// Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

// @license magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt AGPL-3.0

function element(id: string): HTMLElement {
    const value = document.getElementById(id);
    if (!(value !== null)) throw new Error(`Missing interface element: ${id}`);
    return value;
}

function input(id: string): HTMLInputElement {
    const value = element(id);
    if (!(value instanceof HTMLInputElement)) throw new Error(`Expected input: ${id}`);
    return value;
}

function form(id: string): HTMLFormElement {
    const value = element(id);
    if (!(value instanceof HTMLFormElement)) throw new Error(`Expected form: ${id}`);
    return value;
}

function messageInput(): HTMLTextAreaElement {
    const value = element('text');
    if (!(value instanceof HTMLTextAreaElement)) throw new Error('Missing message input');
    return value;
}

const show = (id: string, visible = true): void => { element(id).hidden = !visible; };
const setStatus = (message: string): void => { element('status').textContent = message; };
const errorMessage = (error: unknown): string => error instanceof Error ? error.message : 'Unexpected operation failure';
let config: StackChat.Configuration | undefined;
let wasm: Promise<ArrayBuffer> | undefined;
let credentials: StackChat.Credentials | undefined;
let session: StackChat.Session | undefined;
let selected: StackChat.Conversation | undefined;
let before = 0;
let pendingFile: string | undefined;
let setupToken: string | undefined;
let pendingSend: StackChat.SendRequest | undefined;
let generation = 0;
let busy = false;
const workers = new Map<Worker, () => void>();
const blobs = new Set<string>();

function configuration(): StackChat.Configuration {
    if (config === undefined) throw new Error('Chat configuration is not loaded');
    return config;
}

function hasOwner(): boolean {
    const owner = config?.owner;
    return owner !== undefined && owner !== null && owner.length > 0;
}

function ownerKey(): string {
    const owner = configuration().owner;
    if (owner === null || owner.length === 0) throw new Error('Owner setup is required first');
    return owner;
}

function activeSession(): StackChat.Session {
    if (session === undefined) throw new Error('Unlock your identity file first');
    return session;
}

function conversation(): StackChat.Conversation {
    if (selected === undefined) throw new Error('Choose a conversation first');
    return selected;
}

function isRecord(value: unknown): value is Record<string, unknown> {
    return typeof value === 'object' && value !== null && !Array.isArray(value);
}

function record(value: unknown): Record<string, unknown> {
    if (!isRecord(value)) throw new Error('Invalid response object');
    return value;
}

function stringField(value: Record<string, unknown>, key: string): string {
    const field = value[key];
    if (typeof field !== 'string') throw new Error(`Invalid response field: ${key}`);
    return field;
}

function countField(value: Record<string, unknown>, key: string): number {
    const field = value[key];
    if (typeof field !== 'number' || !Number.isSafeInteger(field) || field < 0) throw new Error(`Invalid response count: ${key}`);
    return field;
}

function booleanField(value: Record<string, unknown>, key: string): boolean {
    const field = value[key];
    if (typeof field !== 'boolean') throw new Error(`Invalid response flag: ${key}`);
    return field;
}

function arrayField(value: Record<string, unknown>, key: string): unknown[] {
    const field: unknown = value[key];
    if (!Array.isArray(field)) throw new Error(`Invalid response list: ${key}`);
    return field;
}

function decodeConversation(value: unknown): StackChat.Conversation {
    const item = record(value);
    const total = countField(item, 'total');
    const visitor = countField(item, 'visitor_sent');
    const owner = countField(item, 'owner_sent');
    if (total > 10000 || visitor + owner !== total) throw new Error('Invalid conversation count');
    const profile = item['profile'];
    if (profile !== undefined && profile !== null && typeof profile !== 'string') throw new Error('Invalid conversation profile');
    return { id: stringField(item, 'id'), public: stringField(item, 'public'), total, visitor_sent: visitor, owner_sent: owner, ...(profile === undefined ? {} : { profile }) };
}

function decodeMessage(value: unknown): StackChat.Message {
    const item = record(value);
    return { seq: countField(item, 'seq'), id: stringField(item, 'id'), sender: stringField(item, 'sender'), ciphertext: stringField(item, 'ciphertext') };
}

function decodeDecryption(value: unknown): StackChat.Decryption {
    const item = record(value);
    return { signer: stringField(item, 'signer'), payload: stringField(item, 'payload') };
}

const apiReaders: { [K in keyof StackChat.Api]: (value: unknown) => StackChat.Api[K]['response'] } = {
    config(value) {
        const item = record(value);
        const owner = item['owner'];
        if (owner !== null && typeof owner !== 'string') throw new Error('Invalid owner configuration');
        return { owner, origin: stringField(item, 'origin'), protocol: stringField(item, 'protocol') };
    },
    challenge(value) { const item = record(value); return { id: stringField(item, 'id'), challenge: stringField(item, 'challenge') }; },
    authenticate(value) { const item = record(value); return { token: stringField(item, 'token'), id: stringField(item, 'id'), owner: booleanField(item, 'owner'), expires_seconds: countField(item, 'expires_seconds') }; },
    profile(value) { return { stored: booleanField(record(value), 'stored') }; },
    inbox(value) { return { conversations: arrayField(record(value), 'conversations').map(decodeConversation) }; },
    history(value) { const item = record(value); return { conversation: decodeConversation(item['conversation']), messages: arrayField(item, 'messages').map(decodeMessage) }; },
    send(value) { const item = record(value); return { seq: countField(item, 'seq'), conversation: decodeConversation(item['conversation']) }; },
    lock(value) { return { locked: booleanField(record(value), 'locked') }; },
};

const cryptoReaders: { [K in keyof StackChat.Crypto]: (value: unknown) => StackChat.Crypto[K]['response'] } = {
    create(value) { return { file: stringField(record(value), 'file') }; },
    open(value) { const item = record(value); return { public: stringField(item, 'public'), fingerprint: stringField(item, 'fingerprint'), owner: stringField(item, 'owner'), name: stringField(item, 'name') }; },
    proof(value) { return { signature: stringField(record(value), 'signature') }; },
    encrypt(value) { return { ciphertext: stringField(record(value), 'ciphertext') }; },
    decrypt: decodeDecryption,
    decrypt_batch(value) {
        return { messages: arrayField(record(value), 'messages').map(entry => {
            const item = record(entry);
            return 'error' in item ? { error: stringField(item, 'error') } : decodeDecryption(item);
        }) };
    },
};

async function api<K extends keyof StackChat.Api>(request: StackChat.Api[K]['request'] & { op: K }): Promise<StackChat.Api[K]['response']> {
    const current = generation;
    const response = await fetch('/api', {
        method: 'POST', credentials: 'omit', cache: 'no-store', redirect: 'error',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ ...request, token: session?.token }),
        signal: AbortSignal.timeout(20000),
    });
    const result = record(await response.json());
    if (current !== generation) throw new Error('Session locked');
    if (!response.ok || 'error' in result) throw new Error(typeof result['error'] === 'string' ? result['error'] : 'Server request failed');
    return apiReaders[request.op](result);
}

async function cryptoOperation<K extends keyof StackChat.Crypto>(request: StackChat.Crypto[K]['request'] & { op: K }): Promise<StackChat.Crypto[K]['response']> {
    const current = generation;
    if (wasm === undefined) throw new Error('Cryptographic module is not loaded');
    const bytes = await wasm;
    if (current !== generation) throw new Error('Session locked');
    return new Promise<StackChat.Crypto[K]['response']>((resolve, reject) => {
        const worker = new Worker('/worker.js');

        const stop = (): void => { worker.terminate(); workers.delete(worker); clearTimeout(timer); };
        const timer = setTimeout(() => { stop(); reject(new Error('Cryptographic operation timed out')); }, 90000);
        workers.set(worker, () => { stop(); reject(new Error('Session locked')); });
        worker.onerror = (): void => { stop(); reject(new Error('Cryptographic worker failed')); };
        worker.onmessage = (event: MessageEvent<unknown>): void => {
            stop();
            if (current !== generation) { reject(new Error('Session locked')); return; }
            try {
                const message = record(event.data);
                if ('error' in message) throw new Error(stringField(message, 'error'));
                resolve(cryptoReaders[request.op](message['result']));
            } catch (error) { reject(error instanceof Error ? error : new Error('Cryptographic response rejected', { cause: error })); }
        };
        worker.postMessage({ bytes, request });
    });
}

function protectRequest<K extends 'encrypt' | 'decrypt' | 'decrypt_batch'>(op: K, fields: Omit<StackChat.Crypto[K]['request'], keyof StackChat.Protected | 'op'>): StackChat.Protected & { op: K } & typeof fields {
    if (credentials === undefined) throw new Error('Unlock your identity file first');
    return { op, ...credentials, origin: location.origin, ...fields };
}

function clearState(): void {
    generation += 1;
    busy = false;
    for (const button of document.querySelectorAll('button')) button.disabled = false;
    for (const cancel of workers.values()) cancel();
    workers.clear();
    for (const url of blobs) URL.revokeObjectURL(url);
    blobs.clear();
    credentials = undefined;
    session = undefined;
    selected = undefined;
    pendingFile = undefined;
    pendingSend = undefined;
    setupToken = undefined;
    before = 0;
    input('history-count').max = '0';
    element('history-range').textContent = 'Latest messages (0-0)';
    for (const input of document.querySelectorAll<HTMLInputElement | HTMLTextAreaElement>('input,textarea')) {
        if (input.id === 'history-count') input.value = '0'; else input.value = '';
    }
    for (const id of ['messages', 'conversations', 'who', 'fingerprint', 'counts', 'thread-name', 'conversation-fingerprint']) element(id).replaceChildren();
    for (const id of ['create', 'unlock', 'chat', 'thread', 'inbox', 'older', 'retry', 'owner-access']) show(id, false);
    show('entry', hasOwner());
    show('owner-entry');
    setStatus('Locked. Select your file and enter its password to return.');
}

function background(operation: () => Promise<void>): void {
    const current = generation;
    operation().catch((error: unknown) => { if (current === generation) setStatus(errorMessage(error)); });
}

function action(id: string, callback: () => void | Promise<void>): void {
    const handler = async (event: Event): Promise<void> => {
        event.preventDefault();
        if (busy) return;
        busy = true;
        setStatus('Working locally...');
        const current = generation;
        for (const button of document.querySelectorAll<HTMLButtonElement>('button:not(#lock)')) button.disabled = true;
        try { await callback(); }
        catch (error) { if (generation === current) setStatus(errorMessage(error)); }
        finally {
            if (generation === current) {
                busy = false;
                for (const button of document.querySelectorAll('button')) button.disabled = false;
            }
        }
    };
    element(id).addEventListener(id.endsWith('-form') ? 'submit' : 'click', event => { background(() => handler(event)); });
}

function download(file: string): void {
    const url = URL.createObjectURL(new Blob([file], { type: 'application/octet-stream' }));
    blobs.add(url);
    const link = document.createElement('a');
    link.href = url;
    link.download = 'stack-chat-identity.chat';
    link.click();
    setTimeout(() => { URL.revokeObjectURL(url); blobs.delete(url); }, 30000);
}

async function createIdentity(): Promise<void> {
    const password = input('new-password').value;
    if (password !== input('confirm-password').value) throw new Error('Passwords do not match');
    if (!hasOwner() && element('setup-label').hasAttribute('hidden')) throw new Error('Owner setup is required first');
    setupToken = !hasOwner() ? input('setup-token').value : undefined;
    setStatus('Generating your purpose-specific identity and protecting its file...');
    const result = await cryptoOperation({ op: 'create', origin: location.origin, name: input('name').value, password, owner: configuration().owner ?? '' });
    pendingFile = result.file;
    download(result.file);
    form('create-form').reset();
    show('create', false);
    show('unlock');
    element('reopen-note').textContent = 'Your file was downloaded. Reopen that exact saved file and enter its password before any message can be sent. Keep a safe backup.';
    setStatus('Reopen your downloaded identity file to verify recovery.');
}

async function unlockIdentity(): Promise<void> {
    const file = input('file').files?.[0];
    if (file === undefined || file.size > 262144) throw new Error('Choose an identity file no larger than 256 KiB');
    const fileText = await file.text();
    if (((pendingFile ?? '').length > 0) && fileText !== pendingFile) throw new Error('Reopen the exact identity file you just downloaded');
    const candidate = { file: fileText, password: input('password').value };
    form('unlock-form').reset();
    setStatus('Unlocking locally and verifying your identity...');
    const identity = await cryptoOperation({ op: 'open', ...candidate, origin: location.origin });
    if (hasOwner() && identity.owner !== configuration().owner) throw new Error('Pinned owner key differs from this server. Stop and verify the change with Doan.');
    const challenge = await api({ op: 'challenge', public: identity.public, setup_token: setupToken });
    const proof = await cryptoOperation({ op: 'proof', ...candidate, origin: location.origin, challenge: challenge.challenge });
    const authenticated = await api({ op: 'authenticate', id: challenge.id, signature: proof.signature });
    if (authenticated.id !== identity.fingerprint || typeof authenticated.owner !== 'boolean') throw new Error('Authenticated identity mismatch');
    credentials = candidate;
    session = { ...identity, ...authenticated };
    pendingFile = undefined;
    setupToken = undefined;
    config = await api({ op: 'config' });
    show('entry', false);
    show('owner-entry', false);
    show('owner-access', false);
    show('unlock', false);
    show('chat');
    element('who').textContent = `${identity.name} [${activeSession().owner ? 'OWNER' : 'VISITOR'}]`;
    element('fingerprint').textContent = `Identity: ${identity.fingerprint}`;
    if (authenticated.owner) {
        activeSession().owner = true;
        show('inbox');
        await inbox();
    } else {
        activeSession().owner = false;
        const profile = await cryptoOperation(protectRequest('encrypt', { recipient: ownerKey(), payload: JSON.stringify({ v: 1, kind: 'profile', origin: location.origin, conversation: activeSession().id, sender: activeSession().id, name: identity.name }) }));
        await api({ op: 'profile', conversation: activeSession().id, ciphertext: profile.ciphertext });
        selected = { id: activeSession().id, public: identity.public, total: 0, visitor_sent: 0, owner_sent: 0 };
        element('conversation-fingerprint').textContent = `Conversation: ${activeSession().id}`;
        show('thread');
        element('thread-name').textContent = 'You <-> Doan';
        await loadHistory(0);
    }
    setStatus('Unlocked in memory only. No history loaded automatically. Lock or leave to forget this session.');
}

function checkedPayload(payload: string, kind: 'profile', conversation: string, sender: string): { name: string };
function checkedPayload(payload: string, kind: 'message', conversation: string, sender: string): { id: string; text: string };
function checkedPayload(payload: string, kind: 'profile' | 'message', conversation: string, sender: string): { name: string } | { id: string; text: string } {
    const value = record(JSON.parse(payload));
    if (value['v'] !== 1 || value['kind'] !== kind || value['origin'] !== location.origin || value['conversation'] !== conversation || value['sender'] !== sender) throw new Error('Signed message binding mismatch');
    if (kind === 'profile') return { name: stringField(value, 'name') };
    return { id: stringField(value, 'id'), text: stringField(value, 'text') };
}

async function inbox(): Promise<void> {
    const result = await api({ op: 'inbox' });
    element('conversations').replaceChildren();
    for (const conversation of result.conversations) {
        const button = document.createElement('button');
        button.textContent = `${conversation.id.slice(0, 12)} / ${String(conversation.total)} messages`;
        const handler = async (): Promise<void> => {
            if (busy) return;
            if ((pendingSend !== undefined)) { setStatus('Retry the pending message, or lock before switching conversations.'); return; }
            busy = true;
            const current = generation;
            setStatus('Opening conversation...');
            try {
                selected = conversation;
                element('conversation-fingerprint').textContent = `Conversation: ${conversation.id}`;
                element('thread-name').textContent = `Doan <-> ${conversation.id.slice(0, 12)}`;
                pendingSend = undefined;
                messageInput().value = '';
                show('retry', false);
                element('messages').replaceChildren();
                show('thread');
                let name = conversation.id.slice(0, 12);
                const certificate = conversation.profile;
                if (certificate !== undefined && certificate !== null && certificate.length > 0) {
                    const result = await cryptoOperation(protectRequest('decrypt', { sender: conversation.public, ciphertext: certificate }));
                    if (result.signer !== conversation.id) throw new Error('Profile signer fingerprint mismatch');
                    const profile = checkedPayload(result.payload, 'profile', conversation.id, conversation.id);
                    if (typeof profile.name !== 'string' || profile.name.length > 80) throw new Error('Invalid encrypted profile');
                    name = profile.name;
                }
                element('thread-name').textContent = `Doan <-> ${name}`;
                await loadHistory(0);
                setStatus('Conversation opened. Choose how many messages to load.');
            } catch (error) { setStatus(errorMessage(error)); }
            finally { if (generation === current) busy = false; }
        };
        button.addEventListener('click', () => { background(handler); });
        element('conversations').append(button);
    }
}

function counters(conversation: StackChat.Conversation): void {
    if (!Number.isSafeInteger(conversation.total) || conversation.total < 0 || conversation.total > 10000) throw new Error('Invalid conversation count');
    input('history-count').max = String(conversation.total);
    element('history-range').textContent = `Latest messages (0-${String(conversation.total)})`;
    const sent = activeSession().owner ? conversation.owner_sent : conversation.visitor_sent;
    const received = activeSession().owner ? conversation.visitor_sent : conversation.owner_sent;
    element('counts').textContent = `Total: ${String(conversation.total)} | Sent: ${String(sent)} | Received: ${String(received)}`;
}

async function renderHistoryBatch(messages: StackChat.Message[]): Promise<void> {
    const requests = messages.map(message => ({ sender: message.sender === conversation().id ? conversation().public : ownerKey(), ciphertext: message.ciphertext }));
    const decrypted = await cryptoOperation(protectRequest('decrypt_batch', { messages: requests }));
    for (let index = 0; index < messages.length; index += 1) {
        const message = messages[index];
        if (message === undefined) throw new Error('Missing history message');
        const item = document.createElement('li');
        const label = document.createElement('small');
        label.textContent = `#${String(message.seq)} / ${message.sender === activeSession().id ? 'YOU' : 'THEM'}`;
        const text = document.createElement('p');
        try {
            const entry = decrypted.messages[index];
            if (entry === undefined || 'error' in entry) throw new Error('Invalid ciphertext or signature');
            if (entry.signer !== message.sender) throw new Error('Sender fingerprint mismatch');
            const payload = checkedPayload(entry.payload, 'message', conversation().id, message.sender);
            if (payload.id !== message.id || typeof payload.text !== 'string' || new TextEncoder().encode(payload.text).length > 8192) throw new Error('Message binding mismatch');
            text.textContent = payload.text;
        } catch { text.textContent = '[Message rejected: invalid ciphertext, signature, or conversation binding.]'; }
        item.append(label, text);
        element('messages').prepend(item);
    }
}

async function refreshCounts(): Promise<StackChat.Conversation> {
    const conversationId = conversation().id;
    const result = await api({ op: 'history', conversation: conversationId, count: 0, before: 0 });
    if (selected?.id === conversationId) counters(result.conversation);
    return result.conversation;
}

async function loadHistory(count: number, cursor = 0): Promise<void> {
    if (selected === undefined) throw new Error('Choose a conversation first');
    const currentConversation = await refreshCounts();
    if (!Number.isSafeInteger(count) || count < 0 || count > currentConversation.total) throw new Error(`Choose 0 to ${String(currentConversation.total)} messages`);
    if (!(cursor !== 0)) { element('messages').replaceChildren(); before = 0; }
    if (count === 0) {
        input('history-count').value = '0';
        show('older', false);
        setStatus('No message history loaded.');
        return;
    }
    let remaining = count;
    let next = cursor;
    let exhausted = false;
    while (remaining > 0) {
        const size = Math.min(50, remaining);
        const result = await api({ op: 'history', conversation: conversation().id, count: size, before: next });
        counters(result.conversation);
        if (!Array.isArray(result.messages) || result.messages.length > size) throw new Error('Invalid history response');
        if (!(result.messages.length !== 0)) { exhausted = true; break; }
        const sequence = Math.min(...result.messages.map(message => message.seq));
        if (!Number.isSafeInteger(sequence) || sequence <= 0 || (next > 0 && sequence >= next)) throw new Error('Invalid history cursor');
        setStatus(`Decrypting and verifying selected messages locally (${String(count - remaining + result.messages.length)}/${String(count)})...`);
        await renderHistoryBatch(result.messages);
        remaining -= result.messages.length;
        next = sequence;
        before = next;
        if (result.messages.length < size) { exhausted = true; break; }
    }
    show('older', !exhausted && element('messages').children.length < Number(input('history-count').max));
    setStatus('Selected history decrypted and verified locally.');
}

async function submitPending(): Promise<void> {
    if (pendingSend === undefined) throw new Error('No pending message');
    const result = await api(pendingSend);
    counters(result.conversation);
    pendingSend = undefined;
    messageInput().value = '';
    show('retry', false);
    setStatus('Encrypted message stored. Load history to read messages.');
}

async function send(): Promise<void> {
    if (selected === undefined) throw new Error('Choose a conversation first');
    if ((pendingSend !== undefined)) throw new Error('Retry or lock before composing another message');
    const text = messageInput().value;
    if (!((text.trim()).length > 0) || new TextEncoder().encode(text).length > 8192) throw new Error('Enter 1 to 8192 UTF-8 bytes of text');
    const id = Array.from(crypto.getRandomValues(new Uint8Array(32)), byte => byte.toString(16).padStart(2, '0')).join('');
    const recipient = activeSession().owner ? conversation().public : ownerKey();
    setStatus('Signing and encrypting for both participants locally...');
    const result = await cryptoOperation(protectRequest('encrypt', { recipient, payload: JSON.stringify({ v: 1, kind: 'message', origin: location.origin, conversation: conversation().id, sender: activeSession().id, id, text }) }));
    pendingSend = { op: 'send', conversation: conversation().id, id, ciphertext: result.ciphertext };
    show('retry');
    await submitPending();
}

function ownerSetup(): void {
    show('entry', false);
    show('owner-entry', false);
    show('unlock', false);
    show('create', !hasOwner());
    show('owner-access', hasOwner());
    show('setup-label', !hasOwner());
    element('create-title').textContent = 'Create the owner identity (owner only)';
    setStatus('');
}

action('create-choice', () => { show('entry', false); show('owner-entry', false); show('setup-label', false); element('create-title').textContent = 'Create a new chat'; show('create'); setStatus(''); });
action('open-choice', () => { show('entry', false); show('owner-entry', false); show('unlock'); setStatus(''); });
action('owner-choice', () => { window.history.replaceState(null, '', '#setup'); ownerSetup(); });
action('owner-open', () => { show('owner-access', false); show('unlock'); setStatus(''); });
action('create-form', createIdentity);
action('unlock-form', unlockIdentity);
element('history-count').addEventListener('focus', () => {
    const current = generation;
    if ((session !== undefined) && (selected !== undefined) && !busy) refreshCounts().catch((error: unknown) => { if (current === generation) setStatus(errorMessage(error)); });
});
action('history-form', () => loadHistory(Number(input('history-count').value)));
action('send-form', send);
action('retry', submitPending);
action('refresh-inbox', inbox);
action('older', () => loadHistory(Number(input('history-count').value), before));
element('lock').addEventListener('click', () => {
    const current = generation;
    if (session !== undefined) api({ op: 'lock' }).catch((error: unknown) => { if (current === generation) setStatus(errorMessage(error)); });
    clearState();
});
window.addEventListener('pagehide', clearState);
window.addEventListener('pageshow', event => { if (event.persisted) clearState(); });

async function downloadCrypto(): Promise<ArrayBuffer> {
    const controller = new AbortController();
    let timer: ReturnType<typeof setTimeout> | undefined;
    let reader: ReadableStreamDefaultReader<Uint8Array<ArrayBuffer>> | undefined;
    const refreshTimeout = (): void => {
        clearTimeout(timer);
        timer = setTimeout(() => { controller.abort(); }, 45000);
    };
    try {
        refreshTimeout();
        const response = await fetch('/crypto.wasm', { cache: 'no-store', credentials: 'omit', signal: controller.signal });
        if (!response.ok) throw new Error(`Cryptographic module download failed (HTTP ${String(response.status)}). Reload to try again.`);
        const length = ((response.headers.get('content-encoding') ?? '').length > 0) ? 0 : Number(response.headers.get('content-length'));
        const total = Number.isSafeInteger(length) && length > 0 ? length : 0;
        const chunks: Uint8Array<ArrayBuffer>[] = [];
        let received = 0;
        const progress = (): void => {
            const loaded = (received / 1048576).toFixed(1);
            if ((total !== 0)) {
                const percent = Math.min(100, Math.floor(received * 100 / total));
                const filled = Math.floor(percent / 5);
                setStatus(`Downloading cryptographic module... [${'#'.repeat(filled)}${'-'.repeat(20 - filled)}] ${String(percent)}% (${loaded} / ${(total / 1048576).toFixed(1)} MiB)`);
            } else setStatus(`Downloading cryptographic module... ${loaded} MiB received`);
        };
        progress();
        if (!(response.body !== null)) throw new Error('Cryptographic module response has no body');
        reader = response.body.getReader();
        for (;;) {
            const { done, value } = await reader.read();
            if (done) break;
            refreshTimeout();
            chunks.push(value);
            received += value.byteLength;
            progress();
        }
        if (!(received !== 0)) throw new Error('The cryptographic module download was empty. Reload to try again.');
        const bytes = new Uint8Array(received);
        let offset = 0;
        for (const chunk of chunks) { bytes.set(chunk, offset); offset += chunk.byteLength; }
        return bytes.buffer;
    } catch (error) {
        if (controller.signal.aborted) throw new Error('Cryptographic module download stalled for 45 seconds. Check your connection and reload to try again.', { cause: error });
        throw error;
    } finally {
        clearTimeout(timer);
        reader?.releaseLock();
    }
}

async function start(): Promise<void> {
    wasm = downloadCrypto();
    await wasm;
    setStatus('Cryptographic module downloaded. Connecting to chat...');
    config = await api({ op: 'config' });
    if (configuration().origin !== location.origin) throw new Error('Server origin mismatch');
    show('owner-entry');
    show('entry', hasOwner());
    setStatus('');
    if (location.hash === '#setup') ownerSetup();
}

start().catch((error: unknown) => { setStatus(errorMessage(error)); });

// @license-end