// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

import { JupyterLab } from '@jupyterlab/application';
import { PageConfig, URLExt } from '@jupyterlab/coreutils';

// Promise.allSettled polyfill, until our supported browsers implement it
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled
if (Promise.allSettled === undefined) {
  Promise.allSettled = promises =>
    Promise.all(
      promises.map(promise =>
        promise
          .then(value => ({
            status: "fulfilled",
            value,
          }), reason => ({
            status: "rejected",
            reason,
          }))
      )
    );
}

import('./style.js');

async function createModule(scope, module) {
  try {
    const factory = await window._JUPYTERLAB[scope].get(module);
    return factory();  
  } catch(e) {
    console.warn(`Failed to create module: package: ${scope}; module: ${module}`);
    throw e;
  }
}

/**
 * The main entry point for the application.
 */
export async function main() {
  const disabled = [];
  const deferred = [];
  const ignorePlugins = [];
  const pluginsToRegister = [];

  const federatedExtensionPromises = [];
  const federatedMimeExtensionPromises = [];
  const federatedStylePromises = [];

  // This is all the data needed to load and activate plugins. This should be
  // gathered by the server and put onto the initial page template.
  const extensions = JSON.parse(
    PageConfig.getOption('federated_extensions')
  );

  // The set of federated extension names.
  const federatedExtensionNames = new Set();

  extensions.forEach(data => {
    if (data.extension) {
      federatedExtensionNames.add(data.name);
      federatedExtensionPromises.push(createModule(data.name, data.extension));
    }
    if (data.mimeExtension) {
      federatedExtensionNames.add(data.name);
      federatedMimeExtensionPromises.push(createModule(data.name, data.mimeExtension));
    }
    if (data.style) {
      federatedStylePromises.push(createModule(data.name, data.style));
    }
  });

  /**
   * Iterate over active plugins in an extension.
   * 
   * #### Notes
   * This also populates the disabled, deferred, and ignored arrays.
   */
  function* activePlugins(extension) {
    // Handle commonjs or es2015 modules
    let exports;
    if (extension.hasOwnProperty('__esModule')) {
      exports = extension.default;
    } else {
      // CommonJS exports.
      exports = extension;
    }

    let plugins = Array.isArray(exports) ? exports : [exports];
    for (let plugin of plugins) {
      if (PageConfig.Extension.isDisabled(plugin.id)) {
        disabled.push(plugin.id);
        continue;
      }
      if (PageConfig.Extension.isDeferred(plugin.id)) {
        deferred.push(plugin.id);
        ignorePlugins.push(plugin.id);
      }
      yield plugin;
    }
  }

  // Handle the mime extensions.
  const mimeExtensions = [];
  {{#each jupyterlab_mime_extensions}}
  if (!federatedExtensionNames.has('{{@key}}')) {
    try {
      let ext = require('{{@key}}{{#if this}}/{{this}}{{/if}}');
      for (let plugin of activePlugins(ext)) {
        mimeExtensions.push(plugin);
      }
    } catch (e) {
      console.error(e);
    }
  }
  {{/each}}

  // Add the federated mime extensions.
  const federatedMimeExtensions = await Promise.allSettled(federatedMimeExtensionPromises);
  federatedMimeExtensions.forEach(p => {
    if (p.status === "fulfilled") {
      for (let plugin of activePlugins(p.value)) {
        mimeExtensions.push(plugin);
      }
    } else {
      console.error(p.reason);
    }
  });

  // Handled the standard extensions.
  {{#each jupyterlab_extensions}}
  if (!federatedExtensionNames.has('{{@key}}')) {
    try {
      let ext = require('{{@key}}{{#if this}}/{{this}}{{/if}}');
      for (let plugin of activePlugins(ext)) {
        pluginsToRegister.push(plugin);
      }
    } catch (e) {
      console.error(e);
    }
  }
  {{/each}}

  // Add the federated extensions.
  const federatedExtensions = await Promise.allSettled(federatedExtensionPromises);
  federatedExtensions.forEach(p => {
    if (p.status === "fulfilled") {
      for (let plugin of activePlugins(p.value)) {
        pluginsToRegister.push(plugin);
      }
    } else {
      console.error(p.reason);
    }
  });

  // Load all federated component styles and log errors for any that do not
  (await Promise.allSettled(federatedStylePromises)).filter(({status}) => status === "rejected").forEach(({reason}) => {
     console.error(reason);
    });

  // Create a new JupyterLab object and start it
  const lab = new JupyterLab({
    mimeExtensions,
    disabled: {
      matches: disabled,
      patterns: PageConfig.Extension.disabled
        .map(function (val) { return val.raw; })
    },
    deferred: {
      matches: deferred,
      patterns: PageConfig.Extension.deferred
        .map(function (val) { return val.raw; })
    },
  });

  lab.registerPluginModules(pluginsToRegister);
  lab.start({ ignorePlugins });
  lab.restored.then(() => {
    console.debug('Example started!');
  });
}