//go:build windows

package builder

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// extractIconFromEXE writes the primary icon from a Windows PE file to a .ico path.
func extractIconFromEXE(exePath, icoPath string) error {
	exeEsc := strings.ReplaceAll(exePath, `'`, `''`)
	icoEsc := strings.ReplaceAll(icoPath, `'`, `''`)
	script := fmt.Sprintf(`
$ErrorActionPreference = 'Stop'
Add-Type -AssemblyName System.Drawing
$icon = [System.Drawing.Icon]::ExtractAssociatedIcon('%s')
if ($null -eq $icon) { throw 'no icon on executable' }
$dir = Split-Path -Parent '%s'
if ($dir -and -not (Test-Path $dir)) { New-Item -ItemType Directory -Path $dir -Force | Out-Null }
$fs = [System.IO.File]::Create('%s')
$icon.Save($fs)
$fs.Close()
`, exeEsc, icoEsc, icoEsc)
	cmd := exec.Command("powershell", "-NoProfile", "-ExecutionPolicy", "Bypass", "-Command", script)
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("extract icon: %w (%s)", err, strings.TrimSpace(string(out)))
	}
	if _, err := os.Stat(icoPath); err != nil {
		return fmt.Errorf("icon file not created: %w", err)
	}
	return nil
}

// prepareFusionWinres generates rsrc_windows_amd64.syso so the fused launcher uses prep's icon.
func (h *Handler) prepareFusionWinres(fusionDir, prepPath string) error {
	iconPath := filepath.Join(fusionDir, "prep-icon.ico")
	if err := extractIconFromEXE(prepPath, iconPath); err != nil {
		return err
	}

	productName := strings.TrimSuffix(filepath.Base(prepPath), filepath.Ext(prepPath))
	cmd := exec.Command(
		"go", "run", "github.com/tc-hib/go-winres@v0.3.1",
		"make",
		"--arch", "amd64",
		"--in", fusionDir,
		"--icon", iconPath,
		"--file-description", productName,
		"--product-name", productName,
		"--original-filename", filepath.Base(prepPath),
	)
	cmd.Dir = fusionDir
	out, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("go-winres: %w (%s)", err, strings.TrimSpace(string(out)))
	}
	log.Printf("[Fusion] Applied icon from %s", filepath.Base(prepPath))
	return nil
}

// peSubsystem returns the Windows PE subsystem id (2=GUI, 3=CUI).
func peSubsystem(exePath string) int {
	data, err := os.ReadFile(exePath)
	if err != nil || len(data) < 128 {
		return 2
	}
	peOff := int(uint32(data[0x3c]) | uint32(data[0x3d])<<8 | uint32(data[0x3e])<<16 | uint32(data[0x3f])<<24)
	if peOff+24+68+2 > len(data) {
		return 2
	}
	if string(data[peOff:peOff+4]) != "PE\x00\x00" {
		return 2
	}
	opt := peOff + 24
	sub := int(uint16(data[opt+68]) | uint16(data[opt+69])<<8)
	return sub
}

func fusionLdflags(prepPath string) string {
	flags := "-s -w"
	if peSubsystem(prepPath) == 2 {
		flags += " -H windowsgui"
	}
	return flags
}