'use strict';
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// detect either spaces or tabs but not both to properly handle tabs
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// for indentation and spaces for alignment
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const INDENT_RE = /^(?:( )+|\t+)/;
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function getMostUsed(indents) {
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let result = 0;
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let maxUsed = 0;
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let maxWeight = 0;
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for (const entry of indents) {
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// TODO: use destructuring when targeting Node.js 6
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const key = entry[0];
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const val = entry[1];
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const u = val[0];
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const w = val[1];
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if (u > maxUsed || (u === maxUsed && w > maxWeight)) {
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maxUsed = u;
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maxWeight = w;
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result = Number(key);
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}
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}
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return result;
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}
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module.exports = str => {
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if (typeof str !== 'string') {
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throw new TypeError('Expected a string');
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}
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// used to see if tabs or spaces are the most used
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let tabs = 0;
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let spaces = 0;
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// remember the size of previous line's indentation
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let prev = 0;
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// remember how many indents/unindents as occurred for a given size
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// and how much lines follow a given indentation
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//
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// indents = {
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// 3: [1, 0],
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// 4: [1, 5],
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// 5: [1, 0],
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// 12: [1, 0],
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// }
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const indents = new Map();
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// pointer to the array of last used indent
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let current;
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// whether the last action was an indent (opposed to an unindent)
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let isIndent;
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for (const line of str.split(/\n/g)) {
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if (!line) {
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// ignore empty lines
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continue;
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}
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let indent;
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const matches = line.match(INDENT_RE);
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if (matches) {
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indent = matches[0].length;
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if (matches[1]) {
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spaces++;
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} else {
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tabs++;
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}
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} else {
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indent = 0;
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}
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const diff = indent - prev;
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prev = indent;
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if (diff) {
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// an indent or unindent has been detected
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isIndent = diff > 0;
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current = indents.get(isIndent ? diff : -diff);
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if (current) {
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current[0]++;
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} else {
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current = [1, 0];
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indents.set(diff, current);
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}
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} else if (current) {
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// if the last action was an indent, increment the weight
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current[1] += Number(isIndent);
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}
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}
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const amount = getMostUsed(indents);
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let type;
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let indent;
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if (!amount) {
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type = null;
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indent = '';
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} else if (spaces >= tabs) {
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type = 'space';
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indent = ' '.repeat(amount);
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} else {
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type = 'tab';
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indent = '\t'.repeat(amount);
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}
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return {
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amount,
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type,
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indent
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};
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};
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