phase3: HTTP server with converter, one-shot preview store, and middleware
This commit is contained in:
Sergey Filkin
@@ -0,0 +1,248 @@
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package server
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import (
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"log/slog"
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"mime"
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"net/http"
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"strings"
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"github.com/fserg/md-to-html/internal/converter"
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"github.com/fserg/md-to-html/internal/version"
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"github.com/go-chi/chi/v5"
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)
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const defaultDocumentTitle = "Document"
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type Server struct {
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cfg Config
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conv *converter.Converter
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store *PreviewStore
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log *slog.Logger
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}
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type convertRequest struct {
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Markdown string `json:"markdown"`
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Title string `json:"title,omitempty"`
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}
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func (s *Server) handleConvert(w http.ResponseWriter, r *http.Request) {
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if !hasJSONContentType(r.Header.Get("Content-Type")) {
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writeJSON(w, http.StatusUnsupportedMediaType, map[string]string{
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"detail": "content-type must be application/json",
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})
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return
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}
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var payload convertRequest
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if err := decodeJSON(r, &payload); err != nil {
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s.writeDecodeError(w, err)
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return
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}
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result, err := s.convertMarkdown(payload.Markdown, payload.Title)
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if err != nil {
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s.writeConvertError(w, err)
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return
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}
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write(result.HTML)
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}
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func (s *Server) handleHealth(w http.ResponseWriter, _ *http.Request) {
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writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
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}
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func (s *Server) handleVersion(w http.ResponseWriter, _ *http.Request) {
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writeJSON(w, http.StatusOK, map[string]string{"version": version.Version})
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}
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func (s *Server) handleReady(w http.ResponseWriter, _ *http.Request) {
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writeJSON(w, http.StatusOK, map[string]any{
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"status": "ok",
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"template_loaded": s.conv != nil,
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})
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}
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func (s *Server) handleHome(w http.ResponseWriter, _ *http.Request) {
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write([]byte("UI coming in phase 4"))
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}
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func (s *Server) handleUIConvert(w http.ResponseWriter, r *http.Request) {
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if err := r.ParseForm(); err != nil {
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s.writeDecodeError(w, err)
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return
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}
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result, err := s.convertMarkdown(r.Form.Get("markdown"), r.Form.Get("title"))
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if err != nil {
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s.writeConvertError(w, err)
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return
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}
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filename := htmlFilename(result.Title)
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previewID := s.store.Put(result.HTML, "text/html; charset=utf-8", filename)
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downloadID := s.store.Put(result.HTML, "text/html; charset=utf-8", filename)
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fragment := fmt.Sprintf(
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`<div><p>Result ready</p><a href="/preview/%s" target="_blank" rel="noopener">Preview</a> <a href="/download/%s">Download</a></div>`,
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previewID,
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downloadID,
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)
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write([]byte(fragment))
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}
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func (s *Server) handlePreview(w http.ResponseWriter, r *http.Request) {
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id := chi.URLParam(r, "id")
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item, ok := s.store.Take(id)
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if !ok {
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http.NotFound(w, r)
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return
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}
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w.Header().Set("Cache-Control", "no-store")
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w.Header().Set("Content-Type", contentTypeOrDefault(item.mime))
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write(item.html)
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}
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func (s *Server) handleDownload(w http.ResponseWriter, r *http.Request) {
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id := chi.URLParam(r, "id")
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item, ok := s.store.Take(id)
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if !ok {
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http.NotFound(w, r)
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return
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}
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w.Header().Set("Cache-Control", "no-store")
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w.Header().Set("Content-Type", contentTypeOrDefault(item.mime))
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w.Header().Set("Content-Disposition", mime.FormatMediaType("attachment", map[string]string{
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"filename": item.filename,
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}))
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write(item.html)
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}
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func (s *Server) convertMarkdown(markdown, title string) (converter.Result, error) {
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if strings.TrimSpace(markdown) == "" {
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return converter.Result{}, errEmptyMarkdown
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}
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if int64(len([]byte(markdown))) > s.cfg.MaxMarkdownBytes {
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return converter.Result{}, errMarkdownTooLarge{limit: s.cfg.MaxMarkdownBytes}
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}
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fallbackTitle := strings.TrimSpace(title)
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if fallbackTitle == "" {
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fallbackTitle = defaultDocumentTitle
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}
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result, err := s.conv.Convert([]byte(markdown), fallbackTitle)
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if err != nil {
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return converter.Result{}, fmt.Errorf("convert markdown: %w", err)
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}
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return result, nil
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}
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func (s *Server) writeDecodeError(w http.ResponseWriter, err error) {
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var maxBytesErr *http.MaxBytesError
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if errors.As(err, &maxBytesErr) {
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writeJSON(w, http.StatusRequestEntityTooLarge, map[string]string{
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"detail": fmt.Sprintf("request exceeds %d bytes", s.cfg.MaxRequestBytes),
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})
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return
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}
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writeJSON(w, http.StatusBadRequest, map[string]string{"detail": "invalid request payload"})
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}
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func (s *Server) writeConvertError(w http.ResponseWriter, err error) {
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var markdownTooLarge errMarkdownTooLarge
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switch {
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case errors.Is(err, errEmptyMarkdown):
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writeJSON(w, http.StatusBadRequest, map[string]string{"detail": err.Error()})
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case errors.As(err, &markdownTooLarge):
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writeJSON(w, http.StatusRequestEntityTooLarge, map[string]string{
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"detail": markdownTooLarge.Error(),
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})
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default:
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s.log.Error("convert_failed", "error", err)
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writeJSON(w, http.StatusBadGateway, map[string]string{"detail": err.Error()})
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}
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}
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func hasJSONContentType(value string) bool {
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mediaType, _, err := mime.ParseMediaType(value)
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return err == nil && mediaType == "application/json"
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}
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func decodeJSON(r *http.Request, dst any) error {
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dec := json.NewDecoder(r.Body)
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dec.DisallowUnknownFields()
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if err := dec.Decode(dst); err != nil {
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return err
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}
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var extra json.RawMessage
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if err := dec.Decode(&extra); err != nil && !errors.Is(err, io.EOF) {
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return err
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}
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if len(extra) > 0 {
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return errors.New("unexpected trailing JSON data")
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}
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return nil
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}
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func writeJSON(w http.ResponseWriter, status int, payload any) {
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w.Header().Set("Content-Type", "application/json; charset=utf-8")
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w.WriteHeader(status)
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enc := json.NewEncoder(w)
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enc.SetEscapeHTML(false)
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_ = enc.Encode(payload)
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}
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func htmlFilename(title string) string {
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name := strings.TrimSpace(title)
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if name == "" {
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name = "document"
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}
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replacer := strings.NewReplacer("/", "-", "\\", "-", "\"", "", "\n", " ", "\r", " ")
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name = strings.TrimSpace(replacer.Replace(name))
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if name == "" {
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name = "document"
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}
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return name + ".html"
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}
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func contentTypeOrDefault(value string) string {
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if strings.TrimSpace(value) == "" {
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return "text/html; charset=utf-8"
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}
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return value
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}
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var errEmptyMarkdown = errors.New("markdown must not be empty")
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type errMarkdownTooLarge struct {
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limit int64
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}
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func (e errMarkdownTooLarge) Error() string {
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return fmt.Sprintf("markdown exceeds %d bytes", e.limit)
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}
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