.AddFile("test", -1, len(input))

	var ok bool
	defer func() {
		if !ok {
			// print trace
			tr := &parseTracer{}
			p := NewParser(testFile, []byte(input), tr)
			_, _ = p.ParseFile()
			t.Logf("Trace:\n%s", strings.Join(tr.out, ""))
		}
	}()

	p := NewParser(testFile, []byte(input), nil)
	_, err := p.ParseFile()
	require.Error(t, err)
	ok = true
}

func expectParseString(t *testing.T, input, expected string) {
	var ok bool
	defer func() {
		if !ok {
			// print trace
			tr := &parseTracer{}
			_, _ = parseSource("test", []byte(input), tr)
			t.Logf("Trace:\n%s", strings.Join(tr.out, ""))
		}
	}()

	actual, err := parseSource("test", []byte(input), nil)
	require.NoError(t, err)
	require.Equal(t, expected, actual.String())
	ok = true
}

func stmts(s ...Stmt) []Stmt {
	return s
}

func exprStmt(x Expr) *ExprStmt {
	return &ExprStmt{Expr: x}
}

func assignStmt(
	lhs, rhs []Expr,
	token token.Token,
	pos Pos,
) *AssignStmt {
	return &AssignStmt{LHS: lhs, RHS: rhs, Token: token, TokenPos: pos}
}

func emptyStmt(implicit bool, pos Pos) *EmptyStmt {
	return &EmptyStmt{Implicit: implicit, Semicolon: pos}
}

func returnStmt(pos Pos, result Expr) *ReturnStmt {
	return &ReturnStmt{Result: result, ReturnPos: pos}
}

func forStmt(
	init Stmt,
	cond Expr,
	post Stmt,
	body *BlockStmt,
	pos Pos,
) *ForStmt {
	return &ForStmt{
		Cond: cond, Init: init, Post: post, Body: body, ForPos: pos,
	}
}

func forInStmt(
	key, value *Ident,
	seq Expr,
	body *BlockStmt,
	pos Pos,
) *ForInStmt {
	return &ForInStmt{
		Key: key, Value: value, Iterable: seq, Body: body, ForPos: pos,
	}
}

func ifStmt(
	init Stmt,
	cond Expr,
	body *BlockStmt,
	elseStmt Stmt,
	pos Pos,
) *IfStmt {
	return &IfStmt{
		Init: init, Cond: cond, Body: body, Else: elseStmt, IfPos: pos,
	}
}

func incDecStmt(
	expr Expr,
	tok token.Token,
	pos Pos,
) *IncDecStmt {
	return &IncDecStmt{Expr: expr, Token: tok, TokenPos: pos}
}

func funcType(params *IdentList, pos Pos) *FuncType {
	return &FuncType{Params: params, FuncPos: pos}
}

func blockStmt(lbrace, rbrace Pos, list ...Stmt) *BlockStmt {
	return &BlockStmt{Stmts: list, LBrace: lbrace, RBrace: rbrace}
}

func ident(name string, pos Pos) *Ident {
	return &Ident{Name: name, NamePos: pos}
}

func identList(
	opening, closing Pos,
	varArgs bool,
	list ...*Ident,
) *IdentList {
	return &IdentList{
		VarArgs: varArgs, List: list, LParen: opening, RParen: closing,
	}
}

func binaryExpr(
	x, y Expr,
	op token.Token,
	pos Pos,
) *BinaryExpr {
	return &BinaryExpr{LHS: x, RHS: y, Token: op, TokenPos: pos}
}

func condExpr(
	cond, trueExpr, falseExpr Expr,
	questionPos, colonPos Pos,
) *CondExpr {
	return &CondExpr{
		Cond: cond, True: trueExpr, False: falseExpr,
		QuestionPos: questionPos, ColonPos: colonPos,
	}
}

func unaryExpr(x Expr, op token.Token, pos Pos) *UnaryExpr {
	return &UnaryExpr{Expr: x, Token: op, TokenPos: pos}
}

func importExpr(moduleName string, pos Pos) *ImportExpr {
	return &ImportExpr{
		ModuleName: moduleName, Token: token.Import, TokenPos: pos,
	}
}

func exprs(list ...Expr) []Expr {
	return list
}

func intLit(value int64, pos Pos) *IntLit {
	return &IntLit{Value: value, ValuePos: pos}
}

func floatLit(value float64, pos Pos) *FloatLit {
	return &FloatLit{Value: value, ValuePos: pos}
}

func stringLit(value string, pos Pos) *StringLit {
	return &StringLit{Value: value, ValuePos: pos}
}

func charLit(value rune, pos Pos) *CharLit {
	return &CharLit{
		Value: value, ValuePos: pos, Literal: fmt.Sprintf("'%c'", value),
	}
}

func boolLit(value bool, pos Pos) *BoolLit {
	return &BoolLit{Value: value, ValuePos: pos}
}

func arrayLit(lbracket, rbracket Pos, list ...Expr) *ArrayLit {
	return &ArrayLit{LBrack: lbracket, RBrack: rbracket, Elements: list}
}

func mapElementLit(
	key string,
	keyPos Pos,
	colonPos Pos,
	value Expr,
) *MapElementLit {
	return &MapElementLit{
		Key: key, KeyPos: keyPos, ColonPos: colonPos, Value: value,
	}
}

func mapLit(
	lbrace, rbrace Pos,
	list ...*MapElementLit,
) *MapLit {
	return &MapLit{LBrace: lbrace, RBrace: rbrace, Elements: list}
}

func funcLit(funcType *FuncType, body *BlockStmt) *FuncLit {
	return &FuncLit{Type: funcType, Body: body}
}

func parenExpr(x Expr, lparen, rparen Pos) *ParenExpr {
	return &ParenExpr{Expr: x, LParen: lparen, RParen: rparen}
}

func callExpr(
	f Expr,
	lparen, rparen, ellipsis Pos,
	args ...Expr,
) *CallExpr {
	return &CallExpr{Func: f, LParen: lparen, RParen: rparen,
		Ellipsis: ellipsis, Args: args}
}

func indexExpr(
	x, index Expr,
	lbrack, rbrack Pos,
) *IndexExpr {
	return &IndexExpr{
		Expr: x, Index: index, LBrack: lbrack, RBrack: rbrack,
	}
}

func sliceExpr(
	x, low, high Expr,
	lbrack, rbrack Pos,
) *SliceExpr {
	return &SliceExpr{
		Expr: x, Low: low, High: high, LBrack: lbrack, RBrack: rbrack,
	}
}

func errorExpr(
	pos Pos,
	x Expr,
	lparen, rparen Pos,
) *ErrorExpr {
	return &ErrorExpr{
		Expr: x, ErrorPos: pos, LParen: lparen, RParen: rparen,
	}
}

func selectorExpr(x, sel Expr) *SelectorExpr {
	return &SelectorExpr{Expr: x, Sel: sel}
}

func equalStmt(t *testing.T, expected, actual Stmt) {
	if expected == nil || reflect.ValueOf(expected).IsNil() {
		require.Nil(t, actual, "expected nil, but got not nil")
		return
	}
	require.NotNil(t, actual, "expected not nil, but got nil")
	require.IsType(t, expected, actual)

	switch expected := expected.(type) {
	case *ExprStmt:
		equalExpr(t, expected.Expr, actual.(*ExprStmt).Expr)
	case *EmptyStmt:
		require.Equal(t, expected.Implicit,
			actual.(*EmptyStmt).Implicit)
		require.Equal(t, expected.Semicolon,
			actual.(*EmptyStmt).Semicolon)
	case *BlockStmt:
		require.Equal(t, expected.LBrace,
			actual.(*BlockStmt).LBrace)
		require.Equal(t, expected.RBrace,
			actual.(*BlockStmt).RBrace)
		equalStmts(t, expected.Stmts,
			actual.(*BlockStmt).Stmts)
	case *AssignStmt:
		equalExprs(t, expected.LHS,
			actual.(*AssignStmt).LHS)
		equalExprs(t, expected.RHS,
			actual.(*AssignStmt).RHS)
		require.Equal(t, int(expected.Token),
			int(actual.(*AssignStmt).Token))
		require.Equal(t, int(expected.TokenPos),
			int(actual.(*AssignStmt).TokenPos))
	case *IfStmt:
		equalStmt(t, expected.Init, actual.(*IfStmt).Init)
		equalExpr(t, expected.Cond, actual.(*IfStmt).Cond)
		equalStmt(t, expected.Body, actual.(*IfStmt).Body)
		equalStmt(t, expected.Else, actual.(*IfStmt).Else)
		require.Equal(t, expected.IfPos, actual.(*IfStmt).IfPos)
	case *IncDecStmt:
		equalExpr(t, expected.Expr,
			actual.(*IncDecStmt).Expr)
		require.Equal(t, expected.Token,
			actual.(*IncDecStmt).Token)
		require.Equal(t, expected.TokenPos,
			actual.(*IncDecStmt).TokenPos)
	case *ForStmt:
		equalStmt(t, expected.Init, actual.(*ForStmt).Init)
		equalExpr(t, expected.Cond, actual.(*ForStmt).Cond)
		equalStmt(t, expected.Post, actual.(*ForStmt).Post)
		equalStmt(t, expected.Body, actual.(*ForStmt).Body)
		require.Equal(t, expected.ForPos, actual.(*ForStmt).ForPos)
	case *ForInStmt:
		equalExpr(t, expected.Key,
			actual.(*ForInStmt).Key)
		equalExpr(t, expected.Value,
			actual.(*ForInStmt).Value)
		equalExpr(t, expected.Iterable,
			actual.(*ForInStmt).Iterable)
		equalStmt(t, expected.Body,
			actual.(*ForInStmt).Body)
		require.Equal(t, expected.ForPos,
			actual.(*ForInStmt).ForPos)
	case *ReturnStmt:
		equalExpr(t, expected.Result,
			actual.(*ReturnStmt).Result)
		require.Equal(t, expected.ReturnPos,
			actual.(*ReturnStmt).ReturnPos)
	case *BranchStmt:
		equalExpr(t, expected.Label,
			actual.(*BranchStmt).Label)
		require.Equal(t, expected.Token,
			actual.(*BranchStmt).Token)
		require.Equal(t, expected.TokenPos,
			actual.(*BranchStmt).TokenPos)
	default:
		panic(fmt.Errorf("unknown type: %T", expected))
	}
}

func equalExpr(t *testing.T, expected, actual Expr) {
	if expected == nil || reflect.ValueOf(expected).IsNil() {
		require.Nil(t, actual, "expected nil, but got not nil")
		return
	}
	require.NotNil(t, actual, "expected not nil, but got nil")
	require.IsType(t, expected, actual)

	switch expected := expected.(type) {
	case *Ident:
		require.Equal(t, expected.Name,
			actual.(*Ident).Name)
		require.Equal(t, int(expected.NamePos),
			int(actual.(*Ident).NamePos))
	case *IntLit:
		require.Equal(t, expected.Value,
			actual.(*IntLit).Value)
		require.Equal(t, int(expected.ValuePos),
			int(actual.(*IntLit).ValuePos))
	case *FloatLit:
		require.Equal(t, expected.Value,
			actual.(*FloatLit).Value)
		require.Equal(t, int(expected.ValuePos),
			int(actual.(*FloatLit).ValuePos))
	case *BoolLit:
		require.Equal(t, expected.Value,
			actual.(*BoolLit).Value)
		require.Equal(t, int(expected.ValuePos),
			int(actual.(*BoolLit).ValuePos))
	case *CharLit:
		require.Equal(t, expected.Value,
			actual.(*CharLit).Value)
		require.Equal(t, int(expected.ValuePos),
			int(actual.(*CharLit).ValuePos))
	case *StringLit:
		require.Equal(t, expected.Value,
			actual.(*StringLit).Value)
		require.Equal(t, int(expected.ValuePos),
			int(actual.(*StringLit).ValuePos))
	case *ArrayLit:
		require.Equal(t, expected.LBrack,
			actual.(*ArrayLit).LBrack)
		require.Equal(t, expected.RBrack,
			actual.(*ArrayLit).RBrack)
		equalExprs(t, expected.Elements,
			actual.(*ArrayLit).Elements)
	case *MapLit:
		require.Equal(t, expected.LBrace,
			actual.(*MapLit).LBrace)
		require.Equal(t, expected.RBrace,
			actual.(*MapLit).RBrace)
		equalMapElements(t, expected.Elements,
			actual.(*MapLit).Elements)
	case *BinaryExpr:
		equalExpr(t, expected.LHS,
			actual.(*BinaryExpr).LHS)
		equalExpr(t, expected.RHS,
			actual.(*BinaryExpr).RHS)
		require.Equal(t, expected.Token,
			actual.(*BinaryExpr).Token)
		require.Equal(t, expected.TokenPos,
			actual.(*BinaryExpr).TokenPos)
	case *UnaryExpr:
		equalExpr(t, expected.Expr,
			actual.(*UnaryExpr).Expr)
		require.Equal(t, expected.Token,
			actual.(*UnaryExpr).Token)
		require.Equal(t, expected.TokenPos,
			actual.(*UnaryExpr).TokenPos)
	case *FuncLit:
		equalFuncType(t, expected.Type,
			actual.(*FuncLit).Type)
		equalStmt(t, expected.Body,
			actual.(*FuncLit).Body)
	case *CallExpr:
		equalExpr(t, expected.Func,
			actual.(*CallExpr).Func)
		require.Equal(t, expected.LParen,
			actual.(*CallExpr).LParen)
		require.Equal(t, expected.RParen,
			actual.(*CallExpr).RParen)
		equalExprs(t, expected.Args,
			actual.(*CallExpr).Args)
	case *ParenExpr:
		equalExpr(t, expected.Expr,
			actual.(*ParenExpr).Expr)
		require.Equal(t, expected.LParen,
			actual.(*ParenExpr).LParen)
		require.Equal(t, expected.RParen,
			actual.(*ParenExpr).RParen)
	case *IndexExpr:
		equalExpr(t, expected.Expr,
			actual.(*IndexExpr).Expr)
		equalExpr(t, expected.Index,
			actual.(*IndexExpr).Index)
		require.Equal(t, expected.LBrack,
			actual.(*IndexExpr).LBrack)
		require.Equal(t, expected.RBrack,
			actual.(*IndexExpr).RBrack)
	case *SliceExpr:
		equalExpr(t, expected.Expr,
			actual.(*SliceExpr).Expr)
		equalExpr(t, expected.Low,
			actual.(*SliceExpr).Low)
		equalExpr(t, expected.High,
			actual.(*SliceExpr).High)
		require.Equal(t, expected.LBrack,
			actual.(*SliceExpr).LBrack)
		require.Equal(t, expected.RBrack,
			actual.(*SliceExpr).RBrack)
	case *SelectorExpr:
		equalExpr(t, expected.Expr,
			actual.(*SelectorExpr).Expr)
		equalExpr(t, expected.Sel,
			actual.(*SelectorExpr).Sel)
	case *ImportExpr:
		require.Equal(t, expected.ModuleName,
			actual.(*ImportExpr).ModuleName)
		require.Equal(t, int(expected.TokenPos),
			int(actual.(*ImportExpr).TokenPos))
		require.Equal(t, expected.Token,
			actual.(*ImportExpr).Token)
	case *ErrorExpr:
		equalExpr(t, expected.Expr,
			actual.(*ErrorExpr).Expr)
		require.Equal(t, int(expected.ErrorPos),
			int(actual.(*ErrorExpr).ErrorPos))
		require.Equal(t, int(expected.LParen),
			int(actual.(*ErrorExpr).LParen))
		require.Equal(t, int(expected.RParen),
			int(actual.(*ErrorExpr).RParen))
	case *CondExpr:
		equalExpr(t, expected.Cond,
			actual.(*CondExpr).Cond)
		equalExpr(t, expected.True,
			actual.(*CondExpr).True)
		equalExpr(t, expected.False,
			actual.(*CondExpr).False)
		require.Equal(t, expected.QuestionPos,
			actual.(*CondExpr).QuestionPos)
		require.Equal(t, expected.ColonPos,
			actual.(*CondExpr).ColonPos)
	default:
		panic(fmt.Errorf("unknown type: %T", expected))
	}
}

func equalFuncType(t *testing.T, expected, actual *FuncType) {
	require.Equal(t, expected.Params.LParen, actual.Params.LParen)
	require.Equal(t, expected.Params.RParen, actual.Params.RParen)
	equalIdents(t, expected.Params.List, actual.Params.List)
}

func equalIdents(t *testing.T, expected, actual []*Ident) {
	require.Equal(t, len(expected), len(actual))
	for i := 0; i < len(expected); i++ {
		equalExpr(t, expected[i], actual[i])
	}
}

func equalExprs(t *testing.T, expected, actual []Expr) {
	require.Equal(t, len(expected), len(actual))
	for i := 0; i < len(expected); i++ {
		equalExpr(t, expected[i], actual[i])
	}
}

func equalStmts(t *testing.T, expected, actual []Stmt) {
	require.Equal(t, len(expected), len(actual))
	for i := 0; i < len(expected); i++ {
		equalStmt(t, expected[i], actual[i])
	}
}

func equalMapElements(
	t *testing.T,
	expected, actual []*MapElementLit,
) {
	require.Equal(t, len(expected), len(actual))
	for i := 0; i < len(expected); i++ {
		require.Equal(t, expected[i].Key, actual[i].Key)
		require.Equal(t, expected[i].KeyPos, actual[i].KeyPos)
		require.Equal(t, expected[i].ColonPos, actual[i].ColonPos)
		equalExpr(t, expected[i].Value, actual[i].Value)
	}
}

func parseSource(
	filename string,
	src []byte,
	trace io.Writer,
) (res *File, err error) {
	fileSet := NewFileSet()
	file := fileSet.AddFile(filename, -1, len(src))

	p := NewParser(file, src, trace)
	return p.ParseFile()
}