// WhatsApp messages -> RFC 5322 (eml) / mboxrd. The base piece for neomutt:
// `--format mbox` opens directly with `neomutt -f`, and a Maildir bridge (like gwsmail)
// only has to write the `--format eml` output to ~/Mail/<account>/<folder>/new.
//
// Conventions (the sending side must follow them):
//   addresses     the JID as is: 5491122334455@c.us, 1203630...@g.us, 1234@lid
//   Message-ID    <stanzaId@wa>        (stanzaId = the "stanzaId" JSON field)
//   In-Reply-To   <quotedStanzaId@wa>  -> neomutt threads quoted replies
//   Reply-To      in groups, the group (so `r` answers the group, not privately)
//   X-WA-Id       serialized ID, for later actions (react, delete, download)
//   X-WA-Chat-Id  chat it belongs to

import crypto from 'node:crypto';
import { describeContent } from './text.js';

const ASCII = /^[\x20-\x7e]*$/;

function encodedWords(s) {
    const words = [];
    let chunk = '';
    for (const ch of s) {
        if (Buffer.byteLength(chunk + ch) > 45) {
            words.push(chunk);
            chunk = '';
        }
        chunk += ch;
    }
    if (chunk) words.push(chunk);
    return words.map((w) => `=?UTF-8?B?${Buffer.from(w).toString('base64')}?=`).join('\n ');
}

const headerText = (s) => (ASCII.test(s) ? s : encodedWords(s));

function address(name, addr) {
    if (!addr) return 'undisclosed-recipients:;';
    if (!name || name === addr.split('@')[0]) return `<${addr}>`;
    const display = ASCII.test(name) ? `"${name.replace(/[\\"]/g, '\\$&')}"` : encodedWords(name);
    return `${display} <${addr}>`;
}

function rfc2822Date(ts) {
    const d = new Date(ts * 1000);
    const days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
    const months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
    const p = (n) => String(n).padStart(2, '0');
    const off = -d.getTimezoneOffset();
    const sign = off >= 0 ? '+' : '-';
    return `${days[d.getDay()]}, ${d.getDate()} ${months[d.getMonth()]} ${d.getFullYear()} ` +
        `${p(d.getHours())}:${p(d.getMinutes())}:${p(d.getSeconds())} ` +
        `${sign}${p(Math.floor(Math.abs(off) / 60))}${p(Math.abs(off) % 60)}`;
}

function quotedPrintable(text) {
    const out = [];
    for (const line of text.split('\n')) {
        const bytes = Buffer.from(line);
        let cur = '';
        for (let i = 0; i < bytes.length; i++) {
            const b = bytes[i];
            const last = i === bytes.length - 1;
            let tok;
            // "From " at the start of a line becomes =46rom: the mbox then needs no escaping
            // (and mboxo readers such as mutt do not show ">From").
            const fromLine = i === 0 && b === 70 && line.startsWith('From ');
            if (!fromLine && ((b >= 33 && b <= 126 && b !== 61) || ((b === 32 || b === 9) && !last))) {
                tok = String.fromCharCode(b);
            }
            if (!tok) tok = `=${b.toString(16).toUpperCase().padStart(2, '0')}`;
            if (cur.length + tok.length > 75) {
                out.push(`${cur}=`);
                cur = '';
            }
            cur += tok;
        }
        out.push(cur);
    }
    return out.join('\n');
}

const base64Lines = (b64) => b64.replace(/\s+/g, '').match(/.{1,76}/g)?.join('\n') ?? '';

function filenameParams(name) {
    if (ASCII.test(name)) return `; name="${name.replace(/"/g, '')}"`;
    return `; name="${encodedWords(name).replace(/\n /g, '')}"`;
}
function dispositionParams(name) {
    if (ASCII.test(name)) return `; filename="${name.replace(/"/g, '')}"`;
    return `; filename*=UTF-8''${encodeURIComponent(name)}`;
}

function bodyText(m) {
    const lines = [];
    const content = describeContent(m);
    if (m.hasMedia && !m.media?.data) {
        const size = m.media?.size ? `, ${Math.round(m.media.size / 1024)} KB` : '';
        lines.push(`[attachment not downloaded: ${m.media?.mimetype ?? m.type}${size}]`);
        lines.push(`[wa messages download --params '{"messageId":"${m.id}"}']`);
        if (m.body) lines.push('', m.body);
    } else {
        lines.push(m.hasMedia ? m.body : content);
    }
    if (m.location) lines.push('', `https://maps.google.com/?q=${m.location.latitude},${m.location.longitude}`);
    if (m.links?.length && m.type !== 'chat') lines.push('', ...m.links);
    return lines.join('\n');
}

export function messageToEml(m) {
    const isGroup = m.chatId?.endsWith('@g.us');
    const subject = describeContent(m).split('\n')[0].slice(0, 80) || '(no text)';
    const from = address(m.senderName, m.sender);
    const to = isGroup ? address(m.chatName, m.chatId) : address(m.fromMe ? m.chatName : null, m.fromMe ? m.chatId : m.to);

    const h = [
        `From: ${from}`,
        `To: ${to}`,
        ...(isGroup ? [`Reply-To: ${address(m.chatName, m.chatId)}`] : []),
        `Subject: ${headerText(subject)}`,
        `Date: ${rfc2822Date(m.timestamp)}`,
        `Message-ID: <${m.stanzaId}@wa>`,
        ...(m.quotedStanzaId ? [`In-Reply-To: <${m.quotedStanzaId}@wa>`, `References: <${m.quotedStanzaId}@wa>`] : []),
        `X-WA-Id: ${m.id}`,
        `X-WA-Chat-Id: ${m.chatId}`,
        ...(m.chatName ? [`X-WA-Chat-Name: ${headerText(m.chatName)}`] : []),
        `X-WA-Type: ${m.type}`,
        `X-WA-From-Me: ${m.fromMe ? 'yes' : 'no'}`,
        ...(m.isForwarded ? ['X-WA-Forwarded: yes'] : []),
        'MIME-Version: 1.0',
    ];

    const textPart = [
        'Content-Type: text/plain; charset=utf-8',
        'Content-Transfer-Encoding: quoted-printable',
        '',
        quotedPrintable(bodyText(m)),
    ].join('\n');

    const attachments = [];
    if (m.media?.data) {
        const name = m.media.filename || `${m.stanzaId}`;
        const mimetype = (m.media.mimetype || 'application/octet-stream').split(';')[0];
        attachments.push([
            `Content-Type: ${mimetype}${filenameParams(name)}`,
            'Content-Transfer-Encoding: base64',
            `Content-Disposition: ${mimetype.startsWith('image/') ? 'inline' : 'attachment'}${dispositionParams(name)}`,
            '',
            base64Lines(m.media.data),
        ].join('\n'));
    }
    (m.vCards || []).forEach((vc, i) => attachments.push([
        `Content-Type: text/vcard; charset=utf-8; name="contacto-${i + 1}.vcf"`,
        'Content-Transfer-Encoding: quoted-printable',
        `Content-Disposition: attachment; filename="contacto-${i + 1}.vcf"`,
        '',
        quotedPrintable(vc.replace(/\r\n/g, '\n')),
    ].join('\n')));

    if (!attachments.length) return `${h.join('\n')}\n${textPart}\n`;

    const boundary = `wa-${crypto.randomBytes(12).toString('hex')}`;
    return [
        ...h,
        `Content-Type: multipart/mixed; boundary="${boundary}"`,
        '',
        ...[textPart, ...attachments].map((part) => `--${boundary}\n${part}`),
        `--${boundary}--`,
        '',
    ].join('\n');
}

function asMessages(data) {
    const list = Array.isArray(data) ? data : [data];
    if (!list.every((m) => m && typeof m === 'object' && 'stanzaId' in m)) {
        throw Object.assign(new Error('the eml/mbox formats only apply to messages'), { code: 'EINVAL' });
    }
    return list;
}

export function toEml(data) {
    const list = asMessages(data);
    if (list.length !== 1) {
        throw Object.assign(new Error(`eml is for a single message (there are ${list.length}); use --format mbox`), { code: 'EINVAL' });
    }
    return messageToEml(list[0]).replace(/\n$/, '');
}

export function toMbox(data) {
    return asMessages(data)
        .slice()
        .sort((a, b) => a.timestamp - b.timestamp)
        .map((m) => {
            const asctime = new Date(m.timestamp * 1000).toUTCString()
                .replace(/^(\w+), (\d+) (\w+) (\d+) ([\d:]+) GMT$/, (_, dow, d, mon, y, t) => `${dow} ${mon} ${d.padStart(2)} ${t} ${y}`);
            const body = messageToEml(m).replace(/^(>*From )/gm, '>$1');
            return `From ${m.sender || 'unknown@wa'} ${asctime}\n${body}`;
        })
        .join('\n')
        .replace(/\n$/, '');
}