package app

import (
	"context"
	"crypto/tls"
	"errors"
	"fmt"
	"net"
	"strings"
	"time"

	"git.yuntuo.hk/k2safe/go-omni/config"
	h2transport "git.yuntuo.hk/k2safe/go-omni/transport/http2"
	"git.yuntuo.hk/k2safe/go-omni/transport/native"
)

// ServeContext serves a caller-created listener using the configured transport
// and TLS. App takes ownership of the listener, including on startup failure,
// and runs resource cleanup after the server has stopped.
func (a *App) ServeContext(ctx context.Context, listener net.Listener) error {
	if listener == nil {
		return errors.Join(errors.New("go-omni: nil listener"), a.Close())
	}
	defer listener.Close()
	if ctx == nil {
		ctx = context.Background()
	}
	if ctx.Err() != nil {
		_ = listener.Close()
		return a.Close()
	}
	serve, err := a.prepareTransport()
	if err != nil {
		_ = listener.Close()
		return errors.Join(err, a.Close())
	}
	return errors.Join(serve(ctx, listener), a.Close())
}

func (a *App) prepareTransport() (func(context.Context, net.Listener) error, error) {
	if err := a.config.ValidateTransport(); err != nil {
		return nil, err
	}
	shutdownTimeout := a.config.ShutdownTimeout
	if shutdownTimeout <= 0 {
		shutdownTimeout = 10 * time.Second
	}
	var tlsConfig *tls.Config
	if strings.TrimSpace(a.config.TLS.CertFile) != "" {
		certificate, err := tls.LoadX509KeyPair(a.config.TLS.CertFile, a.config.TLS.KeyFile)
		if err != nil {
			return nil, fmt.Errorf("go-omni: load TLS certificate: %w", err)
		}
		tlsConfig = &tls.Config{Certificates: []tls.Certificate{certificate}, MinVersion: tls.VersionTLS12}
	}
	switch a.config.Transport {
	case config.TransportNative:
		server := native.New(a)
		server.ShutdownTimeout = shutdownTimeout
		if tlsConfig != nil {
			return func(ctx context.Context, listener net.Listener) error {
				return server.ServeTLS(ctx, listener, tlsConfig)
			}, nil
		}
		return server.Serve, nil
	case config.TransportHTTP2:
		server := h2transport.New(a)
		server.ShutdownTimeout = shutdownTimeout
		return func(ctx context.Context, listener net.Listener) error {
			return server.ServeTLS(ctx, listener, tlsConfig)
		}, nil
	default:
		server := a.NewServer("")
		server.TLSConfig = tlsConfig
		return func(ctx context.Context, listener net.Listener) error {
			return a.serveContext(ctx, server, listener)
		}, nil
	}
}