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>
  /// Iterates in reverse order (due to performance reasons) over the type vector using the code on the exec stack.If the vector isn't empty, expands to:
  /// ((first vector) (top-item :exec state) (rest vector) exec_do*vector_type (top-item :exec state) rest_of_program)
  /// </summary>
  /// <typeparam name="T"></typeparam>
  [StorableClass]
  public abstract class VectorIterateExpression<T> : StatelessExpression {
    protected VectorIterateExpression() { }
    [StorableConstructor]
    protected VectorIterateExpression(bool deserializing) : base(deserializing) { }

    protected bool IsNoop(IInternalPushInterpreter interpter, IPushStack<IReadOnlyList<T>> vectorStack) {
      return vectorStack.IsEmpty || interpter.ExecStack.IsEmpty;
    }

    protected void Eval(IInternalPushInterpreter interpter, IPushStack<IReadOnlyList<T>> vectorStack, IPushStack<T> literalStack) {
      var vector = vectorStack.Top;

      if (vector.Count == 0) {
        interpter.ExecStack.Pop();
        vectorStack.Pop();
      } else if (vector.Count == 1) {
        literalStack.Push(vector[0]);
        vectorStack.Pop();
      } else {
        interpter.ExecStack.Push(this, interpter.ExecStack.Top);

        var last = vector.Count - 1;
        literalStack.Push(vector[last]);

        var list = vector as List<T>;
        if (list != null) {
          var newTop = new T[last];
          list.CopyTo(0, newTop, 0, last);
          vectorStack.Top = newTop;
          return;
        }

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

        vectorStack.Top = vector.Take(last).ToList();
      }
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.IntegerVector,
    "INTEGER[].ITERATE",
    "Iterates in reverse order (due to performance reasons) over the top INTEGER[] using the top item of the EXEC stack.",
    StackTypes.Integer | StackTypes.Exec,
    requiredBlockCount: 1)]
  public class IntegerVectorIterateExpression : VectorIterateExpression<long> {
    public IntegerVectorIterateExpression() { }
    [StorableConstructor]
    protected IntegerVectorIterateExpression(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, interpreter.IntegerStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.FloatVector,
    "FLOAT[].ITERATE",
    "Iterates in reverse order (due to performance reasons) over the top FLOAT[] using the top item of the EXEC stack.",
    StackTypes.Float | StackTypes.Exec, requiredBlockCount: 1)]
  public class FloatVectorIterateExpression : VectorIterateExpression<double> {
    public FloatVectorIterateExpression() { }
    [StorableConstructor]
    protected FloatVectorIterateExpression(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, interpreter.FloatStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.BooleanVector,
    "BOOLEAN[].ITERATE",
    "Iterates in reverse order (due to performance reasons) over the top BOOLEAN[] using the top item of the EXEC stack.",
    StackTypes.Boolean | StackTypes.Exec, requiredBlockCount: 1)]
  public class BooleanVectorIterateExpression : VectorIterateExpression<bool> {
    public BooleanVectorIterateExpression() { }
    [StorableConstructor]
    protected BooleanVectorIterateExpression(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, interpreter.BooleanStack);
    }
  }

  [StorableClass]
  [PushExpression(
    StackTypes.StringVector,
    "STRING[].ITERATE",
    "Iterates in reverse order (due to performance reasons) over the top STRING[] using the top item of the EXEC stack.",
    StackTypes.String | StackTypes.Exec, requiredBlockCount: 1)]
  public class StringVectorIterateExpression : VectorIterateExpression<string> {
    public StringVectorIterateExpression() { }
    [StorableConstructor]
    protected StringVectorIterateExpression(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, interpreter.StringStack);
    }
  }
}