package app

import (
	"context"
	"errors"
	"log/slog"
	"net/http"
	"time"

	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/config"
	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/gateway"
)

// Serve builds the router from config, connects upstreams, and runs the HTTP
// gateway until ctx is cancelled, then shuts down gracefully.
func Serve(ctx context.Context, cfg *config.Config, log *slog.Logger) error {
	r, err := BuildRouter(cfg, log)
	if err != nil {
		return err
	}
	defer r.Close()

	log.Info("connecting upstreams", "count", len(cfg.Upstreams))
	connectCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	r.ConnectAll(connectCtx)
	cancel()
	for _, s := range r.Statuses() {
		if s.Ready {
			log.Info("upstream ready", "namespace", s.Namespace, "server", s.Server)
		} else {
			log.Warn("upstream unavailable", "namespace", s.Namespace, "error", s.Error)
		}
	}

	gw := gateway.New(gateway.Options{
		Name:    cfg.Gateway.Name,
		Version: cfg.Gateway.Version,
		MCPPath: cfg.Gateway.MCPPath,
		Router:  r,
		Logger:  log,
	})

	srv := &http.Server{
		Addr:              cfg.Server.Address,
		Handler:           gw.Handler(),
		ReadHeaderTimeout: 10 * time.Second,
	}

	errCh := make(chan error, 1)
	go func() {
		log.Info("gateway listening",
			"address", cfg.Server.Address,
			"mcp_endpoint", cfg.Gateway.MCPPath,
			"tools", len(r.ListTools()))
		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			errCh <- err
		}
	}()

	select {
	case <-ctx.Done():
		log.Info("shutting down")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		return srv.Shutdown(shutdownCtx)
	case err := <-errCh:
		return err
	}
}