package api

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

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

// base64Decode handles both standard and url-safe base64 (with or without padding).
func base64Decode(s string) ([]byte, error) {
	// Try url-safe first (no padding), then standard
	s = strings.TrimRight(s, "=")
	b, err := base64.RawURLEncoding.DecodeString(s)
	if err != nil {
		b, err = base64.RawStdEncoding.DecodeString(s)
	}
	return b, err
}

// base64UrlEncode encodes bytes as base64url without padding.
func base64UrlEncode(b []byte) string {
	return base64.RawURLEncoding.EncodeToString(b)
}

type contextKey string

const (
	ctxActor    contextKey = "actor"
	ctxSession  contextKey = "session"
	ctxAgent    contextKey = "agent"
	ctxDB       contextKey = "db"
	ctxVaultKey contextKey = "vault_key"
	ctxVaultID  contextKey = "vault_id"
)

// 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
}

// AgentFromContext returns the agent from request context (nil if not an agent request).
func AgentFromContext(ctx context.Context) *lib.Agent {
	v, _ := ctx.Value(ctxAgent).(*lib.Agent)
	return v
}

// DBFromContext returns the vault DB from request context (nil in self-hosted mode).
func DBFromContext(ctx context.Context) *lib.DB {
	v, _ := ctx.Value(ctxDB).(*lib.DB)
	return v
}

// VaultKeyFromContext returns the derived vault key from request context (nil in self-hosted mode).
func VaultKeyFromContext(ctx context.Context) []byte {
	v, _ := ctx.Value(ctxVaultKey).([]byte)
	return v
}

// VaultIDFromContext returns the vault ID from request context (0 in self-hosted mode).
func VaultIDFromContext(ctx context.Context) int64 {
	v, _ := ctx.Value(ctxVaultID).(int64)
	return v
}

// L1Middleware extracts L1 from Bearer token and opens the vault DB.
// Fully stateless: L1 arrives with every request, is used, then forgotten.
// No sessions, no stored keys. The server has zero keys of its own.
//
// Self-hosted mode: finds vault DB by globbing clavitor-* files.
// Hosted mode: finds vault DB by base64url(L1[0:4]) → filename.
func L1Middleware(dataDir string) 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")

			// No auth = unauthenticated request (registration, login begin, etc.)
			if auth == "" || !strings.HasPrefix(auth, "Bearer ") {
				// Try to open vault DB without L1 (for unauthenticated endpoints)
				matches, _ := filepath.Glob(filepath.Join(dataDir, "clavitor-*"))
				if len(matches) > 0 {
					db, err := lib.OpenDB(matches[0])
					if err == nil {
						defer db.Close()
						ctx := context.WithValue(r.Context(), ctxDB, db)
						next.ServeHTTP(w, r.WithContext(ctx))
						return
					}
				}
				// Also try legacy .db files for migration
				matches, _ = filepath.Glob(filepath.Join(dataDir, "????????.db"))
				if len(matches) > 0 {
					db, err := lib.OpenDB(matches[0])
					if err == nil {
						defer db.Close()
						ctx := context.WithValue(r.Context(), ctxDB, db)
						next.ServeHTTP(w, r.WithContext(ctx))
						return
					}
				}
				next.ServeHTTP(w, r)
				return
			}

			bearerVal := strings.TrimPrefix(auth, "Bearer ")

			var l1Raw []byte
			var agent *lib.Agent

			if strings.HasPrefix(bearerVal, "cvt_") {
				// --- Agent token: cvt_ prefix ---
				// Extract L1 and look up agent by token hash.
				var hash string
				var err error
				l1Raw, hash, err = lib.ParseToken(bearerVal)
				if err != nil {
					ErrorResponse(w, http.StatusUnauthorized, "invalid_token", "Invalid agent token")
					return
				}

				// Open vault DB from L1
				l1Key := lib.NormalizeKey(l1Raw)
				vaultPrefix := base64UrlEncode(l1Raw[:4])
				dbPath := filepath.Join(dataDir, "clavitor-"+vaultPrefix)

				db, err := lib.OpenDB(dbPath)
				if err != nil {
					ErrorResponse(w, http.StatusNotFound, "vault_not_found", "Vault not found")
					return
				}
				defer db.Close()

				// Look up agent
				agent, err = lib.AgentGetByToken(db, hash)
				if err != nil {
					ErrorResponse(w, http.StatusInternalServerError, "agent_error", "Agent lookup failed")
					return
				}
				if agent == nil {
					ErrorResponse(w, http.StatusUnauthorized, "unknown_token", "Invalid or revoked token")
					return
				}

				ctx := context.WithValue(r.Context(), ctxDB, db)
				ctx = context.WithValue(ctx, ctxVaultKey, l1Key)
				ctx = context.WithValue(ctx, ctxActor, lib.ActorAgent)
				ctx = context.WithValue(ctx, ctxAgent, agent)
				next.ServeHTTP(w, r.WithContext(ctx))

			} else {
				// --- Legacy L1 bearer (web UI / extension) ---
				// 8 bytes base64url = vault owner, full access, no agent.
				l1Raw, err := base64Decode(bearerVal)
				if err != nil || len(l1Raw) != 8 {
					ErrorResponse(w, http.StatusUnauthorized, "invalid_l1", "Invalid L1 key in Bearer")
					return
				}

				l1Key := lib.NormalizeKey(l1Raw)
				vaultPrefix := base64UrlEncode(l1Raw[:4])
				dbPath := filepath.Join(dataDir, "clavitor-"+vaultPrefix)

				var db *lib.DB
				if _, err := os.Stat(dbPath); err == nil {
					db, err = lib.OpenDB(dbPath)
					if err != nil {
						log.Printf("vault open error (%s): %v", dbPath, err)
						ErrorResponse(w, http.StatusInternalServerError, "db_error", "Failed to open vault")
						return
					}
				}
				if db == nil {
					ErrorResponse(w, http.StatusNotFound, "vault_not_found", "Vault not found")
					return
				}
				defer db.Close()

				ctx := context.WithValue(r.Context(), ctxDB, db)
				ctx = context.WithValue(ctx, ctxVaultKey, l1Key)
				ctx = context.WithValue(ctx, ctxActor, lib.ActorWeb)
				// No agent in context = vault owner (full access)

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

// IsAgentRequest returns true if the request was made with a cvt_ agent token.
func IsAgentRequest(r *http.Request) bool {
	return AgentFromContext(r.Context()) != nil
}

// 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)
}

// tarpitHandler holds unrecognized requests for 30 seconds.
// Drips one byte per second to keep the connection alive and waste
// scanner resources. Capped at 1000 concurrent tarpit slots —
// beyond that, connections are dropped immediately.
var (
	tarpitSem = make(chan struct{}, 1000)
)

func tarpitHandler(w http.ResponseWriter, r *http.Request) {
	select {
	case tarpitSem <- struct{}{}:
		defer func() { <-tarpitSem }()
	default:
		// Tarpit full — drop immediately, no response
		if hj, ok := w.(http.Hijacker); ok {
			conn, _, err := hj.Hijack()
			if err == nil {
				conn.Close()
			}
		}
		return
	}

	log.Printf("tarpit: %s %s from %s", r.Method, r.URL.Path, realIP(r))

	// Chunked response: drip one space per second for 30s
	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(200)
	flusher, canFlush := w.(http.Flusher)
	for i := 0; i < 30; i++ {
		_, err := w.Write([]byte(" "))
		if err != nil {
			return // client gave up
		}
		if canFlush {
			flusher.Flush()
		}
		time.Sleep(time.Second)
	}
}

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
}