package main

import (
	"context"
	"flag"
	"fmt"
	"net"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"gopkg.in/yaml.v2"

	"github.com/beckn-one/beckn-onix/core/module"
	"github.com/beckn-one/beckn-onix/core/module/handler"
	"github.com/beckn-one/beckn-onix/pkg/log"
	"github.com/beckn-one/beckn-onix/pkg/plugin"
	"github.com/beckn-one/beckn-onix/pkg/telemetry"
)

// ApplicationPlugins holds application-level plugin configurations.
type ApplicationPlugins struct {
	OtelSetup *plugin.Config `yaml:"otelsetup,omitempty"`
}

// Config struct holds all configurations.
type Config struct {
	AppName       string                `yaml:"appName"`
	Log           log.Config            `yaml:"log"`
	Plugins       ApplicationPlugins    `yaml:"plugins,omitempty"`
	PluginManager *plugin.ManagerConfig `yaml:"pluginManager"`
	Modules       []module.Config       `yaml:"modules"`
	HTTP          httpConfig            `yaml:"http"`
}

type httpConfig struct {
	Port     string        `yaml:"port"`
	Timeouts timeoutConfig `yaml:"timeout"`
}

type timeoutConfig struct {
	Read  time.Duration `yaml:"read"`
	Write time.Duration `yaml:"write"`
	Idle  time.Duration `yaml:"idle"`
}

var configPath string
var runFunc = run

func main() {
	// Define and parse command-line flags.
	flag.StringVar(&configPath, "config", "../../config/onix/adapter.yaml", "Path to the configuration file")
	flag.Parse()

	// Use custom log for initial setup messages.
	log.Infof(context.Background(), "Starting application with config: %s", configPath)

	// Run the application within a context.
	if err := runFunc(context.Background(), configPath); err != nil {
		log.Fatalf(context.Background(), err, "Application failed: %v", err)
	}
	log.Infof(context.Background(), "Application finished")
}

// initConfig loads and validates the configuration.
func initConfig(ctx context.Context, path string) (*Config, error) {
	// Open the configuration file.
	file, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("could not open config file: %w", err)
	}
	defer file.Close()

	// Decode the YAML configuration.
	var cfg Config
	if err := yaml.NewDecoder(file).Decode(&cfg); err != nil {
		return nil, fmt.Errorf("could not decode config: %w", err)
	}
	log.Debugf(ctx, "Read config: %#v", cfg)
	// Validate the configuration.
	if err := validateConfig(&cfg); err != nil {
		return nil, fmt.Errorf("invalid config: %w", err)
	}

	return &cfg, nil
}

// validateConfig validates the configuration.
func validateConfig(cfg *Config) error {
	if strings.TrimSpace(cfg.AppName) == "" {
		return fmt.Errorf("missing app name")
	}
	if strings.TrimSpace(cfg.HTTP.Port) == "" {
		return fmt.Errorf("missing port")
	}
	return nil
}

// loadAppPlugin is a generic function to load and validate application-level plugins.
func loadAppPlugin[T any](ctx context.Context, name string, cfg *plugin.Config, mgrFunc func(context.Context, *plugin.Config) (T, error)) error {
	if cfg == nil {
		log.Debugf(ctx, "Skipping %s plugin: not configured", name)
		return nil
	}

	_, err := mgrFunc(ctx, cfg)
	if err != nil {
		return fmt.Errorf("failed to load %s plugin (%s): %w", name, cfg.ID, err)
	}

	log.Debugf(ctx, "Loaded %s plugin: %s", name, cfg.ID)
	return nil
}

// initAppPlugins initializes application-level plugins including telemetry.
// This function is designed to be extensible for future plugin types.
func initAppPlugins(ctx context.Context, mgr *plugin.Manager, cfg ApplicationPlugins) error {
	if err := loadAppPlugin(ctx, "OtelSetup", cfg.OtelSetup, func(ctx context.Context, cfg *plugin.Config) (*telemetry.Provider, error) {
		return mgr.OtelSetup(ctx, cfg)
	}); err != nil {
		return fmt.Errorf("failed to initialize application plugins: %w", err)
	}

	return nil
}

// newServer creates and initializes the HTTP server.
func newServer(ctx context.Context, mgr handler.PluginManager, cfg *Config) (http.Handler, error) {
	mux := http.NewServeMux()

	if err := module.Register(ctx, cfg.Modules, mux, mgr); err != nil {
		return nil, fmt.Errorf("failed to register modules: %w", err)
	}
	return mux, nil
}

var newManagerFunc = plugin.NewManager
var newServerFunc = newServer

// run encapsulates the application logic.
func run(ctx context.Context, configPath string) error {
	closers := []func(){}
	// Initialize configuration and logger.
	cfg, err := initConfig(ctx, configPath)
	if err != nil {
		return fmt.Errorf("failed to initialize config: %w", err)
	}
	log.Infof(ctx, "Initializing logger with config: %+v", cfg.Log)
	if err := log.InitLogger(cfg.Log); err != nil {
		return fmt.Errorf("failed to initialize logger: %w", err)
	}

	// Initialize plugin manager.
	log.Infof(ctx, "Initializing plugin manager")
	mgr, closer, err := newManagerFunc(ctx, cfg.PluginManager)
	if err != nil {
		return fmt.Errorf("failed to create plugin manager: %w", err)
	}
	closers = append(closers, closer)
	log.Debug(ctx, "Plugin manager loaded.")

	// Initialize plugins including telemetry.
	if err := initAppPlugins(ctx, mgr, cfg.Plugins); err != nil {
		return fmt.Errorf("failed to initialize plugins: %w", err)
	}

	// Initialize HTTP server.
	log.Infof(ctx, "Initializing HTTP server")
	srv, err := newServerFunc(ctx, mgr, cfg)
	if err != nil {
		return fmt.Errorf("failed to initialize server: %w", err)
	}

	// Configure HTTP server.
	httpServer := &http.Server{
		Addr:         net.JoinHostPort("", cfg.HTTP.Port),
		Handler:      srv,
		ReadTimeout:  cfg.HTTP.Timeouts.Read * time.Second,
		WriteTimeout: cfg.HTTP.Timeouts.Write * time.Second,
		IdleTimeout:  cfg.HTTP.Timeouts.Idle * time.Second,
	}

	// Start HTTP server.
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		log.Infof(ctx, "Server listening on %s", httpServer.Addr)
		if err := httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Errorf(ctx, fmt.Errorf("http server ListenAndServe: %w", err), "error listening and serving")
		}
	}()

	// Handle shutdown.
	shutdown(ctx, httpServer, &wg, closers)
	wg.Wait()
	log.Infof(ctx, "Server shutdown complete")
	return nil
}

// shutdown handles server shutdown.
func shutdown(ctx context.Context, httpServer *http.Server, wg *sync.WaitGroup, closers []func()) {
	wg.Add(1)
	go func() {
		defer wg.Done()
		<-ctx.Done()
		log.Infof(ctx, "Shutting down server...")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		if err := httpServer.Shutdown(shutdownCtx); err != nil {
			log.Errorf(ctx, fmt.Errorf("http server Shutdown: %w", err), "error shutting down http server")
		}

		// Call all closer functions.
		for _, closer := range closers {
			closer()
		}
	}()
}