//
// Copyright © 2025 Hardcore Engineering Inc.
//
// Licensed under the Eclipse Public License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License. You may
// obtain a copy of the License at https://www.eclipse.org/legal/epl-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//
// See the License for the specific language governing permissions and
// limitations under the License.
//

export interface ChunkReadResult {
  done: boolean
  value: Blob | undefined
}

export class ChunkReader {
  private readonly chunks: Blob[] = []
  private done: boolean = false
  private awaitingResolve: ((val: ChunkReadResult | Promise<ChunkReadResult>) => void) | null = null

  public async read (): Promise<ChunkReadResult> {
    if (this.done && this.chunks.length === 0) {
      return { done: true, value: undefined }
    }
    if (this.chunks.length === 0) {
      return await new Promise<ChunkReadResult>((resolve) => {
        this.awaitingResolve = resolve
      })
    }
    return { done: false, value: this.chunks.shift() }
  }

  public push (blob: Blob): void {
    if (this.done) {
      console.warn('ChunkReader: push into closed stream')
      // close just in case someone is waiting for a chunk
      if (this.awaitingResolve !== null) {
        this.awaitingResolve({ done: true, value: undefined })
      }
      return
    }

    this.chunks.push(blob)
    if (this.awaitingResolve !== null) {
      this.awaitingResolve(this.read())
      this.awaitingResolve = null
    }
  }

  public close (): void {
    this.done = true
    if (this.awaitingResolve !== null) {
      this.awaitingResolve(this.read())
      this.awaitingResolve = null
    }
  }
}