import * as Error from "@effect/platform/Error"
import * as FileSystem from "@effect/platform/FileSystem"
import * as ParcelWatcher from "@parcel/watcher"
import * as Chunk from "effect/Chunk"
import * as Effect from "effect/Effect"
import * as Layer from "effect/Layer"
import * as Option from "effect/Option"
import * as Stream from "effect/Stream"

const watchParcel = (path: string) =>
  Stream.asyncScoped<FileSystem.WatchEvent, Error.PlatformError>((emit) =>
    Effect.acquireRelease(
      Effect.tryPromise({
        try: () =>
          ParcelWatcher.subscribe(path, (cause, events) => {
            if (cause) {
              emit.fail(
                new Error.SystemError({
                  reason: "Unknown",
                  module: "FileSystem",
                  method: "watch",
                  pathOrDescriptor: path,
                  cause
                })
              )
            } else {
              emit.chunk(Chunk.unsafeFromArray(events.map((event) => {
                switch (event.type) {
                  case "create": {
                    return FileSystem.WatchEventCreate({ path: event.path })
                  }
                  case "update": {
                    return FileSystem.WatchEventUpdate({ path: event.path })
                  }
                  case "delete": {
                    return FileSystem.WatchEventRemove({ path: event.path })
                  }
                }
              })))
            }
          }),
        catch: (cause) =>
          new Error.SystemError({
            reason: "Unknown",
            module: "FileSystem",
            method: "watch",
            pathOrDescriptor: path,
            cause
          })
      }),
      (sub) => Effect.promise(() => sub.unsubscribe())
    )
  )

const backend = FileSystem.WatchBackend.of({
  register(path, stat, _options) {
    if (stat.type !== "Directory") {
      return Option.none()
    }
    return Option.some(watchParcel(path))
  }
})

export const layer = Layer.succeed(FileSystem.WatchBackend, backend)