locutus/python/re/subn.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.subn = subn;
const PY_RE_IGNORECASE = 2;
const PY_RE_MULTILINE = 8;
const PY_RE_DOTALL = 16;
function subn(pattern, replacement, source, count = 0, flags = 0) {
    //      discuss at: https://locutus.io/python/re/subn/
    // parity verified: Python 3.12
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Returns the substituted string together with the number of replacements applied.
    //          note 2: Supports a subset of numeric flags (IGNORECASE=2, MULTILINE=8, DOTALL=16).
    //       example 1: subn('a+', '-', 'caaab')
    //       returns 1: ['c-b', 1]
    //       example 2: subn('(\\d+)', '#', 'a1b22c333')
    //       returns 2: ['a#b#c#', 3]
    //       example 3: subn('x', 'y', 'xxx', 2)
    //       returns 3: ['yyx', 2]
    //       example 4: subn('abc', 'X', 'ABC abc', 0, 2)
    //       returns 4: ['X X', 2]
    const input = String(source);
    const maxCount = normalizeCount(count);
    const regex = createGlobalRegex(pattern, flags);
    const replacementFn = typeof replacement === 'function' ? replacement : null;
    const replacementTemplate = typeof replacement === 'string' ? replacement : '';
    let out = '';
    let lastIndex = 0;
    let replaced = 0;
    regex.lastIndex = 0;
    while (maxCount === 0 || replaced < maxCount) {
        const match = regex.exec(input);
        if (!match) {
            break;
        }
        const full = match[0] ?? '';
        const start = match.index;
        const end = start + full.length;
        out += input.slice(lastIndex, start);
        out +=
            replacementFn !== null
                ? String(replacementFn(full, ...match.slice(1)))
                : applyPythonReplacementTemplate(replacementTemplate, full, match.slice(1), match.groups);
        lastIndex = end;
        replaced += 1;
        if (full === '') {
            if (regex.lastIndex >= input.length) {
                break;
            }
            regex.lastIndex += 1;
        }
    }
    out += input.slice(lastIndex);
    return [replaced > 0 ? out : input, replaced];
}
function normalizeCount(count) {
    const n = Number(count);
    if (!Number.isFinite(n) || n <= 0) {
        return 0;
    }
    return Math.floor(n);
}
function createGlobalRegex(pattern, flags) {
    const source = pattern instanceof RegExp ? pattern.source : String(pattern);
    const base = pattern instanceof RegExp ? pattern.flags : '';
    const extra = normalizeRegexFlags(flags);
    const combined = dedupeFlags((base + extra).replace(/g/g, '').replace(/y/g, ''));
    return new RegExp(source, `${combined}g`);
}
function normalizeRegexFlags(flags) {
    if (typeof flags === 'string') {
        return dedupeFlags(flags.replace(/[^dgimsuvy]/g, ''));
    }
    let out = '';
    if (flags & PY_RE_IGNORECASE) {
        out += 'i';
    }
    if (flags & PY_RE_MULTILINE) {
        out += 'm';
    }
    if (flags & PY_RE_DOTALL) {
        out += 's';
    }
    return out;
}
function dedupeFlags(flags) {
    const seen = new Set();
    let out = '';
    for (const flag of flags) {
        if (!seen.has(flag)) {
            seen.add(flag);
            out += flag;
        }
    }
    return out;
}
function applyPythonReplacementTemplate(template, full, groups, named) {
    let out = '';
    for (let i = 0; i < template.length; i++) {
        const char = template[i];
        if (char !== '\\') {
            out += char;
            continue;
        }
        const next = template[i + 1];
        if (!next) {
            out += '\\';
            continue;
        }
        if (next === '0') {
            let token = '0';
            let j = i + 2;
            while (j < template.length && /[0-7]/.test(template[j] ?? '') && token.length < 3) {
                token += template[j];
                j += 1;
            }
            out += String.fromCharCode(Number.parseInt(token, 8));
            i = j - 1;
            continue;
        }
        if (/\d/.test(next)) {
            let token = next;
            let j = i + 2;
            while (j < template.length && /\d/.test(template[j] ?? '') && token.length < 2) {
                token += template[j];
                j += 1;
            }
            out += groups[Number.parseInt(token, 10) - 1] ?? '';
            i = j - 1;
            continue;
        }
        if (next === 'g' && template[i + 2] === '<') {
            const close = template.indexOf('>', i + 3);
            if (close > -1) {
                const token = template.slice(i + 3, close);
                if (/^\d+$/.test(token)) {
                    const index = Number.parseInt(token, 10);
                    out += index === 0 ? full : (groups[index - 1] ?? '');
                }
                else {
                    out += named?.[token] ?? '';
                }
                i = close;
                continue;
            }
        }
        const simpleEscapes = {
            '\\': '\\',
            n: '\n',
            r: '\r',
            t: '\t',
            f: '\f',
            v: '\v',
            a: '\x07',
            b: '\b',
        };
        if (simpleEscapes[next] !== undefined) {
            out += simpleEscapes[next];
            i += 1;
            continue;
        }
        out += next;
        i += 1;
    }
    return out;
}