FutureExChain.swift

import NIO

extension EventLoop {
    func chain<V0>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>
    ) -> EventLoopFuture<V0> {
        self.tryFlatSubmit { try v0() }
    }

    func chain<V0, V1>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>,
        _ v1: @escaping (V0) throws -> EventLoopFuture<V1>
    ) -> EventLoopFuture<(V0, V1)> {
        self.tryFlatSubmit { try v0() }.flatMap { (v0) in
            self.tryFlatSubmit { try v1(v0) }.map { (v1) in
                (v0, v1)
            }
        }
    }

    func chain<V0, V1, V2>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>,
        _ v1: @escaping (V0) throws -> EventLoopFuture<V1>,
        _ v2: @escaping (V0, V1) throws -> EventLoopFuture<V2>
    ) -> EventLoopFuture<(V0, V1, V2)> {
        self.tryFlatSubmit { try v0() }.flatMap { (v0) in
            self.tryFlatSubmit { try v1(v0) }.flatMap { (v1) in
                self.tryFlatSubmit { try v2(v0, v1) }.map { (v2) in
                    (v0, v1, v2)
                }
            }
        }
    }

    func chain<V0, V1, V2, V3>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>,
        _ v1: @escaping (V0) throws -> EventLoopFuture<V1>,
        _ v2: @escaping (V0, V1) throws -> EventLoopFuture<V2>,
        _ v3: @escaping (V0, V1, V2) throws -> EventLoopFuture<V3>
    ) -> EventLoopFuture<(V0, V1, V2, V3)> {
        self.tryFlatSubmit { try v0() }.flatMap { (v0) in
            self.tryFlatSubmit { try v1(v0) }.flatMap { (v1) in
                self.tryFlatSubmit { try v2(v0, v1) }.flatMap { (v2) in
                    self.tryFlatSubmit { try v3(v0, v1, v2) }.map { (v3) in
                        (v0, v1, v2, v3)
                    }
                }
            }
        }
    }

    func chain<V0, V1, V2, V3, V4>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>,
        _ v1: @escaping (V0) throws -> EventLoopFuture<V1>,
        _ v2: @escaping (V0, V1) throws -> EventLoopFuture<V2>,
        _ v3: @escaping (V0, V1, V2) throws -> EventLoopFuture<V3>,
        _ v4: @escaping (V0, V1, V2, V3) throws -> EventLoopFuture<V4>
    ) -> EventLoopFuture<(V0, V1, V2, V3, V4)> {
        self.tryFlatSubmit { try v0() }.flatMap { (v0) in
            self.tryFlatSubmit { try v1(v0) }.flatMap { (v1) in
                self.tryFlatSubmit { try v2(v0, v1) }.flatMap { (v2) in
                    self.tryFlatSubmit { try v3(v0, v1, v2) }.flatMap { (v3) in
                        self.tryFlatSubmit { try v4(v0, v1, v2, v3) }.map { (v4) in
                            (v0, v1, v2, v3, v4)
                        }
                    }
                }
            }
        }
    }

    func chain<V0, V1, V2, V3, V4, V5>(
        _ v0: @escaping () throws -> EventLoopFuture<V0>,
        _ v1: @escaping (V0) throws -> EventLoopFuture<V1>,
        _ v2: @escaping (V0, V1) throws -> EventLoopFuture<V2>,
        _ v3: @escaping (V0, V1, V2) throws -> EventLoopFuture<V3>,
        _ v4: @escaping (V0, V1, V2, V3) throws -> EventLoopFuture<V4>,
        _ v5: @escaping (V0, V1, V2, V3, V4) throws -> EventLoopFuture<V5>
    ) -> EventLoopFuture<(V0, V1, V2, V3, V4, V5)> {
        self.tryFlatSubmit { try v0() }.flatMap { (v0) in
            self.tryFlatSubmit { try v1(v0) }.flatMap { (v1) in
                self.tryFlatSubmit { try v2(v0, v1) }.flatMap { (v2) in
                    self.tryFlatSubmit { try v3(v0, v1, v2) }.flatMap { (v3) in
                        self.tryFlatSubmit { try v4(v0, v1, v2, v3) }.flatMap { (v4) in
                            self.tryFlatSubmit { try v5(v0, v1, v2, v3, v4) }.map { (v5) in
                                (v0, v1, v2, v3, v4, v5)
                            }
                        }
                    }
                }
            }
        }
    }
}