package http2

import (
	"context"
	"encoding/base64"
	"fmt"
	"net/http"
	"net/http/httputil"
	"os"
	"strconv"
	"strings"

	"github.com/go-gost/core/auth"
	"github.com/go-gost/core/logger"
)

func (h *http2Handler) basicProxyAuth(proxyAuth string) (username, password string, ok bool) {
	if proxyAuth == "" {
		return
	}

	if !strings.HasPrefix(proxyAuth, "Basic ") {
		return
	}
	c, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(proxyAuth, "Basic "))
	if err != nil {
		return
	}
	cs := string(c)
	s := strings.IndexByte(cs, ':')
	if s < 0 {
		return
	}

	return cs[:s], cs[s+1:], true
}

func (h *http2Handler) authenticate(ctx context.Context, w http.ResponseWriter, r *http.Request, resp *http.Response, log logger.Logger) (id string, ok bool, pipeTo string) {
	u, p, _ := h.basicProxyAuth(r.Header.Get("Proxy-Authorization"))
	if h.options.Auther == nil {
		return "", true, ""
	}
	if id, ok = h.options.Auther.Authenticate(ctx, u, p, auth.WithService(h.options.Service)); ok {
		return
	}

	pr := h.md.probeResistance
	// probing resistance is enabled, and knocking host is mismatch.
	if pr != nil && (pr.Knock == "" || !knockMatch(r.URL.Hostname(), pr.Knock)) {
		resp.StatusCode = http.StatusServiceUnavailable // default status code
		switch pr.Type {
		case "code":
			resp.StatusCode, _ = strconv.Atoi(pr.Value)
		case "web":
			url := pr.Value
			if !strings.HasPrefix(url, "http") {
				url = "http://" + url
			}
			req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
			if err != nil {
				log.Error(err)
				break
			}
			r, err := http.DefaultClient.Do(req)
			if err != nil {
				log.Error(err)
				break
			}
			resp = r
			defer resp.Body.Close()
		case "host":
			return "", false, pr.Value
		case "file":
			f, _ := os.Open(pr.Value)
			if f != nil {
				defer f.Close()

				resp.StatusCode = http.StatusOK
				if finfo, _ := f.Stat(); finfo != nil {
					resp.ContentLength = finfo.Size()
				}
				resp.Header.Set("Content-Type", "text/html")
				resp.Body = f
			}
		}
	}

	if resp.StatusCode == 0 {
		realm := defaultRealm
		if h.md.authBasicRealm != "" {
			realm = h.md.authBasicRealm
		}
		resp.StatusCode = http.StatusProxyAuthRequired
		resp.Header.Add("Proxy-Authenticate", fmt.Sprintf("Basic realm=\"%s\"", realm))
		if strings.ToLower(r.Header.Get("Proxy-Connection")) == "keep-alive" {
			// XXX libcurl will keep sending auth request in same conn
			// which we don't supported yet.
			resp.Header.Set("Connection", "close")
			resp.Header.Set("Proxy-Connection", "close")
		}

		log.Debug("proxy authentication required")
	} else {
		resp.Header = http.Header{}
		// resp.Header.Set("Server", "nginx/1.20.1")
		// resp.Header.Set("Date", time.Now().Format(http.TimeFormat))
		if resp.StatusCode == http.StatusOK {
			resp.Header.Set("Connection", "keep-alive")
		}
	}

	if log.IsLevelEnabled(logger.TraceLevel) {
		dump, _ := httputil.DumpResponse(resp, false)
		log.Trace(string(dump))
	}

	h.writeResponse(w, resp)

	return
}

// knockMatch reports whether hostname matches any entry in the
// comma-separated knock list. Matching is case-insensitive. An empty
// knock string returns false (no match).
func knockMatch(hostname, knock string) bool {
	if knock == "" {
		return false
	}
	for _, h := range strings.Split(knock, ",") {
		if strings.EqualFold(hostname, strings.TrimSpace(h)) {
			return true
		}
	}
	return false
}