/**
 * List of translation functions exposed by the `@wordpress/i18n` package.
 *
 * @type {Set<string>} Translation functions.
 */
const TRANSLATION_FUNCTIONS = new Set( [ '__', '_x', '_n', '_nx' ] );

/**
 * Regular expression matching format placeholder syntax.
 *
 * The pattern for matching named arguments is a naive and incomplete matcher
 * against valid JavaScript identifier names.
 *
 * via Mathias Bynens:
 *
 * >An identifier must start with $, _, or any character in the Unicode
 * >categories “Uppercase letter (Lu)”, “Lowercase letter (Ll)”, “Titlecase
 * >letter (Lt)”, “Modifier letter (Lm)”, “Other letter (Lo)”, or “Letter
 * >number (Nl)”.
 * >
 * >The rest of the string can contain the same characters, plus any U+200C zero
 * >width non-joiner characters, U+200D zero width joiner characters, and
 * >characters in the Unicode categories “Non-spacing mark (Mn)”, “Spacing
 * >combining mark (Mc)”, “Decimal digit number (Nd)”, or “Connector
 * >punctuation (Pc)”.
 *
 * If browser support is constrained to those supporting ES2015, this could be
 * made more accurate using the `u` flag:
 *
 * ```
 * /^[$_\p{L}\p{Nl}][$_\p{L}\p{Nl}\u200C\u200D\p{Mn}\p{Mc}\p{Nd}\p{Pc}]*$/u;
 * ```
 *
 * @see http://www.pixelbeat.org/programming/gcc/format_specs.html
 * @see https://mathiasbynens.be/notes/javascript-identifiers#valid-identifier-names
 *
 * @type {RegExp}
 */
const REGEXP_SPRINTF_PLACEHOLDER =
	/%(((\d+)\$)|(\(([$_a-zA-Z][$_a-zA-Z0-9]*)\)))?[ +0#-]*\d*(\.(\d+|\*))?(ll|[lhqL])?([cduxXefgsp%])/g;
//               ▲         ▲                    ▲       ▲  ▲            ▲           ▲ type
//               │         │                    │       │  │            └ Length (unsupported)
//               │         │                    │       │  └ Precision / max width
//               │         │                    │       └ Min width (unsupported)
//               │         │                    └ Flags (unsupported)
//               └ Index   └ Name (for named arguments)

/**
 * "Unordered" means there's no position specifier: '%s', not '%2$s'.
 *
 * @see https://github.com/WordPress/WordPress-Coding-Standards/blob/2f927b0ba2bfcbffaa8f3251c086e109302d6622/WordPress/Sniffs/WP/I18nSniff.php#L62-L81
 *
 * @type {RegExp}
 */
const REGEXP_SPRINTF_PLACEHOLDER_UNORDERED =
	/(?:(?<!%)%[+-]?(?:(?:0|'.)?-?[0-9]*(?:\.(?:[ 0]|'.)?[0-9]+)?|(?:[ ])?-?[0-9]+(?:\.(?:[ 0]|'.)?[0-9]+)?)[bcdeEfFgGosuxX])/;

module.exports = {
	TRANSLATION_FUNCTIONS,
	REGEXP_SPRINTF_PLACEHOLDER,
	REGEXP_SPRINTF_PLACEHOLDER_UNORDERED,
};