import {
  Server, LIST_ARG, decodeServer, encodeBinaryInput, encodeCommand, encodeInit,
  encodeInput, encodeResize, parseListOutput, stripAnsi, tokenUrl, wsUrl, FlowControl,
} from './protocol.js';

export class AuthExpiredError extends Error {}
export class UnauthorizedError extends Error {}

// GET /token. Through NPM this also exercises the Authelia gate, so it doubles
// as the session probe: a redirect means the SSO session expired.
export async function fetchToken() {
  const res = await fetch(tokenUrl(window.location), {
    cache: 'no-store', credentials: 'same-origin', redirect: 'manual',
  });
  if (res.type === 'opaqueredirect') {
    // Any request can discover an expired Authelia session; the header shows
    // "Sign in again" when this fires (devdesk#13).
    window.dispatchEvent(new CustomEvent('devdesk:auth', { detail: 'expired' }));
    throw new AuthExpiredError('SSO session expired');
  }
  if (res.status === 401 || res.status === 403 || res.status === 407) {
    throw new UnauthorizedError(`HTTP ${res.status}`);
  }
  if (!res.ok) throw new Error(`token request failed: HTTP ${res.status}`);
  window.dispatchEvent(new CustomEvent('devdesk:auth', { detail: 'ok' }));
  const body = await res.json();
  return body.token || '';
}

// One WebSocket to ttyd, i.e. one `devdesk attach <arg>` process on the server.
export class TtydConnection {
  constructor({ arg, size, onOpen, onOutput, onClose, onPreferences }) {
    Object.assign(this, { arg, size, onOpen, onOutput, onClose, onPreferences });
    this.flow = new FlowControl();
    this.socket = null;
    this.disposed = false;
  }

  async open() {
    const token = await fetchToken();
    if (this.disposed) return;
    const socket = new WebSocket(wsUrl(window.location, this.arg), ['tty']);
    socket.binaryType = 'arraybuffer';
    this.socket = socket;
    socket.onopen = () => {
      const { cols, rows } = this.size();
      socket.send(encodeInit(token, cols, rows));
      this.onOpen?.();
    };
    socket.onmessage = (event) => {
      const { type, payload } = decodeServer(event.data);
      if (type === Server.OUTPUT) this.onOutput?.(payload);
      else if (type === Server.SET_PREFERENCES) this.onPreferences?.(payload);
      // SET_WINDOW_TITLE only carries ttyd's "<command> (<host>)"; real titles come via OSC.
    };
    socket.onclose = (event) => {
      if (this.socket === socket) this.socket = null;
      if (!this.disposed) this.onClose?.(event.code, event.reason);
    };
  }

  get isOpen() {
    return this.socket?.readyState === WebSocket.OPEN;
  }

  send(frame) {
    if (this.isOpen) this.socket.send(frame);
  }

  sendInput(text) {
    this.send(encodeInput(text));
  }

  sendBinary(binary) {
    this.send(encodeBinaryInput(binary));
  }

  resize(cols, rows) {
    this.send(encodeResize(cols, rows));
  }

  // Called with each output chunk; returns a write-callback when tracking is needed.
  flowWrite(length) {
    const { command, track } = this.flow.onData(length);
    if (command) this.send(encodeCommand(command));
    if (!track) return undefined;
    return () => {
      const resume = this.flow.release();
      if (resume) this.send(encodeCommand(resume));
    };
  }

  dispose() {
    this.disposed = true;
    if (this.socket) {
      this.socket.onclose = null;
      this.socket.close(1000);
      this.socket = null;
    }
  }
}

// Side-channel commands each occupy a ttyd client slot and a server process:
// run at most two at a time (devdesk#8).
let active = 0;
const waiting = [];
async function limited(task) {
  if (active >= 2) await new Promise((resolve) => waiting.push(resolve));
  active += 1;
  try {
    return await task();
  } finally {
    active -= 1;
    waiting.shift()?.();
  }
}

// Run a short-lived `devdesk attach <args…>` and return its output as text.
// ttyd is the only server-side endpoint, so session actions travel this way.
export function runCommand(args, timeoutMs = 8000) {
  return limited(() => runCommandNow(args, timeoutMs));
}

async function runCommandNow(args, timeoutMs) {
  const token = await fetchToken();
  return new Promise((resolve, reject) => {
    const socket = new WebSocket(wsUrl(window.location, args), ['tty']);
    socket.binaryType = 'arraybuffer';
    const chunks = [];
    const timer = setTimeout(() => {
      socket.close();
      reject(new Error('devdesk did not answer'));
    }, timeoutMs);
    socket.onopen = () => socket.send(encodeInit(token, 240, 24));
    socket.onmessage = (event) => {
      const { type, payload } = decodeServer(event.data);
      if (type === Server.OUTPUT) chunks.push(payload.slice());
    };
    socket.onerror = () => {};
    socket.onclose = () => {
      clearTimeout(timer);
      resolve(new TextDecoder().decode(concat(chunks)));
    };
  });
}

// Sessions, projects and per-session Claude context (`devdesk attach --list`).
export async function fetchSessionList() {
  return parseListOutput(await runCommand([LIST_ARG]));
}

// Firing/pending Grafana alerts (`devdesk attach --alerts`).
export async function fetchAlerts() {
  return parseListOutput(await runCommand(['--alerts']));
}

function toBase64(bytes) {
  let binary = '';
  for (let i = 0; i < bytes.length; i += 0x8000) {
    binary += String.fromCharCode.apply(null, bytes.subarray(i, i + 0x8000));
  }
  return btoa(binary);
}

const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

export const UPLOAD_MAX = 25 * 1024 * 1024;

// Upload a file into the session's upload folder through ttyd: wait for the
// server's ready line, stream the file as base64 input in slices (never the
// whole file in memory), read back {ok, path}. Fails on 20 s of inactivity
// rather than a fixed total, so slow links still work (devdesk#9).
export function uploadFile(session, file, onProgress) {
  if (!file.size) return Promise.reject(new Error('file is empty'));
  if (file.size > UPLOAD_MAX) return Promise.reject(new Error('larger than 25 MB'));
  return limited(() => uploadNow(session, file, onProgress));
}

async function uploadNow(session, file, onProgress) {
  const token = await fetchToken();
  const name = (file.name || 'pasted-image.png').slice(-100);
  const slice = 3 * 16 * 1024; // multiple of 3: base64 of slices concatenates cleanly
  return new Promise((resolve, reject) => {
    const socket = new WebSocket(wsUrl(window.location, ['--upload', session, name, String(file.size)]), ['tty']);
    socket.binaryType = 'arraybuffer';
    const decoder = new TextDecoder();
    let output = '';
    let sending = false;
    let idle = 0;
    const touch = () => {
      clearTimeout(idle);
      idle = setTimeout(() => socket.close(), 20000);
    };
    const send = async () => {
      for (let offset = 0; offset < file.size; offset += slice) {
        while (socket.bufferedAmount > 1 << 20) await sleep(20);
        if (socket.readyState !== WebSocket.OPEN) return;
        const bytes = new Uint8Array(await file.slice(offset, offset + slice).arrayBuffer());
        socket.send(encodeInput(toBase64(bytes)));
        touch();
        onProgress?.(Math.min(1, (offset + slice) / file.size));
      }
    };
    touch();
    socket.onopen = () => socket.send(encodeInit(token, 240, 24));
    socket.onmessage = (event) => {
      touch();
      const { type, payload } = decodeServer(event.data);
      if (type !== Server.OUTPUT) return;
      output += decoder.decode(payload, { stream: true });
      if (!sending && output.includes('DEVDESK-UPLOAD-READY')) {
        sending = true;
        send();
      }
    };
    socket.onerror = () => {};
    socket.onclose = () => {
      clearTimeout(idle);
      const text = stripAnsi(output.replace(/^[\s\S]*DEVDESK-UPLOAD-READY/, ''));
      try {
        const result = parseListOutput(text);
        if (result.ok && result.path) {
          resolve(result.path);
          return;
        }
      } catch {
        // fall through to the error message
      }
      const message = text.split(/\r?\n/).map((l) => l.trim()).filter(Boolean).pop();
      reject(new Error((message || 'upload failed').replace(/^devdesk:\s*/, '')));
    };
  });
}

// Git + Gitea CI status for a session's folder (`devdesk attach --repo NAME`).
export async function fetchRepo(session) {
  return parseListOutput(await runCommand(['--repo', session]));
}

// `devdesk attach --new|--rename|--end …`: resolves on {"ok":true}, otherwise
// rejects with devdesk's own error message.
export async function sessionAction(action, ...args) {
  const output = stripAnsi(await runCommand([`--${action}`, ...args])).trim();
  if (/"ok"\s*:\s*true/.test(output)) return;
  const message = output.split(/\r?\n/).filter(Boolean).pop() || 'no response';
  throw new Error(message.replace(/^devdesk:\s*/, ''));
}

function concat(chunks) {
  const total = chunks.reduce((n, c) => n + c.length, 0);
  const out = new Uint8Array(total);
  let offset = 0;
  for (const c of chunks) {
    out.set(c, offset);
    offset += c.length;
  }
  return out;
}