// 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 sb-builder's two config.toml files, tested by
// test_toml.js under node. Walked a line at a time like Ini.js, so comments
// and order survive: a key unset is commented out with #, a commented key
// set again is activated. Top-level keys are section "".
//
// ponytail: the TOML these files use, one key per line: strings, integers,
// booleans, one-line arrays. A value with anything but a comment after it
// (multi-line strings and arrays included) is refused: entries() skips it and
// set() throws rather than write a duplicate key; such a file is edited by
// hand. Also not recognised: CRLF line endings, `[ spaced ]` and `[[array]]`
// headers, and 'literal' keys.

const HEADER = /^\s*\[([A-Za-z0-9_.-]+)\]\s*(#.*)?$/;
const KEY = /^(\s*)(#\s*)?("(?:[^"\\]|\\.)*"|[A-Za-z0-9_-]+)\s*=\s*(.*)$/;

function unkey(k) {
    if (!k.startsWith('"')) return k;
    try { return JSON.parse(k); } catch (e) { return k; }
}
function enkey(k) { return /^[A-Za-z0-9_-]+$/.test(k) ? k : enc(k); }

// JSON's escapes are a subset of TOML basic strings', bar a raw DEL.
function enc(v) {
    if (Array.isArray(v)) return "[" + v.map(enc).join(", ") + "]";
    if (typeof v === "string") return JSON.stringify(v).replace(/\x7f/g, "\\u007f");
    return String(v);
}

function skip(s, i) { while (s[i] === " " || s[i] === "\t") i++; return i; }

// {v, i}: the value at s[i] and the index after it, or null.
function val(s, i) {
    const c = s[i];
    if (c === '"') {
        let j = i + 1;
        while (j < s.length && s[j] !== '"') j += s[j] === "\\" ? 2 : 1;
        if (j >= s.length) return null;
        try { return { v: JSON.parse(s.slice(i, j + 1)), i: j + 1 }; } catch (e) { return null; }
    }
    if (c === "'") {
        const j = s.indexOf("'", i + 1);
        return j < 0 ? null : { v: s.slice(i + 1, j), i: j + 1 };
    }
    if (c === "[") {
        const out = [];
        i = skip(s, i + 1);
        while (s[i] !== "]") {
            const e = val(s, i);
            if (!e) return null;
            out.push(e.v);
            i = skip(s, e.i);
            if (s[i] === ",") i = skip(s, i + 1);
            else if (s[i] !== "]") return null;
        }
        return { v: out, i: i + 1 };
    }
    const m = /^(true|false|[+-]?[0-9][0-9_]*)(?=[\s#,\]]|$)/.exec(s.slice(i));
    if (!m) return null;
    const v = m[1] === "true" ? true : m[1] === "false" ? false : Number(m[1].replace(/_/g, ""));
    return { v: v, i: i + m[1].length };
}

// A whole line's value: the rest of the line must be blank or a comment.
function whole(s) {
    const p = val(s, 0);
    return p && /^\s*(#.*)?$/.test(s.slice(p.i)) ? p : null;
}

// [{name, h, end}]: the header's line and the line after the section. The
// top-level keys are a section "" with its header at -1.
function ranges(lines) {
    const out = [{ name: "", h: -1, end: lines.length }];
    lines.forEach((l, i) => {
        const m = HEADER.exec(l);
        if (!m) return;
        out[out.length - 1].end = i;
        out.push({ name: m[1], h: i, end: lines.length });
    });
    return out;
}

// [{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]);
        const p = m && !m[2] ? whole(m[4]) : null;
        if (p) out.push({ key: unkey(m[3]), value: p.v });
    }
    return out;
}

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

// v null unsets: the key is commented out where it stands.
function set(text, section, key, v) {
    const lines = text.split("\n");
    const r = ranges(lines).find(x => x.name === section);
    const line = enkey(key) + " = " + (v === null ? "" : enc(v));
    if (!r) {
        if (v === null) return text;
        return text.replace(/\n*$/, "") + (text.trim() ? "\n\n" : "") + "[" + section + "]\n" + line + "\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 (!m) continue;
        if (!m[2]) last = i;
        if (unkey(m[3]) !== key) continue;
        const p = whole(m[4]);
        if (!m[2]) {
            if (!p) throw new Error(key + ": a value this page cannot edit; change it in the file");
            lines[i] = v === null ? m[1] + "# " + lines[i].slice(m[1].length)
                                  : m[1] + line + m[4].slice(p.i);
            return lines.join("\n");
        }
        if (p && commented < 0) commented = i;
    }
    if (v === null) return text;
    if (commented >= 0) {
        const m = KEY.exec(lines[commented]);
        lines[commented] = m[1] + line + m[4].slice(val(m[4], 0).i);
        return lines.join("\n");
    }
    // No key yet at the top: after the leading comments, not above them.
    if (last < 0) while (last + 1 < r.end && lines[last + 1].trim().startsWith("#")) last++;
    lines.splice(last + 1, 0, line);
    return lines.join("\n");
}

// Deletes an active key's line outright, for [manifests] rows.
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] && unkey(m[3]) === key) { lines.splice(i, 1); return lines.join("\n"); }
    }
    return text;
}