package forge

import (
	"encoding/base64"
	"errors"
	"html/template"
	"io"
	"mime"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"slices"
	"strconv"
	"strings"
	"unicode/utf8"
)

var fullOID = regexp.MustCompile(`^[0-9a-f]{40}$`)

func (s *Server) gistIndex(w http.ResponseWriter, r *http.Request) {
	user := s.current(r)
	gists, err := s.store.Gists(0, false, 50)
	if err != nil {
		s.fail(w, r, 500, err.Error())
		return
	}
	s.render(w, r, "gists", page{Title: "Gists", User: user, Data: map[string]any{"Items": s.gistItems(gists)}})
}

func (s *Server) userGists(w http.ResponseWriter, r *http.Request, owner User, user *User) {
	own := user != nil && user.ID == owner.ID
	gists, err := s.store.Gists(owner.ID, own, 200)
	if err != nil {
		s.fail(w, r, 500, err.Error())
		return
	}
	data := map[string]any{"Owner": owner, "Items": s.gistItems(gists), "Own": own, "Count": len(gists)}
	if r.URL.Query().Get("tab") == "starred" {
		starred, _ := s.store.StarredGists(owner.ID)
		data["Items"], data["Starred"] = s.gistItems(starred), true
	}
	s.render(w, r, "gists", page{Title: "~" + owner.Name + " gists", User: user, Data: data})
}

func formFiles(r *http.Request) []gistFile {
	names, contents, origs := r.PostForm["name"], r.PostForm["content"], r.PostForm["orig"]
	var files []gistFile
	for i := range min(len(contents), gistFormFiles) {
		f := gistFile{Content: strings.ReplaceAll(contents[i], "\r\n", "\n")}
		if i < len(names) {
			f.Name = strings.TrimSpace(names[i])
		}
		if i < len(origs) {
			f.Orig = origs[i]
		}
		files = append(files, f)
	}
	return files
}

func (s *Server) newGistForm(w http.ResponseWriter, r *http.Request) {
	u := s.require(w, r)
	if u == nil {
		return
	}
	s.render(w, r, "gistform", page{Title: "New gist", User: u, Data: map[string]any{"Files": []gistFile{{}}, "Action": "/gists"}})
}

func (s *Server) postGist(w http.ResponseWriter, r *http.Request) {
	u := s.require(w, r)
	if u == nil {
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, 8<<20)
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, 400, "The gist is too large")
		return
	}
	files := formFiles(r)
	data := map[string]any{"Files": files, "Action": "/gists", "Description": r.FormValue("description"), "Secret": r.FormValue("visibility") == "secret"}
	if r.FormValue("action") == "add" {
		data["Files"] = append(files, gistFile{})
		s.render(w, r, "gistform", page{Title: "New gist", User: u, Data: data})
		return
	}
	gist, err := s.createGist(*u, r.FormValue("description"), r.FormValue("visibility") == "secret", files)
	if err != nil {
		w.WriteHeader(400)
		s.render(w, r, "gistform", page{Title: "New gist", User: u, Error: err.Error(), Data: data})
		return
	}
	http.Redirect(w, r, "/gist/"+gist.ID, http.StatusSeeOther)
}

func (s *Server) gistRoute(w http.ResponseWriter, r *http.Request) {
	id, sub, _ := strings.Cut(strings.TrimPrefix(r.URL.Path, "/gist/"), "/")
	id = strings.TrimSuffix(id, ".git")
	if !gistID.MatchString(id) {
		s.fail(w, r, 404, "No such gist")
		return
	}
	gist, err := s.store.Gist(id)
	if err != nil {
		if isSmart(r, sub) {
			http.Error(w, "gist not found", 404)
			return
		}
		s.fail(w, r, 404, "No such gist")
		return
	}
	if isSmart(r, sub) {
		s.gistSmart(w, r, gist, sub)
		return
	}
	user := s.current(r)
	back := "/gist/" + gist.ID
	switch {
	case sub == "" && r.Method == "GET":
		s.gistPage(w, r, gist, user)
	case sub == "revisions" && r.Method == "GET":
		s.gistRevisions(w, r, gist, user)
	case sub == "edit":
		s.editGist(w, r, gist, user)
	case strings.HasPrefix(sub, "raw/") && r.Method == "GET":
		http.Redirect(w, r, "https://"+s.rawHost()+"/raw/"+gist.ID+"/"+escapePath(strings.TrimPrefix(sub, "raw/")), http.StatusFound)
	case r.Method != "POST":
		s.fail(w, r, 404, "Page not found")
	case user == nil:
		http.Redirect(w, r, "/login", http.StatusSeeOther)
	case sub == "star":
		s.store.StarGist(user.ID, gist.ID, !s.store.GistStarred(user.ID, gist.ID))
		http.Redirect(w, r, back, http.StatusSeeOther)
	case sub == "fork":
		fork, err := s.forkGistFor(*user, gist)
		if err != nil {
			s.fail(w, r, problemCode(err), err.Error())
			return
		}
		http.Redirect(w, r, "/gist/"+fork.ID, http.StatusSeeOther)
	case sub == "delete":
		if err := s.removeGist(*user, gist); err != nil {
			s.fail(w, r, problemCode(err), err.Error())
			return
		}
		if user.ID != gist.Owner.ID {
			http.Redirect(w, r, "/admin?s=gists", http.StatusSeeOther)
			return
		}
		http.Redirect(w, r, "/~"+gist.Owner.Name+"/gists", http.StatusSeeOther)
	case sub == "comment":
		s.settle(w, r, back+"#comments", s.commentGist(*user, gist, r.FormValue("body")))
	case strings.HasPrefix(sub, "comment/") && strings.HasSuffix(sub, "/delete"):
		cid, _ := strconv.ParseInt(strings.TrimSuffix(strings.TrimPrefix(sub, "comment/"), "/delete"), 10, 64)
		s.settle(w, r, back+"#comments", s.dropGistComment(*user, gist, cid))
	default:
		s.fail(w, r, 404, "Page not found")
	}
}

func (s *Server) gistPage(w http.ResponseWriter, r *http.Request, gist Gist, user *User) {
	head := s.gistHead(gist)
	commit := head
	if rev := r.URL.Query().Get("rev"); fullOID.MatchString(rev) {
		if c, err := s.gistGit(gist).Resolve(rev + "^{commit}"); err == nil {
			commit = c
		}
	}
	views := s.gistViews(gist, commit, 0)
	var files []string
	for _, v := range views {
		files = append(files, v.Name)
	}
	comments := s.store.GistComments(gist.ID)
	rendered := make([]map[string]any, len(comments))
	math := false
	for i, c := range comments {
		body := s.renderMarkdown([]byte(c.Body))
		math = math || hasMath(body)
		rendered[i] = map[string]any{"Comment": c, "Body": body}
	}
	for _, v := range views {
		math = math || hasMath(v.Markdown)
	}
	data := map[string]any{
		"Gist": gist, "Files": views, "Title": gist.Title(files), "Commit": commit, "Head": head, "Old": commit != head,
		"Comments": rendered, "Owner": user != nil && user.ID == gist.Owner.ID,
		"Admin": user != nil && s.store.IsAdmin(user.ID), "Starred": user != nil && s.store.GistStarred(user.ID, gist.ID),
		"Clone": "https://" + s.host + "/gist/" + gist.ID + ".git", "SSH": s.sshUser + "@" + s.sshHost + ":gist/" + gist.ID + ".git",
		"Embed": `<iframe src="https://` + s.rawHost() + `/embed/` + gist.ID + `" style="width:100%;height:24em;border:0" loading="lazy"></iframe>`,
	}
	if c, err := s.gistGit(gist).Commit(commit); err == nil {
		data["Last"] = c
	}
	if gist.Parent != "" {
		if p, err := s.store.Gist(gist.Parent); err == nil && !p.Secret {
			data["Parent"] = p
		}
	}
	if forks, _ := s.store.GistForks(gist.ID); len(forks) > 0 {
		data["Forks"] = forks
	}
	s.render(w, r, "gist", page{Title: gist.Title(files), User: user, Error: r.URL.Query().Get("error"), Math: math, Data: data})
}

func (s *Server) gistRevisions(w http.ResponseWriter, r *http.Request, gist Gist, user *User) {
	g := s.gistGit(gist)
	from, _ := strconv.Atoi(r.URL.Query().Get("from"))
	from = max(from, 0)
	commits, _ := g.Log(s.gistHead(gist), gistRevisionPage+1, "", "--skip="+strconv.Itoa(from))
	type revision struct {
		Commit Commit
		Files  []File
	}
	data := map[string]any{"Gist": gist, "Total": s.gistRevisionCount(gist)}
	if len(commits) > gistRevisionPage {
		commits = commits[:gistRevisionPage]
		data["Next"] = from + gistRevisionPage
	}
	if from > 0 {
		data["Prev"] = max(0, from-gistRevisionPage)
		data["Paged"] = true
	}
	revs := make([]revision, 0, len(commits))
	for _, c := range commits {
		files, _ := g.Diff(c.Hash)
		revs = append(revs, revision{Commit: c, Files: files})
	}
	data["Revisions"] = revs
	s.render(w, r, "gistlog", page{Title: "Revisions of gist " + gist.ID[:8], User: user, Data: data})
}

const gistRevisionPage = 30

func (s *Server) gistRevisionCount(gist Gist) int {
	out, err := s.gistGit(gist).run(nil, "rev-list", "--count", "refs/heads/main")
	if err != nil {
		return 0
	}
	n, _ := strconv.Atoi(strings.TrimSpace(string(out)))
	return n
}

func (s *Server) editGist(w http.ResponseWriter, r *http.Request, gist Gist, user *User) {
	if user == nil {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}
	if user.ID != gist.Owner.ID {
		s.fail(w, r, 403, "Only the owner can edit this gist")
		return
	}
	g := s.gistGit(gist)
	head := s.gistHead(gist)
	if r.Method == "POST" {
		r.Body = http.MaxBytesReader(w, r.Body, 8<<20)
		if err := r.ParseForm(); err != nil {
			s.fail(w, r, 400, "The gist is too large")
			return
		}
		head = r.FormValue("head")
	}
	entries, err := g.gistTree(head)
	if err != nil {
		s.fail(w, r, 409, "The gist changed while you were editing it, reload and try again")
		return
	}
	var files []gistFile
	var keep []gistEntry
	for _, e := range entries {
		if e.Size <= gistWebFile {
			if content, err := g.run(nil, "cat-file", "blob", e.OID); err == nil && !isBinary(content) {
				files = append(files, gistFile{Orig: e.Name, Name: e.Name, Content: string(content)})
				continue
			}
		}
		keep = append(keep, e)
	}
	data := map[string]any{"Gist": gist, "Files": files, "Keep": keep, "Head": head, "Action": "/gist/" + gist.ID + "/edit", "Description": gist.Description, "Secret": gist.Secret}
	if r.Method != "POST" {
		s.render(w, r, "gistform", page{Title: "Edit gist", User: user, Data: data})
		return
	}
	posted := formFiles(r)
	secret := r.FormValue("visibility") == "secret"
	data["Files"], data["Description"], data["Secret"] = posted, r.FormValue("description"), secret
	if r.FormValue("action") == "add" {
		data["Files"] = append(posted, gistFile{})
		s.render(w, r, "gistform", page{Title: "Edit gist", User: user, Data: data})
		return
	}
	retry := func(msg string) {
		w.WriteHeader(400)
		s.render(w, r, "gistform", page{Title: "Edit gist", User: user, Error: msg, Data: data})
	}
	description, err := cleanDescription(r.FormValue("description"))
	if err != nil {
		retry(err.Error())
		return
	}
	if over, used, quota := overQuota(s.root, user.Name); over {
		retry(quotaMessage(used, quota))
		return
	}
	if _, err := s.writeGist(g, head, posted, keep, *user, "Edit gist"); err != nil && !errors.Is(err, errNoChange) {
		retry(err.Error())
		return
	}
	s.store.UpdateGist(gist.ID, description, secret)
	http.Redirect(w, r, "/gist/"+gist.ID, http.StatusSeeOther)
}

func (s *Server) gistSmart(w http.ResponseWriter, r *http.Request, gist Gist, rest string) {
	service := r.URL.Query().Get("service")
	if rest != "info/refs" {
		service = rest
	}
	if service != "git-upload-pack" && service != "git-receive-pack" {
		http.Error(w, "unsupported service", 403)
		return
	}
	var recv, env []string
	limit := int64(0)
	if service == "git-receive-pack" {
		ip := clientIP(r)
		if s.limiter.blocked(ip) {
			http.Error(w, "too many failed attempts", 429)
			return
		}
		u, scope, ok := s.basicUser(r)
		if ok && scope == scopeRead {
			http.Error(w, "this token is read only", 403)
			return
		}
		if !ok || u.ID != gist.Owner.ID {
			if _, _, given := r.BasicAuth(); given {
				s.limiter.fail(ip)
			}
			w.Header().Set("WWW-Authenticate", `Basic realm="`+s.host+`"`)
			http.Error(w, "authentication required", 401)
			return
		}
		if !hooksReady(s.root) {
			http.Error(w, "pushes are unavailable right now", 503)
			return
		}
		over, used, quota := overQuota(s.root, gist.Owner.Name)
		if over {
			http.Error(w, quotaMessage(used, quota), 403)
			return
		}
		if quota > 0 {
			limit = quota - used + 1<<20
		}
		recv, env = gistReceiveArgs(s.root, gist.Owner.Name), gistEnv(gist, u)
	}
	s.gitService(w, r, s.gistGit(gist).Dir, service, rest, recv, env, limit)
	if service == "git-receive-pack" && rest != "info/refs" {
		s.store.TouchGist(gist.ID)
	}
}

const rawPolicy = "default-src 'none'; img-src data:; style-src 'unsafe-inline'; sandbox"

const embedPolicy = "default-src 'none'; style-src 'unsafe-inline'; img-src https: data:; base-uri 'none'; form-action 'none'; frame-ancestors *"

func (s *Server) serveGistRaw(w http.ResponseWriter, r *http.Request) {
	h := w.Header()
	h.Set("X-Content-Type-Options", "nosniff")
	h.Set("Referrer-Policy", "no-referrer")
	if r.Method != "GET" && r.Method != "HEAD" {
		h.Set("Allow", "GET, HEAD")
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if !s.requests.allow(clientIP(r)) {
		h.Set("Retry-After", "10")
		http.Error(w, "too many requests, slow down", http.StatusTooManyRequests)
		return
	}
	notFound := func() { http.Error(w, "not found", http.StatusNotFound) }
	kind, rest, _ := strings.Cut(strings.TrimPrefix(r.URL.Path, "/"), "/")
	id, rest, _ := strings.Cut(rest, "/")
	if kind == "" {
		http.Redirect(w, r, "https://"+s.host+"/gists", http.StatusFound)
		return
	}
	if !gistID.MatchString(id) {
		notFound()
		return
	}
	gist, err := s.store.Gist(id)
	if err != nil {
		notFound()
		return
	}
	g := s.gistGit(gist)
	switch kind {
	case "embed":
		if rest != "" {
			notFound()
			return
		}
		s.gistEmbed(w, r, gist)
	case "raw":
		commit, file := s.gistHead(gist), rest
		pinned := false
		if rev, name, ok := strings.Cut(rest, "/"); ok && fullOID.MatchString(rev) {
			c, err := g.Resolve(rev + "^{commit}")
			if err != nil {
				notFound()
				return
			}
			commit, file, pinned = c, name, true
		}
		if commit == "" || checkGistName(file) != nil {
			notFound()
			return
		}
		mode, oid, ok := g.pageEntry(commit, file)
		if !ok || (mode != "100644" && mode != "100755") {
			notFound()
			return
		}
		data, err := g.run(nil, "cat-file", "blob", oid)
		if err != nil || len(data) > gistPushFile {
			notFound()
			return
		}
		ctype := "text/plain; charset=utf-8"
		if kind := mediaTypes[strings.ToLower(filepath.Ext(file))]; strings.HasPrefix(kind, "image/") {
			ctype = kind
		}
		h.Set("Content-Type", ctype)
		h.Set("Content-Security-Policy", rawPolicy)
		h.Set("Access-Control-Allow-Origin", "*")
		h.Set("Cross-Origin-Resource-Policy", "cross-origin")
		h.Set("Content-Disposition", mime.FormatMediaType("inline", map[string]string{"filename": file}))
		if pinned {
			h.Set("Cache-Control", "public, max-age=31536000, immutable")
			h.Set("Cloudflare-CDN-Cache-Control", "max-age=3600")
		} else {
			h.Set("Cache-Control", "public, max-age=60")
		}
		h.Set("Content-Length", strconv.Itoa(len(data)))
		w.Write(data)
	default:
		notFound()
	}
}

var embedTemplate = template.Must(template.New("embed").Funcs(template.FuncMap{
	"lines": func(b []byte) []string { return strings.Split(strings.TrimSuffix(string(b), "\n"), "\n") },
	"inc":   func(i int) int { return i + 1 },
}).Parse(`<!doctype html>
<html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1"><title>{{.Title}}</title>
<style>
body{margin:0;font:14px/1.5 system-ui,sans-serif;color:#1f2328;background:#fff}
.file{border:1px solid #d0d7de;border-radius:6px;margin:0 0 12px;overflow:hidden}
.head{display:flex;justify-content:space-between;gap:8px;padding:6px 10px;background:#f6f8fa;border-bottom:1px solid #d0d7de;font-size:12px}
.head a{color:#0969da;text-decoration:none}
.body{overflow:auto;max-height:40em}
pre,code,table.blob{font:12px/1.45 ui-monospace,SFMono-Regular,Menlo,monospace;margin:0}
.chroma{padding:8px 0}
.chroma .lntd:first-child{padding:0 8px;color:#8c959f;user-select:none}
.chroma .lnlinks{color:#8c959f;text-decoration:none}
table.blob td.n{padding:0 8px;color:#8c959f;text-align:right;user-select:none}
table.blob td.l{white-space:pre;padding-right:8px}
.readme{padding:8px 16px}
img{max-width:100%}
.note{padding:8px 10px;color:#59636e}
{{.CSS}}
</style></head><body>
{{range .Files}}<div class="file"><div class="head"><span>{{.Name}}</span><span><a href="{{.Raw}}" target="_blank" rel="noopener">raw</a> · <a href="{{$.Link}}" target="_blank" rel="noopener">hosted on {{$.Host}}</a></span></div><div class="body">
{{if .Image}}<img src="{{.Raw}}" alt="{{.Name}}">{{else if .Binary}}<p class="note">Binary file.</p>{{else if .Large}}<p class="note">File too large to display.</p>{{else if .Markdown}}<div class="readme">{{.Markdown}}</div>{{else if .Highlighted}}{{.Highlighted}}{{else}}<table class="blob">{{range $i, $l := lines .Content}}<tr><td class="n">{{inc $i}}</td><td class="l">{{$l}}</td></tr>{{end}}</table>{{end}}
</div></div>{{end}}
</body></html>
`))

func (s *Server) gistEmbed(w http.ResponseWriter, r *http.Request, gist Gist) {
	head := s.gistHead(gist)
	if head == "" {
		http.Error(w, "not found", http.StatusNotFound)
		return
	}
	views := s.gistViews(gist, head, 0)
	var names []string
	for _, v := range views {
		names = append(names, v.Name)
	}
	h := w.Header()
	h.Set("Content-Type", "text/html; charset=utf-8")
	h.Set("Content-Security-Policy", embedPolicy)
	h.Set("Cache-Control", "public, max-age=60")
	embedTemplate.Execute(w, map[string]any{
		"Title": gist.Title(names), "Files": views, "Host": s.host, "Link": "https://" + s.host + "/gist/" + gist.ID,
		"CSS": template.CSS(highlightCSS()),
	})
}

type gistFileDoc struct {
	Name      string `json:"name"`
	Size      int64  `json:"size"`
	Raw       string `json:"raw"`
	Encoding  string `json:"encoding,omitempty"`
	Content   string `json:"content,omitempty"`
	Truncated bool   `json:"truncated,omitempty"`
}

type gistDoc struct {
	ID          string        `json:"id"`
	Description string        `json:"description"`
	Visibility  string        `json:"visibility"`
	Owner       string        `json:"owner"`
	Head        string        `json:"head"`
	Files       []gistFileDoc `json:"files"`
	Stars       int           `json:"stars"`
	Forks       int           `json:"forks"`
	Comments    int           `json:"comments"`
	ForkOf      *string       `json:"fork_of"`
	Created     *string       `json:"created"`
	Updated     *string       `json:"updated"`
	Clone       cloneSet      `json:"clone"`
	Embed       string        `json:"embed"`
	URL         string        `json:"url"`
	API         string        `json:"api"`
}

func (s *Server) gistDoc(gist Gist, content bool) gistDoc {
	g := s.gistGit(gist)
	head := s.gistHead(gist)
	vis := "public"
	if gist.Secret {
		vis = "secret"
	}
	out := gistDoc{ID: gist.ID, Description: gist.Description, Visibility: vis, Owner: handle(gist.Owner.Name), Head: head, Files: []gistFileDoc{},
		Stars: gist.Stars, Forks: gist.Forks, Comments: gist.Comments, Created: iso(gist.Created), Updated: iso(gist.Updated),
		Clone: cloneSet{HTTPS: "https://" + s.host + "/gist/" + gist.ID + ".git", SSH: s.sshUser + "@" + s.sshHost + ":gist/" + gist.ID + ".git"},
		Embed: "https://" + s.rawHost() + "/embed/" + gist.ID, URL: "https://" + s.host + "/gist/" + gist.ID, API: "https://" + s.host + "/api/gists/" + gist.ID}
	if gist.Parent != "" {
		if p, err := s.store.Gist(gist.Parent); err == nil && !p.Secret {
			out.ForkOf = &p.ID
		}
	}
	entries, _ := g.gistTree(head)
	for _, e := range entries {
		f := gistFileDoc{Name: e.Name, Size: e.Size, Raw: s.rawURL(gist, head, e.Name)}
		if content {
			if e.Size > gistWebFile {
				f.Truncated = true
			} else if data, err := g.run(nil, "cat-file", "blob", e.OID); err == nil {
				if isBinary(data) || !utf8.Valid(data) {
					f.Encoding, f.Content = "base64", base64.StdEncoding.EncodeToString(data)
				} else {
					f.Encoding, f.Content = "utf-8", string(data)
				}
			}
		}
		out.Files = append(out.Files, f)
	}
	return out
}

func (s *Server) removeGist(u User, gist Gist) error {
	if u.ID != gist.Owner.ID && !s.store.IsAdmin(u.ID) {
		return refuse(403, "Only the owner can delete this gist")
	}
	s.store.DeleteGist(gist.ID)
	os.RemoveAll(s.gistGit(gist).Dir)
	s.store.CloseReports("gist", gist.Owner.Name+"/"+gist.ID, "resolved", u.ID)
	return nil
}

func (s *Server) commentGist(u User, gist Gist, body string) error {
	if s.store.Blocked(gist.Owner.ID, u.ID) {
		return refuse(403, "You cannot comment here")
	}
	return s.store.AddGistComment(gist.ID, u.ID, body)
}

func (s *Server) dropGistComment(u User, gist Gist, cid int64) error {
	author, ok := s.store.GistCommentAuthor(gist.ID, cid)
	if !ok {
		return refuse(404, "No such comment")
	}
	if author != u.ID && gist.Owner.ID != u.ID && !s.store.IsAdmin(u.ID) {
		return refuse(403, "You cannot delete that comment")
	}
	s.store.DeleteGistComment(cid)
	return nil
}

func (s *Server) forkGistFor(u User, gist Gist) (Gist, error) {
	if u.ID == gist.Owner.ID {
		return Gist{}, refuse(409, "You already own this gist")
	}
	return s.forkGist(u, gist)
}

type gistChange struct {
	Name    string  `json:"name"`
	Content *string `json:"content"`
	Rename  string  `json:"rename"`
	Delete  bool    `json:"delete"`
}

func (s *Server) changeGist(u User, gist Gist, head string, changes []gistChange) error {
	g := s.gistGit(gist)
	current := s.gistHead(gist)
	if head == "" {
		head = current
	}
	if head != current {
		return refuse(409, "The gist moved on to "+short(current)+", fetch it again")
	}
	keep, err := g.gistTree(head)
	if err != nil {
		return refuse(409, "The gist has no files yet")
	}
	var files []gistFile
	for _, ch := range changes {
		i := slices.IndexFunc(keep, func(e gistEntry) bool { return e.Name == ch.Name })
		if i < 0 {
			if ch.Delete || ch.Content == nil {
				return refuse(404, "No file called "+ch.Name)
			}
			files = append(files, gistFile{Name: ch.Name, Content: *ch.Content})
			continue
		}
		e := keep[i]
		keep = slices.Delete(keep, i, i+1)
		if ch.Delete {
			continue
		}
		name := ch.Name
		if ch.Rename != "" {
			name = ch.Rename
		}
		if ch.Content == nil {
			if err := checkGistName(name); err != nil {
				return err
			}
			e.Name = name
			keep = append(keep, e)
			continue
		}
		files = append(files, gistFile{Orig: ch.Name, Name: name, Content: *ch.Content})
	}
	_, err = s.writeGist(g, head, files, keep, u, "Edit gist")
	if errors.Is(err, errNoChange) {
		return nil
	}
	return err
}

func (s *Server) gistRoutes() []apiRoute {
	return []apiRoute{
		{"GET", "/gists", needNone, "public gists, newest first", s.apiGists, nil},
		{"POST", "/gists", needGist, "create from {description, visibility, files: [{name, content}]}, or send the raw file with ?name=&description=&visibility= and get its address back as text", s.apiCreateGist, nil},
		{"GET", "/gists/:id", needNone, "a gist with every file's content, secret gists only need their id", s.apiGist, nil},
		{"PATCH", "/gists/:id", needGist, "change description or visibility, and files with [{name, content, rename, delete}], head guards against lost updates", s.apiPatchGist, nil},
		{"DELETE", "/gists/:id", needGist, "delete the gist", s.apiDeleteGist, nil},
		{"PUT", "/gists/:id/files/*name", needGist, "write one file from the raw request body, creating it when missing", s.apiPutGistFile, nil},
		{"DELETE", "/gists/:id/files/*name", needGist, "remove one file", s.apiPutGistFile, nil},
		{"GET", "/gists/:id/revisions", needNone, "revisions, newest first, ?patch=1 adds the hunks", s.apiGistRevisions, nil},
		{"PUT", "/gists/:id/star", needGist, "star", s.apiStarGist, nil},
		{"DELETE", "/gists/:id/star", needGist, "unstar", s.apiStarGist, nil},
		{"GET", "/gists/:id/forks", needNone, "forks", s.apiGistForks, nil},
		{"POST", "/gists/:id/forks", needGist, "fork into your account", s.apiForkGist, nil},
		{"GET", "/gists/:id/comments", needNone, "comments, oldest first", s.apiGistComments, nil},
		{"POST", "/gists/:id/comments", needGist, "comment with {body}", s.apiCommentGist, nil},
		{"DELETE", "/gists/:id/comments/:cid", needGist, "delete a comment, yours or one on your gist", s.apiDropGistComment, nil},
		{"GET", "/~:owner/gists", needNone, "an account's public gists, its secret ones too when it is you, ?starred=1 for the gists it starred", s.apiAccountGists, nil},
	}
}

func (c *call) gist() (Gist, bool) {
	id := c.arg("id")
	if !gistID.MatchString(id) {
		c.fail(404, "No such gist")
		return Gist{}, false
	}
	gist, err := c.s.store.Gist(id)
	if err != nil {
		c.fail(404, "No such gist")
		return Gist{}, false
	}
	return gist, true
}

func (s *Server) gistDocs(gists []Gist) []gistDoc {
	return mapped(gists, func(g Gist) gistDoc { return s.gistDoc(g, false) })
}

func (s *Server) apiGists(c *call) {
	gists, err := s.store.Gists(0, false, 1000)
	if err != nil {
		c.err(err)
		return
	}
	paged(c, s.gistDocs(gists))
}

func (s *Server) apiAccountGists(c *call) {
	owner, ok := c.account()
	if !ok {
		return
	}
	var gists []Gist
	var err error
	if c.query("starred") == "1" {
		gists, err = s.store.StarredGists(owner.ID)
		gists = slices.DeleteFunc(gists, func(g Gist) bool { return g.Secret && (c.user == nil || c.user.ID != g.Owner.ID) })
	} else {
		gists, err = s.store.Gists(owner.ID, c.user != nil && c.user.ID == owner.ID, 1000)
	}
	if err != nil {
		c.err(err)
		return
	}
	paged(c, s.gistDocs(gists))
}

func (s *Server) apiCreateGist(c *call) {
	var description, vis string
	var files []gistFile
	if strings.HasPrefix(c.r.Header.Get("Content-Type"), "application/json") {
		var in struct {
			Description string `json:"description"`
			Visibility  string `json:"visibility"`
			Files       []struct {
				Name    string `json:"name"`
				Content string `json:"content"`
			} `json:"files"`
		}
		if !c.decode(&in) {
			return
		}
		description, vis = in.Description, in.Visibility
		for _, f := range in.Files {
			files = append(files, gistFile{Name: f.Name, Content: f.Content})
		}
	} else {
		body, err := io.ReadAll(http.MaxBytesReader(c.w, c.r.Body, gistWebFile+1))
		if err != nil {
			c.fail(413, "The file is larger than "+humanSize(gistWebFile)+", push it with git instead")
			return
		}
		name := c.query("name")
		if name == "" {
			name = c.query("file")
		}
		description, vis = c.query("description"), c.query("visibility")
		files = []gistFile{{Name: name, Content: string(body)}}
	}
	if vis != "" && vis != "public" && vis != "secret" {
		c.fail(400, "Visibility must be public or secret")
		return
	}
	gist, err := s.createGist(*c.user, description, vis != "public", files)
	if err != nil {
		c.err(err)
		return
	}
	doc := s.gistDoc(gist, true)
	c.w.Header().Set("Location", doc.API)
	if !strings.HasPrefix(c.r.Header.Get("Content-Type"), "application/json") && !strings.Contains(c.r.Header.Get("Accept"), "application/json") {
		c.w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		c.w.WriteHeader(201)
		io.WriteString(c.w, doc.URL+"\n")
		return
	}
	c.reply(201, doc)
}

func (s *Server) apiGist(c *call) {
	if gist, ok := c.gist(); ok {
		c.reply(200, s.gistDoc(gist, true))
	}
}

func (s *Server) apiPatchGist(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	if c.user.ID != gist.Owner.ID {
		c.fail(403, "Only the owner can edit this gist")
		return
	}
	var in struct {
		Description *string      `json:"description"`
		Visibility  *string      `json:"visibility"`
		Head        string       `json:"head"`
		Files       []gistChange `json:"files"`
	}
	if !c.decode(&in) {
		return
	}
	description, secret := gist.Description, gist.Secret
	if in.Description != nil {
		d, err := cleanDescription(*in.Description)
		if err != nil {
			c.err(err)
			return
		}
		description = d
	}
	if in.Visibility != nil {
		if *in.Visibility != "public" && *in.Visibility != "secret" {
			c.fail(400, "Visibility must be public or secret")
			return
		}
		secret = *in.Visibility == "secret"
	}
	if len(in.Files) > 0 {
		if over, used, quota := overQuota(s.root, gist.Owner.Name); over {
			c.fail(403, quotaMessage(used, quota))
			return
		}
		if err := s.changeGist(*c.user, gist, in.Head, in.Files); err != nil {
			c.err(err)
			return
		}
	}
	s.store.UpdateGist(gist.ID, description, secret)
	gist, _ = s.store.Gist(gist.ID)
	c.reply(200, s.gistDoc(gist, true))
}

func (s *Server) apiPutGistFile(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	if c.user.ID != gist.Owner.ID {
		c.fail(403, "Only the owner can edit this gist")
		return
	}
	change := gistChange{Name: c.arg("name"), Delete: c.r.Method == "DELETE"}
	if !change.Delete {
		if over, used, quota := overQuota(s.root, gist.Owner.Name); over {
			c.fail(403, quotaMessage(used, quota))
			return
		}
		body, err := io.ReadAll(http.MaxBytesReader(c.w, c.r.Body, gistWebFile+1))
		if err != nil {
			c.fail(413, "The file is larger than "+humanSize(gistWebFile)+", push it with git instead")
			return
		}
		content := string(body)
		change.Content = &content
	}
	if err := s.changeGist(*c.user, gist, c.r.Header.Get("If-Match"), []gistChange{change}); err != nil {
		c.err(err)
		return
	}
	gist, _ = s.store.Gist(gist.ID)
	c.reply(200, s.gistDoc(gist, false))
}

func (s *Server) apiDeleteGist(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	if err := s.removeGist(*c.user, gist); err != nil {
		c.err(err)
		return
	}
	c.done()
}

func (s *Server) apiGistRevisions(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	g := s.gistGit(gist)
	commits, _ := g.Log(s.gistHead(gist), 1000, "")
	patch := c.query("patch") == "1"
	views := mapped(commits, func(cm Commit) commitView {
		v := s.commitView(cm)
		if files, err := g.Diff(cm.Hash); err == nil {
			v.Files = nonNil(fileViews(files, patch))
		}
		return v
	})
	paged(c, views)
}

func (s *Server) apiStarGist(c *call) {
	if gist, ok := c.gist(); ok {
		s.store.StarGist(c.user.ID, gist.ID, c.r.Method == "PUT")
		c.done()
	}
}

func (s *Server) apiGistForks(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	forks, err := s.store.GistForks(gist.ID)
	if err != nil {
		c.err(err)
		return
	}
	paged(c, s.gistDocs(forks))
}

func (s *Server) apiForkGist(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	fork, err := s.forkGistFor(*c.user, gist)
	if err != nil {
		c.err(err)
		return
	}
	c.reply(201, s.gistDoc(fork, false))
}

func gistCommentViews(comments []GistComment) []commentView {
	return mapped(comments, func(gc GistComment) commentView {
		return commentView{gc.ID, handle(gc.Author.Name), gc.Body, iso(gc.Created)}
	})
}

func (s *Server) apiGistComments(c *call) {
	if gist, ok := c.gist(); ok {
		paged(c, gistCommentViews(s.store.GistComments(gist.ID)))
	}
}

func (s *Server) apiCommentGist(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	var in struct {
		Body string `json:"body"`
	}
	if !c.decode(&in) {
		return
	}
	if err := s.commentGist(*c.user, gist, in.Body); err != nil {
		c.err(err)
		return
	}
	comments := s.store.GistComments(gist.ID)
	c.reply(201, gistCommentViews(comments[len(comments)-1:])[0])
}

func (s *Server) apiDropGistComment(c *call) {
	gist, ok := c.gist()
	if !ok {
		return
	}
	cid, ok := c.id("cid")
	if !ok {
		return
	}
	if err := s.dropGistComment(*c.user, gist, cid); err != nil {
		c.err(err)
		return
	}
	c.done()
}