【愚公系列】2021年12月 二十三种设计模式(十三)-职责链模式(Chain of Responsibility Pattern)

public class LeaveRequest {
    public int Days { get; set; }
    public string Name { get; set; }
    public LeaveRequest(int days, string name) {
        Days = days;
        Name = name;
    }
}

public abstract class Leader {
    protected string Name { get; set; }
    protected Leader(string name) {
        this.Name = name;
    }
    public static LeaderChain Chain { protected get; set; }
    public abstract void ProcessRequest(LeaveRequest request);
    protected void Delivery(LeaveRequest request) {
        Chain.DoChain(request);
    }
}

public class Manager : Leader {
    public Manager(string name) : base(name) { }
    public override void ProcessRequest(LeaveRequest request) {
        if (request.Days <= 2) {
            Console.WriteLine($"{this.Name} approved {request.Name}'s " +
                                $"leave request for {request.Days} days!");
            return;
        }
        Delivery(request);
    }
}

public class Inspector : Leader {
    public Inspector(string name) : base(name) { }
    public override void ProcessRequest(LeaveRequest request) {
        if (request.Days <= 4) {
            Console.WriteLine($"{this.Name} approved {request.Name}'s " +
                                $"leave request for {request.Days} days!");
            return;
        }
        Delivery(request);
    }
}

public class President : Leader {
    public President(string name) : base(name) { }
    public override void ProcessRequest(LeaveRequest request) {
        if (request.Days <= 8) {
            Console.WriteLine($"{this.Name} approved {request.Name}'s " +
                                $"leave request for {request.Days} days!");
            return;
        }
        Delivery(request);
    }
}

public class Directorate : Leader {
    public Directorate(string name) : base(name) { }
    public override void ProcessRequest(LeaveRequest request) {
        if (request.Days > 8) {
            Console.WriteLine($"{this.Name} approved {request.Name}'s " +
                                $"leave request for {request.Days} days!");
            return;
        }
        Delivery(request);
    }
}

public class LeaderChain {
    private List<Leader> _leaders = new List<Leader>();
    private int _cursor = 0;
    public void Attach(Leader leader) {
        if (leader == null) throw new ArgumentNullException();
        _leaders.Add(leader);
    }
    public bool Detach(Leader leader) {
        if (leader == null) throw new ArgumentNullException();
        return _leaders.Remove(leader);
    }
    public void DoChain(LeaveRequest request) {
        if (_cursor <= _leaders.Count - 2) {
            _leaders[++_cursor].ProcessRequest(request);
        }
        _cursor = 0;
    }
}

public class Program {
    public static void Main(string[] args) {
        var leaders = new List<Leader>{
            new Manager("Tom"),
            new Inspector("Juice"),
            new President("Iori"),
            new Directorate("Marin")
        };
        var chain = new LeaderChain();
        foreach (var leader in leaders) {
            chain.Attach(leader);
        }
        Leader.Chain = chain;
        var requests = new List<LeaveRequest> {
            new LeaveRequest(1, "Zhao"),
            new LeaveRequest(3, "Qian"),
            new LeaveRequest(5, "Sun"),
            new LeaveRequest(7, "Li"),
            new LeaveRequest(12, "Zhou")
        };
        foreach (var request in requests) {
            leaders[0].ProcessRequest(request);
        }
        Console.ReadKey();
    }
}

Tom approved Zhao's leave request for 1 days!
Juice approved Qian's leave request for 3 days!
Iori approved Sun's leave request for 5 days!
Iori approved Li's leave request for 7 days!
Marin approved Zhou's leave request for 12 days!