package connectors

import (
	"context"
	"encoding/base64"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/google/go-github/v58/github"
	"github.com/yourusername/markedit/internal/database"
	"github.com/yourusername/markedit/internal/markdown"
	"golang.org/x/oauth2"
	"golang.org/x/sync/singleflight"
)

// fileTreeCache is an in-memory LRU cache for file tree data
type fileTreeCache struct {
	mu      sync.RWMutex
	entries map[string]*cacheEntry
	maxSize int
	ttl     time.Duration
	sfGroup singleflight.Group // Request deduplication
}

type cacheEntry struct {
	data      *FileNode
	expiresAt time.Time
	etag      string // For future ETag support
	fetchedAt time.Time
}

var globalCache = &fileTreeCache{
	entries: make(map[string]*cacheEntry),
	maxSize: 100, // Configurable via env
	ttl:     5 * time.Minute,
}

func init() {
	// Configure cache from environment
	if ttlStr := os.Getenv("FILE_TREE_CACHE_TTL"); ttlStr != "" {
		if ttl, err := time.ParseDuration(ttlStr); err == nil {
			globalCache.ttl = ttl
		}
	}

	if sizeStr := os.Getenv("FILE_TREE_CACHE_SIZE"); sizeStr != "" {
		if size, err := strconv.Atoi(sizeStr); err == nil {
			globalCache.maxSize = size
		}
	}
}

// Get retrieves from cache if not expired
func (c *fileTreeCache) Get(key string) (*FileNode, bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()

	entry, exists := c.entries[key]
	if !exists || time.Now().After(entry.expiresAt) {
		return nil, false
	}
	return entry.data, true
}

// Set stores in cache with TTL
func (c *fileTreeCache) Set(key string, data *FileNode) {
	c.mu.Lock()
	defer c.mu.Unlock()

	// LRU eviction if at capacity
	if len(c.entries) >= c.maxSize {
		c.evictOldest()
	}

	c.entries[key] = &cacheEntry{
		data:      data,
		expiresAt: time.Now().Add(c.ttl),
		fetchedAt: time.Now(),
	}
}

// Invalidate removes specific cache entry
func (c *fileTreeCache) Invalidate(key string) {
	c.mu.Lock()
	defer c.mu.Unlock()
	delete(c.entries, key)
}

// InvalidatePattern removes all matching keys (e.g., "owner/repo/*")
func (c *fileTreeCache) InvalidatePattern(pattern string) int {
	c.mu.Lock()
	defer c.mu.Unlock()

	count := 0
	for key := range c.entries {
		if matchesPattern(key, pattern) {
			delete(c.entries, key)
			count++
		}
	}
	return count
}

// evictOldest removes the oldest entry (LRU)
func (c *fileTreeCache) evictOldest() {
	var oldestKey string
	var oldestTime time.Time

	for key, entry := range c.entries {
		if oldestKey == "" || entry.fetchedAt.Before(oldestTime) {
			oldestKey = key
			oldestTime = entry.fetchedAt
		}
	}

	if oldestKey != "" {
		delete(c.entries, oldestKey)
	}
}

// generateCacheKey creates consistent cache key
func generateCacheKey(owner, repo, branch, path string, extensions []string) string {
	extStr := strings.Join(extensions, ",")
	return fmt.Sprintf("%s/%s/%s/%s/%s", owner, repo, branch, path, extStr)
}

// matchesPattern checks if key matches pattern (simple glob)
func matchesPattern(key, pattern string) bool {
	// Simple implementation: pattern can end with /* for prefix match
	if strings.HasSuffix(pattern, "/*") {
		prefix := strings.TrimSuffix(pattern, "/*")
		return strings.HasPrefix(key, prefix)
	}
	return key == pattern
}

// GitHubConnector implements the Connector interface for GitHub
type GitHubConnector struct {
	client *github.Client
	db     *database.DB // For logging
	userID *int         // For logging
}

// NewGitHubConnector creates a new GitHub connector with an access token
func NewGitHubConnector(accessToken string, db *database.DB, userID *int) *GitHubConnector {
	ctx := context.Background()
	ts := oauth2.StaticTokenSource(
		&oauth2.Token{AccessToken: accessToken},
	)
	tc := oauth2.NewClient(ctx, ts)
	client := github.NewClient(tc)

	return &GitHubConnector{
		client: client,
		db:     db,
		userID: userID,
	}
}

// GetType returns the connector type
func (g *GitHubConnector) GetType() string {
	return "github"
}

// logCacheEvent logs cache events to the database
func (g *GitHubConnector) logCacheEvent(cacheKey, eventType string, responseTimeMs int) {
	if g.db != nil {
		_ = g.db.LogCacheEvent(cacheKey, "file_tree", eventType, g.userID, responseTimeMs)
	}
}

// ListRepositories lists all repositories for the authenticated user
func (g *GitHubConnector) ListRepositories(ctx context.Context, sortBy string) ([]Repository, error) {
	// Map sort parameter
	sort := "updated"
	switch sortBy {
	case "created":
		sort = "created"
	case "name":
		sort = "full_name"
	default:
		sort = "updated"
	}

	opts := &github.RepositoryListOptions{
		Sort:        sort,
		Direction:   "desc",
		Affiliation: "owner,collaborator,organization_member", // Include all repos user has access to
		ListOptions: github.ListOptions{
			PerPage: 100,
		},
	}

	var allRepos []Repository

	for {
		repos, resp, err := g.client.Repositories.List(ctx, "", opts)
		if err != nil {
			return nil, fmt.Errorf("failed to list repositories (status: %v): %w", resp.StatusCode, err)
		}

		for _, repo := range repos {
			allRepos = append(allRepos, Repository{
				ID:            repo.GetID(),
				FullName:      repo.GetFullName(),
				Name:          repo.GetName(),
				Owner:         repo.GetOwner().GetLogin(),
				Private:       repo.GetPrivate(),
				DefaultBranch: repo.GetDefaultBranch(),
				UpdatedAt:     repo.GetUpdatedAt().Time,
			})
		}

		if resp.NextPage == 0 {
			break
		}
		opts.Page = resp.NextPage
	}

	return allRepos, nil
}

// ListFiles lists files in a repository path using GitHub Tree API with caching
func (g *GitHubConnector) ListFiles(ctx context.Context, owner, repo, path, branch string, extensions []string) (*FileNode, error) {
	// Resolve default branch first to ensure consistent cache keys
	if branch == "" {
		repository, _, err := g.client.Repositories.Get(ctx, owner, repo)
		if err != nil {
			return nil, fmt.Errorf("failed to get repository: %w", err)
		}
		branch = repository.GetDefaultBranch()
	}

	cacheKey := generateCacheKey(owner, repo, branch, path, extensions)

	// Try cache first
	if cached, found := globalCache.Get(cacheKey); found {
		g.logCacheEvent(cacheKey, "hit", 0)
		return cached, nil
	}

	// Use singleflight to deduplicate concurrent requests
	result, err, _ := globalCache.sfGroup.Do(cacheKey, func() (interface{}, error) {
		startTime := time.Now()

		// Fetch from GitHub Tree API
		data, err := g.fetchTreeFromGitHub(ctx, owner, repo, branch, path, extensions)
		if err != nil {
			return nil, err
		}

		responseTime := int(time.Since(startTime).Milliseconds())

		// Store in cache
		globalCache.Set(cacheKey, data)
		g.logCacheEvent(cacheKey, "miss", responseTime)

		return data, nil
	})

	if err != nil {
		return nil, err
	}
	return result.(*FileNode), nil
}

// fetchTreeFromGitHub fetches file tree from GitHub using Tree API
func (g *GitHubConnector) fetchTreeFromGitHub(ctx context.Context, owner, repo, branch, path string, extensions []string) (*FileNode, error) {
	// Step 1: Get branch to get commit SHA
	branchRef, _, err := g.client.Repositories.GetBranch(ctx, owner, repo, branch, 0)
	if err != nil {
		return nil, fmt.Errorf("failed to get branch: %w", err)
	}
	commitSHA := branchRef.GetCommit().GetSHA()

	// Step 2: Fetch tree recursively (single API call)
	tree, _, err := g.client.Git.GetTree(ctx, owner, repo, commitSHA, true)
	if err != nil {
		return nil, fmt.Errorf("failed to get tree: %w", err)
	}

	// Check for truncated response
	if tree.Truncated != nil && *tree.Truncated {
		return nil, fmt.Errorf("repository tree is truncated (>100k entries) - repository too large")
	}

	// Step 3: Filter tree entries by path and extensions
	var filteredEntries []*github.TreeEntry
	for _, entry := range tree.Entries {
		// Skip if not in requested path
		if path != "" && !strings.HasPrefix(*entry.Path, path) {
			continue
		}

		// Filter by extensions (only for blobs/files)
		if len(extensions) > 0 && *entry.Type == "blob" {
			if !matchesExtensions(*entry.Path, extensions) {
				continue
			}
		}

		filteredEntries = append(filteredEntries, entry)
	}

	// Step 4: Build hierarchical FileNode tree from flat structure
	root := buildFileTree(filteredEntries, path, extensions, repo)

	return root, nil
}

// matchesExtensions checks if file matches extension filter
func matchesExtensions(filename string, extensions []string) bool {
	if len(extensions) == 0 {
		return true
	}

	ext := strings.TrimPrefix(filepath.Ext(filename), ".")
	for _, e := range extensions {
		if strings.EqualFold(ext, e) {
			return true
		}
	}
	return false
}

// buildFileTree converts flat GitHub tree entries to hierarchical FileNode structure
func buildFileTree(entries []*github.TreeEntry, rootPath string, extensions []string, repoName string) *FileNode {
	root := &FileNode{
		Name:     repoName,
		Path:     rootPath,
		Type:     "directory",
		IsDir:    true,
		Children: []*FileNode{},
	}

	if rootPath != "" {
		root.Name = filepath.Base(rootPath)
	}

	// Group entries by their first path component
	pathGroups := make(map[string][]*github.TreeEntry)

	for _, entry := range entries {
		relativePath := *entry.Path
		if rootPath != "" {
			relativePath = strings.TrimPrefix(relativePath, rootPath)
			relativePath = strings.TrimPrefix(relativePath, "/")
		}

		if relativePath == "" {
			continue
		}

		// Get first component
		parts := strings.SplitN(relativePath, "/", 2)
		firstComponent := parts[0]

		pathGroups[firstComponent] = append(pathGroups[firstComponent], entry)
	}

	// Build tree recursively
	for name, groupEntries := range pathGroups {
		// Check if this is a file or directory
		isFile := len(groupEntries) == 1 && *groupEntries[0].Type == "blob" && !strings.Contains(strings.TrimPrefix(*groupEntries[0].Path, rootPath+"/"), "/")

		if isFile {
			// It's a file
			filePath := *groupEntries[0].Path
			root.Children = append(root.Children, &FileNode{
				Name:  name,
				Path:  filePath,
				Type:  "file",
				IsDir: false,
				SHA:   *groupEntries[0].SHA,
				Size:  int64(*groupEntries[0].Size),
			})
		} else {
			// It's a directory - collect all direct children
			dirNode := &FileNode{
				Name:     name,
				Path:     filepath.Join(rootPath, name),
				Type:     "directory",
				IsDir:    true,
				Children: []*FileNode{},
			}

			// Get direct children of this directory
			directChildren := make(map[string][]*github.TreeEntry)
			dirPrefix := dirNode.Path + "/"

			for _, entry := range groupEntries {
				relativeToDir := strings.TrimPrefix(*entry.Path, dirPrefix)
				parts := strings.SplitN(relativeToDir, "/", 2)
				directChildren[parts[0]] = append(directChildren[parts[0]], entry)
			}

			// Recursively build subtree
			subTree := buildFileTree(groupEntries, dirNode.Path, extensions, name)
			dirNode.Children = subTree.Children

			// Only add directory if it has children (matching files)
			if len(dirNode.Children) > 0 {
				root.Children = append(root.Children, dirNode)
			}
		}
	}

	// Sort: directories first, then alphabetically
	sort.Slice(root.Children, func(i, j int) bool {
		if root.Children[i].IsDir != root.Children[j].IsDir {
			return root.Children[i].IsDir
		}
		return root.Children[i].Name < root.Children[j].Name
	})

	return root
}

// GetFileContent retrieves the content of a file
func (g *GitHubConnector) GetFileContent(ctx context.Context, owner, repo, path, branch string) (*FileContent, error) {
	if branch == "" {
		// Get default branch
		repository, _, err := g.client.Repositories.Get(ctx, owner, repo)
		if err != nil {
			return nil, fmt.Errorf("failed to get repository: %w", err)
		}
		branch = repository.GetDefaultBranch()
	}

	opts := &github.RepositoryContentGetOptions{
		Ref: branch,
	}

	fileContent, _, _, err := g.client.Repositories.GetContents(ctx, owner, repo, path, opts)
	if err != nil {
		return nil, fmt.Errorf("failed to get file content: %w", err)
	}

	if fileContent == nil {
		return nil, fmt.Errorf("file not found")
	}

	content, err := fileContent.GetContent()
	if err != nil {
		return nil, fmt.Errorf("failed to decode content: %w", err)
	}

	// Parse markdown with frontmatter
	parsed, err := markdown.Parse(content)
	if err != nil {
		return nil, fmt.Errorf("failed to parse markdown: %w", err)
	}

	return &FileContent{
		Content:     parsed.Content,
		Frontmatter: parsed.Frontmatter,
		Path:        path,
		SHA:         fileContent.GetSHA(),
		Branch:      branch,
	}, nil
}

// InvalidateCacheForRepo invalidates all cache entries for a repository
func InvalidateCacheForRepo(owner, repo string) int {
	pattern := fmt.Sprintf("%s/%s/*", owner, repo)
	return globalCache.InvalidatePattern(pattern)
}

// CreateFile creates a new file in the repository
func (g *GitHubConnector) CreateFile(ctx context.Context, owner, repo, path, content, message string) error {
	if message == "" {
		message = fmt.Sprintf("Create %s", path)
	}

	// Get default branch
	repository, _, err := g.client.Repositories.Get(ctx, owner, repo)
	if err != nil {
		return fmt.Errorf("failed to get repository: %w", err)
	}
	branch := repository.GetDefaultBranch()

	// Encode content to base64
	encodedContent := github.String(base64.StdEncoding.EncodeToString([]byte(content)))

	// Create file options
	opts := &github.RepositoryContentFileOptions{
		Message: github.String(message),
		Content: []byte(*encodedContent),
		Branch:  github.String(branch),
	}

	// Create the file
	_, _, err = g.client.Repositories.CreateFile(ctx, owner, repo, path, opts)
	if err != nil {
		return fmt.Errorf("failed to create file: %w", err)
	}

	return nil
}

// RenameItem renames a file or folder by deleting the old path and creating at the new path
func (g *GitHubConnector) RenameItem(ctx context.Context, owner, repo, oldPath, newPath, message string) error {
	if message == "" {
		message = fmt.Sprintf("Rename %s to %s", oldPath, newPath)
	}

	// Get default branch
	repository, _, err := g.client.Repositories.Get(ctx, owner, repo)
	if err != nil {
		return fmt.Errorf("failed to get repository: %w", err)
	}
	branch := repository.GetDefaultBranch()

	// Get the content of the old file/path
	fileContent, _, _, err := g.client.Repositories.GetContents(ctx, owner, repo, oldPath, &github.RepositoryContentGetOptions{
		Ref: branch,
	})
	if err != nil {
		return fmt.Errorf("failed to get file content: %w", err)
	}

	// If it's a directory, we need to handle all files in it
	if fileContent == nil {
		// It's a directory - get all files in it
		_, directoryContent, _, err := g.client.Repositories.GetContents(ctx, owner, repo, oldPath, &github.RepositoryContentGetOptions{
			Ref: branch,
		})
		if err != nil {
			return fmt.Errorf("failed to get directory contents: %w", err)
		}

		// Rename each file in the directory
		for _, item := range directoryContent {
			if item.GetType() == "file" {
				oldFilePath := item.GetPath()
				newFilePath := strings.Replace(oldFilePath, oldPath, newPath, 1)

				// Get file content
				content, err := item.GetContent()
				if err != nil {
					return fmt.Errorf("failed to get content for %s: %w", oldFilePath, err)
				}

				// Create new file
				encodedContent := base64.StdEncoding.EncodeToString([]byte(content))
				opts := &github.RepositoryContentFileOptions{
					Message: github.String(message),
					Content: []byte(encodedContent),
					Branch:  github.String(branch),
				}
				_, _, err = g.client.Repositories.CreateFile(ctx, owner, repo, newFilePath, opts)
				if err != nil {
					return fmt.Errorf("failed to create file %s: %w", newFilePath, err)
				}

				// Delete old file
				deleteOpts := &github.RepositoryContentFileOptions{
					Message: github.String(message),
					SHA:     github.String(item.GetSHA()),
					Branch:  github.String(branch),
				}
				_, _, err = g.client.Repositories.DeleteFile(ctx, owner, repo, oldFilePath, deleteOpts)
				if err != nil {
					return fmt.Errorf("failed to delete file %s: %w", oldFilePath, err)
				}
			}
		}
	} else {
		// It's a single file
		content, err := fileContent.GetContent()
		if err != nil {
			return fmt.Errorf("failed to get file content: %w", err)
		}

		// Create new file at new path
		encodedContent := base64.StdEncoding.EncodeToString([]byte(content))
		opts := &github.RepositoryContentFileOptions{
			Message: github.String(message),
			Content: []byte(encodedContent),
			Branch:  github.String(branch),
		}
		_, _, err = g.client.Repositories.CreateFile(ctx, owner, repo, newPath, opts)
		if err != nil {
			return fmt.Errorf("failed to create file at new path: %w", err)
		}

		// Delete old file
		deleteOpts := &github.RepositoryContentFileOptions{
			Message: github.String(message),
			SHA:     github.String(fileContent.GetSHA()),
			Branch:  github.String(branch),
		}
		_, _, err = g.client.Repositories.DeleteFile(ctx, owner, repo, oldPath, deleteOpts)
		if err != nil {
			return fmt.Errorf("failed to delete old file: %w", err)
		}
	}

	return nil
}