package sync

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sync"
	"time"

	"gitm/internal/database"
	"gitm/internal/gitea"
	"gitm/internal/models"
)

type Engine struct {
	maxConcurrent int
	mu            sync.Mutex
	activeTasks   map[int64]string
}

func NewEngine(maxConcurrent int) *Engine {
	return &Engine{
		maxConcurrent: maxConcurrent,
		activeTasks:   make(map[int64]string),
	}
}

func (e *Engine) SyncServer(serverID int64) error {
	e.mu.Lock()
	if _, active := e.activeTasks[serverID]; active {
		e.mu.Unlock()
		return fmt.Errorf("sync already in progress for server %d", serverID)
	}
	taskID := fmt.Sprintf("%d-%d", serverID, time.Now().Unix())
	e.activeTasks[serverID] = taskID
	e.mu.Unlock()

	defer func() {
		e.mu.Lock()
		delete(e.activeTasks, serverID)
		e.mu.Unlock()
	}()

	server, err := database.GetServer(serverID)
	if err != nil || server == nil {
		return fmt.Errorf("failed to get server: %w", err)
	}

	syncLog := &models.SyncLog{
		ServerID:  serverID,
		Status:    "in_progress",
		Message:   "Starting sync",
		StartedAt: time.Now(),
	}
	if err := database.CreateSyncLog(syncLog); err != nil {
		return fmt.Errorf("failed to create sync log: %w", err)
	}

	client, err := gitea.NewClient(server.URL, server.Token)
	if err != nil {
		e.finishLog(syncLog, "failed", fmt.Sprintf("Failed to create client: %v", err))
		return err
	}

	if _, err := client.ValidateToken(); err != nil {
		e.finishLog(syncLog, "failed", fmt.Sprintf("Authentication failed: %v", err))
		return err
	}

	giteaRepos, err := client.GetAllRepos()
	if err != nil {
		e.finishLog(syncLog, "failed", fmt.Sprintf("Failed to fetch repos: %v", err))
		return err
	}

	reposDir, _ := database.GetSetting("repos_dir")
	if reposDir == "" {
		reposDir = "./data/repos"
	}
	serverDir := filepath.Join(reposDir, fmt.Sprintf("server_%d_%s", serverID, server.Name))
	os.MkdirAll(serverDir, 0755)

	successCount := 0
	failedCount := 0
	sem := make(chan struct{}, e.maxConcurrent)
	var wg sync.WaitGroup
	var resultsMu sync.Mutex

	for _, gr := range giteaRepos {
		wg.Add(1)
		go func(giteaRepo gitea.GiteaRepo) {
			defer wg.Done()
			sem <- struct{}{}
			defer func() { <-sem }()

			localPath := filepath.Join(serverDir, giteaRepo.FullName+".git")
			existingRepo, _ := database.GetRepoByFullName(serverID, giteaRepo.FullName)

			var err error
			if existingRepo == nil {
				err = e.cloneMirror(giteaRepo.CloneURL, localPath)
				if err == nil {
					repo := &models.Repo{
						ServerID:   serverID,
						Name:       giteaRepo.Name,
						FullName:   giteaRepo.FullName,
						CloneURL:   giteaRepo.CloneURL,
						LocalPath:  localPath,
						SyncStatus: "success",
					}
					database.CreateRepo(repo)
				}
			} else {
				err = e.fetchMirror(localPath)
				if err == nil {
					database.UpdateRepoSyncStatus(existingRepo.ID, "success")
				}
			}

			resultsMu.Lock()
			if err != nil {
				failedCount++
				failLog := &models.SyncLog{
					ServerID:  serverID,
					RepoID:    getRepoID(serverID, giteaRepo.FullName),
					Status:    "failed",
					Message:   err.Error(),
					StartedAt: time.Now(),
				}
				database.CreateSyncLog(failLog)
			} else {
				successCount++
			}
			resultsMu.Unlock()
		}(gr)
	}

	wg.Wait()
	database.UpdateServerLastSync(serverID)

	message := fmt.Sprintf("Sync completed: %d succeeded, %d failed", successCount, failedCount)
	e.finishLog(syncLog, "success", message)
	return nil
}

func (e *Engine) cloneMirror(url, path string) error {
	if _, err := os.Stat(path); err == nil {
		return nil
	}
	os.MkdirAll(filepath.Dir(path), 0755)
	cmd := exec.Command("git", "clone", "--mirror", url, path)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("clone failed: %w - %s", err, string(output))
	}
	return nil
}

func (e *Engine) fetchMirror(path string) error {
	cmd := exec.Command("git", "--git-dir", path, "fetch", "--all", "--prune")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("fetch failed: %w - %s", err, string(output))
	}
	return nil
}

func (e *Engine) finishLog(log *models.SyncLog, status, message string) {
	now := time.Now()
	log.Status = status
	log.Message = message
	log.FinishedAt = &now
	database.UpdateSyncLog(log.ID, status, message, log.FinishedAt)
}

func (e *Engine) IsSyncing(serverID int64) bool {
	e.mu.Lock()
	defer e.mu.Unlock()
	_, active := e.activeTasks[serverID]
	return active
}

func getRepoID(serverID int64, fullName string) *int64 {
	repo, _ := database.GetRepoByFullName(serverID, fullName)
	if repo != nil {
		return &repo.ID
	}
	return nil
}