# This file defines functions for generating an Atom feed. { depot, lib, ... }: with depot.nix.yants; let inherit (builtins) map readFile replaceStrings; inherit (lib) concatStrings concatStringsSep removeSuffix; inherit (depot.third_party) runCommandNoCC; # '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. This element is technically optional, but # only if an alternate link is provided. In practice it should # always be present in the feeds generated by this code. content = 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). Recommended element. updated = 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 (runCommandNoCC "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} ${elem "updated" (renderEpoch e.updated)} <content type="html">${escape e.content}</content> ${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> ''); 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)} ${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 f.entries)} </feed> ''); in { inherit entry feed renderFeed renderEpoch; }