import { readFile } from "node:fs/promises";
import { defineConfig } from "vite";

import {
  SERVICE_WORKER_CACHE_SCHEMA_VERSION,
  SERVICE_WORKER_PROTOCOL_VERSION,
  SERVICE_WORKER_SCRIPT_PATH,
} from "./src/contracts/service-worker.ts";
import { INSTALLED_RUNTIME_CAPABILITIES } from "./src/features/installed-runtime-capabilities.ts";
import { resolveServiceWorkerBuildInput } from "./scripts/lib/service-worker-build-input.ts";

/**
 * §17.2.2 step 5. The Service Worker build.
 *
 * Runs only when the static selection is `ACTIVE`, after the app build has
 * completed and the hashed asset list has been generated. `emptyOutDir` is
 * false so it adds `service-worker.js` beside the already-built app rather than
 * replacing it.
 */

const selection = INSTALLED_RUNTIME_CAPABILITIES.serviceWorker;

async function readGenerated<T>(path: string, exportName: string): Promise<T> {
  try {
    const module = (await import(path)) as Record<string, unknown>;
    if (!(exportName in module)) {
      throw new TypeError(`Generated module does not export ${exportName}.`);
    }
    return module[exportName] as T;
  } catch (error) {
    throw new TypeError(`Required generated module is unavailable: ${path}`, {
      cause: error,
    });
  }
}

const assets = await readGenerated(
  "./.generated/frontend-runtime/service-worker-assets.ts",
  "SERVICE_WORKER_ASSETS",
);
const contractSet = await readGenerated<{ setDigest?: string }>(
  "./.generated/frontend-runtime/contract-set.ts",
  "BUILD_CONTRACT_SET",
);
const runtimeConfig = JSON.parse(
  await readFile("public/config.json", "utf8"),
) as Record<string, string>;

const buildId = process.env.VITE_BUILD_ID ?? "local-build";
const releaseId = process.env.RELEASE_ID ?? "local-release";
const buildInput = resolveServiceWorkerBuildInput({
  selection,
  assets,
  contractSet,
  runtimeConfig,
  buildId,
  releaseId,
});

export default defineConfig({
  build: {
    // §17.2.2: exactly one input, exactly one output, no additional chunk.
    emptyOutDir: false,
    sourcemap: false,
    rollupOptions: {
      input: "src/adapters/service-worker/service-worker-entry.ts",
      output: {
        format: "es",
        inlineDynamicImports: true,
        entryFileNames: SERVICE_WORKER_SCRIPT_PATH,
      },
    },
  },
  define: {
    __CA_SERVICE_WORKER_BUILD_INFO__: JSON.stringify({
      serviceWorkerProtocolVersion: SERVICE_WORKER_PROTOCOL_VERSION,
      cacheSchemaVersion: SERVICE_WORKER_CACHE_SCHEMA_VERSION,
      buildId,
      releaseId,
      contractSetDigest: buildInput.contractSetDigest,
      staticAssetSetDigest: buildInput.assets.setDigest,
    }),
    __CA_SERVICE_WORKER_ASSETS__: JSON.stringify(buildInput.assets),
    __CA_SERVICE_WORKER_HANDLERS__: JSON.stringify(buildInput.handlers),
    __CA_RUNTIME_CONFIG_URL__: JSON.stringify(
      process.env.VITE_RUNTIME_CONFIG_URL ?? "/config.json",
    ),
    __CA_RELEASE_MANIFEST_URL__: JSON.stringify(
      buildInput.releaseManifestUrl,
    ),
  },
});