// vite and its plugins live only as long as one frontend build subprocess.

import { encodeBase64 } from "@std/encoding/base64";
import { fromFileUrl, isAbsolute } from "@std/path";
import aftercare from "@char/aftercare/vite";
import deno from "@deno/vite-plugin";
import { build, type Plugin, type Rolldown } from "vite";
import { HOST_GLOBAL, HOST_MODULES } from "@berry/api/host.ts";

export type FrontendBuild = {
  chunks: { fileName: string; code: string; isEntry: boolean }[];
  assets: { fileName: string; source: string; binary: boolean }[];
  dependencies: string[];
};

const isHost = (specifier: unknown): specifier is string =>
  (HOST_MODULES as readonly unknown[]).includes(specifier);

/** Imports of the host's modules become reads of the instances the app published, as `const { … } = host[…]`. */
function hostModules(): Plugin {
  return {
    name: "berry-host-modules",
    renderChunk(code) {
      let rewritten = "";
      let at = 0;
      for (const node of this.parse(code).body) {
        if (node.type !== "ImportDeclaration" || !isHost(node.source.value)) continue;
        const host = `globalThis[${JSON.stringify(HOST_GLOBAL)}][${
          JSON.stringify(node.source.value)
        }]`;
        const bindings: string[] = [];
        const statements: string[] = [];
        for (const specifier of node.specifiers) {
          if (specifier.type === "ImportNamespaceSpecifier") {
            statements.push(`const ${specifier.local.name} = ${host};`);
            continue;
          }
          const imported = specifier.type === "ImportDefaultSpecifier"
            ? "default"
            : specifier.imported.type === "Identifier"
            ? specifier.imported.name
            : JSON.stringify(specifier.imported.value);
          bindings.push(
            imported === specifier.local.name ? imported : `${imported}: ${specifier.local.name}`,
          );
        }
        if (bindings.length > 0) statements.push(`const { ${bindings.join(", ")} } = ${host};`);
        // one line for one line, so the source map still lines up
        rewritten += code.slice(at, node.start) + statements.join(" ");
        at = node.end;
      }
      return at === 0 ? null : { code: rewritten + code.slice(at), map: null };
    },
  };
}

async function buildFrontend(entry: string): Promise<FrontendBuild> {
  const root = fromFileUrl(new URL("../", import.meta.url));
  const dependencies = new Set([entry]);
  function track<C extends Rolldown.PluginContext, A extends unknown[], R>(
    hook: (this: C, ...args: A) => R,
  ): (this: C, ...args: A) => R {
    return function (this: C, ...args: A): R {
      const context = new Proxy(this, {
        get(target, key) {
          if (key === "addWatchFile") {
            return (path: string) => {
              if (isAbsolute(path)) dependencies.add(path);
              target.addWatchFile(path);
            };
          }
          const value = Reflect.get(target, key, target);
          return typeof value === "function" ? value.bind(target) : value;
        },
      });
      return Reflect.apply(hook, context, args);
    };
  }
  const result = await build({
    root,
    configFile: false,
    mode: "production",
    // a failure rejects with its message; the caller reports it
    logLevel: "silent",
    publicDir: false,
    // assets resolve against the module that names them, beside it under /ext/<name>/
    base: "./",
    plugins: [
      deno({
        onLoad({ id }) {
          if (id.startsWith("file:")) dependencies.add(fromFileUrl(id));
        },
      }),
      aftercare(),
      hostModules(),
      {
        name: "berry-build-inputs",
        configResolved(config) {
          // vite hides rolldown's watched files, including css imports and worker dependencies
          for (const plugin of config.plugins) {
            const load = plugin.load;
            if (load) {
              plugin.load = typeof load === "function"
                ? track(load)
                : { ...load, handler: track(load.handler) };
            }
            const transform = plugin.transform;
            if (transform) {
              plugin.transform = typeof transform === "function"
                ? track(transform)
                : { ...transform, handler: track(transform.handler) };
            }
          }
        },
        generateBundle() {
          for (const id of this.getModuleIds()) {
            const path = id.split("?")[0];
            if (isAbsolute(path)) dependencies.add(path);
          }
        },
      },
    ],
    build: {
      write: false,
      minify: false,
      sourcemap: "inline",
      modulePreload: false,
      // not library mode, which inlines every asset however large, such as a wasm module
      rolldownOptions: {
        input: entry,
        external: [...HOST_MODULES],
        preserveEntrySignatures: "strict",
        output: {
          format: "es",
          // a dynamic import is a chunk of its own, so an extension can leave heavy code until it needs it
          entryFileNames: "[name]-[hash].js",
          chunkFileNames: "[name]-[hash].js",
          assetFileNames: "[name]-[hash][extname]",
        },
      },
    },
  });
  const outputs = (Array.isArray(result) ? result : [result as Rolldown.RolldownOutput])
    .flatMap((r) => r.output);
  return {
    chunks: outputs.filter((o): o is Rolldown.OutputChunk => o.type === "chunk")
      .map(({ fileName, code, isEntry }) => ({ fileName, code, isEntry })),
    assets: outputs.filter((o): o is Rolldown.OutputAsset => o.type === "asset")
      .map(({ fileName, source }) => ({
        fileName,
        source: typeof source === "string" ? source : encodeBase64(source),
        binary: typeof source !== "string",
      })),
    dependencies: [...dependencies],
  };
}

if (import.meta.main) {
  try {
    console.log(JSON.stringify(await buildFrontend(Deno.args[0])));
  } catch (error) {
    console.error(error instanceof Error ? error.message : String(error));
    Deno.exit(1);
  }
}