//go:build windows

package update

import (
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"syscall"
)

// Apply downloads the new build into the user Downloads folder.
// It does NOT replace the running exe or spawn a self-updater (AV false-positive pattern).
func Apply(ctx context.Context, manifestURL string) (string, error) {
	st, err := Check(ctx, manifestURL)
	if err != nil {
		return "", err
	}
	if !st.Available {
		if st.Error != "" {
			return "", fmt.Errorf("%s", st.Error)
		}
		return "", fmt.Errorf("обновление не найдено")
	}
	if !allowedDownloadURL(st.URL) {
		return "", fmt.Errorf("URL обновления должен быть на git.evilfox.cc или files.de4ima.uk")
	}

	dir, err := downloadsDir()
	if err != nil {
		return "", err
	}
	_ = os.MkdirAll(dir, 0o755)
	dest := filepath.Join(dir, fmt.Sprintf("Navis-%s-windows-amd64.exe", sanitizeFileVer(st.Latest)))
	tmp := dest + ".part"
	_ = os.Remove(tmp)
	_ = os.Remove(dest)

	if err := downloadFile(ctx, st.URL, tmp); err != nil {
		return "", err
	}
	if st.SHA256 != "" {
		sum, err := fileSHA256(tmp)
		if err != nil {
			_ = os.Remove(tmp)
			return "", err
		}
		if !equalFoldHex(sum, st.SHA256) {
			_ = os.Remove(tmp)
			return "", fmt.Errorf("checksum mismatch")
		}
	}
	if err := os.Rename(tmp, dest); err != nil {
		_ = os.Remove(tmp)
		return "", err
	}

	_ = revealInExplorer(dest)
	return fmt.Sprintf("Скачано v%s:\n%s\nЗакройте Navis и запустите новый файл.", st.Latest, dest), nil
}

func downloadsDir() (string, error) {
	if u := os.Getenv("USERPROFILE"); u != "" {
		return filepath.Join(u, "Downloads"), nil
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(home, "Downloads"), nil
}

func revealInExplorer(path string) error {
	path, err := filepath.Abs(path)
	if err != nil {
		return err
	}
	cmd := exec.Command("explorer.exe", "/select,", path)
	const createNoWindow = 0x08000000
	cmd.SysProcAttr = &syscall.SysProcAttr{CreationFlags: createNoWindow}
	return cmd.Start()
}

func sanitizeFileVer(v string) string {
	out := make([]rune, 0, len(v))
	for _, r := range v {
		switch {
		case r >= '0' && r <= '9', r >= 'a' && r <= 'z', r >= 'A' && r <= 'Z', r == '.', r == '-':
			out = append(out, r)
		}
	}
	if len(out) == 0 {
		return "update"
	}
	return string(out)
}

func equalFoldHex(a, b string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := 0; i < len(a); i++ {
		ca, cb := a[i], b[i]
		if ca >= 'A' && ca <= 'F' {
			ca += 'a' - 'A'
		}
		if cb >= 'A' && cb <= 'F' {
			cb += 'a' - 'A'
		}
		if ca != cb {
			return false
		}
	}
	return true
}