48 lines
1.5 KiB
TypeScript
48 lines
1.5 KiB
TypeScript
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const subsChrs = " !#$%&'()*+,-./<=>?@[]^_`{|}~";
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const Word = /^[a-z]*$/i;
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function unfold(words: Array<string>, sep: string): Array<string> {
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let initial = 97;
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return words.reduce((accum, word) => {
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if (word === sep) {
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initial++;
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} else if (word.match(Word)) {
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accum.push(String.fromCharCode(initial) + word);
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} else {
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initial = 97;
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accum.push(word);
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}
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return accum;
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}, <Array<string>>[]);
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}
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export function decode(data: string, subs: string): Array<string> {
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// Replace all the substitutions with their expanded form
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for (let i = subsChrs.length - 1; i >= 0; i--) {
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data = data.split(subsChrs[i]).join(subs.substring(2 * i, 2 * i + 2));
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}
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// Get all tle clumps; each suffix, first-increment and second-increment
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const clumps: Array<string> = [ ];
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const leftover = data.replace(/(:|([0-9])|([A-Z][a-z]*))/g, (all, item, semi, word) => {
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if (semi) {
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for (let i = parseInt(semi); i >= 0; i--) { clumps.push(";"); }
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} else {
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clumps.push(item.toLowerCase());
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}
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return "";
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});
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if (leftover) { throw new Error(`leftovers: ${ JSON.stringify(leftover) }`); }
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return unfold(unfold(clumps, ";"), ":");
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}
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export function decodeOwl(data: string): Array<string> {
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if (data[0] !== "0") { throw TypeError("unsupported auwl data"); }
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return decode(
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data.substring(1 + 2 * subsChrs.length),
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data.substring(1, 1 + 2 * subsChrs.length));
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}
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