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