package pages

import (
	"fmt"
	"io"
	"mime"
	"net/http"
	"strings"
	"time"

	"github.com/patrickmn/go-cache"
	log "github.com/sirupsen/logrus"
)

const (
	// The branch name on which files must reside.
	PagesBranch = "pages"
)

var (
	pageCache = cache.New(6*time.Hour, 1*time.Hour)
)

type PageContentCache struct {
	Content     []byte
	mimeType    string
	RequestedAt time.Time
}

func makePageContentCacheEntry(username, path string) string {
	return username + ":" + path
}

func ServeFile(username, reponame, path, giteaUrl string, w http.ResponseWriter) {
	// Provide a default
	if path == "" {
		path = "/index.html"
	}

	// Strip away a starting / as it messes with Gitea
	if path[:1] == "/" {
		path = path[1:]
	}

	key := makePageContentCacheEntry(username, path)
	entry, found := pageCache.Get(key)
	var content []byte
	var mimeType string
	var err error
	if found {
		log.Debugf("Returning %s from cache", path)
		content = entry.(PageContentCache).Content
		mimeType = entry.(PageContentCache).mimeType
	}

	// We have to do the raw request manually because the Gitea SDK does not allow
	// passing the If-Modfied-Since header.
	apiUrl := fmt.Sprintf(
		"%s/api/v1/repos/%s/%s/raw/%s?ref=%s",
		giteaUrl,
		username,
		reponame,
		path,
		PagesBranch,
	)
	client := &http.Client{}
	req, err := http.NewRequest("GET", apiUrl, nil)
	if found {
		since := entry.(PageContentCache).RequestedAt.Format(time.RFC1123)
		log.Debugf("Found %s in cache. Adding '%s' as If-Modified-Since", key, since)
		req.Header.Add("If-Modified-Since", since)
	}
	resp, err := client.Do(req)
	if err != nil {
		if !found {
			log.Errorf("Failed to get file %s/%s/%s (%s)", username, reponame, path, err)
			w.WriteHeader(404)
		} else {
			log.Debugf("Request failed but page %s is cached in memory", path)
			w.WriteHeader(200)
			w.Header().Set("Content-Type", mimeType)
			w.Write(content)
		}

		return
	}
	defer resp.Body.Close()

	log.Debugf("Gitea API request returned %d", resp.StatusCode)
	if found && resp.StatusCode == 302 {
		log.Debugf("Page %s is unchanged and cached in memory", path)
		w.WriteHeader(200)
		w.Header().Set("Content-Type", mimeType)
		w.Write(content)
		return
	}

	// Correctly propagate 404s.
	if resp.StatusCode == 404 {
		w.WriteHeader(404)
		return
	}

	content, err = io.ReadAll(resp.Body)
	if err != nil {
		log.Errorf("Failed to get file %s/%s/%s (%s)", username, reponame, path, err)
		w.WriteHeader(404)
		return
	}

	pathParts := strings.Split(path, ".")
	ext := pathParts[len(pathParts)-1]
	mimeType = mime.TypeByExtension("." + ext)

	now := time.Now()
	pageCache.Set(
		key,
		PageContentCache{
			content,
			mimeType,
			now,
		},
		cache.DefaultExpiration,
	)

	log.Debugf("Page %s requested from Gitea and cached in memory at %v", path, now)
	w.WriteHeader(200)
	w.Header().Set("Content-Type", mimeType)
	w.Write(content)
}