package commands

import (
	"fmt"
	"strings"

	"c65gm/internal/compiler"
	"c65gm/internal/preproc"
	"c65gm/internal/utils"
)

// DefaultCommand handles DEFAULT statements within SWITCH
// Syntax: DEFAULT
type DefaultCommand struct {
}

func (c *DefaultCommand) WillHandle(line preproc.Line) bool {
	params, err := utils.ParseParams(line.Text)
	if err != nil || len(params) == 0 {
		return false
	}
	return strings.ToUpper(params[0]) == "DEFAULT"
}

func (c *DefaultCommand) Interpret(line preproc.Line, ctx *compiler.CompilerContext) error {
	params, err := utils.ParseParams(line.Text)
	if err != nil {
		return err
	}

	if len(params) != 1 {
		return fmt.Errorf("DEFAULT: expected 1 parameter (DEFAULT), got %d", len(params))
	}

	// Check if we're inside a SWITCH
	if ctx.SwitchStack.IsEmpty() {
		return fmt.Errorf("DEFAULT: not inside a SWITCH statement")
	}

	switchInfo, err := ctx.SwitchStack.Peek()
	if err != nil {
		return fmt.Errorf("DEFAULT: %w", err)
	}

	// Check if DEFAULT has already been seen
	if switchInfo.HasDefault {
		return fmt.Errorf("DEFAULT: multiple DEFAULT statements in same SWITCH")
	}

	return nil
}

func (c *DefaultCommand) Generate(ctx *compiler.CompilerContext) ([]string, error) {
	switchInfo, err := ctx.SwitchStack.Peek()
	if err != nil {
		return nil, fmt.Errorf("DEFAULT: %w", err)
	}

	var asm []string

	// If there was a previous CASE, emit implicit break and skip label
	if switchInfo.NeedsPendingCode {
		// Implicit break: jump to end of switch
		asm = append(asm, fmt.Sprintf("\tjmp %s", switchInfo.EndLabel))

		// Emit the pending skip label (where previous case jumps if not matched)
		asm = append(asm, switchInfo.PendingSkipLabel)
	}

	// Mark that we've seen DEFAULT
	switchInfo.HasDefault = true

	// DEFAULT doesn't need a skip label, so clear pending code
	switchInfo.NeedsPendingCode = false
	switchInfo.PendingSkipLabel = ""

	return asm, nil
}