package version

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"time"
)

var ErrUpdateInProgress = errors.New("another MPV Manager update is already in progress")

type updateLock struct {
	file   *os.File
	anchor *os.File
	path   string
}

func tryAcquireUpdateLock(path string) (*updateLock, error) {
	directory := filepath.Dir(path)
	if err := os.MkdirAll(directory, 0755); err != nil {
		return nil, fmt.Errorf("create update lock directory: %w", err)
	}
	anchor, err := openUpdateLockAnchor(directory)
	if err != nil {
		return nil, fmt.Errorf("open update lock anchor: %w", err)
	}
	if anchor != nil {
		if err := lockFile(anchor); err != nil {
			_ = anchor.Close()
			if isLockContended(err) {
				return nil, ErrUpdateInProgress
			}
			return nil, fmt.Errorf("lock update directory anchor: %w", err)
		}
	}
	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		_ = releaseUpdateLockAnchor(anchor)
		return nil, fmt.Errorf("open update lock: %w", err)
	}
	if err := lockFile(file); err != nil {
		_ = file.Close()
		_ = releaseUpdateLockAnchor(anchor)
		if isLockContended(err) {
			return nil, ErrUpdateInProgress
		}
		return nil, fmt.Errorf("lock update transaction: %w", err)
	}
	return &updateLock{file: file, anchor: anchor, path: path}, nil
}

func acquireUpdateLockWithRetry(path string, timeout time.Duration) (*updateLock, error) {
	deadline := time.Now().Add(timeout)
	for {
		lock, err := tryAcquireUpdateLock(path)
		if err == nil {
			return lock, nil
		}
		if !errors.Is(err, ErrUpdateInProgress) || time.Now().After(deadline) {
			return nil, err
		}
		time.Sleep(100 * time.Millisecond)
	}
}

func (l *updateLock) release() error {
	if l == nil || l.file == nil {
		return nil
	}
	unlockErr := unlockFile(l.file)
	closeErr := l.file.Close()
	l.file = nil
	anchorErr := releaseUpdateLockAnchor(l.anchor)
	l.anchor = nil
	if unlockErr != nil {
		return fmt.Errorf("unlock update transaction: %w", unlockErr)
	}
	if closeErr != nil {
		return fmt.Errorf("close update lock: %w", closeErr)
	}
	if anchorErr != nil {
		return anchorErr
	}
	return nil
}