package handlers

import (
	"encoding/json"
	"encoding/xml"
	"fmt"
	"net/http"
	"net/url"
	"sitemap-api/crawler"
	"sitemap-api/database"
	"sitemap-api/models"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
)

type Handler struct {
	db            *database.DB
	crawler       *crawler.Crawler
	streamManager *StreamManager
}

func NewHandler(db *database.DB, streamManager *StreamManager) *Handler {
	return &Handler{
		db:            db,
		crawler:       crawler.NewCrawler(db),
		streamManager: streamManager,
	}
}

// StreamManager handles multiple concurrent SSE connections
type StreamManager struct {
	mu      sync.RWMutex
	streams map[string]chan models.Event
}

func NewStreamManager() *StreamManager {
	return &StreamManager{
		streams: make(map[string]chan models.Event),
	}
}

func (sm *StreamManager) CreateStream(uuid string) chan models.Event {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	ch := make(chan models.Event, 100)
	sm.streams[uuid] = ch
	return ch
}

func (sm *StreamManager) GetStream(uuid string) (chan models.Event, bool) {
	sm.mu.RLock()
	defer sm.mu.RUnlock()

	ch, exists := sm.streams[uuid]
	return ch, exists
}

func (sm *StreamManager) CloseStream(uuid string) {
	sm.mu.Lock()
	defer sm.mu.Unlock()

	if ch, exists := sm.streams[uuid]; exists {
		close(ch)
		delete(sm.streams, uuid)
	}
}

// GenerateSitemapXML handles POST /generate-sitemap-xml
func (h *Handler) GenerateSitemapXML(w http.ResponseWriter, r *http.Request) {
	var req struct {
		URL      string `json:"url"`
		MaxDepth int    `json:"max_depth"`
	}

	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid request body", http.StatusBadRequest)
		return
	}

	// Validate URL
	if req.URL == "" {
		http.Error(w, "URL is required", http.StatusBadRequest)
		return
	}

	parsedURL, err := url.Parse(req.URL)
	if err != nil || parsedURL.Scheme == "" || parsedURL.Host == "" {
		http.Error(w, "Invalid URL format", http.StatusBadRequest)
		return
	}

	// Set default max depth
	if req.MaxDepth <= 0 || req.MaxDepth > 5 {
		req.MaxDepth = 5
	}

	// Generate UUID server-side
	generatedUUID := uuid.New().String()

	// Extract client metadata
	ip := getClientIP(r)
	userAgent := r.Header.Get("User-Agent")
	browser, browserVersion := parseBrowser(userAgent)
	os := parseOS(userAgent)
	deviceType := parseDeviceType(userAgent)
	sessionID := getOrCreateSession(r)
	cookies := extractCookies(r)
	referrer := r.Header.Get("Referer")

	// Extract domain from URL
	domain := parsedURL.Host

	// Create site record
	site := &models.Site{
		UUID:           generatedUUID,
		Domain:         domain,
		URL:            req.URL,
		MaxDepth:       req.MaxDepth,
		Status:         "processing",
		IPAddress:      ip,
		UserAgent:      userAgent,
		Browser:        browser,
		BrowserVersion: browserVersion,
		OS:             os,
		DeviceType:     deviceType,
		SessionID:      sessionID,
		Cookies:        cookies,
		Referrer:       referrer,
	}

	siteID, err := h.db.CreateSite(site)
	if err != nil {
		http.Error(w, fmt.Sprintf("Failed to create site: %v", err), http.StatusInternalServerError)
		return
	}

	// Create SSE stream for this UUID
	eventChan := h.streamManager.CreateStream(generatedUUID)

	// Start crawling in background (non-blocking)
	go func() {
		h.crawler.Crawl(generatedUUID, req.URL, req.MaxDepth, eventChan)
		// Close stream after crawl completes
		time.Sleep(2 * time.Second) // Give time for final events to be sent
		h.streamManager.CloseStream(generatedUUID)
	}()

	// Add UUID to user UUIDs cookie
	userUUIDs := getUserUUIDsFromCookie(r)
	userUUIDs = append(userUUIDs, generatedUUID)

	// Keep only last 20 UUIDs and remove duplicates
	uniqueUUIDs := removeDuplicateUUIDs(userUUIDs)
	if len(uniqueUUIDs) > 20 {
		uniqueUUIDs = uniqueUUIDs[len(uniqueUUIDs)-20:]
	}

	// Set cookie with user UUIDs
	http.SetCookie(w, &http.Cookie{
		Name:     "user_uuids",
		Value:    strings.Join(uniqueUUIDs, ","),
		Path:     "/",
		MaxAge:   86400 * 90, // 90 days
		HttpOnly: false,
		SameSite: http.SameSiteLaxMode,
	})

	// Return immediately with UUID
	response := map[string]interface{}{
		"uuid":       generatedUUID,
		"site_id":    siteID,
		"status":     "processing",
		"stream_url": "/stream/" + generatedUUID,
		"message":    "Sitemap generation started",
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(response)
}

// StreamSSE handles GET /stream/{uuid}
func (h *Handler) StreamSSE(w http.ResponseWriter, r *http.Request) {
	uuid := chi.URLParam(r, "uuid")

	// Get event channel for this UUID
	eventChan, exists := h.streamManager.GetStream(uuid)
	if !exists {
		http.Error(w, "Stream not found", http.StatusNotFound)
		return
	}

	// Set SSE headers
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Access-Control-Allow-Origin", "*")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "Streaming unsupported", http.StatusInternalServerError)
		return
	}

	// Send connected event
	connectedData := map[string]string{
		"uuid":    uuid,
		"message": "Connected to stream",
	}
	connectedJSON, _ := json.Marshal(connectedData)
	fmt.Fprintf(w, "event: connected\ndata: %s\n\n", connectedJSON)
	flusher.Flush()

	// Stream events
	for event := range eventChan {
		data, err := json.Marshal(event.Data)
		if err != nil {
			continue
		}
		fmt.Fprintf(w, "event: %s\ndata: %s\n\n", event.Type, data)
		flusher.Flush()
	}
}

// DownloadSitemap handles GET /download/{uuid}
func (h *Handler) DownloadSitemap(w http.ResponseWriter, r *http.Request) {
	uuidParam := chi.URLParam(r, "uuid")

	// Get site by UUID
	site, err := h.db.GetSiteByUUID(uuidParam)
	if err != nil {
		http.Error(w, "Sitemap not found", http.StatusNotFound)
		return
	}

	// Get all pages for this site
	pages, err := h.db.GetPagesBySiteID(site.ID)
	if err != nil {
		http.Error(w, "Failed to retrieve pages", http.StatusInternalServerError)
		return
	}

	// Generate XML sitemap
	sitemap := generateXMLSitemap(pages)

	// Set headers
	filename := fmt.Sprintf("sitemap-%s.xml", strings.ReplaceAll(site.Domain, ".", "-"))
	w.Header().Set("Content-Type", "application/xml; charset=utf-8")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))
	w.Header().Set("X-Generated-At", time.Now().Format(time.RFC3339))

	// Write XML
	w.Write([]byte(xml.Header))
	w.Write([]byte(sitemap))
}

// GetSites handles GET /sites
func (h *Handler) GetSites(w http.ResponseWriter, r *http.Request) {
	// Get user's UUIDs from cookie
	userUUIDs := getUserUUIDsFromCookie(r)

	var sites []*models.Site
	var err error

	if len(userUUIDs) > 0 {
		// Get only user's sites
		sites, err = h.db.GetSitesByUUIDs(userUUIDs)
	} else {
		// No UUIDs found, return empty list
		sites = []*models.Site{}
	}

	if err != nil {
		http.Error(w, "Failed to retrieve sites", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(sites)
}

// GetSite handles GET /sites/{id}
func (h *Handler) GetSite(w http.ResponseWriter, r *http.Request) {
	idParam := chi.URLParam(r, "id")
	id, err := strconv.Atoi(idParam)
	if err != nil {
		http.Error(w, "Invalid site ID", http.StatusBadRequest)
		return
	}

	site, err := h.db.GetSiteByID(id)
	if err != nil {
		http.Error(w, "Site not found", http.StatusNotFound)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(site)
}

// DeleteSite handles DELETE /sites/{id}
func (h *Handler) DeleteSite(w http.ResponseWriter, r *http.Request) {
	idParam := chi.URLParam(r, "id")
	id, err := strconv.Atoi(idParam)
	if err != nil {
		http.Error(w, "Invalid site ID", http.StatusBadRequest)
		return
	}

	if err := h.db.DeleteSite(id); err != nil {
		http.Error(w, "Failed to delete site", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"success": true,
		"message": "Site deleted successfully",
	})
}

// Health handles GET /health
func (h *Handler) Health(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]string{
		"status": "healthy",
		"time":   time.Now().Format(time.RFC3339),
	})
}

// Helper functions

func getClientIP(r *http.Request) string {
	// Check X-Forwarded-For header first
	forwarded := r.Header.Get("X-Forwarded-For")
	if forwarded != "" {
		// Get first IP if multiple
		ips := strings.Split(forwarded, ",")
		return strings.TrimSpace(ips[0])
	}

	// Check X-Real-IP header
	realIP := r.Header.Get("X-Real-IP")
	if realIP != "" {
		return realIP
	}

	// Fallback to RemoteAddr
	ip := r.RemoteAddr
	if strings.Contains(ip, ":") {
		ip = strings.Split(ip, ":")[0]
	}
	return ip
}

func parseBrowser(userAgent string) (string, string) {
	ua := strings.ToLower(userAgent)

	browsers := map[string]string{
		"edg":     "Edge",
		"chrome":  "Chrome",
		"firefox": "Firefox",
		"safari":  "Safari",
		"opera":   "Opera",
	}

	for key, name := range browsers {
		if strings.Contains(ua, key) {
			// Extract version
			version := extractVersion(ua, key)
			return name, version
		}
	}

	return "Unknown", ""
}

func extractVersion(ua, browser string) string {
	idx := strings.Index(ua, browser)
	if idx == -1 {
		return ""
	}

	versionStart := idx + len(browser)
	if versionStart >= len(ua) {
		return ""
	}

	// Skip forward to version number
	for versionStart < len(ua) && (ua[versionStart] == '/' || ua[versionStart] == ' ') {
		versionStart++
	}

	versionEnd := versionStart
	for versionEnd < len(ua) && (ua[versionEnd] >= '0' && ua[versionEnd] <= '9' || ua[versionEnd] == '.') {
		versionEnd++
	}

	return ua[versionStart:versionEnd]
}

func parseOS(userAgent string) string {
	ua := strings.ToLower(userAgent)

	oses := []struct {
		keyword string
		name    string
	}{
		{"windows nt 10", "Windows 10"},
		{"windows nt 11", "Windows 11"},
		{"mac os x", "macOS"},
		{"android", "Android"},
		{"iphone", "iOS"},
		{"ipad", "iOS"},
		{"linux", "Linux"},
	}

	for _, os := range oses {
		if strings.Contains(ua, os.keyword) {
			return os.name
		}
	}

	return "Unknown"
}

func parseDeviceType(userAgent string) string {
	ua := strings.ToLower(userAgent)

	if strings.Contains(ua, "mobile") || strings.Contains(ua, "android") || strings.Contains(ua, "iphone") {
		return "Mobile"
	}

	if strings.Contains(ua, "tablet") || strings.Contains(ua, "ipad") {
		return "Tablet"
	}

	return "Desktop"
}

func getOrCreateSession(r *http.Request) string {
	// Try to get existing session from cookie
	cookie, err := r.Cookie("session_id")
	if err == nil && cookie.Value != "" {
		return cookie.Value
	}

	// Generate new session ID
	return uuid.New().String()
}

func getUserUUIDsFromCookie(r *http.Request) []string {
	// Get user UUIDs from cookie
	cookie, err := r.Cookie("user_uuids")
	if err != nil || cookie.Value == "" {
		return []string{}
	}

	// Parse comma-separated UUIDs
	uuids := strings.Split(cookie.Value, ",")
	// Filter out empty strings
	var result []string
	for _, uuid := range uuids {
		if strings.TrimSpace(uuid) != "" {
			result = append(result, strings.TrimSpace(uuid))
		}
	}
	return result
}

func removeDuplicateUUIDs(uuids []string) []string {
	seen := make(map[string]bool)
	var result []string

	for _, uuid := range uuids {
		if !seen[uuid] {
			seen[uuid] = true
			result = append(result, uuid)
		}
	}

	return result
}

func extractCookies(r *http.Request) string {
	cookies := r.Cookies()
	if len(cookies) == 0 {
		return ""
	}

	cookieData := make(map[string]string)
	for _, cookie := range cookies {
		cookieData[cookie.Name] = cookie.Value
	}

	data, _ := json.Marshal(cookieData)
	return string(data)
}

func generateXMLSitemap(pages []*models.Page) string {
	var sb strings.Builder

	sb.WriteString("<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">\n")

	for _, page := range pages {
		sb.WriteString("  <url>\n")
		sb.WriteString(fmt.Sprintf("    <loc>%s</loc>\n", xmlEscape(page.URL)))
		sb.WriteString(fmt.Sprintf("    <lastmod>%s</lastmod>\n", page.LastModified.Format("2006-01-02")))
		sb.WriteString(fmt.Sprintf("    <changefreq>%s</changefreq>\n", page.ChangeFreq))
		sb.WriteString(fmt.Sprintf("    <priority>%.2f</priority>\n", page.Priority))
		sb.WriteString("  </url>\n")
	}

	sb.WriteString("</urlset>")

	return sb.String()
}

func xmlEscape(s string) string {
	s = strings.ReplaceAll(s, "&", "&amp;")
	s = strings.ReplaceAll(s, "<", "&lt;")
	s = strings.ReplaceAll(s, ">", "&gt;")
	s = strings.ReplaceAll(s, "\"", "&quot;")
	s = strings.ReplaceAll(s, "'", "&apos;")
	return s
}