package gateway

import (
	"context"
	"net/http"
	"net/http/httputil"
	"net/url"

	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type ReverseProxy struct {
	addr   string
	target string
	server *http.Server
}

func (p *ReverseProxy) Start(ctx context.Context, addr, target string) error {
	alreadyRunning := p.server != nil && target == p.target && addr == p.target

	if alreadyRunning {
		return nil
	}

	if p.server != nil {
		if err := p.Stop(); err != nil {
			return errors.WithStack(err)
		}
	}

	server := &http.Server{
		Addr: addr,
	}

	url, err := url.Parse(target)
	if err != nil {
		return errors.WithStack(err)
	}

	proxy := httputil.NewSingleHostReverseProxy(url)

	server.Handler = proxy

	p.server = server
	p.addr = addr
	p.target = target

	go func() {
		if err := server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			logger.Error(ctx, "error while listening", logger.E(errors.WithStack(err)))
		}

		if err := p.Stop(); err != nil {
			logger.Error(ctx, "error while stopping gateway", logger.E(errors.WithStack(err)))
		}
	}()

	return nil
}

func (p *ReverseProxy) Stop() error {
	if p.server == nil {
		return nil
	}

	if err := p.server.Close(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		return errors.WithStack(err)
	}

	p.server = nil

	return nil
}

func NewReverseProxy() *ReverseProxy {
	return &ReverseProxy{}
}