170 lines
6.5 KiB
Plaintext
170 lines
6.5 KiB
Plaintext
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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const boundaries_1 = require("./boundaries");
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// BreakTypes
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// @type {BreakType}
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const NotBreak = 0;
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const BreakStart = 1;
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const Break = 2;
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const BreakLastRegional = 3;
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const BreakPenultimateRegional = 4;
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class GraphemerHelper {
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/**
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* Check if the the character at the position {pos} of the string is surrogate
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* @param str {string}
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* @param pos {number}
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* @returns {boolean}
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*/
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static isSurrogate(str, pos) {
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return (0xd800 <= str.charCodeAt(pos) &&
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str.charCodeAt(pos) <= 0xdbff &&
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0xdc00 <= str.charCodeAt(pos + 1) &&
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str.charCodeAt(pos + 1) <= 0xdfff);
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}
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/**
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* The String.prototype.codePointAt polyfill
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* Private function, gets a Unicode code point from a JavaScript UTF-16 string
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* handling surrogate pairs appropriately
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* @param str {string}
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* @param idx {number}
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* @returns {number}
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*/
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static codePointAt(str, idx) {
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if (idx === undefined) {
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idx = 0;
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}
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const code = str.charCodeAt(idx);
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// if a high surrogate
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if (0xd800 <= code && code <= 0xdbff && idx < str.length - 1) {
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const hi = code;
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const low = str.charCodeAt(idx + 1);
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if (0xdc00 <= low && low <= 0xdfff) {
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return (hi - 0xd800) * 0x400 + (low - 0xdc00) + 0x10000;
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}
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return hi;
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}
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// if a low surrogate
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if (0xdc00 <= code && code <= 0xdfff && idx >= 1) {
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const hi = str.charCodeAt(idx - 1);
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const low = code;
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if (0xd800 <= hi && hi <= 0xdbff) {
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return (hi - 0xd800) * 0x400 + (low - 0xdc00) + 0x10000;
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}
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return low;
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}
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// just return the char if an unmatched surrogate half or a
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// single-char codepoint
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return code;
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}
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//
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/**
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* Private function, returns whether a break is allowed between the two given grapheme breaking classes
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* Implemented the UAX #29 3.1.1 Grapheme Cluster Boundary Rules on extended grapheme clusters
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* @param start {number}
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* @param mid {Array<number>}
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* @param end {number}
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* @param startEmoji {number}
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* @param midEmoji {Array<number>}
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* @param endEmoji {number}
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* @returns {number}
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*/
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static shouldBreak(start, mid, end, startEmoji, midEmoji, endEmoji) {
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const all = [start].concat(mid).concat([end]);
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const allEmoji = [startEmoji].concat(midEmoji).concat([endEmoji]);
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const previous = all[all.length - 2];
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const next = end;
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const nextEmoji = endEmoji;
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// Lookahead terminator for:
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// GB12. ^ (RI RI)* RI ? RI
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// GB13. [^RI] (RI RI)* RI ? RI
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const rIIndex = all.lastIndexOf(boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR);
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if (rIIndex > 0 &&
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all.slice(1, rIIndex).every(function (c) {
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return c === boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR;
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}) &&
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[boundaries_1.CLUSTER_BREAK.PREPEND, boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR].indexOf(previous) === -1) {
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if (all.filter(function (c) {
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return c === boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR;
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}).length %
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2 ===
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1) {
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return BreakLastRegional;
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}
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else {
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return BreakPenultimateRegional;
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}
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}
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// GB3. CR × LF
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if (previous === boundaries_1.CLUSTER_BREAK.CR && next === boundaries_1.CLUSTER_BREAK.LF) {
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return NotBreak;
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}
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// GB4. (Control|CR|LF) ÷
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else if (previous === boundaries_1.CLUSTER_BREAK.CONTROL ||
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previous === boundaries_1.CLUSTER_BREAK.CR ||
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previous === boundaries_1.CLUSTER_BREAK.LF) {
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return BreakStart;
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}
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// GB5. ÷ (Control|CR|LF)
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else if (next === boundaries_1.CLUSTER_BREAK.CONTROL ||
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next === boundaries_1.CLUSTER_BREAK.CR ||
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next === boundaries_1.CLUSTER_BREAK.LF) {
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return BreakStart;
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}
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// GB6. L × (L|V|LV|LVT)
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else if (previous === boundaries_1.CLUSTER_BREAK.L &&
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(next === boundaries_1.CLUSTER_BREAK.L ||
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next === boundaries_1.CLUSTER_BREAK.V ||
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next === boundaries_1.CLUSTER_BREAK.LV ||
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next === boundaries_1.CLUSTER_BREAK.LVT)) {
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return NotBreak;
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}
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// GB7. (LV|V) × (V|T)
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else if ((previous === boundaries_1.CLUSTER_BREAK.LV || previous === boundaries_1.CLUSTER_BREAK.V) &&
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(next === boundaries_1.CLUSTER_BREAK.V || next === boundaries_1.CLUSTER_BREAK.T)) {
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return NotBreak;
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}
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// GB8. (LVT|T) × (T)
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else if ((previous === boundaries_1.CLUSTER_BREAK.LVT || previous === boundaries_1.CLUSTER_BREAK.T) &&
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next === boundaries_1.CLUSTER_BREAK.T) {
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return NotBreak;
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}
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// GB9. × (Extend|ZWJ)
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else if (next === boundaries_1.CLUSTER_BREAK.EXTEND || next === boundaries_1.CLUSTER_BREAK.ZWJ) {
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return NotBreak;
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}
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// GB9a. × SpacingMark
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else if (next === boundaries_1.CLUSTER_BREAK.SPACINGMARK) {
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return NotBreak;
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}
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// GB9b. Prepend ×
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else if (previous === boundaries_1.CLUSTER_BREAK.PREPEND) {
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return NotBreak;
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}
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// GB11. \p{Extended_Pictographic} Extend* ZWJ × \p{Extended_Pictographic}
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const previousNonExtendIndex = allEmoji
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.slice(0, -1)
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.lastIndexOf(boundaries_1.EXTENDED_PICTOGRAPHIC);
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if (previousNonExtendIndex !== -1 &&
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allEmoji[previousNonExtendIndex] === boundaries_1.EXTENDED_PICTOGRAPHIC &&
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all.slice(previousNonExtendIndex + 1, -2).every(function (c) {
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return c === boundaries_1.CLUSTER_BREAK.EXTEND;
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}) &&
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previous === boundaries_1.CLUSTER_BREAK.ZWJ &&
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nextEmoji === boundaries_1.EXTENDED_PICTOGRAPHIC) {
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return NotBreak;
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}
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// GB12. ^ (RI RI)* RI × RI
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// GB13. [^RI] (RI RI)* RI × RI
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if (mid.indexOf(boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR) !== -1) {
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return Break;
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}
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if (previous === boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR &&
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next === boundaries_1.CLUSTER_BREAK.REGIONAL_INDICATOR) {
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return NotBreak;
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}
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// GB999. Any ? Any
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return BreakStart;
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}
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}
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exports.default = GraphemerHelper;
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