golox/interpreter/interpreter_test.go

// FILE: interpreter_test.go
package interpreter

import (
	"bytes"
	"golox/ast"
	"golox/errors"
	"golox/token"
	"io"
	"os"
	"testing"
)

func TestInterpretLiteralExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42}

	result := i.VisitLiteralExpr(literal)
	if result != 42 {
		t.Errorf("expected 42, got %v", result)
	}
}

func TestInterpretGroupingExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42}
	grouping := &ast.GroupingExpr{Expression: literal}

	result := i.VisitGroupingExpr(grouping)
	if result != 42 {
		t.Errorf("expected 42, got %v", result)
	}
}

func TestInterpretUnaryExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42.0}
	unary := &ast.UnaryExpr{
		Operator: token.Token{Type: token.MINUS, Lexeme: "-"},
		Right:    literal,
	}

	result := i.VisitUnaryExpr(unary)
	if result != -42.0 {
		t.Errorf("expected -42, got %v", result)
	}
}

func TestInterpretUnaryExprBang(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: true}
	unary := &ast.UnaryExpr{
		Operator: token.Token{Type: token.BANG, Lexeme: "!"},
		Right:    literal,
	}

	result := i.VisitUnaryExpr(unary)
	if result != false {
		t.Errorf("expected false, got %v", result)
	}
}

func TestInterpretErrorExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	errorExpr := &ast.ErrorExpr{Value: "error"}

	defer func() {
		if r := recover(); r != "error" {
			t.Errorf("expected panic with 'error', got %v", r)
		}
	}()

	i.VisitErrorExpr(errorExpr)
}

func TestInterpretExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42.0}

	defer func() {
		if r := recover(); r != nil {
			t.Errorf("unexpected panic: %v", r)
		}
	}()

	result := i.InterpretExpr(literal)
	if result != "42" {
		t.Errorf("expected '42', got %v", result)
	}
}

func TestInterpretBinaryExpr(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.STAR, Lexeme: "*"},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != 84.0 {
		t.Errorf("expected 84, got %v", result)
	}
}

func TestInterpretBinaryExprDivisionByZero(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 0.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.SLASH, Lexeme: "/"},
		Right:    right,
	}

	defer func() {
		if r := recover(); r != "Division by zero [line 0]" {
			t.Errorf("expected panic with 'division by zero', got %v", r)
		}
	}()

	i.VisitBinaryExpr(binary)
}

func TestInterpretBinaryExprAddition(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.PLUS, Lexeme: "+"},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != 44.0 {
		t.Errorf("expected 44, got %v", result)
	}
}

func TestInterpretBinaryExprSubtraction(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.MINUS, Lexeme: "-"},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != 40.0 {
		t.Errorf("expected 40, got %v", result)
	}
}

func TestInterpretBinaryExprStringConcatenation(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: "foo"}
	right := &ast.LiteralExpr{Value: "bar"}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.PLUS, Lexeme: "+"},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != "foobar" {
		t.Errorf("expected 'foobar', got %v", result)
	}
}

func TestInterpretBinaryExprInvalidOperands(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: "foo"}
	right := &ast.LiteralExpr{Value: 42.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.PLUS, Lexeme: "+"},
		Right:    right,
	}

	defer func() {
		if r := recover(); r != "Operands must be two numbers or two strings [line 0]" {
			t.Errorf("expected panic with 'operands must be two numbers or two strings', got %v", r)
		}
	}()

	i.VisitBinaryExpr(binary)
}

func TestInterpretBinaryExprComparison(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.GREATER, Lexeme: ">"},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != true {
		t.Errorf("expected true, got %v", result)
	}
}

func TestInterpretBinaryExprComparisonEqual(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 42.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.EQUAL_EQUAL, Lexeme: "=="},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != true {
		t.Errorf("expected true, got %v", result)
	}
}

func TestInterpretBinaryExprComparisonNotEqual(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.BANG_EQUAL, Lexeme: "!="},
		Right:    right,
	}

	result := i.VisitBinaryExpr(binary)
	if result != true {
		t.Errorf("expected true, got %v", result)
	}
}

func TestInterpretBinaryExprComparisonInvalidOperands(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: "foo"}
	right := &ast.LiteralExpr{Value: 42.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.GREATER, Lexeme: ">"},
		Right:    right,
	}

	defer func() {
		if r := recover(); r != "Operands of operator '>' must be numbers [line 0]" {
			t.Errorf("expected panic with 'operands must be numbers', got %v", r)
		}
	}()

	i.VisitBinaryExpr(binary)
}

func TestInterpretBinaryExprInvalidOperatorType(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	left := &ast.LiteralExpr{Value: 42.0}
	right := &ast.LiteralExpr{Value: 2.0}
	binary := &ast.BinaryExpr{
		Left:     left,
		Operator: token.Token{Type: token.EOF, Lexeme: ""},
		Right:    right,
	}

	defer func() {
		if r := recover(); r != "Unknown binary operator '' [line 0]" {
			t.Errorf("expected panic with 'unknown operator type', got %v", r)
		}
	}()

	i.VisitBinaryExpr(binary)
}

func TestInterpretErrorStatement(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	errorStmt := &ast.ErrorStmt{Value: "error"}

	defer func() {
		if r := recover(); r != "error" {
			t.Errorf("expected panic with 'error', got %v", r)
		}
	}()

	i.VisitErrorStmt(errorStmt)
}

func TestInterpretExprStatement(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42.0}
	exprStmt := &ast.ExpressionStmt{Expression: literal}

	result := i.VisitExpressionStmt(exprStmt)
	if result != nil {
		t.Errorf("expected nil, got %v", result)
	}
}

func TestInterpretPrintStatement(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	i := New(errors.NewMockErrorLogger())
	literal := &ast.LiteralExpr{Value: 42.0}
	printStmt := &ast.PrintStmt{Expression: literal}

	result := i.VisitPrintStmt(printStmt)
	if result != nil {
		t.Errorf("expected nil, got %v", result)
	}

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := "42\n"
	if out != expected {
		t.Errorf("run() = %v; want %v", out, expected)
	}
}

func TestInterpretVarStatement(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	varStmt := &ast.VarStmt{
		Name:        token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
		Initializer: &ast.LiteralExpr{Value: 42.0},
	}

	i.VisitVarStmt(varStmt)
	result := i.env.get("foo")
	if result != 42.0 {
		t.Errorf("expected 42, got %v", result)
	}
}

func TestInterpretVarStatementNoInitializer(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	varStmt := &ast.VarStmt{
		Name: token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
	}

	i.VisitVarStmt(varStmt)
	result := i.env.get("foo")
	if result != nil {
		t.Errorf("expected nil, got %v", result)
	}
}

func TestInterpretAssignment(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	varStmt := &ast.VarStmt{
		Name: token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
	}

	i.VisitVarStmt(varStmt)
	result := i.env.get("foo")
	if result != nil {
		t.Errorf("expected nil, got %v", result)
	}

	assign := &ast.AssignExpr{
		Name:  token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
		Value: &ast.LiteralExpr{Value: 42.0},
	}

	i.VisitAssignExpr(assign)
	result = i.env.get("foo")
	if result != 42.0 {
		t.Errorf("expected 42, got %v", result)
	}
}

func TestInterpretAssignmentUndefinedVariable(t *testing.T) {
	i := New(errors.NewMockErrorLogger())
	assign := &ast.AssignExpr{
		Name:  token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
		Value: &ast.LiteralExpr{Value: 42.0},
	}

	defer func() {
		if r := recover(); r != "Undefined variable 'foo'." {
			t.Errorf("expected panic with 'undefined variable', got %v", r)
		}
	}()

	i.VisitAssignExpr(assign)
}

func TestInterpretBlockStatement(t *testing.T) {
	old := os.Stdout // keep backup of the real stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}
	os.Stdout = w

	outC := make(chan string)
	// copy the output in a separate goroutine so printing can't block indefinitely
	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		outC <- buf.String()
	}()

	// begin unit test
	i := New(errors.NewMockErrorLogger())
	block := &ast.BlockStmt{
		Statements: []ast.Stmt{
			&ast.VarStmt{
				Name:        token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
				Initializer: &ast.LiteralExpr{Value: 42.0},
			},
			&ast.PrintStmt{
				Expression: &ast.VariableExpr{
					Name: token.Token{Type: token.IDENTIFIER, Lexeme: "foo"},
				},
			},
		},
	}

	i.VisitBlockStmt(block)
	_, found := i.env.values["foo"]
	if found {
		t.Errorf("expected to not find 'foo' in environment")
	}
	// end unit test

	// back to normal state
	w.Close()
	os.Stdout = old // restoring the real stdout
	out := <-outC

	// reading our temp stdout
	expected := "42\n"
	if out != expected {
		t.Errorf("run() = %v; want %v", out, expected)
	}
}