package gateway

import (
	"context"
	"fmt"
	"net/http/httputil"
	"net/url"
	"sync/atomic"

	"esway/internal/log"
	"esway/internal/opt"

	"github.com/loveuer/nf"
)

func proxy(ctx context.Context) (nf.HandlerFunc, error) {
	if len(opt.Cfg.Endpoints) == 0 {
		return nil, fmt.Errorf("gateway: 必须要指定 elasticsearch endpoints")
	}

	urls := make([]*url.URL, 0)
	for _, item := range opt.Cfg.Endpoints {
		ins, err := url.Parse(item)
		if err != nil {
			log.Warn(ctx, "gateway: endpoint invalid, endpoint = %s, err = %s", item, err.Error())
		}

		urls = append(urls, ins)
	}

	if len(urls) == 0 {
		return nil, fmt.Errorf("gateway: no valid elasticsearch endpoint")
	}

	svcs := make([]*httputil.ReverseProxy, len(urls))
	for idx, item := range urls {
		svcs[idx] = httputil.NewSingleHostReverseProxy(item)
	}

	var (
		round  int64 = 0
		length       = int64(len(svcs))
	)
	return func(c *nf.Ctx) error {
		svc := svcs[atomic.SwapInt64(&round, (round+1)%length)]

		svc.ServeHTTP(c.Writer, c.Request)

		return nil
	}, nil
}