forked from treehouse/mastodon
332 lines
11 KiB
JavaScript
332 lines
11 KiB
JavaScript
/*
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`util/bio_metadata`
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===================
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> For more information on the contents of this file, please contact:
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>
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> - kibigo! [@kibi@glitch.social]
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This file provides two functions for dealing with bio metadata. The
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functions are:
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- __`processBio(content)` :__
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Processes `content` to extract any frontmatter. The returned
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object has two properties: `text`, which contains the text of
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`content` sans-frontmatter, and `metadata`, which is an array
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of key-value pairs (in two-element array format). If no
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frontmatter was provided in `content`, then `metadata` will be
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an empty array.
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- __`createBio(note, data)` :__
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Reverses the process in `processBio()`; takes a `note` and an
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array of two-element arrays (which should give keys and values)
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and outputs a string containing a well-formed bio with
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frontmatter.
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*/
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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/*********************************************************************\
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To my lovely code maintainers,
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The syntax recognized by the Mastodon frontend for its bio metadata
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feature is a subset of that provided by the YAML 1.2 specification.
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In particular, Mastodon recognizes metadata which is provided as an
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implicit YAML map, where each key-value pair takes up only a single
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line (no multi-line values are permitted). To simplify the level of
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processing required, Mastodon metadata frontmatter has been limited
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to only allow those characters in the `c-printable` set, as defined
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by the YAML 1.2 specification, instead of permitting those from the
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`nb-json` characters inside double-quoted strings like YAML proper.
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¶ It is important to note that Mastodon only borrows the *syntax*
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of YAML, not its semantics. This is to say, Mastodon won't make any
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attempt to interpret the data it receives. `true` will not become a
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boolean; `56` will not be interpreted as a number. Rather, each key
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and every value will be read as a string, and as a string they will
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remain. The order of the pairs is unchanged, and any duplicate keys
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are preserved. However, YAML escape sequences will be replaced with
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the proper interpretations according to the YAML 1.2 specification.
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¶ The implementation provided below interprets `<br>` as `\n` and
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allows for an open <p> tag at the beginning of the bio. It replaces
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the escaped character entities `'` and `"` with single or
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double quotes, respectively, prior to processing. However, no other
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escaped characters are replaced, not even those which might have an
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impact on the syntax otherwise. These minor allowances are provided
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because the Mastodon backend will insert these things automatically
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into a bio before sending it through the API, so it is important we
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account for them. Aside from this, the YAML frontmatter must be the
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very first thing in the bio, leading with three consecutive hyphen-
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minues (`---`), and ending with the same or, alternatively, instead
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with three periods (`...`). No limits have been set with respect to
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the number of characters permitted in the frontmatter, although one
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should note that only limited space is provided for them in the UI.
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¶ The regular expression used to check the existence of, and then
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process, the YAML frontmatter has been split into a number of small
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components in the code below, in the vain hope that it will be much
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easier to read and to maintain. I leave it to the future readers of
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this code to determine the extent of my successes in this endeavor.
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UPDATE 19 Oct 2017: We no longer allow character escapes inside our
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double-quoted strings for ease of processing. We now internally use
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the name "ƔAML" in our code to clarify that this is Not Quite YAML.
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Sending love + warmth eternal,
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- kibigo [@kibi@glitch.social]
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\*********************************************************************/
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/* "u" FLAG COMPATABILITY */
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let compat_mode = false;
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try {
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new RegExp('.', 'u');
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} catch (e) {
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compat_mode = true;
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}
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/* CONVENIENCE FUNCTIONS */
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const unirex = str => compat_mode ? new RegExp(str) : new RegExp(str, 'u');
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const rexstr = exp => '(?:' + exp.source + ')';
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/* CHARACTER CLASSES */
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const DOCUMENT_START = /^/;
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const DOCUMENT_END = /$/;
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const ALLOWED_CHAR = unirex( // `c-printable` in the YAML 1.2 spec.
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compat_mode ? '[\t\n\r\x20-\x7e\x85\xa0-\ufffd]' : '[\t\n\r\x20-\x7e\x85\xa0-\ud7ff\ue000-\ufffd\u{10000}-\u{10FFFF}]'
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);
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const WHITE_SPACE = /[ \t]/;
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const LINE_BREAK = /\r?\n|\r|<br\s*\/?>/;
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const INDICATOR = /[-?:,[\]{}&#*!|>'"%@`]/;
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const FLOW_CHAR = /[,[\]{}]/;
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/* NEGATED CHARACTER CLASSES */
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const NOT_WHITE_SPACE = unirex('(?!' + rexstr(WHITE_SPACE) + ')[^]');
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const NOT_LINE_BREAK = unirex('(?!' + rexstr(LINE_BREAK) + ')[^]');
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const NOT_INDICATOR = unirex('(?!' + rexstr(INDICATOR) + ')[^]');
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const NOT_FLOW_CHAR = unirex('(?!' + rexstr(FLOW_CHAR) + ')[^]');
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const NOT_ALLOWED_CHAR = unirex(
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'(?!' + rexstr(ALLOWED_CHAR) + ')[^]'
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);
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/* BASIC CONSTRUCTS */
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const ANY_WHITE_SPACE = unirex(rexstr(WHITE_SPACE) + '*');
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const ANY_ALLOWED_CHARS = unirex(rexstr(ALLOWED_CHAR) + '*');
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const NEW_LINE = unirex(
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rexstr(ANY_WHITE_SPACE) + rexstr(LINE_BREAK)
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);
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const SOME_NEW_LINES = unirex(
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'(?:' + rexstr(NEW_LINE) + ')+'
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);
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const POSSIBLE_STARTS = unirex(
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rexstr(DOCUMENT_START) + rexstr(/<p[^<>]*>/) + '?'
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);
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const POSSIBLE_ENDS = unirex(
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rexstr(SOME_NEW_LINES) + '|' +
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rexstr(DOCUMENT_END) + '|' +
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rexstr(/<\/p>/)
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);
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const QUOTE_CHAR = unirex(
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'(?=' + rexstr(NOT_LINE_BREAK) + ')[^"]'
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);
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const ANY_QUOTE_CHAR = unirex(
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rexstr(QUOTE_CHAR) + '*'
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);
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const ESCAPED_APOS = unirex(
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' + rexstr(/[^']|''/)
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);
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const ANY_ESCAPED_APOS = unirex(
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rexstr(ESCAPED_APOS) + '*'
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);
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const FIRST_KEY_CHAR = unirex(
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')' +
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rexstr(NOT_INDICATOR) + '|' +
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rexstr(/[?:-]/) +
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')' +
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'(?=' + rexstr(NOT_FLOW_CHAR) + ')'
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);
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const FIRST_VALUE_CHAR = unirex(
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')' +
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rexstr(NOT_INDICATOR) + '|' +
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rexstr(/[?:-]/) +
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')'
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// Flow indicators are allowed in values.
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);
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const LATER_KEY_CHAR = unirex(
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rexstr(WHITE_SPACE) + '|' +
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')' +
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'(?=' + rexstr(NOT_FLOW_CHAR) + ')' +
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rexstr(/[^:#]#?/) + '|' +
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rexstr(/:/) + '(?=' + rexstr(NOT_WHITE_SPACE) + ')'
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);
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const LATER_VALUE_CHAR = unirex(
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rexstr(WHITE_SPACE) + '|' +
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'(?=' + rexstr(NOT_LINE_BREAK) + ')' +
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'(?=' + rexstr(NOT_WHITE_SPACE) + ')' +
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// Flow indicators are allowed in values.
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rexstr(/[^:#]#?/) + '|' +
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rexstr(/:/) + '(?=' + rexstr(NOT_WHITE_SPACE) + ')'
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);
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/* YAML CONSTRUCTS */
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const ƔAML_START = unirex(
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rexstr(ANY_WHITE_SPACE) + '---'
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);
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const ƔAML_END = unirex(
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rexstr(ANY_WHITE_SPACE) + '(?:---|\.\.\.)'
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);
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const ƔAML_LOOKAHEAD = unirex(
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'(?=' +
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rexstr(ƔAML_START) +
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rexstr(ANY_ALLOWED_CHARS) + rexstr(NEW_LINE) +
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rexstr(ƔAML_END) + rexstr(POSSIBLE_ENDS) +
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')'
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);
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const ƔAML_DOUBLE_QUOTE = unirex(
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'"' + rexstr(ANY_QUOTE_CHAR) + '"'
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);
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const ƔAML_SINGLE_QUOTE = unirex(
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'\'' + rexstr(ANY_ESCAPED_APOS) + '\''
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);
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const ƔAML_SIMPLE_KEY = unirex(
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rexstr(FIRST_KEY_CHAR) + rexstr(LATER_KEY_CHAR) + '*'
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);
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const ƔAML_SIMPLE_VALUE = unirex(
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rexstr(FIRST_VALUE_CHAR) + rexstr(LATER_VALUE_CHAR) + '*'
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);
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const ƔAML_KEY = unirex(
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rexstr(ƔAML_DOUBLE_QUOTE) + '|' +
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rexstr(ƔAML_SINGLE_QUOTE) + '|' +
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rexstr(ƔAML_SIMPLE_KEY)
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);
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const ƔAML_VALUE = unirex(
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rexstr(ƔAML_DOUBLE_QUOTE) + '|' +
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rexstr(ƔAML_SINGLE_QUOTE) + '|' +
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rexstr(ƔAML_SIMPLE_VALUE)
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);
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const ƔAML_SEPARATOR = unirex(
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rexstr(ANY_WHITE_SPACE) +
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':' + rexstr(WHITE_SPACE) +
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rexstr(ANY_WHITE_SPACE)
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);
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const ƔAML_LINE = unirex(
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'(' + rexstr(ƔAML_KEY) + ')' +
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rexstr(ƔAML_SEPARATOR) +
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'(' + rexstr(ƔAML_VALUE) + ')'
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);
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/* FRONTMATTER REGEX */
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const ƔAML_FRONTMATTER = unirex(
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rexstr(POSSIBLE_STARTS) +
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rexstr(ƔAML_LOOKAHEAD) +
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rexstr(ƔAML_START) + rexstr(SOME_NEW_LINES) +
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'(?:' +
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rexstr(ANY_WHITE_SPACE) + rexstr(ƔAML_LINE) + rexstr(SOME_NEW_LINES) +
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'){0,5}' +
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rexstr(ƔAML_END) + rexstr(POSSIBLE_ENDS)
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);
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/* SEARCHES */
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const FIND_ƔAML_LINE = unirex(
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rexstr(NEW_LINE) + rexstr(ANY_WHITE_SPACE) + rexstr(ƔAML_LINE)
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);
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/* STRING PROCESSING */
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function processString (str) {
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switch (str.charAt(0)) {
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case '"':
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return str.substring(1, str.length - 1);
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case '\'':
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return str
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.substring(1, str.length - 1)
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.replace(/''/g, '\'');
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default:
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return str;
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}
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}
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/* BIO PROCESSING */
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export function processBio(content) {
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content = content.replace(/"/g, '"').replace(/'/g, '\'');
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let result = {
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text: content,
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metadata: [],
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};
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let ɣaml = content.match(ƔAML_FRONTMATTER);
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if (!ɣaml) {
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return result;
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} else {
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ɣaml = ɣaml[0];
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}
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const start = content.search(ƔAML_START);
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const end = start + ɣaml.length - ɣaml.search(ƔAML_START);
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result.text = content.substr(end);
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let metadata = null;
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let query = new RegExp(rexstr(FIND_ƔAML_LINE), 'g'); // Some browsers don't allow flags unless both args are strings
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while ((metadata = query.exec(ɣaml))) {
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result.metadata.push([
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processString(metadata[1]),
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processString(metadata[2]),
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]);
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}
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return result;
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}
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/* BIO CREATION */
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export function createBio(note, data) {
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if (!note) note = '';
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let frontmatter = '';
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if ((data && data.length) || note.match(/^\s*---\s+/)) {
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if (!data) frontmatter = '---\n...\n';
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else {
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frontmatter += '---\n';
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for (let i = 0; i < data.length; i++) {
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let key = '' + data[i][0];
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let val = '' + data[i][1];
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// Key processing
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if (key === (key.match(ƔAML_SIMPLE_KEY) || [])[0]) /* do nothing */;
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else if (key === (key.match(ANY_QUOTE_CHAR) || [])[0]) key = '"' + key + '"';
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else {
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key = key
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.replace(/'/g, '\'\'')
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.replace(new RegExp(rexstr(NOT_ALLOWED_CHAR), compat_mode ? 'g' : 'gu'), '<27>');
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key = '\'' + key + '\'';
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}
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// Value processing
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if (val === (val.match(ƔAML_SIMPLE_VALUE) || [])[0]) /* do nothing */;
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else if (val === (val.match(ANY_QUOTE_CHAR) || [])[0]) val = '"' + val + '"';
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else {
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key = key
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.replace(/'/g, '\'\'')
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.replace(new RegExp(rexstr(NOT_ALLOWED_CHAR), compat_mode ? 'g' : 'gu'), '<27>');
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key = '\'' + key + '\'';
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}
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frontmatter += key + ': ' + val + '\n';
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}
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frontmatter += '...\n';
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}
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}
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return frontmatter + note;
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}
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