using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;

namespace Cosmos.IL2CPU {
  public class ILScanner {
    //Note: We have both HashSet and List because HashSet.Contains is much faster
    // than List.Contains. Also in the future we may remove items from the List
    // which have already been processed yet need to keep them in HashSet.
    //TODO: When we go threaded, these two should be encapselated into a single
    // class with thread safety.
    //TODO: These store the MethodBase which also have the IL for the body in memory
    // For large asms this could eat lot of RAM. Should convert this to remove
    // items from the list after they are processed but keep them in HashSet so we
    // know they are already done. Currently HashSet uses a refernece though, so we
    // need to hash on some UID instead of the refernce. Do not use strings, they are
    // super slow.
    private HashSet<MethodBase> mMethodsSet = new HashSet<MethodBase>();
    private List<MethodBase> mMethods = new List<MethodBase>();
    private HashSet<Type> mTypesSet = new HashSet<Type>();
    private List<Type> mTypes = new List<Type>();
    protected ILReader mReader;

    public ILScanner(Type aAssemblerBaseOp) {
      mReader = new ILReader(aAssemblerBaseOp);
    }

    public void Execute(MethodInfo aEntry) {
      // IL Operations implicitly require these types
      QueueType(typeof(string));
      QueueType(typeof(int));

      QueueMethod(aEntry);

      // Cannot use foreach, the list changes as we go
      for (int i = 0; i < mMethods.Count; i++) {
        ScanMethod(mMethods[i]);
      }
    }

    private void ScanMethod(MethodBase aMethodBase) {
      if ((aMethodBase.Attributes & MethodAttributes.PinvokeImpl) != 0) {
        // pinvoke methods dont have an embedded implementation
        return;
      } else if (aMethodBase.IsAbstract) {
        // abstract methods dont have an implementation
        return;
      }

      var xImplFlags = aMethodBase.GetMethodImplementationFlags();
      if ((xImplFlags & MethodImplAttributes.Native) != 0) {
        // native implementations cannot be compiled
        return;
      }

      var xOpCodes = mReader.ProcessMethod(aMethodBase);
      if (xOpCodes != null) {
        foreach (var xOpCode in xOpCodes) {
          //InstructionCount++;
          //xOpCode.Scan(xReader, this);
        }
      }
    }

    public void QueueMethod(MethodBase aMethod) {
      if (!mMethodsSet.Contains(aMethod)) {
        mMethodsSet.Add(aMethod);
        mMethods.Add(aMethod);
        QueueType(aMethod.DeclaringType);
      }
    }

    public void QueueType(Type aType) {
      if (aType != null) {
        if (!mTypesSet.Contains(aType)) {
          mTypesSet.Add(aType);
          mTypes.Add(aType);
          QueueType(aType.BaseType);
          foreach (var xMethod in aType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)) {
            if (xMethod.DeclaringType == aType) {
              if (xMethod.IsVirtual) {
                QueueMethod(xMethod);
              }
            }
          }
        }
      }
    }

    public int MethodCount {
      get {
        return mMethods.Count;
      }
    }

  }
}