import fs from "node:fs";
import path from "node:path";

import type { EnvironmentModuleNode, Plugin } from "vite";

import { renderRemote } from "../../render-remote";
import { FEDERATION_FILE_NAME, RUNTIME_DIR } from "../constants";

const REMOTE_ENTRY_FILE = `${FEDERATION_FILE_NAME}.jsx`;

// The studio wraps `Studio` with the user's config; HMR re-renders through the
// new module so a config edit takes effect.
const STUDIO_ENTRY = renderRemote({
  preamble: `import { Studio } from 'sanity'
import config from %STUDIO_CONFIG%`,
  app: `(props) => createElement(Studio, { config, ...props })`,
  hmr: true,
});

// An SDK app's default export is the component; it Fast-Refreshes through its
// own dev server, so the wrapper needs no HMR boundary.
const APP_ENTRY = renderRemote({ preamble: `import App from %APP_ENTRY%` });

// A branded app that declares no `entry` (e.g. a dock-only panel/worker app, US5)
// has no navigable full-page view, so there's no `App` to import. The runtime
// still needs a valid module for the federation build input, but it exposes no
// `./App` (see `plugin.ts`) — its `render` is unreachable and throws if reached.
const HEADLESS_APP_ENTRY = `\
// This file is auto-generated on 'sanity dev'
// Modifications to this file are automatically discarded
// This application declares no app view (no \`entry\`): it isn't navigable as a
// full-page app, only its panels/services are exposed.
export function render() {
  throw new Error('This application has no app view: it declares no \`entry\`.')
}
`;

export type FederationRuntimeOptions =
  | { isApp: true; appEntry?: string }
  | { isApp: false; studioConfigPath: string };

export function sanityFederationRuntime(
  options: FederationRuntimeOptions,
): Plugin {
  let content: string;
  if (options.isApp) {
    content = options.appEntry
      ? APP_ENTRY.replace(/%APP_ENTRY%/, JSON.stringify(options.appEntry))
      : HEADLESS_APP_ENTRY;
  } else {
    content = STUDIO_ENTRY.replace(
      /%STUDIO_CONFIG%/,
      JSON.stringify(options.studioConfigPath),
    );
  }

  let entryFileAbsPath = "";

  return {
    name: "sanity/federation-runtime",
    configResolved(config) {
      const dir = path.resolve(config.root, RUNTIME_DIR);
      entryFileAbsPath = path.join(dir, REMOTE_ENTRY_FILE);

      fs.mkdirSync(dir, { recursive: true });
      fs.writeFileSync(entryFileAbsPath, content);
    },
    hotUpdate({ file, modules, timestamp }) {
      if (options.isApp) return;
      if (this.environment.name !== "client") return;

      const { moduleGraph } = this.environment;
      const studioMods = moduleGraph.getModulesByFile(entryFileAbsPath);
      if (!studioMods?.size) return;

      // Is the changed file reachable from the studio entry?
      const visited = new Set<EnvironmentModuleNode>();
      const queue: EnvironmentModuleNode[] = [...studioMods];
      while (queue.length > 0) {
        const mod = queue.pop()!;
        if (visited.has(mod)) continue;
        visited.add(mod);
        if (mod.file === file) {
          // The walk from `file` up through importers dead-ends at federation
          // gaps, so invalidate changed modules ourselves and route HMR to the
          // self-accepting studio entry.
          const seen = new Set<EnvironmentModuleNode>();
          for (const m of modules) {
            moduleGraph.invalidateModule(m, seen, timestamp, true);
          }
          return [...studioMods];
        }
        for (const dep of mod.importedModules) queue.push(dep);
      }
    },
  };
}