package parser

import (
	"fmt"
	"mana/ast"
	"mana/lexer"
	"testing"
)

func TestLetStatements(t *testing.T) {
	const input string = `
		let x = 5;
		let y = 10;
		let foobar = 838383;
	`

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)

	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if program == nil {
		t.Fatalf("ParseProgram() returned nil")
	}

	if len(program.Statements) != 3 {
		t.Fatalf("program.Statements does not contain 3 statements. got=%d", len(program.Statements))
	}

	var tests = []struct {
		expectedIdentifier string
	}{
		{"x"},
		{"y"},
		{"foobar"},
	}

	for i, tt := range tests {
		var stmt ast.Statement = program.Statements[i]

		if !testLetStatement(t, stmt, tt.expectedIdentifier) {
			return
		}
	}
}

func checkParserErrors(t *testing.T, p *Parser) {
	var errors []string = p.Errors()

	if len(errors) == 0 {
		return
	}

	t.Errorf("parser has %d errors", len(errors))

	for _, msg := range errors {
		t.Errorf("parser error: %q", msg)
	}

	t.FailNow()
}

func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
	if s.TokenLiteral() != "let" {
		t.Errorf("s.TokenLiteral not 'let'. got=%q", s.TokenLiteral())

		return false
	}

	var letStmt, ok = s.(*ast.LetStatement)

	if !ok {
		t.Errorf("s not *ast.LetStatement. got=%T", s)

		return false
	}

	if letStmt.Name.Value != name {
		t.Errorf("letStmt.Name.Value not '%s'. got=%s", name, letStmt.Name.Value)

		return false
	}

	if letStmt.Name.TokenLiteral() != name {
		t.Errorf("letStmt.Name.TokenLiteral() not '%s'. got=%s", name, letStmt.Name.TokenLiteral())

		return false
	}

	return true
}

// Return statement tests.
func TestReturnStatements(t *testing.T) {
	var input string = `
		return 5;
		return 10;
		return 993322;
	`

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)

	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 3 {
		t.Fatalf("program.Statements does not contain 3 statements. got=%d", len(program.Statements))
	}

	for _, stmt := range program.Statements {
		var returnStmt, ok = stmt.(*ast.ReturnStatement)

		if !ok {
			t.Errorf("stmt not *ast.ReturnStatement. got=%T", stmt)

			continue
		}

		if returnStmt.TokenLiteral() != "return" {
			t.Errorf("returnStmt.TokenLiteral not 'return', got %q", returnStmt.TokenLiteral())
		}
	}
}

func testIdentifier(t *testing.T, exp ast.Expression, value string) bool {
	ident, ok := exp.(*ast.Identifier)

	if !ok {
		t.Errorf("exp not *ast.Identifier. got=%T", exp)
		return false
	}

	if ident.Value != value {
		t.Errorf("ident.Value not %s. got=%s", value, ident.Value)
		return false
	}

	if ident.TokenLiteral() != value {
		t.Errorf("ident.TokenLiteral not %s. got =%s", value, ident.TokenLiteral())

		return false
	}

	return true
}

func testLiteralExpression(
	t *testing.T,
	exp ast.Expression,
	expected interface{},
) bool {
	switch v := expected.(type) {
	case int:
		return testIntegerLiteral(t, exp, int64(v))
	case int64:
		return testIntegerLiteral(t, exp, v)
	case string:
		return testIdentifier(t, exp, v)
	case bool:
		return testBooleanLiteral(t, exp, v)
	}

	t.Errorf("type of exp not handled. got=%T", exp)
	return false
}

func testInfixExpression(
	t *testing.T,
	exp ast.Expression,
	left interface{},
	operator string,
	right interface{},
) bool {
	opExp, ok := exp.(*ast.InfixExpression)

	if !ok {
		t.Errorf("exp is not ast.InfixExpression. got =%T(%s)", exp, exp)
		return false
	}

	if !testLiteralExpression(t, opExp.Left, left) {
		return false
	}

	if opExp.Operator != operator {
		t.Errorf("exp.Operator is not '%s'. got=%q", operator, opExp.Operator)
		return false
	}

	if !testLiteralExpression(t, opExp.Right, right) {
		return false
	}

	return true
}

// Identifier expression tests.
func TestIdentifierExpression(t *testing.T) {
	var input string = "foobar;"

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)
	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program has not enough statements. got=%d", len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}

	ident, ok := stmt.Expression.(*ast.Identifier)

	if !ok {
		t.Fatalf("exp not *ast.Identifier. got=%T", stmt.Expression)
	}

	if ident.Value != "foobar" {
		t.Errorf("ident.Value not %s. got=%s", "foobar", ident.Value)
	}

	if ident.TokenLiteral() != "foobar" {
		t.Errorf("ident.TokenLiteral not %s. got=%s", "foobar", ident.TokenLiteral())
	}
}

// Integer literal expression tests.
func TestIntegerLiteralExpression(t *testing.T) {
	var input string = "5;"

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)
	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program has not enough statements. got=%d", len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}

	literal, ok := stmt.Expression.(*ast.IntegerLiteral)

	if !ok {
		t.Fatalf("exp not *ast.IntegerLiteral. got=%T", stmt.Expression)
	}

	if literal.Value != 5 {
		t.Errorf("literal.Value not %d. got=%d", 5, literal.Value)
	}

	if literal.TokenLiteral() != "5" {
		t.Errorf("literal.TokenLiteral not %s. got=%s", "5", literal.TokenLiteral())
	}
}

// Boolean expression tests.

func TestBooleanExpression(t *testing.T) {
	tests := []struct {
		input           string
		expectedBoolean bool
	}{
		{"true;", true},
		{"false;", false},
	}

	for _, tt := range tests {
		var l *lexer.Lexer = lexer.New(tt.input)
		var p *Parser = New(l)
		var program *ast.Program = p.ParseProgram()
		checkParserErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program has not enough statements. got=%d", len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
		}

		boolean, ok := stmt.Expression.(*ast.Boolean)

		if !ok {
			t.Fatalf("exp not *ast.Boolean. got=%T", stmt.Expression)
		}

		if boolean.Value != tt.expectedBoolean {
			t.Errorf("boolean.Value not %t. got=%t", tt.expectedBoolean, boolean.Value)
		}
	}
}

// Prefix expression tests.
func TestParsingPrefixExpressions(t *testing.T) {
	var prefixTests = []struct {
		input        string
		operator     string
		value 	  	 interface{}
	}{
		{"!5;", "!", 5},
		{"-15;", "-", 15},
		{"!true;", "!", true},
		{"!false;", "!", false},
	}

	for _, tt := range prefixTests {
		var l *lexer.Lexer = lexer.New(tt.input)
		var p *Parser = New(l)
		var program *ast.Program = p.ParseProgram()
		checkParserErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statements does not contain %d statements. got=%d", 1, len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
		}

		exp, ok := stmt.Expression.(*ast.PrefixExpression)

		if !ok {
			t.Fatalf("stmt is not ast.PrefixExpression. got=%T", stmt.Expression)
		}

		if exp.Operator != tt.operator {
			t.Fatalf("exp.Operator is not '%s'. got=%s", tt.operator, exp.Operator)
		}

		// if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
		// 	return
		// }

		if !testLiteralExpression(t, exp.Right, tt.value) {
			return
		}
	}
}

func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
	var integ, ok = il.(*ast.IntegerLiteral)

	if !ok {
		t.Errorf("il not *ast.IntegerLiteral. got=%T", il)

		return false
	}

	if integ.Value != value {
		t.Errorf("integ.Value not %d. got=%d", value, integ.Value)

		return false
	}

	if integ.TokenLiteral() != fmt.Sprintf("%d", value) {
		t.Errorf("integ.TokenLiteral not %d. got=%s", value, integ.TokenLiteral())

		return false
	}

	return true
}

// Infix expression tests.

func TestParsingInfixExpressions(t *testing.T) {
	var infixTests = []struct {
		input      string
		leftValue  interface{}
		operator   string
		rightValue interface{}
	}{
		{"5 + 5;", 5, "+", 5},
		{"5 - 5;", 5, "-", 5},
		{"5 * 5;", 5, "*", 5},
		{"5 / 5;", 5, "/", 5},
		{"5 > 5;", 5, ">", 5},
		{"5 < 5;", 5, "<", 5},
		{"5 == 5;", 5, "==", 5},
		{"5 != 5;", 5, "!=", 5},
		{"true == true", true, "==", true},
		{"true != false", true, "!=", false},
		{"false == false", false, "==", false},
	}

	for _, tt := range infixTests {
		var l *lexer.Lexer = lexer.New(tt.input)
		var p *Parser = New(l)

		var program *ast.Program = p.ParseProgram()
		checkParserErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statements does not contain %d statements, got=%d\n", 1, len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement, got=%T", program.Statements[0])
		}

		// exp, ok := stmt.Expression.(*ast.InfixExpression)

		// if !ok {
		// 	t.Fatalf("exp is not ast.InfixExpression. got=%T", stmt.Expression)
		// }

		// if !testIntegerLiteral(t, exp.Left, tt.leftValue) {
		// 	return
		// }

		// if exp.Operator != tt.operator {
		// 	t.Fatalf("exp.Operator is not '%s', got=%s", tt.operator, exp.Operator)
		// }

		// if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
		// 	return
		// }

		if !testInfixExpression(t, stmt.Expression, tt.leftValue, tt.operator, tt.rightValue) {
			return
		}
	}
}

// Operator precedence tests.

func TestOperatorPrecedenceParsing(t *testing.T) {
	tests := []struct {
		input    string
		expected string
	}{
		{
			"-a * b",
			"((-a) * b)",
		},
		{
			"!-a",
			"(!(-a))",
		},
		{
			"a + b + c",
			"((a + b) + c)",
		},
		{
			"a + b - c",
			"((a + b) - c)",
		},
		{
			"a * b * c",
			"((a * b) * c)",
		},
		{
			"a * b / c",
			"((a * b) / c)",
		},
		{
			"a + b / c",
			"(a + (b / c))",
		},
		{
			"a + b * c + d / e - f",
			"(((a + (b * c)) + (d / e)) - f)",
		},
		{
			"3 + 4; -5 * 5",
			"(3 + 4)((-5) * 5)",
		},
		{
			"5 > 4 == 3 < 4",
			"((5 > 4) == (3 < 4))",
		},
		{
			"5 < 4 != 3 > 4",
			"((5 < 4) != (3 > 4))",
		},
		{
			"3 + 4 * 5 == 3 * 1 + 4 * 5",
			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
		},
		{
			"true",
			"true",
		},
		{
			"false",
			"false",
		},
		{
			"3 > 5 == false",
			"((3 > 5) == false)",
		},
		{
			"3 < 5 == true",
			"((3 < 5) == true)",
		},
	}

	for _, tt := range tests {
		var l *lexer.Lexer = lexer.New(tt.input)
		var p *Parser = New(l)
		var program *ast.Program = p.ParseProgram()
		checkParserErrors(t, p)

		var actual string = program.String()

		if actual != tt.expected {
			t.Errorf("expected=%q, got=%q", tt.expected, actual)
		}
	}
}

func testBooleanLiteral(t *testing.T, exp ast.Expression, value bool) bool {
	boo, ok := exp.(*ast.Boolean)

	if !ok {
		t.Errorf("exp not *ast.Boolean. got=%T", exp)
		return false
	}

	if boo.Value != value {
		t.Errorf("boo.Value not %t. got=%t", value, boo.Value)
		return false
	}

	if boo.TokenLiteral() != fmt.Sprintf("%t", value) {
		t.Errorf("boo.TokenLiteral not %t. got=%s", value, boo.TokenLiteral())
		return false
	}

	return true
}

// If expression tests.

func TestIfExpression(t *testing.T) {
	input := "if (x < y) { x }"

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)
	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program.Statements does not contain %d statements. got=%d", 1, len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}

	exp, ok := stmt.Expression.(*ast.IfExpression)

	if !ok {
		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
	}

	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
		return
	}

	if len(exp.Consequence.Statements) != 1 {
		t.Errorf("consequence is not 1 statements. got=%d", len(exp.Consequence.Statements))
	}

	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.Consequence.Statements[0])
	}

	if !testIdentifier(t, consequence.Expression, "x") {
		return
	}

	if exp.Alternative != nil {
		t.Errorf("exp.Alternative.Statements was not nil. got=%+v", exp.Alternative)
	}
}

func TestIfElseExpression(t *testing.T) {
	input := "if (x < y) { x } else { y }"

	var l *lexer.Lexer = lexer.New(input)
	var p *Parser = New(l)
	var program *ast.Program = p.ParseProgram()
	checkParserErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program.Statements does not contain %d statements. got=%d", 1, len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}

	exp, ok := stmt.Expression.(*ast.IfExpression)

	if !ok {
		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
	}

	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
		return
	}

	if len(exp.Consequence.Statements) != 1 {
		t.Errorf("consequence is not 1 statements. got=%d", len(exp.Consequence.Statements))
	}

	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.Consequence.Statements[0])
	}

	if !testIdentifier(t, consequence.Expression, "x") {
		return
	}

	if len(exp.Alternative.Statements) != 1 {
		t.Errorf("consequence is not 1 statements. got=%d", len(exp.Alternative.Statements))
	}

	alternative, ok := exp.Alternative.Statements[0].(*ast.ExpressionStatement)

	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.Alternative.Statements[0])
	}

	if !testIdentifier(t, alternative.Expression, "y") {
		return
	}
}