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Diffstat (limited to 'web/atom-feed/default.nix')
| -rw-r--r-- | web/atom-feed/default.nix | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/web/atom-feed/default.nix b/web/atom-feed/default.nix new file mode 100644 index 000000000000..27c90a7b919c --- /dev/null +++ b/web/atom-feed/default.nix @@ -0,0 +1,153 @@ +# This file defines functions for generating an Atom feed. + +{ depot, lib, pkgs, ... }: + +with depot.nix.yants; + +let + inherit (builtins) foldl' map readFile replaceStrings sort; + inherit (lib) concatStrings concatStringsSep max removeSuffix; + inherit (pkgs) runCommand; + + # 'link' describes a related link to a feed, or feed element. + # + # https://validator.w3.org/feed/docs/atom.html#link + link = struct "link" { + rel = string; + href = string; + }; + + # 'entry' describes a feed entry, for example a single post on a + # blog. Some optional fields have been omitted. + # + # https://validator.w3.org/feed/docs/atom.html#requiredEntryElements + entry = struct "entry" { + # Identifies the entry using a universally unique and permanent URI. + id = string; + + # Contains a human readable title for the entry. This value should + # not be blank. + title = string; + + # Content of the entry. + content = option string; + + # Indicates the last time the entry was modified in a significant + # way (in seconds since epoch). + updated = int; + + # Names authors of the entry. Recommended element. + authors = option (list string); + + # Related web pages, such as the web location of a blog post. + links = option (list link); + + # Conveys a short summary, abstract, or excerpt of the entry. + summary = option string; + + # Contains the time of the initial creation or first availability + # of the entry. + published = option int; + + # Conveys information about rights, e.g. copyrights, held in and + # over the entry. + rights = option string; + }; + + # 'feed' describes the metadata of the Atom feed itself. + # + # Some optional fields have been omitted. + # + # https://validator.w3.org/feed/docs/atom.html#requiredFeedElements + feed = struct "feed" { + # Identifies the feed using a universally unique and permanent URI. + id = string; + + # Contains a human readable title for the feed. + title = string; + + # Indicates the last time the feed was modified in a significant + # way (in seconds since epoch). Will be calculated based on most + # recently updated entry if unset. + updated = option int; + + # Entries contained within the feed. + entries = list entry; + + # Names authors of the feed. Recommended element. + authors = option (list string); + + # Related web locations. Recommended element. + links = option (list link); + + # Conveys information about rights, e.g. copyrights, held in and + # over the feed. + rights = option string; + + # Contains a human-readable description or subtitle for the feed. + subtitle = option string; + }; + + # Feed generation functions: + + renderEpoch = epoch: removeSuffix "\n" (readFile (runCommand "date-${toString epoch}" { } '' + date --date='@${toString epoch}' --utc --iso-8601='seconds' > $out + '')); + + escape = replaceStrings [ "<" ">" "&" "'" ] [ "<" ">" "&" "'" ]; + + elem = name: content: ''<${name}>${escape content}</${name}>''; + + renderLink = defun [ link string ] (l: '' + <link href="${escape l.href}" rel="${escape l.rel}" /> + ''); + + # Technically the author element can also contain 'uri' and 'email' + # fields, but they are not used for the purpose of this feed and are + # omitted. + renderAuthor = author: ''<author><name>${escape author}</name></author>''; + + renderEntry = defun [ entry string ] (e: '' + <entry> + ${elem "title" e.title} + ${elem "id" e.id} + ${elem "updated" (renderEpoch e.updated)} + ${if e ? published + then elem "published" (renderEpoch e.published) + else "" + } + ${if e ? content + then ''<content type="html">${escape e.content}</content>'' + else "" + } + ${if e ? summary then elem "summary" e.summary else ""} + ${concatStrings (map renderAuthor (e.authors or []))} + ${if e ? subtitle then elem "subtitle" e.subtitle else ""} + ${if e ? rights then elem "rights" e.rights else ""} + ${concatStrings (map renderLink (e.links or []))} + </entry> + ''); + + mostRecentlyUpdated = defun [ (list entry) int ] (entries: + foldl' max 0 (map (e: e.updated) entries) + ); + + sortEntries = sort (a: b: a.published > b.published); + + renderFeed = defun [ feed string ] (f: '' + <?xml version="1.0" encoding="utf-8"?> + <feed xmlns="http://www.w3.org/2005/Atom"> + ${elem "id" f.id} + ${elem "title" f.title} + ${elem "updated" (renderEpoch (f.updated or (mostRecentlyUpdated f.entries)))} + ${concatStringsSep "\n" (map renderAuthor (f.authors or []))} + ${if f ? subtitle then elem "subtitle" f.subtitle else ""} + ${if f ? rights then elem "rights" f.rights else ""} + ${concatStrings (map renderLink (f.links or []))} + ${concatStrings (map renderEntry (sortEntries f.entries))} + </feed> + ''); +in +{ + inherit entry feed renderFeed renderEpoch; +} |