// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

.pragma library

// Pure helpers for qtmaildir.conf, tested by test_ini.js under node.
//
// The file is walked a line at a time, never cut at the next "[": values
// hold brackets ([Gmail]/Bozze), and a section body taken as "everything up
// to the next [" once lost three accounts their labels (AGENTS.md). A header
// is a line that is only "[name]". Comments and order are kept: a key unset
// is commented out in place, a commented key that is set again is activated,
// and anything this file does not touch passes through.
//
// Values follow QSettings' INI reading: an unquoted ; starts a comment, and
// a "quoted" value may hold one.

const HEADER = /^\s*\[([^\]]+)\]\s*(;.*)?$/;
const KEY = /^(\s*)(;\s*)?([^=;\s][^=]*?)\s*=\s*(.*)$/;

function value(rest) {
    if (rest.startsWith('"')) {
        let out = "";
        for (let i = 1; i < rest.length; i++) {
            const c = rest[i];
            if (c === '"') return { v: out, end: i + 1 };
            if (c === "\\" && i + 1 < rest.length) out += rest[++i];
            else out += c;
        }
        return { v: out, end: rest.length };
    }
    const semi = rest.search(/\s*;/);
    const raw = semi < 0 ? rest : rest.slice(0, semi);
    return { v: raw.trim(), end: raw.replace(/\s+$/, "").length };
}

function quote(v) {
    return /[;"]|^\s|\s$/.test(v) ? '"' + v.replace(/[\\"]/g, c => "\\" + c) + '"' : v;
}

// [{name, h, end}]: the header's line and the line after the section.
function ranges(lines) {
    const out = [];
    lines.forEach((l, i) => {
        const m = HEADER.exec(l);
        if (!m) return;
        if (out.length) out[out.length - 1].end = i;
        out.push({ name: m[1].trim(), h: i, end: lines.length });
    });
    return out;
}

function sections(text) { return ranges(text.split("\n")).map(r => r.name); }

// [{key, value}] for the active keys of a section, in file order.
function entries(text, section) {
    const lines = text.split("\n");
    const r = ranges(lines).find(x => x.name === section);
    if (!r) return [];
    const out = [];
    for (let i = r.h + 1; i < r.end; i++) {
        const m = KEY.exec(lines[i]);
        if (m && !m[2]) out.push({ key: m[3].trim(), value: value(m[4]).v });
    }
    return out;
}

function get(text, section, key) {
    const e = entries(text, section).find(x => x.key === key);
    return e ? e.value : undefined;
}

// value null unsets: the key is commented out where it stands.
function set(text, section, key, val) {
    const lines = text.split("\n");
    const r = ranges(lines).find(x => x.name === section);
    if (!r) {
        if (val === null) return text;
        return text.replace(/\n*$/, "") + "\n\n[" + section + "]\n" + key + " = " + quote(val) + "\n";
    }
    let commented = -1;
    let last = r.h;
    for (let i = r.h + 1; i < r.end; i++) {
        const m = KEY.exec(lines[i]);
        if (lines[i].trim() !== "") last = i;
        if (!m || m[3].trim() !== key) continue;
        const tail = m[4].slice(value(m[4]).end);
        if (!m[2]) {
            lines[i] = val === null ? m[1] + "; " + key + " = " + m[4]
                                    : m[1] + key + " = " + quote(val) + tail;
            return lines.join("\n");
        }
        if (commented < 0) commented = i;
    }
    if (val === null) return text;
    if (commented >= 0) {
        const m = KEY.exec(lines[commented]);
        lines[commented] = m[1] + key + " = " + quote(val) + m[4].slice(value(m[4]).end);
    } else lines.splice(last + 1, 0, key + " = " + quote(val));
    return lines.join("\n");
}

// Deletes an active key's line outright, for the free-form sections
// ([tagcolors], [keys]) where a commented-out row would only pile up.
function remove(text, section, key) {
    const lines = text.split("\n");
    const r = ranges(lines).find(x => x.name === section);
    if (!r) return text;
    for (let i = r.h + 1; i < r.end; i++) {
        const m = KEY.exec(lines[i]);
        if (m && !m[2] && m[3].trim() === key) { lines.splice(i, 1); return lines.join("\n"); }
    }
    return text;
}

// pairs: [[key, value], ...]
function addSection(text, section, pairs) {
    return text.replace(/\n*$/, "") + "\n\n[" + section + "]\n"
        + pairs.map(p => p[0] + " = " + quote(p[1])).join("\n") + "\n";
}

// The header through the line before the next header, which takes the blank
// line that separated it from the next section with it.
function removeSection(text, section) {
    const lines = text.split("\n");
    const r = ranges(lines).find(x => x.name === section);
    if (!r) return text;
    lines.splice(r.h, r.end - r.h);
    return lines.join("\n");
}