helpers.go
| 1 | package handler |
| 2 | |
| 3 | import ( |
| 4 | "html/template" |
| 5 | "log/slog" |
| 6 | "math" |
| 7 | "net/http" |
| 8 | "strconv" |
| 9 | |
| 10 | "github.com/go-chi/chi/v5" |
| 11 | ) |
| 12 | |
| 13 | // parseID reads the {id} route parameter. It writes a 400 and reports false when |
| 14 | // the value isn't a valid id, so callers can simply return. |
| 15 | func parseID(w http.ResponseWriter, r *http.Request) (int64, bool) { |
| 16 | id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64) |
| 17 | if err != nil { |
| 18 | http.Error(w, "Invalid ID", http.StatusBadRequest) |
| 19 | return 0, false |
| 20 | } |
| 21 | return id, true |
| 22 | } |
| 23 | |
| 24 | // sortFromRequest returns the sort order for a listing page. An explicit ?sort= |
| 25 | // is remembered in a cookie; without one the last choice is restored, so the |
| 26 | // order survives the auto-refresh that reloads these pages. |
| 27 | func sortFromRequest(w http.ResponseWriter, r *http.Request, cookie, defaultSort string) string { |
| 28 | sortBy := r.URL.Query().Get("sort") |
| 29 | if sortBy == "" { |
| 30 | return getCookie(r, cookie, defaultSort) |
| 31 | } |
| 32 | setCookie(w, cookie, sortBy) |
| 33 | return sortBy |
| 34 | } |
| 35 | |
| 36 | // pageSize is how many items a listing page renders. The library page fires one |
| 37 | // thumbnail request per media file, so an unpaginated page of a large archive is |
| 38 | // both a slow render and a request storm. |
| 39 | const pageSize = 50 |
| 40 | |
| 41 | // Pagination carries what a listing template needs for its prev/next links. |
| 42 | // Query holds the request's other parameters (filter, sort, path) with a |
| 43 | // trailing '&', so a link keeps them. It is template.URL because |
| 44 | // url.Values.Encode already percent-encoded it: as a plain string the template |
| 45 | // escaper would treat the whole query as one value and re-encode its '&' and |
| 46 | // '='. |
| 47 | type Pagination struct { |
| 48 | Page int |
| 49 | Prev int |
| 50 | Next int |
| 51 | HasNext bool |
| 52 | Query template.URL |
| 53 | } |
| 54 | |
| 55 | // pageFromRequest reads the 1-based ?page=. Anything unparseable, below 1, or |
| 56 | // large enough that page*pageSize would overflow is page 1: a hand-edited URL |
| 57 | // must not produce a negative offset, which slices a listing out of range. |
| 58 | func pageFromRequest(r *http.Request) int { |
| 59 | p, err := strconv.Atoi(r.URL.Query().Get("page")) |
| 60 | if err != nil || p < 1 || p > math.MaxInt/pageSize { |
| 61 | return 1 |
| 62 | } |
| 63 | return p |
| 64 | } |
| 65 | |
| 66 | // newPagination describes the page links for a request. hasNext comes from the |
| 67 | // caller because each listing determines it differently. |
| 68 | func newPagination(r *http.Request, page int, hasNext bool) Pagination { |
| 69 | q := r.URL.Query() |
| 70 | q.Del("page") |
| 71 | query := q.Encode() |
| 72 | if query != "" { |
| 73 | query += "&" |
| 74 | } |
| 75 | return Pagination{ |
| 76 | Page: page, |
| 77 | Prev: page - 1, |
| 78 | Next: page + 1, |
| 79 | HasNext: hasNext, |
| 80 | Query: template.URL(query), |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | // serverError logs the underlying failure and shows the user a generic message. |
| 85 | // Internal error strings can carry filesystem paths and SQL text, so they are |
| 86 | // kept out of the response. |
| 87 | func (h *Handler) serverError(w http.ResponseWriter, r *http.Request, context string, err error) { |
| 88 | slog.Error(context, "method", r.Method, "path", r.URL.Path, "err", err) |
| 89 | http.Error(w, "Something went wrong. Please try again.", http.StatusInternalServerError) |
| 90 | } |
| 91 | |
| 92 | // redirectWithError flashes a message and redirects, the standard |
| 93 | // Post/Redirect/Get failure path for form submissions. The underlying error is |
| 94 | // logged rather than shown. |
| 95 | func redirectWithError(w http.ResponseWriter, r *http.Request, path, message string, err error) { |
| 96 | if err != nil { |
| 97 | slog.Error(message, "method", r.Method, "path", r.URL.Path, "err", err) |
| 98 | } |
| 99 | flashError(w, message) |
| 100 | http.Redirect(w, r, path, http.StatusSeeOther) |
| 101 | } |
| 102 | |
| 103 | // redirectWithSuccess flashes a confirmation and redirects. |
| 104 | func redirectWithSuccess(w http.ResponseWriter, r *http.Request, path, message string) { |
| 105 | flashSuccess(w, message) |
| 106 | http.Redirect(w, r, path, http.StatusSeeOther) |
| 107 | } |
| 108 | |
| 109 | // parseForm parses a form body and reports whether it succeeded. On failure it |
| 110 | // writes a 400 with a generic message: ParseForm's own error names the offending |
| 111 | // bytes, which is noise to the user and detail we don't need to hand out. |
| 112 | func parseForm(w http.ResponseWriter, r *http.Request) bool { |
| 113 | if err := r.ParseForm(); err != nil { |
| 114 | http.Error(w, "Invalid form", http.StatusBadRequest) |
| 115 | return false |
| 116 | } |
| 117 | return true |
| 118 | } |
| 119 |