import * as Effect from "effect/Effect";
import * as FileSystem from "effect/FileSystem";
import * as Path from "effect/Path";
import { DrizzleV0LayoutError } from "./Format.ts";
import { DRIZZLE_DIR_PATTERN } from "./Records.ts";

/**
 * The on-disk layout of a migrations directory. `directory` covers both
 * drizzle-kit v1 and Prisma layouts (`<ts>_<name>/migration.sql` — records
 * key by directory name); `flat` is plain `.sql` files (records key by file
 * path).
 */
export type MigrationLayout = "directory" | "flat";

/**
 * Fingerprint a migrations directory's layout to pick the record reader.
 *
 * A drizzle **v0** layout (`meta/_journal.json`) fails with a typed error:
 * the fix (`drizzle-kit up`) is upstream of Alchemy.
 */
export const detectLayout = (dir: string) =>
  Effect.gen(function* () {
    const fs = yield* FileSystem.FileSystem;
    const path = yield* Path.Path;
    const exists = (p: string) =>
      fs.exists(p).pipe(Effect.catch(() => Effect.succeed(false)));

    if (yield* exists(path.join(dir, "meta", "_journal.json"))) {
      return yield* new DrizzleV0LayoutError({
        dir,
        message:
          `${dir} uses drizzle-kit's pre-v1 migration layout (meta/_journal.json). ` +
          `Upgrade drizzle-kit and run "drizzle-kit up" to convert it, then redeploy.`,
      });
    }

    const entries = yield* fs
      .readDirectory(dir)
      .pipe(Effect.catch(() => Effect.succeed([] as string[])));
    for (const entry of entries) {
      if (!DRIZZLE_DIR_PATTERN.test(entry)) continue;
      if (yield* exists(path.join(dir, entry, "migration.sql"))) {
        return "directory" as const;
      }
    }
    return "flat" as const;
  });