namespace HeuristicLab.Problems.ProgramSynthesis.Push.Expressions {
  using System;
  using System.Collections.Generic;
  using System.Linq;

  using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Attributes;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Interpreter;
  using HeuristicLab.Problems.ProgramSynthesis.Push.Stack;

  /// <summary>
  /// Takes the rest of the top item on the type stack.
  /// </summary>
  /// <typeparam name="T"></typeparam>
  [StorableClass]
  public abstract class VectorRestExpression<T> : StatelessExpression {
    protected VectorRestExpression() { }
    [StorableConstructor]
    protected VectorRestExpression(bool deserializing) : base(deserializing) { }

    protected bool IsNoop(IPushStack<IReadOnlyList<T>> vectorStack) {
      return vectorStack.IsEmpty || vectorStack.Top.Count < 2;
    }

    protected void Eval(IPushStack<IReadOnlyList<T>> vectorStack) {
      var vector = vectorStack.Top;
      var list = vector as List<T>;
      var newLength = vector.Count - 1;
      if (list != null) {
        var newTop = new T[newLength];
        list.CopyTo(1, newTop, 0, newLength);
        vectorStack.Top = newTop;
        return;
      }

      var array = vector as T[];
      if (array != null) {
        var newTop = new T[newLength];
        Array.Copy(array, 1, newTop, 0, newLength);
        vectorStack.Top = newTop;
        return;
      }

      vectorStack.Top = vector.Skip(1).ToList();
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.IntegerVector,
    "INTEGER[].REST",
    "Removes the first item of the top INTEGER[].")]
  public class IntegerVectorRestExpression : VectorRestExpression<long> {
    public IntegerVectorRestExpression() { }
    [StorableConstructor]
    protected IntegerVectorRestExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.IntegerVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.IntegerVectorStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.FloatVector,
    "FLOAT[].REST",
    "Removes the first item of the top FLOAT[].")]
  public class FloatVectorRestExpression : VectorRestExpression<double> {
    public FloatVectorRestExpression() { }
    [StorableConstructor]
    protected FloatVectorRestExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.FloatVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.FloatVectorStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.BooleanVector,
    "BOOLEAN[].REST",
    "Removes the first item of the top BOOLEAN[].")]
  public class BooleanVectorRestExpression : VectorRestExpression<bool> {
    public BooleanVectorRestExpression() { }
    [StorableConstructor]
    protected BooleanVectorRestExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.BooleanVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.BooleanVectorStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.StringVector,
    "STRING[].REST",
    "Removes the first item of the top STRING[].")]
  public class StringVectorRestExpression : VectorRestExpression<string> {
    public StringVectorRestExpression() { }
    [StorableConstructor]
    protected StringVectorRestExpression(bool deserializing) : base(deserializing) { }

    public override bool IsNoop(IInternalPushInterpreter interpreter) {
      return IsNoop(interpreter.StringVectorStack);
    }

    public override void Eval(IInternalPushInterpreter interpreter) {
      Eval(interpreter.StringVectorStack);
    }
  }
}