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