using System.Collections.Generic;

namespace HeuristicLab.Problems.ProgramSynthesis.Push.Expressions {
  using System;
  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 subvec of the top item on the type stack.
  /// </summary>
  /// <typeparam name="T"></typeparam>
  [StorableClass]
  public abstract class VectorSubExpression<T> : StatelessExpression {
    protected VectorSubExpression() { }
    [StorableConstructor]
    protected VectorSubExpression(bool deserializing) : base(deserializing) { }

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

    protected void Eval(IInternalPushInterpreter interpreter, IPushStack<IReadOnlyList<T>> vectorStack) {
      var first = (int)Math.Min(vectorStack.Top.Count, Math.Max(0, interpreter.IntegerStack[1]));
      var second = (int)Math.Min(vectorStack.Top.Count, Math.Max(first, interpreter.IntegerStack.Top));
      interpreter.IntegerStack.Remove(2);

      if (vectorStack.Top.Count == 0)
        return;

      var vector = vectorStack.Top;
      var list = vector as List<T>;
      var lenght = second - first;

      if (list != null) {
        var newTop = new T[lenght];
        list.CopyTo(first, newTop, 0, lenght);
        vectorStack.Top = newTop;
        return;
      }

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

      vectorStack.Top = vector.Skip(first).Take(lenght).ToList();
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.IntegerVector,
    "INTEGER[].SUB",
    "Pushes the sub vector of the top INTEGER[].",
    StackTypes.Integer)]
  public class IntegerVectorSubExpression : VectorSubExpression<long> {
    public IntegerVectorSubExpression() { }
    [StorableConstructor]
    protected IntegerVectorSubExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.FloatVector,
    "FLOAT[].SUB",
    "Pushes the sub vector of the top FLOAT[].",
    StackTypes.Integer)]
  public class FloatVectorSubExpression : VectorSubExpression<double> {
    public FloatVectorSubExpression() { }
    [StorableConstructor]
    protected FloatVectorSubExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.BooleanVector,
    "BOOLEAN[].SUB",
    "Pushes the sub vector of the top BOOLEAN[].",
    StackTypes.Integer)]
  public class BooleanVectorSubExpression : VectorSubExpression<bool> {
    public BooleanVectorSubExpression() { }
    [StorableConstructor]
    protected BooleanVectorSubExpression(bool deserializing) : base(deserializing) { }

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

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

  [StorableClass]
  [PushExpression(
    StackTypes.StringVector,
    "STRING[].SUB",
    "Pushes the sub vector of the top STRING[].",
    StackTypes.Integer)]
  public class StringVectorSubExpression : VectorSubExpression<string> {
    public StringVectorSubExpression() { }
    [StorableConstructor]
    protected StringVectorSubExpression(bool deserializing) : base(deserializing) { }

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

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