import type { Plugin } from "esbuild";
import type { NodeJSCompatMode } from "miniflare";
import { relative } from "pathe";
import pc from "picocolors";
import { dedent } from "../../util/dedent.ts";
import { logger } from "../../util/logger.ts";
import { NODEJS_MODULES_RE } from "./nodejs-builtin-modules.ts";

/**
 * An esbuild plugin that will:
 * - mark any `node:...` imports as external
 * - warn if there are node imports (if not in v1 mode)
 *
 * Applies to: null, als, legacy and v1 modes.
 */
export const esbuildPluginNodeCompatImports = (
  mode: NodeJSCompatMode,
): Plugin => ({
  name: "nodejs_compat-imports",
  setup(pluginBuild) {
    // Infinite loop detection
    const seen = new Set<string>();

    // Prevent multiple warnings per package
    const warnedPackages = new Map<string, string[]>();

    pluginBuild.onStart(() => {
      seen.clear();
      warnedPackages.clear();
    });
    pluginBuild.onResolve(
      { filter: NODEJS_MODULES_RE },
      async ({ path, kind, resolveDir, importer }) => {
        const specifier = `${path}:${kind}:${resolveDir}:${importer}`;
        if (seen.has(specifier)) {
          return;
        }

        seen.add(specifier);
        // Try to resolve this import as a normal package
        const result = await pluginBuild.resolve(path, {
          kind,
          resolveDir,
          importer,
        });

        if (result.errors.length > 0) {
          // esbuild couldn't resolve the package
          // We should warn the user, but not fail the build
          const pathWarnedPackages = warnedPackages.get(path) ?? [];
          pathWarnedPackages.push(importer);
          warnedPackages.set(path, pathWarnedPackages);

          return { external: true };
        }
        // This is a normal package—don't treat it specially
        return result;
      },
    );

    /**
     * If we are bundling a "Service Worker" formatted Worker, imports of external modules,
     * which won't be inlined/bundled by esbuild, are invalid.
     *
     * This `onEnd()` handler will error if it identifies node.js external imports.
     */
    pluginBuild.onEnd(() => {
      if (
        pluginBuild.initialOptions.format === "iife" &&
        warnedPackages.size > 0
      ) {
        const paths = new Intl.ListFormat("en-US").format(
          Array.from(warnedPackages.keys())
            .map((p) => `"${p}"`)
            .sort(),
        );
        return {
          errors: [
            {
              text: dedent`
                Unexpected external import of ${paths}.
                Your worker has no default export, which means it is assumed to be a Service Worker format Worker.
                Did you mean to create a ES Module format Worker?
                If so, try adding \`export default { ... }\` in your entry-point.
                See https://developers.cloudflare.com/workers/reference/migrate-to-module-workers/.
              `,
            },
          ],
        };
      }
    });

    // Wait until the build finishes to log warnings, so that all files which import a package
    // can be collated
    pluginBuild.onEnd(() => {
      if (mode !== "v1") {
        warnedPackages.forEach((importers: string[], path: string) => {
          logger.warn(
            dedent`
            The package "${path}" wasn't found on the file system but is built into node.
            Your Worker may throw errors at runtime unless you enable the "nodejs_compat" compatibility flag. Refer to https://developers.cloudflare.com/workers/runtime-apis/nodejs/ for more details. Imported from:
            ${toList(importers, pluginBuild.initialOptions.absWorkingDir)}`,
          );
        });
      }
    });
  },
});

function toList(items: string[], absWorkingDir: string | undefined): string {
  return items
    .map((i) => ` - ${pc.blue(relative(absWorkingDir ?? "/", i))}`)
    .join("\n");
}