// Package main implements the fetch_ml API server
package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"syscall"
	"time"

	"github.com/jfraeys/fetch_ml/internal/api"
	"github.com/jfraeys/fetch_ml/internal/auth"
	"github.com/jfraeys/fetch_ml/internal/config"
	"github.com/jfraeys/fetch_ml/internal/experiment"
	"github.com/jfraeys/fetch_ml/internal/fileutil"
	"github.com/jfraeys/fetch_ml/internal/logging"
	"github.com/jfraeys/fetch_ml/internal/middleware"
	"github.com/jfraeys/fetch_ml/internal/queue"
	"github.com/jfraeys/fetch_ml/internal/storage"
	"gopkg.in/yaml.v3"
)

// Config structure matching worker config.
type Config struct {
	BasePath  string                `yaml:"base_path"`
	Auth      auth.Config           `yaml:"auth"`
	Server    ServerConfig          `yaml:"server"`
	Security  SecurityConfig        `yaml:"security"`
	Redis     RedisConfig           `yaml:"redis"`
	Database  DatabaseConfig        `yaml:"database"`
	Logging   logging.Config        `yaml:"logging"`
	Resources config.ResourceConfig `yaml:"resources"`
}

// RedisConfig holds Redis connection configuration.
type RedisConfig struct {
	Addr     string `yaml:"addr"`
	Password string `yaml:"password"`
	DB       int    `yaml:"db"`
	URL      string `yaml:"url"`
}

// DatabaseConfig holds database connection configuration.
type DatabaseConfig struct {
	Type       string `yaml:"type"`
	Connection string `yaml:"connection"`
	Host       string `yaml:"host"`
	Port       int    `yaml:"port"`
	Username   string `yaml:"username"`
	Password   string `yaml:"password"`
	Database   string `yaml:"database"`
}

// SecurityConfig holds security-related configuration.
type SecurityConfig struct {
	RateLimit     RateLimitConfig `yaml:"rate_limit"`
	IPWhitelist   []string        `yaml:"ip_whitelist"`
	FailedLockout LockoutConfig   `yaml:"failed_login_lockout"`
}

// RateLimitConfig holds rate limiting configuration.
type RateLimitConfig struct {
	Enabled           bool `yaml:"enabled"`
	RequestsPerMinute int  `yaml:"requests_per_minute"`
	BurstSize         int  `yaml:"burst_size"`
}

// LockoutConfig holds failed login lockout configuration.
type LockoutConfig struct {
	Enabled         bool   `yaml:"enabled"`
	MaxAttempts     int    `yaml:"max_attempts"`
	LockoutDuration string `yaml:"lockout_duration"`
}

// ServerConfig holds server configuration.
type ServerConfig struct {
	Address string    `yaml:"address"`
	TLS     TLSConfig `yaml:"tls"`
}

// TLSConfig holds TLS configuration.
type TLSConfig struct {
	Enabled  bool   `yaml:"enabled"`
	CertFile string `yaml:"cert_file"`
	KeyFile  string `yaml:"key_file"`
}

// LoadConfig loads configuration from a YAML file.
func LoadConfig(path string) (*Config, error) {
	data, err := fileutil.SecureFileRead(path)
	if err != nil {
		return nil, err
	}

	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, err
	}
	return &cfg, nil
}

func main() {
	configFile := flag.String("config", "configs/config-local.yaml", "Configuration file path")
	apiKey := flag.String("api-key", "", "API key for authentication")
	flag.Parse()

	cfg, err := loadServerConfig(*configFile)
	if err != nil {
		log.Fatalf("Failed to load config: %v", err)
	}

	if err := ensureLogDirectory(cfg.Logging); err != nil {
		log.Fatalf("Failed to prepare log directory: %v", err)
	}

	logger := setupLogger(cfg.Logging)

	expManager, err := initExperimentManager(cfg.BasePath, logger)
	if err != nil {
		logger.Fatal("failed to initialize experiment manager", "error", err)
	}

	taskQueue, queueCleanup := initTaskQueue(cfg, logger)
	if queueCleanup != nil {
		defer queueCleanup()
	}

	db, dbCleanup := initDatabase(cfg, logger)
	if dbCleanup != nil {
		defer dbCleanup()
	}

	authCfg := buildAuthConfig(cfg.Auth, logger)
	sec := newSecurityMiddleware(cfg)

	mux := buildHTTPMux(cfg, logger, expManager, taskQueue, authCfg, db)
	finalHandler := wrapWithMiddleware(cfg, sec, mux)
	server := newHTTPServer(cfg, finalHandler)

	startServer(server, cfg, logger)
	waitForShutdown(server, logger)

	_ = apiKey // Reserved for future authentication enhancements
}

func loadServerConfig(path string) (*Config, error) {
	resolvedConfig, err := config.ResolveConfigPath(path)
	if err != nil {
		return nil, err
	}
	cfg, err := LoadConfig(resolvedConfig)
	if err != nil {
		return nil, err
	}
	cfg.Resources.ApplyDefaults()
	return cfg, nil
}

func ensureLogDirectory(cfg logging.Config) error {
	if cfg.File == "" {
		return nil
	}

	logDir := filepath.Dir(cfg.File)
	log.Printf("Creating log directory: %s", logDir)
	return os.MkdirAll(logDir, 0750)
}

func setupLogger(cfg logging.Config) *logging.Logger {
	logger := logging.NewLoggerFromConfig(cfg)
	ctx := logging.EnsureTrace(context.Background())
	return logger.Component(ctx, "api-server")
}

func initExperimentManager(basePath string, logger *logging.Logger) (*experiment.Manager, error) {
	if basePath == "" {
		basePath = "/tmp/ml-experiments"
	}

	expManager := experiment.NewManager(basePath)
	log.Printf("Initializing experiment manager with base_path: %s", basePath)
	if err := expManager.Initialize(); err != nil {
		return nil, err
	}

	logger.Info("experiment manager initialized", "base_path", basePath)
	return expManager, nil
}

func buildAuthConfig(cfg auth.Config, logger *logging.Logger) *auth.Config {
	if !cfg.Enabled {
		return nil
	}

	logger.Info("authentication enabled")
	return &cfg
}

func newSecurityMiddleware(cfg *Config) *middleware.SecurityMiddleware {
	apiKeys := collectAPIKeys(cfg.Auth.APIKeys)
	rlOpts := buildRateLimitOptions(cfg.Security.RateLimit)
	return middleware.NewSecurityMiddleware(apiKeys, os.Getenv("JWT_SECRET"), rlOpts)
}

func collectAPIKeys(keys map[auth.Username]auth.APIKeyEntry) []string {
	apiKeys := make([]string, 0, len(keys))
	for username := range keys {
		apiKeys = append(apiKeys, string(username))
	}
	return apiKeys
}

func buildRateLimitOptions(cfg RateLimitConfig) *middleware.RateLimitOptions {
	if !cfg.Enabled || cfg.RequestsPerMinute <= 0 {
		return nil
	}

	return &middleware.RateLimitOptions{
		RequestsPerMinute: cfg.RequestsPerMinute,
		BurstSize:         cfg.BurstSize,
	}
}

func initTaskQueue(cfg *Config, logger *logging.Logger) (*queue.TaskQueue, func()) {
	queueCfg := queue.Config{
		RedisAddr:     cfg.Redis.Addr,
		RedisPassword: cfg.Redis.Password,
		RedisDB:       cfg.Redis.DB,
	}
	if queueCfg.RedisAddr == "" {
		queueCfg.RedisAddr = config.DefaultRedisAddr
	}
	if cfg.Redis.URL != "" {
		queueCfg.RedisAddr = cfg.Redis.URL
	}

	taskQueue, err := queue.NewTaskQueue(queueCfg)
	if err != nil {
		logger.Error("failed to initialize task queue", "error", err)
		return nil, nil
	}

	logger.Info("task queue initialized", "redis_addr", queueCfg.RedisAddr)
	cleanup := func() {
		logger.Info("stopping task queue...")
		if err := taskQueue.Close(); err != nil {
			logger.Error("failed to stop task queue", "error", err)
		} else {
			logger.Info("task queue stopped")
		}
	}
	return taskQueue, cleanup
}

func initDatabase(cfg *Config, logger *logging.Logger) (*storage.DB, func()) {
	if cfg.Database.Type == "" {
		return nil, nil
	}

	dbConfig := storage.DBConfig{
		Type:       cfg.Database.Type,
		Connection: cfg.Database.Connection,
		Host:       cfg.Database.Host,
		Port:       cfg.Database.Port,
		Username:   cfg.Database.Username,
		Password:   cfg.Database.Password,
		Database:   cfg.Database.Database,
	}

	db, err := storage.NewDB(dbConfig)
	if err != nil {
		logger.Error("failed to initialize database", "type", cfg.Database.Type, "error", err)
		return nil, nil
	}

	schemaPath := schemaPathForDB(cfg.Database.Type)
	if schemaPath == "" {
		logger.Error("unsupported database type", "type", cfg.Database.Type)
		_ = db.Close()
		return nil, nil
	}

	schema, err := fileutil.SecureFileRead(schemaPath)
	if err != nil {
		logger.Error("failed to read database schema file", "path", schemaPath, "error", err)
		_ = db.Close()
		return nil, nil
	}

	if err := db.Initialize(string(schema)); err != nil {
		logger.Error("failed to initialize database schema", "error", err)
		_ = db.Close()
		return nil, nil
	}

	logger.Info("database initialized", "type", cfg.Database.Type, "connection", cfg.Database.Connection)
	cleanup := func() {
		logger.Info("closing database connection...")
		if err := db.Close(); err != nil {
			logger.Error("failed to close database", "error", err)
		} else {
			logger.Info("database connection closed")
		}
	}
	return db, cleanup
}

func schemaPathForDB(dbType string) string {
	switch dbType {
	case "sqlite":
		return "internal/storage/schema_sqlite.sql"
	case "postgres", "postgresql":
		return "internal/storage/schema_postgres.sql"
	default:
		return ""
	}
}

func buildHTTPMux(
	cfg *Config,
	logger *logging.Logger,
	expManager *experiment.Manager,
	taskQueue *queue.TaskQueue,
	authCfg *auth.Config,
	db *storage.DB,
) *http.ServeMux {
	mux := http.NewServeMux()
	wsHandler := api.NewWSHandler(authCfg, logger, expManager, taskQueue)

	mux.Handle("/ws", wsHandler)
	mux.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = fmt.Fprintf(w, "OK\n")
	})

	mux.HandleFunc("/db-status", func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		if db == nil {
			w.WriteHeader(http.StatusServiceUnavailable)
			_, _ = fmt.Fprintf(w, `{"status":"disconnected","message":"Database not configured or failed to initialize"}`)
			return
		}

		var result struct {
			Status  string `json:"status"`
			Type    string `json:"type"`
			Path    string `json:"path"`
			Message string `json:"message"`
		}
		result.Status = "connected"
		result.Type = cfg.Database.Type
		result.Path = cfg.Database.Connection
		result.Message = fmt.Sprintf("%s database is operational", cfg.Database.Type)

		if err := db.RecordSystemMetric("db_test", "ok"); err != nil {
			result.Status = "error"
			result.Message = fmt.Sprintf("Database query failed: %v", err)
		}

		jsonBytes, _ := json.Marshal(result)
		_, _ = w.Write(jsonBytes)
	})

	return mux
}

func wrapWithMiddleware(cfg *Config, sec *middleware.SecurityMiddleware, mux *http.ServeMux) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/ws" {
			mux.ServeHTTP(w, r)
			return
		}

		handler := sec.RateLimit(mux)
		handler = middleware.SecurityHeaders(handler)
		handler = middleware.CORS(handler)
		handler = middleware.RequestTimeout(30 * time.Second)(handler)
		handler = middleware.AuditLogger(handler)
		if len(cfg.Security.IPWhitelist) > 0 {
			handler = sec.IPWhitelist(cfg.Security.IPWhitelist)(handler)
		}
		handler.ServeHTTP(w, r)
	})
}

func newHTTPServer(cfg *Config, handler http.Handler) *http.Server {
	return &http.Server{
		Addr:         cfg.Server.Address,
		Handler:      handler,
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 30 * time.Second,
		IdleTimeout:  120 * time.Second,
	}
}

func startServer(server *http.Server, cfg *Config, logger *logging.Logger) {
	if !cfg.Server.TLS.Enabled {
		logger.Warn("TLS disabled for API server; do not use this configuration in production", "address", cfg.Server.Address)
	}

	go func() {
		if cfg.Server.TLS.Enabled {
			logger.Info("starting HTTPS server", "address", cfg.Server.Address)
			if err := server.ListenAndServeTLS(
				cfg.Server.TLS.CertFile,
				cfg.Server.TLS.KeyFile,
			); err != nil && err != http.ErrServerClosed {
				logger.Error("HTTPS server failed", "error", err)
			}
		} else {
			logger.Info("starting HTTP server", "address", cfg.Server.Address)
			if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
				logger.Error("HTTP server failed", "error", err)
			}
		}
		os.Exit(1)
	}()
}

func waitForShutdown(server *http.Server, logger *logging.Logger) {
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	sig := <-sigChan
	logger.Info("received shutdown signal", "signal", sig)

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	logger.Info("shutting down http server...")
	if err := server.Shutdown(ctx); err != nil {
		logger.Error("server shutdown error", "error", err)
	} else {
		logger.Info("http server shutdown complete")
	}

	logger.Info("api server stopped")
}