package api

import (
	"context"
	"encoding/json"
	"log"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/johanj/clawvault/lib"
)

type contextKey string

const (
	ctxActor   contextKey = "actor"
	ctxSession contextKey = "session"
)

// ActorFromContext returns the actor type from request context.
func ActorFromContext(ctx context.Context) string {
	v, ok := ctx.Value(ctxActor).(string)
	if !ok {
		return lib.ActorWeb
	}
	return v
}

// SessionFromContext returns the session from request context.
func SessionFromContext(ctx context.Context) *lib.Session {
	v, _ := ctx.Value(ctxSession).(*lib.Session)
	return v
}

// AuthMiddleware validates Bearer tokens and sets session context.
func AuthMiddleware(db *lib.DB) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			auth := r.Header.Get("Authorization")
			if !strings.HasPrefix(auth, "Bearer ") {
				ErrorResponse(w, http.StatusUnauthorized, "missing_token", "Authorization header required")
				return
			}
			token := strings.TrimPrefix(auth, "Bearer ")

			session, err := lib.SessionGet(db, token)
			if err != nil {
				ErrorResponse(w, http.StatusInternalServerError, "session_error", "Session lookup failed")
				return
			}
			if session == nil {
				ErrorResponse(w, http.StatusUnauthorized, "invalid_token", "Invalid or expired token")
				return
			}

			ctx := context.WithValue(r.Context(), ctxActor, session.Actor)
			ctx = context.WithValue(ctx, ctxSession, session)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// LoggingMiddleware logs HTTP requests.
func LoggingMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		wrapped := &statusWriter{ResponseWriter: w, status: 200}
		next.ServeHTTP(wrapped, r)
		log.Printf("%s %s %d %s", r.Method, r.URL.Path, wrapped.status, time.Since(start))
	})
}

type statusWriter struct {
	http.ResponseWriter
	status int
}

func (w *statusWriter) WriteHeader(code int) {
	w.status = code
	w.ResponseWriter.WriteHeader(code)
}

// RateLimitMiddleware implements per-IP rate limiting.
func RateLimitMiddleware(requestsPerMinute int) func(http.Handler) http.Handler {
	var mu sync.Mutex
	clients := make(map[string]*rateLimitEntry)

	go func() {
		for {
			time.Sleep(time.Minute)
			mu.Lock()
			now := time.Now()
			for ip, entry := range clients {
				if now.Sub(entry.windowStart) > time.Minute {
					delete(clients, ip)
				}
			}
			mu.Unlock()
		}
	}()

	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ip := realIP(r)

			mu.Lock()
			entry, exists := clients[ip]
			now := time.Now()
			if !exists || now.Sub(entry.windowStart) > time.Minute {
				entry = &rateLimitEntry{windowStart: now, count: 0}
				clients[ip] = entry
			}
			entry.count++
			count := entry.count
			mu.Unlock()

			if count > requestsPerMinute {
				ErrorResponse(w, http.StatusTooManyRequests, "rate_limited", "Too many requests")
				return
			}

			next.ServeHTTP(w, r)
		})
	}
}

type rateLimitEntry struct {
	windowStart time.Time
	count       int
}

// CORSMiddleware handles CORS headers.
func CORSMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		origin := r.Header.Get("Origin")

		// Allow localhost and 127.0.0.1 for development
		if origin != "" && (strings.Contains(origin, "localhost") || strings.Contains(origin, "127.0.0.1")) {
			w.Header().Set("Access-Control-Allow-Origin", origin)
			w.Header().Set("Vary", "Origin")
		}

		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type")
		w.Header().Set("Access-Control-Max-Age", "86400")

		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusNoContent)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// SecurityHeadersMiddleware adds security headers to all responses.
func SecurityHeadersMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-XSS-Protection", "1; mode=block")
		w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
		// CSP allowing localhost and 127.0.0.1 for development
		w.Header().Set("Content-Security-Policy", "default-src 'self'; script-src 'self' 'unsafe-inline' https://cdn.tailwindcss.com; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' data: https://fonts.gstatic.com; img-src 'self' data: https:; connect-src 'self' localhost 127.0.0.1")

		next.ServeHTTP(w, r)
	})
}

// ErrorResponse sends a standard JSON error response.
func ErrorResponse(w http.ResponseWriter, status int, code, message string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(map[string]string{
		"error": message,
		"code":  code,
	})
}

// JSONResponse sends a standard JSON success response.
func JSONResponse(w http.ResponseWriter, status int, data any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(data)
}

func realIP(r *http.Request) string {
	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
		parts := strings.SplitN(xff, ",", 2)
		return strings.TrimSpace(parts[0])
	}
	if xri := r.Header.Get("X-Real-IP"); xri != "" {
		return xri
	}
	addr := r.RemoteAddr
	if idx := strings.LastIndex(addr, ":"); idx != -1 {
		return addr[:idx]
	}
	return addr
}