package forum

import (
	"dk/internal/store"
	"fmt"
	"sort"
	"strings"
	"sync"
	"time"
)

// Forum represents a forum post or thread in the game
type Forum struct {
	ID       int    `json:"id"`
	Posted   int64  `json:"posted"`
	LastPost int64  `json:"last_post"`
	Author   int    `json:"author"`
	Parent   int    `json:"parent"`
	Replies  int    `json:"replies"`
	Title    string `json:"title"`
	Content  string `json:"content"`
}

func (f *Forum) Save() error {
	forumStore := GetStore()
	forumStore.UpdateForum(f)
	return nil
}

func (f *Forum) Delete() error {
	forumStore := GetStore()
	forumStore.RemoveForum(f.ID)
	return nil
}

// Creates a new Forum with sensible defaults
func New() *Forum {
	now := time.Now().Unix()
	return &Forum{
		Posted:   now,
		LastPost: now,
		Author:   0,
		Parent:   0, // Default to thread (not reply)
		Replies:  0,
		Title:    "",
		Content:  "",
	}
}

// Validate checks if forum has valid values
func (f *Forum) Validate() error {
	if strings.TrimSpace(f.Title) == "" {
		return fmt.Errorf("forum title cannot be empty")
	}
	if strings.TrimSpace(f.Content) == "" {
		return fmt.Errorf("forum content cannot be empty")
	}
	if f.Posted <= 0 {
		return fmt.Errorf("forum Posted timestamp must be positive")
	}
	if f.LastPost <= 0 {
		return fmt.Errorf("forum LastPost timestamp must be positive")
	}
	if f.Parent < 0 {
		return fmt.Errorf("forum Parent cannot be negative")
	}
	if f.Replies < 0 {
		return fmt.Errorf("forum Replies cannot be negative")
	}
	return nil
}

// ForumStore provides in-memory storage with O(1) lookups and forum-specific indices
type ForumStore struct {
	*store.BaseStore[Forum]               // Embedded generic store
	byParent                map[int][]int // Parent -> []ID
	byAuthor                map[int][]int // Author -> []ID
	threadsOnly             []int         // Parent=0 IDs sorted by last_post DESC, id DESC
	allByLastPost           []int         // All IDs sorted by last_post DESC, id DESC
	mu                      sync.RWMutex  // Protects indices
}

// Global in-memory store
var forumStore *ForumStore
var storeOnce sync.Once

// Initialize the in-memory store
func initStore() {
	forumStore = &ForumStore{
		BaseStore:     store.NewBaseStore[Forum](),
		byParent:      make(map[int][]int),
		byAuthor:      make(map[int][]int),
		threadsOnly:   make([]int, 0),
		allByLastPost: make([]int, 0),
	}
}

// GetStore returns the global forum store
func GetStore() *ForumStore {
	storeOnce.Do(initStore)
	return forumStore
}

// AddForum adds a forum post to the in-memory store and updates all indices
func (fs *ForumStore) AddForum(forum *Forum) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	// Validate forum
	if err := forum.Validate(); err != nil {
		return
	}

	// Add to base store
	fs.Add(forum.ID, forum)

	// Rebuild indices
	fs.rebuildIndicesUnsafe()
}

// RemoveForum removes a forum post from the store and updates indices
func (fs *ForumStore) RemoveForum(id int) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	// Remove from base store
	fs.Remove(id)

	// Rebuild indices
	fs.rebuildIndicesUnsafe()
}

// UpdateForum updates a forum post efficiently
func (fs *ForumStore) UpdateForum(forum *Forum) {
	fs.mu.Lock()
	defer fs.mu.Unlock()

	// Validate forum
	if err := forum.Validate(); err != nil {
		return
	}

	// Update base store
	fs.Add(forum.ID, forum)

	// Rebuild indices
	fs.rebuildIndicesUnsafe()
}

// LoadData loads forum data from JSON file, or starts with empty store
func LoadData(dataPath string) error {
	fs := GetStore()

	// Load from base store, which handles JSON loading
	if err := fs.BaseStore.LoadData(dataPath); err != nil {
		return err
	}

	// Rebuild indices from loaded data
	fs.rebuildIndices()
	return nil
}

// SaveData saves forum data to JSON file
func SaveData(dataPath string) error {
	fs := GetStore()
	return fs.BaseStore.SaveData(dataPath)
}

// rebuildIndicesUnsafe rebuilds all indices from base store data (caller must hold lock)
func (fs *ForumStore) rebuildIndicesUnsafe() {
	// Clear indices
	fs.byParent = make(map[int][]int)
	fs.byAuthor = make(map[int][]int)
	fs.threadsOnly = make([]int, 0)
	fs.allByLastPost = make([]int, 0)

	// Collect all forum posts and build indices
	allForums := fs.GetAll()

	for id, forum := range allForums {
		// Parent index
		fs.byParent[forum.Parent] = append(fs.byParent[forum.Parent], id)

		// Author index
		fs.byAuthor[forum.Author] = append(fs.byAuthor[forum.Author], id)

		// Threads only (parent = 0)
		if forum.Parent == 0 {
			fs.threadsOnly = append(fs.threadsOnly, id)
		}

		// All posts
		fs.allByLastPost = append(fs.allByLastPost, id)
	}

	// Sort allByLastPost by last_post DESC, then ID DESC
	sort.Slice(fs.allByLastPost, func(i, j int) bool {
		forumI, _ := fs.GetByID(fs.allByLastPost[i])
		forumJ, _ := fs.GetByID(fs.allByLastPost[j])
		if forumI.LastPost != forumJ.LastPost {
			return forumI.LastPost > forumJ.LastPost // DESC
		}
		return fs.allByLastPost[i] > fs.allByLastPost[j] // DESC
	})

	// Sort threadsOnly by last_post DESC, then ID DESC
	sort.Slice(fs.threadsOnly, func(i, j int) bool {
		forumI, _ := fs.GetByID(fs.threadsOnly[i])
		forumJ, _ := fs.GetByID(fs.threadsOnly[j])
		if forumI.LastPost != forumJ.LastPost {
			return forumI.LastPost > forumJ.LastPost // DESC
		}
		return fs.threadsOnly[i] > fs.threadsOnly[j] // DESC
	})

	// Sort byParent replies by posted ASC, then ID ASC
	for parent := range fs.byParent {
		if parent > 0 { // Only sort replies, not threads
			sort.Slice(fs.byParent[parent], func(i, j int) bool {
				forumI, _ := fs.GetByID(fs.byParent[parent][i])
				forumJ, _ := fs.GetByID(fs.byParent[parent][j])
				if forumI.Posted != forumJ.Posted {
					return forumI.Posted < forumJ.Posted // ASC
				}
				return fs.byParent[parent][i] < fs.byParent[parent][j] // ASC
			})
		}
	}

	// Sort byAuthor by posted DESC, then ID DESC
	for author := range fs.byAuthor {
		sort.Slice(fs.byAuthor[author], func(i, j int) bool {
			forumI, _ := fs.GetByID(fs.byAuthor[author][i])
			forumJ, _ := fs.GetByID(fs.byAuthor[author][j])
			if forumI.Posted != forumJ.Posted {
				return forumI.Posted > forumJ.Posted // DESC
			}
			return fs.byAuthor[author][i] > fs.byAuthor[author][j] // DESC
		})
	}
}

// rebuildIndices rebuilds all forum-specific indices from base store data
func (fs *ForumStore) rebuildIndices() {
	fs.mu.Lock()
	defer fs.mu.Unlock()
	fs.rebuildIndicesUnsafe()
}

// Retrieves a forum post by ID
func Find(id int) (*Forum, error) {
	fs := GetStore()
	forum, exists := fs.GetByID(id)
	if !exists {
		return nil, fmt.Errorf("forum post with ID %d not found", id)
	}
	return forum, nil
}

// Retrieves all forum posts ordered by last post time (most recent first)
func All() ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	result := make([]*Forum, 0, len(fs.allByLastPost))
	for _, id := range fs.allByLastPost {
		if forum, exists := fs.GetByID(id); exists {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Retrieves all top-level forum threads (parent = 0)
func Threads() ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	result := make([]*Forum, 0, len(fs.threadsOnly))
	for _, id := range fs.threadsOnly {
		if forum, exists := fs.GetByID(id); exists {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Retrieves all replies to a specific thread/post
func ByParent(parentID int) ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	ids, exists := fs.byParent[parentID]
	if !exists {
		return []*Forum{}, nil
	}

	result := make([]*Forum, 0, len(ids))
	for _, id := range ids {
		if forum, exists := fs.GetByID(id); exists {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Retrieves forum posts by a specific author
func ByAuthor(authorID int) ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	ids, exists := fs.byAuthor[authorID]
	if !exists {
		return []*Forum{}, nil
	}

	result := make([]*Forum, 0, len(ids))
	for _, id := range ids {
		if forum, exists := fs.GetByID(id); exists {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Retrieves the most recent forum activity (limited by count)
func Recent(limit int) ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	if limit > len(fs.allByLastPost) {
		limit = len(fs.allByLastPost)
	}

	result := make([]*Forum, 0, limit)
	for i := 0; i < limit; i++ {
		if forum, exists := fs.GetByID(fs.allByLastPost[i]); exists {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Retrieves forum posts containing the search term in title or content
func Search(term string) ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	var result []*Forum
	lowerTerm := strings.ToLower(term)

	for _, id := range fs.allByLastPost {
		if forum, exists := fs.GetByID(id); exists {
			if strings.Contains(strings.ToLower(forum.Title), lowerTerm) ||
				strings.Contains(strings.ToLower(forum.Content), lowerTerm) {
				result = append(result, forum)
			}
		}
	}
	return result, nil
}

// Retrieves forum posts with activity since a specific timestamp
func Since(since int64) ([]*Forum, error) {
	fs := GetStore()
	fs.mu.RLock()
	defer fs.mu.RUnlock()

	var result []*Forum
	for _, id := range fs.allByLastPost {
		if forum, exists := fs.GetByID(id); exists && forum.LastPost >= since {
			result = append(result, forum)
		}
	}
	return result, nil
}

// Saves a new forum post to the in-memory store and sets the ID
func (f *Forum) Insert() error {
	fs := GetStore()

	// Validate before insertion
	if err := f.Validate(); err != nil {
		return fmt.Errorf("validation failed: %w", err)
	}

	// Assign new ID if not set
	if f.ID == 0 {
		f.ID = fs.GetNextID()
	}

	// Add to store
	fs.AddForum(f)
	return nil
}

// Returns the posted timestamp as a time.Time
func (f *Forum) PostedTime() time.Time {
	return time.Unix(f.Posted, 0)
}

// Returns the last post timestamp as a time.Time
func (f *Forum) LastPostTime() time.Time {
	return time.Unix(f.LastPost, 0)
}

// Sets the posted timestamp from a time.Time
func (f *Forum) SetPostedTime(t time.Time) {
	f.Posted = t.Unix()
}

// Sets the last post timestamp from a time.Time
func (f *Forum) SetLastPostTime(t time.Time) {
	f.LastPost = t.Unix()
}

// Returns true if this is a top-level thread (parent = 0)
func (f *Forum) IsThread() bool {
	return f.Parent == 0
}

// Returns true if this is a reply to another post (parent > 0)
func (f *Forum) IsReply() bool {
	return f.Parent > 0
}

// Returns true if this post has replies
func (f *Forum) HasReplies() bool {
	return f.Replies > 0
}

// Returns true if there has been activity within the last 24 hours
func (f *Forum) IsRecentActivity() bool {
	return time.Since(f.LastPostTime()) < 24*time.Hour
}

// Returns how long ago the last activity occurred
func (f *Forum) ActivityAge() time.Duration {
	return time.Since(f.LastPostTime())
}

// Returns how long ago the post was originally made
func (f *Forum) PostAge() time.Duration {
	return time.Since(f.PostedTime())
}

// Returns true if the given user ID is the author of this post
func (f *Forum) IsAuthor(userID int) bool {
	return f.Author == userID
}

// Returns a truncated version of the content for previews
func (f *Forum) Preview(maxLength int) string {
	if len(f.Content) <= maxLength {
		return f.Content
	}

	if maxLength < 3 {
		return f.Content[:maxLength]
	}

	return f.Content[:maxLength-3] + "..."
}

// Returns the number of words in the content
func (f *Forum) WordCount() int {
	if f.Content == "" {
		return 0
	}

	// Simple word count by splitting on whitespace
	words := 0
	inWord := false

	for _, char := range f.Content {
		if char == ' ' || char == '\t' || char == '\n' || char == '\r' {
			if inWord {
				words++
				inWord = false
			}
		} else {
			inWord = true
		}
	}

	if inWord {
		words++
	}

	return words
}

// Returns the character length of the content
func (f *Forum) Length() int {
	return len(f.Content)
}

// Returns true if the title or content contains the given term (case-insensitive)
func (f *Forum) Contains(term string) bool {
	lowerTerm := strings.ToLower(term)
	return strings.Contains(strings.ToLower(f.Title), lowerTerm) ||
		strings.Contains(strings.ToLower(f.Content), lowerTerm)
}

// Updates the last_post timestamp to current time
func (f *Forum) UpdateLastPost() {
	f.LastPost = time.Now().Unix()
}

// Increments the reply count
func (f *Forum) IncrementReplies() {
	f.Replies++
}

// Decrements the reply count (minimum 0)
func (f *Forum) DecrementReplies() {
	if f.Replies > 0 {
		f.Replies--
	}
}

// Retrieves all direct replies to this post
func (f *Forum) GetReplies() ([]*Forum, error) {
	return ByParent(f.ID)
}

// Retrieves the parent thread (if this is a reply) or returns self (if this is a thread)
func (f *Forum) GetThread() (*Forum, error) {
	if f.IsThread() {
		return f, nil
	}
	return Find(f.Parent)
}