// 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 desktop-assistant's config.toml, tested by
// test_config.js under node.
//
// The file is edited line by line so its comments survive: the example it
// is copied from documents every key in place. Only the shapes this page
// writes are understood: top-level `key = value` before the first table,
// and `KEY = "value"` lines in [env]. A top-level key that is unset sits
// commented out (`# key = value`), which is how the example ships, so
// setting one activates its line and unsetting comments it back out.
// ponytail: no multi-line strings or arrays; the page never writes one,
// and Save validates the whole file with tomllib before writing.

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

function quote(s) {
    return '"' + String(s).replace(/[\\"]/g, c => "\\" + c)
        .replace(/\n/g, "\\n").replace(/\t/g, "\\t").replace(/\r/g, "\\r") + '"';
}

// The value at the start of rest and where it ends, so what follows (an
// inline comment) can be kept.
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) {
                const n = rest[++i];
                out += n === "n" ? "\n" : n === "t" ? "\t" : n === "r" ? "\r" : n;
            } else out += c;
        }
        return { v: out, end: rest.length };
    }
    const m = /^[^\s#]*/.exec(rest)[0];
    const v = m === "true" ? true : m === "false" ? false
            : m !== "" && !isNaN(Number(m)) ? Number(m) : m;
    return { v: v, end: m.length };
}

function firstHeader(lines) {
    const i = lines.findIndex(l => HEADER.test(l) && !/^\s*#/.test(l));
    return i < 0 ? lines.length : i;
}

// {key: value} for the active top-level keys among keys.
function scalars(text, keys) {
    const lines = text.split("\n");
    const out = {};
    for (let i = 0; i < firstHeader(lines); i++) {
        const m = KEY.exec(lines[i]);
        if (m && !m[2] && keys.includes(m[3])) out[m[3]] = value(m[4]).v;
    }
    return out;
}

// toml is the value already written as TOML (quote() for a string), or null
// to unset.
function setScalar(text, key, toml) {
    const lines = text.split("\n");
    const end = firstHeader(lines);
    let commented = -1;
    for (let i = 0; i < end; i++) {
        const m = KEY.exec(lines[i]);
        if (!m || m[3] !== key) continue;
        if (!m[2]) {
            const tail = m[4].slice(value(m[4]).end);
            lines[i] = toml === null ? m[1] + "# " + key + " = " + m[4]
                                     : m[1] + key + " = " + toml + tail;
            return lines.join("\n");
        }
        if (commented < 0) commented = i;
    }
    if (toml === null) return text;
    if (commented >= 0) {
        const m = KEY.exec(lines[commented]);
        lines[commented] = m[1] + key + " = " + toml + m[4].slice(value(m[4]).end);
    } else {
        // Before the blank line that separates the first table, if any.
        const at = end > 0 && lines[end - 1].trim() === "" ? end - 1 : end;
        lines.splice(at, 0, key + " = " + toml);
    }
    return lines.join("\n");
}

function envRange(lines) {
    const h = lines.findIndex(l => /^\s*\[env\]\s*(#.*)?$/.test(l));
    if (h < 0) return null;
    let e = lines.findIndex((l, i) => i > h && HEADER.test(l));
    return { h: h, end: e < 0 ? lines.length : e };
}

// [{key, value}] for the active lines of [env], in file order.
function env(text) {
    const lines = text.split("\n");
    const r = envRange(lines);
    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], value: String(value(m[4]).v) });
    }
    return out;
}

// value is a plain string, quoted here; null removes the key.
function setEnv(text, key, val) {
    const lines = text.split("\n");
    const r = envRange(lines);
    if (!r) {
        if (val === null) return text;
        return text.replace(/\n*$/, "") + "\n\n[env]\n" + key + " = " + quote(val) + "\n";
    }
    let last = r.h;
    for (let i = r.h + 1; i < r.end; i++) {
        const m = KEY.exec(lines[i]);
        if (!m || m[2]) continue;
        if (m[3] === key) {
            if (val === null) lines.splice(i, 1);
            else lines[i] = m[1] + key + " = " + quote(val) + m[4].slice(value(m[4]).end);
            return lines.join("\n");
        }
        last = i;
    }
    if (val === null) return text;
    lines.splice(last + 1, 0, key + " = " + quote(val));
    return lines.join("\n");
}