/*
 * Copyright 2021, gRPC Authors All rights reserved.
 *
 * Licensed under the Apache 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
 *
 *     http://www.apache.org/licenses/LICENSE-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.
 */
#if compiler(>=5.5)
@testable import GRPC
import XCTest

@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
class PassthroughMessageSourceTests: GRPCTestCase {
  func testBasicUsage() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, Never>()
      let sequence = PassthroughMessageSequence(consuming: source)

      XCTAssertEqual(source.yield("foo"), .accepted(queueDepth: 1))
      XCTAssertEqual(source.yield("bar"), .accepted(queueDepth: 2))
      XCTAssertEqual(source.yield("baz"), .accepted(queueDepth: 3))

      let firstTwo = try await sequence.prefix(2).collect()
      XCTAssertEqual(firstTwo, ["foo", "bar"])

      XCTAssertEqual(source.yield("bar"), .accepted(queueDepth: 2))
      XCTAssertEqual(source.yield("foo"), .accepted(queueDepth: 3))

      XCTAssertEqual(source.finish(), .accepted(queueDepth: 4))

      let theRest = try await sequence.collect()
      XCTAssertEqual(theRest, ["baz", "bar", "foo"])
    }
  }

  func testFinishWithError() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, TestError>()

      XCTAssertEqual(source.yield("one"), .accepted(queueDepth: 1))
      XCTAssertEqual(source.yield("two"), .accepted(queueDepth: 2))
      XCTAssertEqual(source.yield("three"), .accepted(queueDepth: 3))
      XCTAssertEqual(source.finish(throwing: TestError()), .accepted(queueDepth: 4))

      // We should still be able to get the elements before the error.
      let sequence = PassthroughMessageSequence(consuming: source)
      let elements = try await sequence.prefix(3).collect()
      XCTAssertEqual(elements, ["one", "two", "three"])

      do {
        for try await element in sequence {
          XCTFail("Unexpected value '\(element)'")
        }
        XCTFail("AsyncSequence did not throw")
      } catch {
        XCTAssert(error is TestError)
      }
    }
  }

  func testYieldAfterFinish() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, Never>()
      XCTAssertEqual(source.finish(), .accepted(queueDepth: 1))
      XCTAssertEqual(source.yield("foo"), .dropped)

      let sequence = PassthroughMessageSequence(consuming: source)
      let elements = try await sequence.count()
      XCTAssertEqual(elements, 0)
    }
  }

  func testMultipleFinishes() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, TestError>()
      XCTAssertEqual(source.finish(), .accepted(queueDepth: 1))
      XCTAssertEqual(source.finish(), .dropped)
      XCTAssertEqual(source.finish(throwing: TestError()), .dropped)

      let sequence = PassthroughMessageSequence(consuming: source)
      let elements = try await sequence.count()
      XCTAssertEqual(elements, 0)
    }
  }

  func testConsumeBeforeYield() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, Never>()
      let sequence = PassthroughMessageSequence(consuming: source)

      await withThrowingTaskGroup(of: Void.self) { group in
        group.addTask(priority: .high) {
          let iterator = sequence.makeAsyncIterator()
          if let next = try await iterator.next() {
            XCTAssertEqual(next, "one")
          } else {
            XCTFail("No value produced")
          }
        }

        group.addTask(priority: .low) {
          let result = source.yield("one")
          // We can't guarantee that this task will run after the other so we *may* have a queue
          // depth of one.
          XCTAssert(result == .accepted(queueDepth: 0) || result == .accepted(queueDepth: 1))
        }
      }
    }
  }

  func testConsumeBeforeFinish() {
    XCTAsyncTest {
      let source = PassthroughMessageSource<String, TestError>()
      let sequence = PassthroughMessageSequence(consuming: source)

      await withThrowingTaskGroup(of: Void.self) { group in
        group.addTask(priority: .high) {
          let iterator = sequence.makeAsyncIterator()
          await XCTAssertThrowsError(_ = try await iterator.next()) { error in
            XCTAssert(error is TestError)
          }
        }

        group.addTask(priority: .low) {
          let result = source.finish(throwing: TestError())
          // We can't guarantee that this task will run after the other so we *may* have a queue
          // depth of one.
          XCTAssert(result == .accepted(queueDepth: 0) || result == .accepted(queueDepth: 1))
        }
      }
    }
  }
}

fileprivate struct TestError: Error {}

#endif // compiler(>=5.5)