import { devLogger as defaultDevLogger, userLogger as defaultUserLogger } from "./utils/logger.js";
import { FEED_TYPES, FEATURE_TRENDING_FEED } from "./constants.js";

const LEGACY_DOCS_VIEWS = {
  about: "about",
  "community-guidelines": "community-guidelines",
  "getting-started": "getting-started",
  "upload-content": "upload-content",
  roadmap: "roadmap",
  links: "links"
};

const createLoggerFacade = (logger, fallback) => {
  if (logger && typeof logger === "object") {
    return {
      log: typeof logger.log === "function" ? logger.log.bind(logger) : fallback.log,
      warn:
        typeof logger.warn === "function" ? logger.warn.bind(logger) : fallback.warn,
      error:
        typeof logger.error === "function"
          ? logger.error.bind(logger)
          : fallback.error,
    };
  }

  return fallback;
};

const noopLogger = {
  log() {},
  warn() {},
  error() {},
};

export function createHashChangeHandler({
  getApplication,
  getApplicationReady,
  loadView,
  viewInitRegistry,
  devLogger = defaultDevLogger,
  userLogger = defaultUserLogger,
} = {}) {
  const devLog = createLoggerFacade(devLogger, noopLogger);
  const userLog = createLoggerFacade(userLogger, noopLogger);
  let currentViewName = null;

  const getReadyPromise = () => {
    if (typeof getApplicationReady === "function") {
      return getApplicationReady();
    }
    return Promise.resolve();
  };

  const resolveIsLoggedIn = () => {
    if (typeof getApplication !== "function") {
      return false;
    }
    const app = getApplication();
    if (!app || typeof app.isUserLoggedIn !== "function") {
      return false;
    }
    return Boolean(app.isUserLoggedIn());
  };

  return async function handleHashChange() {
    const currentHash =
      typeof window !== "undefined" && window.location
        ? window.location.hash
        : undefined;
    devLog.log("handleHashChange called, current hash =", currentHash);

    try {
      await getReadyPromise();
    } catch (error) {
      userLog.warn(
        "Proceeding with hash handling despite application initialization failure:",
        error,
      );
    }

    const hash =
      typeof window !== "undefined" && window.location && window.location.hash
        ? window.location.hash
        : "";
    if (hash === `#${FEED_TYPES.KIDS}`) {
      window.location.hash = `#view=${FEED_TYPES.KIDS}`;
      return;
    }
    const match = hash.match(/^#view=([^&]+)/);

    try {
      if (!match || !match[1]) {
        // Logged in → personalized For You; logged out → Trending (the best
        // not-personalized landing), falling back to Recent if Trending is off.
        const defaultViewName = resolveIsLoggedIn()
          ? FEED_TYPES.FOR_YOU
          : FEATURE_TRENDING_FEED
          ? FEED_TYPES.TRENDING
          : FEED_TYPES.RECENT;

        if (defaultViewName === currentViewName) {
          return;
        }

        await loadView(`views/${defaultViewName}.html`);
        currentViewName = defaultViewName;

        const initFn = viewInitRegistry?.[defaultViewName];
        if (typeof initFn === "function") {
          await initFn();
        }
        return;
      }

      const viewName = match[1];

      if (Object.prototype.hasOwnProperty.call(LEGACY_DOCS_VIEWS, viewName)) {
        const docSlug = LEGACY_DOCS_VIEWS[viewName];
        window.location.hash = `#view=docs&doc=${docSlug}`;
        return;
      }

      if (viewName === currentViewName) {
        return;
      }

      if (typeof viewName === "string" && viewName.toLowerCase() === FEED_TYPES.HISTORY) {
      }
      const viewUrl = `views/${viewName}.html`;

      await loadView(viewUrl);
      currentViewName = viewName;

      const initFn = viewInitRegistry?.[viewName];
      if (typeof initFn === "function") {
        await initFn();
      }
    } catch (error) {
      userLog.error("Failed to handle hash change:", error);
    }
  };
}