296 lines
9.9 KiB
JavaScript
296 lines
9.9 KiB
JavaScript
/*********************************************************************\
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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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Sending love + warmth eternal,
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- kibigo [@kibi@glitch.social]
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\*********************************************************************/
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/* CONVENIENCE FUNCTIONS */
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const unirex = 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 = // `c-printable` in the YAML 1.2 spec.
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/[\t\n\r\x20-\x7e\x85\xa0-\ud7ff\ue000-\ufffd\u{10000}-\u{10FFFF}]/u;
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const WHITE_SPACE = /[ \t]/;
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const INDENTATION = / */; // Indentation must be only spaces.
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const LINE_BREAK = /\r?\n|\r|<br\s*\/?>/;
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const ESCAPE_CHAR = /[0abt\tnvfre "\/\\N_LP]/;
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const HEXADECIMAL_CHARS = /[0-9a-fA-F]/;
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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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/* 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(ANY_WHITE_SPACE) + rexstr(LINE_BREAK) + ')+'
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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 CHARACTER_ESCAPE = unirex(
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rexstr(/\\/) +
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'(?:' +
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rexstr(ESCAPE_CHAR) + '|' +
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rexstr(/x/) + rexstr(HEXADECIMAL_CHARS) + '{2}' + '|' +
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rexstr(/u/) + rexstr(HEXADECIMAL_CHARS) + '{4}' + '|' +
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rexstr(/U/) + rexstr(HEXADECIMAL_CHARS) + '{8}' +
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')'
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);
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const ESCAPED_CHAR = unirex(
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rexstr(/(?!["\\])/) + rexstr(NOT_LINE_BREAK) + '|' +
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rexstr(CHARACTER_ESCAPE)
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);
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const ANY_ESCAPED_CHARS = unirex(
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rexstr(ESCAPED_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 YAML_START = unirex(
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rexstr(ANY_WHITE_SPACE) + rexstr(/---/)
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);
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const YAML_END = unirex(
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rexstr(ANY_WHITE_SPACE) + rexstr(/(?:---|\.\.\.)/)
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);
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const YAML_LOOKAHEAD = unirex(
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'(?=' +
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rexstr(YAML_START) +
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rexstr(ANY_ALLOWED_CHARS) + rexstr(NEW_LINE) +
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rexstr(YAML_END) + rexstr(POSSIBLE_ENDS) +
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')'
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);
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const YAML_DOUBLE_QUOTE = unirex(
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rexstr(/"/) + rexstr(ANY_ESCAPED_CHARS) + rexstr(/"/)
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);
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const YAML_SINGLE_QUOTE = unirex(
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rexstr(/'/) + rexstr(ANY_ESCAPED_APOS) + rexstr(/'/)
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);
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const YAML_SIMPLE_KEY = unirex(
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rexstr(FIRST_KEY_CHAR) + rexstr(LATER_KEY_CHAR) + '*'
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);
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const YAML_SIMPLE_VALUE = unirex(
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rexstr(FIRST_VALUE_CHAR) + rexstr(LATER_VALUE_CHAR) + '*'
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);
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const YAML_KEY = unirex(
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rexstr(YAML_DOUBLE_QUOTE) + '|' +
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rexstr(YAML_SINGLE_QUOTE) + '|' +
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rexstr(YAML_SIMPLE_KEY)
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);
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const YAML_VALUE = unirex(
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rexstr(YAML_DOUBLE_QUOTE) + '|' +
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rexstr(YAML_SINGLE_QUOTE) + '|' +
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rexstr(YAML_SIMPLE_VALUE)
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);
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const YAML_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 YAML_LINE = unirex(
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'(' + rexstr(YAML_KEY) + ')' +
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rexstr(YAML_SEPARATOR) +
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'(' + rexstr(YAML_VALUE) + ')'
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);
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/* FRONTMATTER REGEX */
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const YAML_FRONTMATTER = unirex(
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rexstr(POSSIBLE_STARTS) +
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rexstr(YAML_LOOKAHEAD) +
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rexstr(YAML_START) + rexstr(SOME_NEW_LINES) +
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'(?:' +
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'(' + rexstr(INDENTATION) + ')' +
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rexstr(YAML_LINE) + rexstr(SOME_NEW_LINES) +
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'(?:' +
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'\\1' + rexstr(YAML_LINE) + rexstr(SOME_NEW_LINES) +
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'){0,4}' +
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')?' +
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rexstr(YAML_END) + rexstr(POSSIBLE_ENDS)
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);
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/* SEARCHES */
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const FIND_YAML_LINES = unirex(
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rexstr(NEW_LINE) + rexstr(INDENTATION) + rexstr(YAML_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
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.substring(1, str.length - 1)
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.replace(/\\0/g, '\x00')
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.replace(/\\a/g, '\x07')
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.replace(/\\b/g, '\x08')
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.replace(/\\t/g, '\x09')
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.replace(/\\n/g, '\x0a')
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.replace(/\\v/g, '\x0b')
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.replace(/\\f/g, '\x0c')
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.replace(/\\r/g, '\x0d')
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.replace(/\\e/g, '\x1b')
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.replace(/\\ /g, '\x20')
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.replace(/\\"/g, '\x22')
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.replace(/\\\//g, '\x2f')
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.replace(/\\\\/g, '\x5c')
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.replace(/\\N/g, '\x85')
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.replace(/\\_/g, '\xa0')
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.replace(/\\L/g, '\u2028')
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.replace(/\\P/g, '\u2029')
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.replace(
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new RegExp(
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unirex(
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rexstr(/\\x/) + '(' + rexstr(HEXADECIMAL_CHARS) + '{2})'
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), 'gu'
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), (_, n) => String.fromCodePoint('0x' + n)
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)
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.replace(
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new RegExp(
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unirex(
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rexstr(/\\u/) + '(' + rexstr(HEXADECIMAL_CHARS) + '{4})'
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), 'gu'
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), (_, n) => String.fromCodePoint('0x' + n)
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)
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.replace(
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new RegExp(
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unirex(
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rexstr(/\\U/) + '(' + rexstr(HEXADECIMAL_CHARS) + '{8})'
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), 'gu'
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), (_, n) => String.fromCodePoint('0x' + n)
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);
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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 yaml = content.match(YAML_FRONTMATTER);
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if (!yaml) return result;
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else yaml = yaml[0];
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let start = content.search(YAML_START);
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let end = start + yaml.length - yaml.search(YAML_START);
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result.text = content.substr(0, start) + content.substr(end);
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let metadata = null;
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let query = new RegExp(FIND_YAML_LINES, 'g');
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while ((metadata = query.exec(yaml))) {
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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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