/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.dev/license
 */

import type { Plugin } from 'esbuild';

/**
 * The internal namespace used by generated locale import statements and Angular locale data plugin.
 */
export const LOCALE_DATA_NAMESPACE = 'angular:locale/data';

/**
 * The base module location used to search for locale specific data.
 */
export const LOCALE_DATA_BASE_MODULE = '@angular/common/locales/global';

/**
 * Creates an esbuild plugin that resolves Angular locale data files from `@angular/common`.
 *
 * @returns An esbuild plugin.
 */
export function createAngularLocaleDataPlugin(): Plugin {
  return {
    name: 'angular-locale-data',
    setup(build): void {
      // If packages are configured to be external then leave the original angular locale import path.
      // This happens when using the development server with caching enabled to allow Vite prebundling to work.
      // There currently is no option on the esbuild resolve function to resolve while disabling the option. To
      // workaround the inability to resolve the full locale location here, the Vite dev server prebundling also
      // contains a plugin to allow the locales to be correctly resolved when prebundling.
      // NOTE: If esbuild eventually allows controlling the external package options in a build.resolve call, this
      //       workaround can be removed.
      if (build.initialOptions.packages === 'external') {
        return;
      }

      build.onResolve({ filter: /^angular:locale\/data:/ }, async ({ path }) => {
        // Extract the locale from the path
        const rawLocaleTag = path.split(':', 3)[2];

        // Extract and normalize the base name of the raw locale tag
        let partialLocaleTag: string;
        try {
          const locale = new Intl.Locale(rawLocaleTag);
          partialLocaleTag = locale.baseName;
        } catch {
          return {
            path: rawLocaleTag,
            namespace: LOCALE_DATA_NAMESPACE,
            errors: [
              {
                text: `Invalid or unsupported locale provided in configuration: "${rawLocaleTag}"`,
              },
            ],
          };
        }

        let exact = true;
        while (partialLocaleTag) {
          // Angular embeds the `en`/`en-US` locale into the framework and it does not need to be included again here.
          // The onLoad hook below for the locale data namespace has an `empty` loader that will prevent inclusion.
          // Angular does not contain exact locale data for `en-US` but `en` is equivalent.
          if (partialLocaleTag === 'en' || partialLocaleTag === 'en-US') {
            return {
              path: rawLocaleTag,
              namespace: LOCALE_DATA_NAMESPACE,
            };
          }

          // Attempt to resolve the locale tag data within the Angular base module location
          const potentialPath = `${LOCALE_DATA_BASE_MODULE}/${partialLocaleTag}`;
          const result = await build.resolve(potentialPath, {
            kind: 'import-statement',
            resolveDir: build.initialOptions.absWorkingDir,
          });
          if (result.path) {
            if (exact) {
              return result;
            } else {
              return {
                ...result,
                warnings: [
                  ...result.warnings,
                  {
                    location: null,
                    text: `Locale data for '${rawLocaleTag}' cannot be found. Using locale data for '${partialLocaleTag}'.`,
                  },
                ],
              };
            }
          }

          // Remove the last subtag and try again with a less specific locale.
          // Usually the match is exact so the string splitting here is not done until actually needed after the exact
          // match fails to resolve.
          const parts = partialLocaleTag.split('-');
          partialLocaleTag = parts.slice(0, -1).join('-');
          exact = false;
        }

        // Not found so issue a warning and use an empty loader. Framework built-in `en-US` data will be used.
        // This retains existing behavior as in the Webpack-based builder.
        return {
          path: rawLocaleTag,
          namespace: LOCALE_DATA_NAMESPACE,
          warnings: [
            {
              location: null,
              text: `Locale data for '${rawLocaleTag}' cannot be found. No locale data will be included for this locale.`,
            },
          ],
        };
      });

      // Locales that cannot be found will be loaded as empty content with a warning from the resolve step
      build.onLoad({ filter: /./, namespace: LOCALE_DATA_NAMESPACE }, () => ({
        contents: '',
        loader: 'empty',
      }));
    },
  };
}
