Sources/ApacheBeam/Core/Fn/ClosureFn.swift

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import Foundation

/// A SerializableFn that holds a reference to a function that takes a single input and produces a variable number of outputs
public final class ClosureFn: SerializableFn {
    let processClosure: (SerializableFnBundleContext, [AnyPCollectionStream], [AnyPCollectionStream]) async throws -> Void

    public init<Of>(_ fn: @Sendable @escaping (PCollection<Of>.Stream) async throws -> Void) {
        processClosure = { _, inputs, _ in
            try await fn(inputs[0].stream())
        }
    }

    public init<Of, O0>(_ fn: @Sendable @escaping (PCollection<Of>.Stream, PCollection<O0>.Stream) async throws -> Void) {
        processClosure = { _, inputs, outputs in
            try await fn(inputs[0].stream(), outputs[0].stream())
        }
    }

    public init<Of, O0, O1>(_ fn: @Sendable @escaping (PCollection<Of>.Stream, PCollection<O0>.Stream, PCollection<O1>.Stream) async throws -> Void) {
        processClosure = { _, inputs, outputs in
            try await fn(inputs[0].stream(), outputs[0].stream(), outputs[1].stream())
        }
    }

    public init<Of, O0, O1, O2>(_ fn: @Sendable @escaping (PCollection<Of>.Stream, PCollection<O0>.Stream, PCollection<O1>.Stream, PCollection<O2>.Stream) async throws -> Void) {
        processClosure = { _, inputs, outputs in
            try await fn(inputs[0].stream(), outputs[0].stream(), outputs[1].stream(), outputs[2].stream())
        }
    }

    public init<Of, O0, O1, O2, O3>(_ fn: @Sendable @escaping (PCollection<Of>.Stream, PCollection<O0>.Stream, PCollection<O1>.Stream, PCollection<O2>.Stream, PCollection<O3>.Stream) async throws -> Void) {
        processClosure = { _, inputs, outputs in
            try await fn(inputs[0].stream(), outputs[0].stream(), outputs[1].stream(), outputs[2].stream(), outputs[3].stream())
        }
    }

    public func process(context: SerializableFnBundleContext, inputs: [AnyPCollectionStream], outputs: [AnyPCollectionStream]) async throws -> (String, String) {
        try await processClosure(context, inputs, outputs)
        outputs.finish()
        return (context.instruction, context.transform)
    }
}