// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

package lib

import (
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
)

type Forgejo struct {
	Server url.URL
	Token  string
	Branch string
}

var ErrNotFound = errors.New("404 not found")

// headers must ot be nil
func (f *Forgejo) GetFile(ctx context.Context, headers map[string]string, user, repo, branch, file string) (ret *http.Response, err error) {
	u := f.Server
	u.Path = "/api/v1/repos/" + user + "/" + repo + "/raw/" + file
	p := u.Query()
	p.Set("ref", branch)
	u.RawQuery = p.Encode()
	fmt.Println(u.String())
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if err != nil {
		return
	}

	for k, v := range headers {
		if v == "" {
			continue
		}
		req.Header.Set(k, v)
	}
	req.Header.Set("Authorization", "token "+f.Token)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return
	}
	if resp.StatusCode == http.StatusNotFound {
		err = ErrNotFound
		return
	}

	return resp, nil
}

func UseAPI(bind string, f *Forgejo) (*http.Server, error) {
	if f == nil {
		return nil, errors.New("forgejo is nil")
	}
	s := &http.Server{
		Addr:    bind,
		Handler: http.HandlerFunc(f.handle),
	}
	return s, nil
}

func trySet(h http.Header, key string, src http.Header) {
	value := src.Get(key)
	if value == "" {
		h.Del(key)
		return
	}
	h.Set(key, value)
}

func (f *Forgejo) handle(w http.ResponseWriter, r *http.Request) {
	arr := strings.Split(r.URL.Path[1:], "/")
	if len(arr) < 2 {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	user, repo := arr[0], arr[1]
	if user == "u" {
		user, repo = repo, f.Branch
	}
	file := "index.html"
	if l := len(arr); l > 2 {
		if arr[l-1] == "" {
			arr[l-1] = "index.html"
		}
		file = strings.Join(arr[2:], "/")
	}

	headers := map[string]string{}
	headers["If-None-Match"] = r.Header.Get("If-None-Match")
	headers["If-Modified-Since"] = r.Header.Get("If-Modified-Since")
	headers["If-Range"] = r.Header.Get("If-Range")
	headers["Range"] = r.Header.Get("Range")
	resp, err := f.GetFile(r.Context(), headers, user, repo, f.Branch, file)
	if err != nil {
		w.WriteHeader(http.StatusNotFound)
		return
	}
	defer resp.Body.Close()

	trySet(w.Header(), "Etag", resp.Header)
	trySet(w.Header(), "Last-Modified", resp.Header)
	trySet(w.Header(), "Content-Length", resp.Header)
	trySet(w.Header(), "Content-Range", resp.Header)

	w.WriteHeader(resp.StatusCode)
	io.Copy(w, resp.Body)
}