chunks.ts

import type { Nitro } from "nitro/types";

// Tests in @test/unit/chunks.test.ts

const virtualRe = /^(?:\0|#|virtual:)/;

export const NODE_MODULES_RE = /node_modules[/\\](?!(?:nitro|nitro-nightly)[/\\])[^.]/;

export function libChunkName(id: string) {
  const pkgName = pathToPkgName(id);
  return pkgName ? `_libs/${pkgName}` : undefined;
}

export function pathToPkgName(path: string): string | undefined {
  let pkgName = path.match(
    /.*(?:[/\\])node_modules(?:[/\\])(?<name>@[^/\\]+[/\\][^/\\]+|[^/\\.][^/\\]*)/
  )?.groups?.name;
  if (pkgName?.endsWith("-nightly")) {
    pkgName = pkgName.slice(0, -8);
  }
  return pkgName;
}

export function getChunkName(chunk: { name: string; moduleIds: string[] }, nitro: Nitro) {
  // Known groups
  if (chunk.name === "rolldown-runtime") {
    return "_runtime.mjs";
  }

  // Library chunks
  if (chunk.moduleIds.every((id) => NODE_MODULES_RE.test(id))) {
    const chunkName = joinPkgNames(chunk.moduleIds);
    if (chunkName.length > 30) {
      return `${chunk.name}+[...].mjs`;
    }
    return `_libs/${chunkName || "_"}.mjs`;
  }

  // _ chunks are preserved (should be after library normalization)
  if (chunk.name.startsWith("_")) {
    return `${chunk.name}.mjs`;
  }

  // No moduleIds
  if (chunk.moduleIds.length === 0) {
    return `_chunks/${chunk.name}.mjs`;
  }

  const ids = chunk.moduleIds.filter((id) => !virtualRe.test(id));

  // All virtual
  if (ids.length === 0) {
    if (chunk.moduleIds.every((id) => id.includes("virtual:raw"))) {
      return `_raw/[name].mjs`;
    }
    return `_virtual/[name].mjs`;
  }

  // WASM chunk
  if (ids.every((id) => id.endsWith(".wasm"))) {
    return `_wasm/[name].mjs`;
  }

  // Chunks generate by other vite environments (we assume SSR for simplicity)
  if (ids.every((id) => id.includes("vite/services"))) {
    return `_ssr/[name].mjs`;
  }

  // Chunks from generated code
  if (ids.every((id) => id.startsWith(nitro.options.buildDir))) {
    return `_build/[name].mjs`;
  }

  // Try to match user defined routes or tasks
  const mainId = ids.at(-1);
  if (mainId) {
    const routeHandler = nitro.routing.routes.routes
      .flatMap((h) => h.data)
      .find((h) => h.handler === mainId);
    if (routeHandler?.route) {
      return `_routes/${routeToFsPath(routeHandler.route).replace(/\[/g, "%5B").replace(/\]/g, "%5D")}.mjs`;
    }

    const taskHandler = Object.entries(nitro.options.tasks).find(
      ([_, task]) => task.handler === mainId
    );
    if (taskHandler) {
      return `_tasks/[name].mjs`;
    }
  }

  return `_chunks/[name].mjs`;
}

function joinPkgNames(moduleIds: string[]): string {
  const names = [
    ...new Set(
      moduleIds
        .map((id) => pathToPkgName(id))
        .filter(Boolean)
        .map((name) => name!.replace(/^@/, "").replace(/[/\\]/g, "__"))
    ),
  ].sort();
  return names.join("+");
}

export function routeToFsPath(route: string) {
  return (
    route
      .split("/")
      .slice(1)
      .map((s) =>
        s
          .replace(/:(\w+)/g, "[$1]")
          .replace(/\*+/g, "[...]")
          .replace(/[^a-zA-Z0-9_.[\]]/g, "_")
      )
      .join("/") || "index"
  );
}