/**
 * Translation service (background): shared translation pipeline.
 *
 * Both entry points use this module so there is exactly one request
 * generation / streaming / state implementation:
 *   - content script (runtime.Port streaming, Design.md §8)
 *   - context menu / popup (translation state, Design.md §9.2)
 *
 * No PDF-specific translation engine exists; `source` is metadata only.
 */

import { getSettings, saveSettings } from './settings-service.js';
import { TranslationSession } from './translation-session.js';
import { chatStream, listModels } from './ollama-client.js';
import { buildSystemPrompt } from '../shared/prompt.js';
import { buildOptions, toApiThinking, sanitizeSettings, defaultSettings } from '../shared/settings-schema.js';
import { BG_TO_CONTENT, MAX_SELECTION_LENGTH, ERROR_CODES } from '../shared/constants.js';

const session = new TranslationSession();

/** User-facing messages per error code (kept minimal; no stack traces). */
const ERROR_MESSAGES = {
  [ERROR_CODES.INVALID_REQUEST]: '要求が不正です。',
  [ERROR_CODES.TEXT_EMPTY]: '選択文字列が空です。',
  [ERROR_CODES.TEXT_TOO_LONG]: `選択文字列が長すぎます（上限 ${MAX_SELECTION_LENGTH} 文字）。`,
  [ERROR_CODES.OLLAMA_UNAVAILABLE]: 'Ollamaに接続できません。Ollamaが起動しているか確認してください。',
  [ERROR_CODES.MODEL_NOT_FOUND]: '指定されたモデルが見つかりません。設定画面でモデルを選び直してください。',
  [ERROR_CODES.INVALID_SETTINGS]: '設定値が不正です。設定画面を確認してください。',
  [ERROR_CODES.REQUEST_ABORTED]: '翻訳を中断しました。',
  [ERROR_CODES.STREAM_ERROR]: '翻訳中にエラーが発生しました。',
  [ERROR_CODES.UNKNOWN_ERROR]: '不明なエラーが発生しました。'
};

const NO_MODEL_MESSAGE = 'モデルが設定されていません。ツールバーアイコンまたは設定画面でモデルを選択してください。';

/**
 * Background translation state (Design.md §9.2). Shared by popup and
 * menu-controller; the popup reads it via GET_POPUP_STATE.
 * @type {{requestId: string|null, sourceText: string, translatedText: string,
 *         status: string, model: string, error: string|null, startedAt: number|null,
 *         source: string}}
 */
const state = {
  requestId: null,
  sourceText: '',
  translatedText: '',
  status: 'idle',
  model: '',
  error: null,
  startedAt: null,
  source: ''
};

/**
 * @returns {object} a copy of the current translation state.
 */
export function getTranslationState() {
  return { ...state, translatedText: state.translatedText };
}

/**
 * Reset the shared state for a new request.
 * @param {string} requestId
 * @param {string} text validated source text
 * @param {string} source 'content' | 'context-menu'
 */
function beginState(requestId, text, source) {
  state.requestId = requestId;
  state.sourceText = text;
  state.translatedText = '';
  state.status = 'starting';
  state.model = '';
  state.error = null;
  state.startedAt = Date.now();
  state.source = source;
}

/**
 * Validate an untrusted selection string (content script or
 * menus.selectionText - both are untrusted, Security.md §7.4).
 * @param {*} text
 * @returns {{ok: true, text: string}|{ok: false, code: string}}
 */
export function validateSelectionText(text) {
  if (typeof text !== 'string') {
    return { ok: false, code: ERROR_CODES.INVALID_REQUEST };
  }
  const trimmed = text.trim();
  if (trimmed.length === 0) {
    return { ok: false, code: ERROR_CODES.TEXT_EMPTY };
  }
  // Strip control characters except tab/newline/CR.
  const cleaned = trimmed.replace(/[\u0000-\u0008\u000B\u000C\u000E-\u001F\u007F]/g, '');
  if (cleaned.length === 0) {
    return { ok: false, code: ERROR_CODES.TEXT_EMPTY };
  }
  if (cleaned.length > MAX_SELECTION_LENGTH) {
    return { ok: false, code: ERROR_CODES.TEXT_TOO_LONG };
  }
  return { ok: true, text: cleaned };
}

/**
 * @param {string} code
 * @returns {string} user-facing message for the code
 */
export function messageForCode(code) {
  return ERROR_MESSAGES[code] || ERROR_MESSAGES[ERROR_CODES.UNKNOWN_ERROR];
}

/**
 * Ensure a model is configured before translating. On a fresh install the
 * user may translate straight from a context menu without ever opening the
 * settings UI, so storage.model would still be ''. In that case pick the
 * first model reported by the running Ollama (best-effort, one attempt per
 * runTranslation call) and persist it so the choice is visible in the UI.
 * This mirrors the popup/options auto-select behavior so every path agrees.
 * @param {object} browserApi injectable for tests
 * @returns {Promise<{settings: object, error: string|null}>}
 */
async function ensureModelConfigured(browserApi) {
  let settings = await getSettings(browserApi);
  if (settings.model) {
    return { settings, error: null };
  }
  try {
    const models = await listModels(settings.ollamaHost);
    if (models.length > 0) {
      const merged = sanitizeSettings({ ...settings, model: models[0] });
      await saveSettings(merged, browserApi);
      settings = merged;
      return { settings, error: null };
    }
    return { settings, error: NO_MODEL_MESSAGE };
  } catch (error) {
    // Ollama unreachable while listing models: report a clear error.
    const code = (error && error.code) || ERROR_CODES.OLLAMA_UNAVAILABLE;
    return { settings, error: messageForCode(code) };
  }
}

/**
 * Popup state subscribers. The popup connects a 'popup-state' port and
 * receives the shared state after every change, so an open popup shows
 * live streaming progress even for sink-less (context-menu) requests.
 * @type {Set<object>}
 */
const popupPorts = new Set();

/**
 * Register a popup port for live state broadcasts.
 * @param {object} port runtime.Port (name 'popup-state')
 */
export function addPopupPort(port) {
  popupPorts.add(port);
  try {
    port.postMessage({ type: 'popup-state', state: getTranslationState() });
  } catch {
    // ignore
  }
}

/**
 * Unregister a popup port.
 * @param {object} port
 */
export function removePopupPort(port) {
  popupPorts.delete(port);
}

/**
 * Broadcast the current state to every connected popup port.
 */
function broadcastState() {
  for (const port of popupPorts) {
    try {
      port.postMessage({ type: 'popup-state', state: getTranslationState() });
    } catch {
      popupPorts.delete(port);
    }
  }
}

/**
 * Run one translation and notify a sink with started/chunk/completed/error.
 *
 * The sink is an object with an optional postMessage(message) method. The
 * content-script port is one sink; the popup state is updated internally and
 * broadcast to connected popups so they can render live progress.
 *
 * @param {object} params
 * @param {string} params.text validated source text
 * @param {string} params.requestId
 * @param {string} params.source 'content' | 'context-menu'
 * @param {object|null} [params.sink] optional message sink (port-like)
 * @returns {Promise<void>}
 */
export async function runTranslation({ text, requestId, source, sink = null, browserApi = null }) {
  let settings = await getSettings(browserApi);

  if (!settings.enabled) {
    state.status = 'error';
    state.error = messageForCode(ERROR_CODES.INVALID_REQUEST);
    broadcastState();
    postToSink(sink, { type: BG_TO_CONTENT.ERROR, requestId, code: ERROR_CODES.INVALID_REQUEST, message: state.error });
    return;
  }

  // Fresh-install path: pick the first model from the running Ollama so a
  // user who never opened the settings UI can still translate.
  const ensured = await ensureModelConfigured(browserApi);
  if (ensured.error) {
    state.status = 'error';
    state.error = ensured.error;
    broadcastState();
    postToSink(sink, { type: BG_TO_CONTENT.ERROR, requestId, code: ERROR_CODES.INVALID_SETTINGS, message: ensured.error });
    return;
  }
  settings = ensured.settings;

  // Registering the new request aborts any previous one.
  const controller = session.start(requestId, sink);

  beginState(requestId, text, source);
  state.model = settings.model;
  broadcastState();

  postToSink(sink, { type: BG_TO_CONTENT.STARTED, requestId, model: settings.model });

  try {
    await chatStream({
      host: settings.ollamaHost,
      model: settings.model,
      messages: [
        { role: 'system', content: buildSystemPrompt(settings) },
        { role: 'user', content: text }
      ],
      think: toApiThinking(settings),
      options: buildOptions(settings),
      signal: controller.signal,
      onChunk: (content) => {
        // Drop chunks if a newer request took over.
        if (!session.isActive(requestId)) return;
        if (content) {
          state.translatedText += content;
          state.status = 'streaming';
          broadcastState();
        }
        postToSink(sink, { type: BG_TO_CONTENT.CHUNK, requestId, text: content });
      }
    });
    if (session.isActive(requestId)) {
      state.status = 'completed';
      broadcastState();
      postToSink(sink, { type: BG_TO_CONTENT.COMPLETED, requestId });
    }
  } catch (error) {
    const code = (error && error.code) || ERROR_CODES.UNKNOWN_ERROR;
    if (code === ERROR_CODES.REQUEST_ABORTED) {
      // Reported by TranslationSession.abortActive() to the old sink; the
      // shared state marks it cancelled so the popup can show it.
      state.status = 'cancelled';
      state.error = messageForCode(code);
      broadcastState();
    } else if (session.isActive(requestId)) {
      state.status = 'error';
      // Fall back to the code's base message when the detail is empty or
      // judged non-user-facing by detailForUser().
      const detail = detailForUser(error);
      state.error = detail ? `${messageForCode(code)}\n(${detail})` : messageForCode(code);
      broadcastState();
      postToSink(sink, { type: BG_TO_CONTENT.ERROR, requestId, code, detail: state.error });
    }
  } finally {
    session.clear(requestId);
  }
}

/**
 * Build a short, user-safe detail string from an error. Low-level exception
 * text and full server responses are not shown unbounded: keep the message
 * short and drop anything that looks like an internal URL or a huge blob.
 * @param {*} error
 * @returns {string} '' when there is nothing worth showing
 */
function detailForUser(error) {
  const base = messageForCode(ERROR_CODES.UNKNOWN_ERROR);
  const raw = error && error.message ? String(error.message) : '';
  if (!raw) return '';
  // Skip raw network errors that leak no useful info beyond the code.
  if (/failed to fetch|networkerror|load failed/i.test(raw)) return '';
  // Strip URLs (internal host names should not be echoed to the UI).
  const cleaned = raw.replace(/\bhttps?:\/\/\S+/gi, '').trim();
  if (!cleaned) return '';
  // Drop obviously non-user-facing payloads (full JSON responses etc.).
  if (cleaned.startsWith('{') || cleaned.startsWith('[')) return '';
  const short = cleaned.length > 120 ? `${cleaned.slice(0, 120)}…` : cleaned;
  return `${short}`;
}

/**
 * @param {object|null} sink
 * @param {object} message
 */
function postToSink(sink, message) {
  if (!sink) return;
  try {
    sink.postMessage(message);
  } catch {
    // sink may be disconnected (e.g. popup closed)
  }
}

/** @returns {TranslationSession} the shared session (for tests / cancel). */
export function getSession() {
  return session;
}

export { ERROR_MESSAGES, NO_MODEL_MESSAGE };