//
//  AsyncPromise.swift
//  punchnet
//
//  Created by 安礼成 on 2026/5/27.
//
import Foundation

public actor AsyncPromise<Value: Sendable> {
    private enum State {
        case pending([CheckedContinuation<Value, Error>])
        case completed(Result<Value, Error>)
    }

    private var state: State = .pending([])

    public init() {
        
    }

    public func value() async throws -> Value {
        try await withCheckedThrowingContinuation { continuation in
            switch state {
            case .pending(var continuations):
                continuations.append(continuation)
                state = .pending(continuations)

            case .completed(let result):
                continuation.resume(with: result)
            }
        }
    }

    public func succeed(_ value: Value) {
        complete(.success(value))
    }

    public func fail(_ error: Error) {
        complete(.failure(error))
    }

    private func complete(_ result: Result<Value, Error>) {
        guard case .pending(let continuations) = state else {
            return
        }

        state = .completed(result)

        for continuation in continuations {
            continuation.resume(with: result)
        }
    }
}