package commands

import (
	"context"
	"fmt"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"tercul/cmd/cli/internal/bootstrap"
	"tercul/internal/adapters/graphql"
	"tercul/internal/observability"
	platform_auth "tercul/internal/platform/auth"
	"tercul/internal/platform/config"
	"tercul/internal/platform/db"
	app_log "tercul/internal/platform/log"

	"github.com/99designs/gqlgen/graphql/handler"
	"github.com/99designs/gqlgen/graphql/playground"
	"github.com/pressly/goose/v3"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/spf13/cobra"
	"github.com/weaviate/weaviate-go-client/v5/weaviate"
	"gorm.io/gorm"
)

// NewServeCommand creates a new Cobra command for serving the API
func NewServeCommand() *cobra.Command {
	cmd := &cobra.Command{
		Use:   "serve",
		Short: "Start the Tercul API server",
		Long: `Start the Tercul GraphQL API server with all endpoints including:
- GraphQL query endpoint (/query)
- GraphQL Playground (/playground)
- Prometheus metrics (/metrics)`,
		RunE: func(cmd *cobra.Command, args []string) error {
			// Load configuration
			cfg, err := config.LoadConfig()
			if err != nil {
				return fmt.Errorf("failed to load config: %w", err)
			}

			// Initialize logger
			app_log.Init("tercul-api", cfg.Environment)
			obsLogger := observability.NewLogger("tercul-api", cfg.Environment)

			// Initialize OpenTelemetry Tracer Provider
			tp, err := observability.TracerProvider("tercul-api", cfg.Environment)
			if err != nil {
				app_log.Fatal(err, "Failed to initialize OpenTelemetry tracer")
			}
			defer func() {
				if err := tp.Shutdown(context.Background()); err != nil {
					app_log.Error(err, "Error shutting down tracer provider")
				}
			}()

			// Initialize Prometheus metrics
			reg := prometheus.NewRegistry()
			metrics := observability.NewMetrics(reg)

			app_log.Info(fmt.Sprintf("Starting Tercul application in %s environment, version 1.0.0", cfg.Environment))

			// Initialize database connection
			database, err := db.InitDB(cfg, metrics)
			if err != nil {
				app_log.Fatal(err, "Failed to initialize database")
			}
			defer func() {
				if err := db.Close(database); err != nil {
					app_log.Error(err, "Error closing database")
				}
			}()

			// Run migrations
			if err := runMigrations(database, cfg.MigrationPath); err != nil {
				app_log.Fatal(err, "Failed to apply database migrations")
			}

			// Initialize Weaviate client
			weaviateCfg := weaviate.Config{
				Host:   cfg.WeaviateHost,
				Scheme: cfg.WeaviateScheme,
			}
			weaviateClient, err := weaviate.NewClient(weaviateCfg)
			if err != nil {
				app_log.Fatal(err, "Failed to create weaviate client")
			}

			// Bootstrap application dependencies
			deps, err := bootstrap.BootstrapWithMetrics(cfg, database, weaviateClient)
			if err != nil {
				return fmt.Errorf("failed to bootstrap application: %w", err)
			}

			// Create GraphQL server
			resolver := &graphql.Resolver{
				App: deps.Application,
			}

			// Create the API server
			apiHandler := newAPIServer(resolver, deps.JWTManager, metrics, obsLogger, reg)

			// Create the main HTTP server
			mainServer := &http.Server{
				Addr:    cfg.ServerPort,
				Handler: apiHandler,
			}
			app_log.Info(fmt.Sprintf("API server listening on port %s", cfg.ServerPort))

			// Start the main server in a goroutine
			go func() {
				if err := mainServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
					app_log.Fatal(err, "Failed to start server")
				}
			}()

			// Wait for interrupt signal to gracefully shutdown the server
			quit := make(chan os.Signal, 1)
			signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
			<-quit
			app_log.Info("Shutting down server...")

			// Graceful shutdown
			ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
			defer cancel()

			if err := mainServer.Shutdown(ctx); err != nil {
				app_log.Error(err, "Server forced to shutdown")
			}

			app_log.Info("Server shut down successfully")
			return nil
		},
	}

	return cmd
}

// runMigrations applies database migrations using goose.
func runMigrations(gormDB *gorm.DB, migrationPath string) error {
	sqlDB, err := gormDB.DB()
	if err != nil {
		return err
	}

	if err := goose.SetDialect("postgres"); err != nil {
		return err
	}

	app_log.Info(fmt.Sprintf("Applying database migrations from %s", migrationPath))
	if err := goose.Up(sqlDB, migrationPath); err != nil {
		return err
	}
	app_log.Info("Database migrations applied successfully")
	return nil
}

// newAPIServer creates a new http.ServeMux and configures it with all the API routes
func newAPIServer(
	resolver *graphql.Resolver,
	jwtManager *platform_auth.JWTManager,
	metrics *observability.Metrics,
	logger *observability.Logger,
	reg *prometheus.Registry,
) *http.ServeMux {
	// Configure the GraphQL server
	c := graphql.Config{Resolvers: resolver}
	c.Directives.Binding = graphql.Binding

	// Create the core GraphQL handler
	graphqlHandler := handler.New(graphql.NewExecutableSchema(c))
	graphqlHandler.SetErrorPresenter(graphql.NewErrorPresenter())

	// Create the middleware chain for the GraphQL endpoint.
	// Middlewares are applied from bottom to top.
	var chain http.Handler
	chain = graphqlHandler
	chain = metrics.PrometheusMiddleware(chain)
	chain = observability.LoggingMiddleware(logger)(chain) // Must run after auth and tracing
	chain = platform_auth.GraphQLAuthMiddleware(jwtManager)(chain)
	chain = observability.TracingMiddleware(chain)
	chain = observability.RequestIDMiddleware(chain)

	// Create a new ServeMux and register all handlers
	mux := http.NewServeMux()
	mux.Handle("/query", chain)
	mux.Handle("/playground", playground.Handler("GraphQL Playground", "/query"))
	mux.Handle("/metrics", observability.PrometheusHandler(reg))

	return mux
}