package compiler_test

import (
	"testing"

	"git.sharkk.net/Sharkk/Mako/compiler"
	"git.sharkk.net/Sharkk/Mako/parser"
)

// Helper function to compile source code and return chunk
func compileSource(t *testing.T, source string) *compiler.Chunk {
	lexer := parser.NewLexer(source)
	p := parser.NewParser(lexer)
	program := p.ParseProgram()

	if p.HasErrors() {
		t.Fatalf("Parser errors: %v", p.ErrorStrings())
	}

	comp := compiler.NewCompiler()
	chunk, errors := comp.Compile(program)

	if len(errors) > 0 {
		t.Fatalf("Compiler errors: %v", errors)
	}

	return chunk
}

// Helper to check instruction at position
func checkInstruction(t *testing.T, chunk *compiler.Chunk, pos int, expected compiler.Opcode, operands ...uint16) {
	if pos >= len(chunk.Code) {
		t.Fatalf("Position %d out of bounds (code length: %d)", pos, len(chunk.Code))
	}

	op, actualOperands, _ := compiler.DecodeInstruction(chunk.Code, pos)

	if op != expected {
		t.Errorf("Expected opcode %v at position %d, got %v", expected, pos, op)
	}

	if len(actualOperands) != len(operands) {
		t.Errorf("Expected %d operands, got %d", len(operands), len(actualOperands))
		return
	}

	for i, expected := range operands {
		if actualOperands[i] != expected {
			t.Errorf("Expected operand %d to be %d, got %d", i, expected, actualOperands[i])
		}
	}
}

// Test literal compilation
func TestNumberLiteral(t *testing.T) {
	chunk := compileSource(t, "echo 42")

	// Should have one constant (42) and load it
	if len(chunk.Constants) != 1 {
		t.Fatalf("Expected 1 constant, got %d", len(chunk.Constants))
	}

	if chunk.Constants[0].Type != compiler.ValueNumber {
		t.Errorf("Expected number constant, got %v", chunk.Constants[0].Type)
	}

	if chunk.Constants[0].Data.(float64) != 42.0 {
		t.Errorf("Expected constant value 42, got %v", chunk.Constants[0].Data)
	}

	// Check bytecode: OpLoadConst 0, OpEcho, OpReturnNil
	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0)
	checkInstruction(t, chunk, 3, compiler.OpEcho)
	checkInstruction(t, chunk, 4, compiler.OpReturnNil)
}

func TestStringLiteral(t *testing.T) {
	chunk := compileSource(t, `echo "hello"`)

	if len(chunk.Constants) != 1 {
		t.Fatalf("Expected 1 constant, got %d", len(chunk.Constants))
	}

	if chunk.Constants[0].Type != compiler.ValueString {
		t.Errorf("Expected string constant, got %v", chunk.Constants[0].Type)
	}

	if chunk.Constants[0].Data.(string) != "hello" {
		t.Errorf("Expected constant value 'hello', got %v", chunk.Constants[0].Data)
	}

	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0)
}

func TestBooleanLiterals(t *testing.T) {
	chunk := compileSource(t, "echo true")

	if chunk.Constants[0].Type != compiler.ValueBool {
		t.Errorf("Expected bool constant, got %v", chunk.Constants[0].Type)
	}

	if chunk.Constants[0].Data.(bool) != true {
		t.Errorf("Expected true, got %v", chunk.Constants[0].Data)
	}
}

func TestNilLiteral(t *testing.T) {
	chunk := compileSource(t, "echo nil")

	if chunk.Constants[0].Type != compiler.ValueNil {
		t.Errorf("Expected nil constant, got %v", chunk.Constants[0].Type)
	}
}

// Test arithmetic operations
func TestArithmetic(t *testing.T) {
	tests := []struct {
		source   string
		expected compiler.Opcode
	}{
		{"echo 1 + 2", compiler.OpAdd},
		{"echo 5 - 3", compiler.OpSub},
		{"echo 4 * 6", compiler.OpMul},
		{"echo 8 / 2", compiler.OpDiv},
	}

	for _, test := range tests {
		chunk := compileSource(t, test.source)

		// Should have: LoadConst 0, LoadConst 1, OpArithmetic, OpEcho, OpReturnNil
		checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0)
		checkInstruction(t, chunk, 3, compiler.OpLoadConst, 1)
		checkInstruction(t, chunk, 6, test.expected)
		checkInstruction(t, chunk, 7, compiler.OpEcho)
	}
}

// Test comparison operations
func TestComparison(t *testing.T) {
	tests := []struct {
		source   string
		expected compiler.Opcode
	}{
		{"echo 1 == 2", compiler.OpEq},
		{"echo 1 != 2", compiler.OpNeq},
		{"echo 1 < 2", compiler.OpLt},
		{"echo 1 <= 2", compiler.OpLte},
		{"echo 1 > 2", compiler.OpGt},
		{"echo 1 >= 2", compiler.OpGte},
	}

	for _, test := range tests {
		chunk := compileSource(t, test.source)
		checkInstruction(t, chunk, 6, test.expected)
	}
}

// Test prefix operations
func TestPrefixOperations(t *testing.T) {
	tests := []struct {
		source   string
		expected compiler.Opcode
	}{
		{"echo -42", compiler.OpNeg},
		{"echo not true", compiler.OpNot},
	}

	for _, test := range tests {
		chunk := compileSource(t, test.source)
		checkInstruction(t, chunk, 3, test.expected)
	}
}

// Test variable assignment
func TestLocalAssignment(t *testing.T) {
	// Test local assignment within a function scope
	chunk := compileSource(t, `
		fn test()
			x: number = 42
		end
	`)

	// This tests function compilation which is not yet implemented
	// For now, just check that it doesn't crash
	if chunk == nil {
		t.Skip("Function compilation not yet implemented")
	}
}

func TestGlobalAssignment(t *testing.T) {
	chunk := compileSource(t, "x = 42")

	// Should have: LoadConst 0, StoreGlobal 1, OpReturnNil
	// Constants: [42, "x"]
	if len(chunk.Constants) != 2 {
		t.Fatalf("Expected 2 constants, got %d", len(chunk.Constants))
	}

	// Check that we have the number and variable name
	if chunk.Constants[0].Data.(float64) != 42.0 {
		t.Errorf("Expected first constant to be 42, got %v", chunk.Constants[0].Data)
	}
	if chunk.Constants[1].Data.(string) != "x" {
		t.Errorf("Expected second constant to be 'x', got %v", chunk.Constants[1].Data)
	}

	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0)   // Load 42
	checkInstruction(t, chunk, 3, compiler.OpStoreGlobal, 1) // Store to "x"
}

// Test echo statement
func TestEchoStatement(t *testing.T) {
	chunk := compileSource(t, "echo 42")

	// Should have: LoadConst 0, OpEcho, OpReturnNil
	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0)
	checkInstruction(t, chunk, 3, compiler.OpEcho)
	checkInstruction(t, chunk, 4, compiler.OpReturnNil)
}

// Test if statement
func TestIfStatement(t *testing.T) {
	chunk := compileSource(t, `
		if true then
			echo 1
		end
	`)

	// Should start with: LoadConst, JumpIfFalse (with offset), Pop
	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0) // Load true

	// JumpIfFalse has 1 operand (the jump offset), but we don't need to check the exact value
	op, operands, _ := compiler.DecodeInstruction(chunk.Code, 3)
	if op != compiler.OpJumpIfFalse {
		t.Errorf("Expected OpJumpIfFalse at position 3, got %v", op)
	}
	if len(operands) != 1 {
		t.Errorf("Expected 1 operand for JumpIfFalse, got %d", len(operands))
	}

	checkInstruction(t, chunk, 6, compiler.OpPop) // Pop condition
}

// Test while loop
func TestWhileLoop(t *testing.T) {
	chunk := compileSource(t, `
		while true do
			break
		end
	`)

	// Should have condition evaluation and loop structure
	checkInstruction(t, chunk, 0, compiler.OpLoadConst, 0) // Load true

	// JumpIfFalse has 1 operand (the jump offset)
	op, operands, _ := compiler.DecodeInstruction(chunk.Code, 3)
	if op != compiler.OpJumpIfFalse {
		t.Errorf("Expected OpJumpIfFalse at position 3, got %v", op)
	}
	if len(operands) != 1 {
		t.Errorf("Expected 1 operand for JumpIfFalse, got %d", len(operands))
	}
}

// Test table creation
func TestTableLiteral(t *testing.T) {
	chunk := compileSource(t, "echo {1, 2, 3}")

	// Should start with OpNewTable
	checkInstruction(t, chunk, 0, compiler.OpNewTable)
}

// Test table with key-value pairs
func TestTableWithKeys(t *testing.T) {
	chunk := compileSource(t, `echo {x = 1, y = 2}`)

	checkInstruction(t, chunk, 0, compiler.OpNewTable)
	// Should have subsequent operations to set fields
}

// Test function call
func TestFunctionCall(t *testing.T) {
	chunk := compileSource(t, "print(42)")

	// Should have: LoadGlobal "print", LoadConst 42, Call 1
	// The exact positions depend on constant ordering
	found := false
	for i := 0; i < len(chunk.Code)-2; i++ {
		op, operands, _ := compiler.DecodeInstruction(chunk.Code, i)
		if op == compiler.OpCall && len(operands) > 0 && operands[0] == 1 {
			found = true
			break
		}
	}
	if !found {
		t.Error("Expected OpCall with 1 argument")
	}
}

// Test constant deduplication
func TestConstantDeduplication(t *testing.T) {
	chunk := compileSource(t, "echo 42\necho 42\necho 42")

	// Should only have one constant despite multiple uses
	if len(chunk.Constants) != 1 {
		t.Errorf("Expected 1 constant (deduplicated), got %d", len(chunk.Constants))
	}
}

// Test short-circuit evaluation
func TestShortCircuitAnd(t *testing.T) {
	chunk := compileSource(t, "echo true and false")

	// Should have conditional jumping for short-circuit
	found := false
	for i := 0; i < len(chunk.Code); i++ {
		op, _, _ := compiler.DecodeInstruction(chunk.Code, i)
		if op == compiler.OpJumpIfFalse {
			found = true
			break
		}
	}
	if !found {
		t.Error("Expected JumpIfFalse for short-circuit and")
	}
}

func TestShortCircuitOr(t *testing.T) {
	chunk := compileSource(t, "echo false or true")

	// Should have conditional jumping for short-circuit
	foundFalseJump := false
	foundJump := false
	for i := 0; i < len(chunk.Code); i++ {
		op, _, _ := compiler.DecodeInstruction(chunk.Code, i)
		if op == compiler.OpJumpIfFalse {
			foundFalseJump = true
		}
		if op == compiler.OpJump {
			foundJump = true
		}
	}
	if !foundFalseJump || !foundJump {
		t.Error("Expected JumpIfFalse and Jump for short-circuit or")
	}
}

// Test complex expressions
func TestComplexExpression(t *testing.T) {
	chunk := compileSource(t, "echo 1 + 2 * 3")

	// Should follow correct precedence: Load 1, Load 2, Load 3, Mul, Add
	if len(chunk.Constants) != 3 {
		t.Fatalf("Expected 3 constants, got %d", len(chunk.Constants))
	}

	// Verify constants
	expected := []float64{1, 2, 3}
	for i, exp := range expected {
		if chunk.Constants[i].Data.(float64) != exp {
			t.Errorf("Expected constant %d to be %v, got %v", i, exp, chunk.Constants[i].Data)
		}
	}
}