package streaming

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/sthmedia/media-node/internal/database"
)

type Server struct {
	store            *database.Store
	listen           string
	maxPerIP         int
	mu               sync.RWMutex
	activeCount      int
	bytesWindow      int64
	lastWindow       time.Time
	bytesPerSecond   int64
	ipConns          map[string]int
	onSessionEnd     func(sessionID, reason string)
	onSessionProgress func(sessionID string, bytesSent, lastByteOffset, fileSizeBytes int64)
	progressMu       sync.Mutex
	progressState    map[string]*progressTracker
}

type progressTracker struct {
	bytesSent  int64
	lastOffset int64
	fileSize   int64
	lastReport time.Time
}

func New(store *database.Store, listen string, maxPerIP int) *Server {
	// Stremio/VLC open many parallel Range requests; behind NPM they often share one IP.
	if maxPerIP <= 0 {
		maxPerIP = 64
	}
	s := &Server{
		store:         store,
		listen:        listen,
		maxPerIP:      maxPerIP,
		lastWindow:    time.Now(),
		ipConns:       make(map[string]int),
		progressState: make(map[string]*progressTracker),
	}
	go s.cleanupLoop()
	go s.bandwidthLoop()
	return s
}

func (s *Server) SetSessionEndHandler(fn func(sessionID, reason string)) {
	s.onSessionEnd = fn
}

func (s *Server) SetSessionProgressHandler(fn func(sessionID string, bytesSent, lastByteOffset, fileSizeBytes int64)) {
	s.onSessionProgress = fn
}

func (s *Server) ListenAndServe() error {
	mux := http.NewServeMux()
	mux.HandleFunc("/play/", s.handlePlay)
	mux.HandleFunc("/health", s.handleHealth)
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		http.NotFound(w, r)
	})

	server := &http.Server{
		Addr:              s.listen,
		Handler:           corsMiddleware(mux),
		ReadHeaderTimeout: 10 * time.Second,
		IdleTimeout:       120 * time.Second,
	}
	log.Printf("Stream server listening on %s", s.listen)
	return server.ListenAndServe()
}

func corsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, HEAD, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Range, Content-Type")
		w.Header().Set("Access-Control-Expose-Headers", "Content-Length, Content-Range, Accept-Ranges")
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	host, _, _ := net.SplitHostPort(r.RemoteAddr)
	if host != "127.0.0.1" && host != "::1" && host != "localhost" {
		// Prefer internal-only health; still allow LAN NPM if needed via 200 for GET from private ranges
		ip := net.ParseIP(host)
		if ip == nil || !ip.IsLoopback() && !ip.IsPrivate() {
			http.NotFound(w, r)
			return
		}
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte(`{"status":"ok"}`))
}

func (s *Server) handlePlay(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		http.NotFound(w, r)
		return
	}

	token := strings.TrimPrefix(r.URL.Path, "/play/")
	if token == "" || strings.Contains(token, "/") {
		http.NotFound(w, r)
		return
	}

	ip := clientIP(r)
	log.Printf("GET /play request from %s method=%s range=%q", ip, r.Method, r.Header.Get("Range"))

	if !s.acquireIP(ip) {
		log.Printf("GET /play/[REDACTED] rejected: too many connections from %s", ip)
		http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
		return
	}
	defer s.releaseIP(ip)

	tokenHash := hashToken(token)
	sess, err := s.store.GetSessionByTokenHash(tokenHash)
	if err != nil {
		// Brief grace: Master may have redirected before WS session landed.
		for i := 0; i < 40 && err != nil; i++ {
			time.Sleep(50 * time.Millisecond)
			sess, err = s.store.GetSessionByTokenHash(tokenHash)
		}
	}
	if err != nil {
		log.Printf("GET /play/[REDACTED] invalid session from %s", ip)
		http.NotFound(w, r)
		return
	}

	now := time.Now().UTC()
	if now.After(sess.AbsoluteExpiresAt) {
		_ = s.store.DeleteSession(sess.SessionID)
		s.clearProgress(sess.SessionID)
		if s.onSessionEnd != nil {
			s.onSessionEnd(sess.SessionID, "absolute_expiry")
		}
		http.NotFound(w, r)
		return
	}
	idleDeadline := sess.LastActivity.Add(time.Duration(sess.IdleTimeoutSeconds) * time.Second)
	if now.After(idleDeadline) {
		_ = s.store.DeleteSession(sess.SessionID)
		s.clearProgress(sess.SessionID)
		if s.onSessionEnd != nil {
			s.onSessionEnd(sess.SessionID, "idle_timeout")
		}
		http.NotFound(w, r)
		return
	}

	file, err := s.store.GetFile(sess.LocalFileID)
	if err != nil {
		log.Printf("GET /play/[REDACTED] unknown localFileId=%s session=%s", sess.LocalFileID, sess.SessionID)
		http.NotFound(w, r)
		return
	}

	f, err := os.Open(file.Path)
	if err != nil {
		log.Printf("GET /play/[REDACTED] file open failed session=%s path=%s err=%v", sess.SessionID, file.Path, err)
		http.NotFound(w, r)
		return
	}
	defer f.Close()

	stat, err := f.Stat()
	if err != nil {
		http.NotFound(w, r)
		return
	}

	fileSize := stat.Size()
	_ = s.store.TouchSession(sess.SessionID)
	s.noteProgress(sess.SessionID, 0, fileSize, 0, true)

	s.mu.Lock()
	s.activeCount++
	s.mu.Unlock()
	defer func() {
		s.mu.Lock()
		s.activeCount--
		s.mu.Unlock()
	}()

	w.Header().Set("Accept-Ranges", "bytes")
	w.Header().Set("Content-Type", contentType(file.Path))
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Expose-Headers", "Content-Length, Content-Range, Accept-Ranges")

	rangeHeader := r.Header.Get("Range")
	if rangeHeader == "" {
		w.Header().Set("Content-Length", strconv.FormatInt(fileSize, 10))
		if r.Method == http.MethodHead {
			w.WriteHeader(http.StatusOK)
			return
		}
		s.streamRange(w, f, 0, fileSize-1, sess.SessionID, fileSize)
		return
	}

	start, end, err := parseRange(rangeHeader, fileSize)
	if err != nil {
		w.Header().Set("Content-Range", fmt.Sprintf("bytes */%d", fileSize))
		http.Error(w, "Invalid Range", http.StatusRequestedRangeNotSatisfiable)
		return
	}

	contentLength := end - start + 1
	w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, fileSize))
	w.Header().Set("Content-Length", strconv.FormatInt(contentLength, 10))
	w.WriteHeader(http.StatusPartialContent)

	if r.Method == http.MethodHead {
		return
	}

	s.noteProgress(sess.SessionID, start, fileSize, 0, true)
	s.streamRange(w, f, start, end, sess.SessionID, fileSize)
}

func (s *Server) streamRange(w http.ResponseWriter, f *os.File, start, end int64, sessionID string, fileSize int64) {
	if _, err := f.Seek(start, io.SeekStart); err != nil {
		return
	}
	remaining := end - start + 1
	buf := make([]byte, 256*1024)
	flusher, canFlush := w.(http.Flusher)
	pos := start

	for remaining > 0 {
		toRead := int64(len(buf))
		if toRead > remaining {
			toRead = remaining
		}
		n, err := f.Read(buf[:toRead])
		if n > 0 {
			atomic.AddInt64(&s.bytesWindow, int64(n))
			if _, werr := w.Write(buf[:n]); werr != nil {
				return
			}
			if canFlush {
				flusher.Flush()
			}
			remaining -= int64(n)
			pos += int64(n)
			s.noteProgress(sessionID, pos, fileSize, int64(n), false)
		}
		if err != nil {
			return
		}
	}
}

func (s *Server) noteProgress(sessionID string, offset, fileSize, deltaBytes int64, force bool) {
	if sessionID == "" {
		return
	}
	_ = s.store.TouchSession(sessionID)

	s.progressMu.Lock()
	st := s.progressState[sessionID]
	if st == nil {
		st = &progressTracker{}
		s.progressState[sessionID] = st
	}
	if deltaBytes > 0 {
		st.bytesSent += deltaBytes
	} else if st.bytesSent == 0 && force {
		// Mark as live even before first chunk (Range open).
		st.bytesSent = 1
	}
	if offset >= st.lastOffset {
		st.lastOffset = offset
	}
	if fileSize > 0 {
		st.fileSize = fileSize
	}
	shouldReport := force || time.Since(st.lastReport) >= 3*time.Second
	bytesSent := st.bytesSent
	lastOffset := st.lastOffset
	size := st.fileSize
	if shouldReport {
		st.lastReport = time.Now()
	}
	s.progressMu.Unlock()

	if shouldReport && s.onSessionProgress != nil {
		s.onSessionProgress(sessionID, bytesSent, lastOffset, size)
	}
}

func (s *Server) ActiveStreams() int {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.activeCount
}

func (s *Server) BytesPerSecond() int64 {
	return atomic.LoadInt64(&s.bytesPerSecond)
}

func (s *Server) CurrentBandwidth() int64 {
	return s.BytesPerSecond()
}

func (s *Server) CreateSession(sess database.PlaybackSession) error {
	return s.store.SaveSession(sess)
}

func (s *Server) RevokeSession(sessionID string) error {
	s.clearProgress(sessionID)
	return s.store.DeleteSession(sessionID)
}

func (s *Server) acquireIP(ip string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.ipConns[ip] >= s.maxPerIP {
		return false
	}
	s.ipConns[ip]++
	return true
}

func (s *Server) releaseIP(ip string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.ipConns[ip] <= 1 {
		delete(s.ipConns, ip)
		return
	}
	s.ipConns[ip]--
}

func (s *Server) bandwidthLoop() {
	ticker := time.NewTicker(time.Second)
	for range ticker.C {
		n := atomic.SwapInt64(&s.bytesWindow, 0)
		atomic.StoreInt64(&s.bytesPerSecond, n)
	}
}

func (s *Server) cleanupLoop() {
	ticker := time.NewTicker(60 * time.Second)
	for range ticker.C {
		sessions, _ := s.store.ActiveSessions()
		now := time.Now().UTC()
		for _, sess := range sessions {
			if now.After(sess.AbsoluteExpiresAt) {
				_ = s.store.DeleteSession(sess.SessionID)
				s.clearProgress(sess.SessionID)
				if s.onSessionEnd != nil {
					s.onSessionEnd(sess.SessionID, "absolute_expiry")
				}
				continue
			}
			idleDeadline := sess.LastActivity.Add(time.Duration(sess.IdleTimeoutSeconds) * time.Second)
			if now.After(idleDeadline) {
				_ = s.store.DeleteSession(sess.SessionID)
				s.clearProgress(sess.SessionID)
				if s.onSessionEnd != nil {
					s.onSessionEnd(sess.SessionID, "idle_timeout")
				}
			}
		}
	}
}

func (s *Server) clearProgress(sessionID string) {
	s.progressMu.Lock()
	delete(s.progressState, sessionID)
	s.progressMu.Unlock()
}

func parseRange(rangeHeader string, size int64) (int64, int64, error) {
	if !strings.HasPrefix(rangeHeader, "bytes=") {
		return 0, 0, fmt.Errorf("invalid range")
	}
	parts := strings.Split(strings.TrimPrefix(rangeHeader, "bytes="), "-")
	if len(parts) != 2 {
		return 0, 0, fmt.Errorf("invalid range")
	}
	var start, end int64
	if parts[0] == "" {
		suffix, err := strconv.ParseInt(parts[1], 10, 64)
		if err != nil {
			return 0, 0, err
		}
		start = size - suffix
		if start < 0 {
			start = 0
		}
		end = size - 1
	} else {
		var err error
		start, err = strconv.ParseInt(parts[0], 10, 64)
		if err != nil {
			return 0, 0, err
		}
		if parts[1] == "" {
			end = size - 1
		} else {
			end, err = strconv.ParseInt(parts[1], 10, 64)
			if err != nil {
				return 0, 0, err
			}
		}
	}
	if start > end || start >= size {
		return 0, 0, fmt.Errorf("invalid range")
	}
	if end >= size {
		end = size - 1
	}
	return start, end, nil
}

func contentType(path string) string {
	switch strings.ToLower(filepath.Ext(path)) {
	case ".mkv":
		return "video/x-matroska"
	case ".mp4", ".m4v":
		return "video/mp4"
	case ".avi":
		return "video/x-msvideo"
	case ".ts", ".m2ts":
		return "video/mp2t"
	default:
		return "application/octet-stream"
	}
}

func hashToken(token string) string {
	sum := sha256.Sum256([]byte(token))
	return hex.EncodeToString(sum[:])
}

func clientIP(r *http.Request) string {
	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
		parts := strings.Split(xff, ",")
		return strings.TrimSpace(parts[0])
	}
	if xri := r.Header.Get("X-Real-IP"); xri != "" {
		return xri
	}
	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return r.RemoteAddr
	}
	return host
}