import path from "node:path";

import type { Plugin } from "vite";

type ModuleInventoryChunk = Readonly<{
  fileName: string;
  modules: readonly string[];
}>;

/**
 * Rollup knows the exact source-module set for every emitted chunk. Persisting
 * that graph makes optional-runtime exclusion verifiable without relying on
 * minified names, error strings, or source maps.
 */
export function viteModuleInventoryPlugin(
  repositoryRoot = process.cwd(),
): Plugin {
  return {
    name: "frontend-module-inventory",
    generateBundle(_options, bundle) {
      const chunks: ModuleInventoryChunk[] = Object.values(bundle)
        .filter((output) => output.type === "chunk")
        .map((chunk) => ({
          fileName: chunk.fileName,
          modules: Object.freeze(
            [...new Set(
              Object.keys(chunk.modules).map((moduleId) =>
                normalizeModuleId(moduleId, repositoryRoot),
              ),
            )].sort(),
          ),
        }))
        .sort((left, right) => left.fileName.localeCompare(right.fileName));

      this.emitFile({
        type: "asset",
        fileName: ".vite/module-inventory.json",
        source: `${JSON.stringify(
          {
            schemaVersion: 1,
            chunks,
          },
          null,
          2,
        )}\n`,
      });
    },
  };
}

function normalizeModuleId(
  moduleId: string,
  repositoryRoot: string,
): string {
  const withoutQuery = moduleId.replace(/^\0/u, "").split("?", 1)[0] ?? "";
  if (!path.isAbsolute(withoutQuery)) {
    return withoutQuery.replaceAll("\\", "/");
  }
  const relative = path.relative(repositoryRoot, withoutQuery);
  return relative.startsWith("..")
    ? `external:${path.basename(withoutQuery)}`
    : relative.replaceAll("\\", "/");
}