//-----------------------------------------------------------------------------
//
// Copyright (C) Microsoft Corporation.  All Rights Reserved.
//
//-----------------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Microsoft.Cci;
using Microsoft.Cci.MetadataReader;
using Microsoft.Cci.MutableCodeModel;
using Microsoft.Cci.Contracts;
using Microsoft.Cci.ILToCodeModel;

using Bpl = Microsoft.Boogie;
using System.Diagnostics.Contracts;


namespace BytecodeTranslator
{
  public class StatementTraverser : BaseCodeTraverser {

    public readonly TraverserFactory factory;

    readonly Sink sink;

    private readonly Bpl.Variable HeapVariable;

    public readonly Bpl.StmtListBuilder StmtBuilder = new Bpl.StmtListBuilder();

    #region Constructors
    public StatementTraverser(Sink sink) {
      this.sink = sink;
      this.factory = sink.Factory;
      HeapVariable = sink.HeapVariable;
    }
    #endregion

    #region Helper Methods

    Bpl.Expr ExpressionFor(IExpression expression) {
      ExpressionTraverser etrav = this.factory.MakeExpressionTraverser(this.sink, this);
      etrav.Visit(expression);
      Contract.Assert(etrav.TranslatedExpressions.Count == 1);
      return etrav.TranslatedExpressions.Pop();
    }

    #endregion

    public override void Visit(IBlockStatement block) {
      Bpl.StmtListBuilder slb = new Bpl.StmtListBuilder();

      foreach (IStatement st in block.Statements) {
        this.Visit(st);
      }
    }

    #region Basic Statements

    public override void Visit(IAssertStatement assertStatement) {
      StmtBuilder.Add(
        new Bpl.AssertCmd(assertStatement.Token(), ExpressionFor(assertStatement.Condition))
        );
    }

    public override void Visit(IAssumeStatement assumeStatement) {
      StmtBuilder.Add(
        new Bpl.AssertCmd(assumeStatement.Token(), ExpressionFor(assumeStatement.Condition))
        );
    }

    /// <summary>
    /// 
    /// </summary>
    /// <remarks>(mschaef) Works, but still a stub</remarks>
    /// <param name="conditionalStatement"></param>
    public override void Visit(IConditionalStatement conditionalStatement) {
      StatementTraverser thenTraverser = this.factory.MakeStatementTraverser(this.sink);
      StatementTraverser elseTraverser = this.factory.MakeStatementTraverser(this.sink);

      ExpressionTraverser condTraverser = this.factory.MakeExpressionTraverser(this.sink, null);
      condTraverser.Visit(conditionalStatement.Condition);
      thenTraverser.Visit(conditionalStatement.TrueBranch);
      elseTraverser.Visit(conditionalStatement.FalseBranch);

      Bpl.IfCmd ifcmd = new Bpl.IfCmd(conditionalStatement.Token(),
          condTraverser.TranslatedExpressions.Pop(),
          thenTraverser.StmtBuilder.Collect(conditionalStatement.TrueBranch.Token()),
          null,
          elseTraverser.StmtBuilder.Collect(conditionalStatement.FalseBranch.Token())
          );

      StmtBuilder.Add(ifcmd);

    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="expressionStatement"></param>
    /// <remarks> TODO: might be wrong for the general case</remarks>
    public override void Visit(IExpressionStatement expressionStatement) {

      ExpressionTraverser etrav = this.factory.MakeExpressionTraverser(this.sink, this);
      etrav.Visit(expressionStatement.Expression);
    }

    /// <summary>
    /// 
    /// </summary>
    /// <remarks>(mschaef) Not Implemented</remarks>
    /// <param name="breakStatement"></param>
    public override void Visit(IBreakStatement breakStatement) {
      StmtBuilder.Add(new Bpl.BreakCmd(breakStatement.Token(), "I dont know"));
    }

    /// <summary>
    /// If the local declaration has an initial value, then generate the
    /// statement "loc := e" from it. Otherwise ignore it.
    /// </summary>
    public override void Visit(ILocalDeclarationStatement localDeclarationStatement) {
      if (localDeclarationStatement.InitialValue == null) return;
      var loc = this.sink.FindOrCreateLocalVariable(localDeclarationStatement.LocalVariable);
      var tok = localDeclarationStatement.Token();
      var e = ExpressionFor(localDeclarationStatement.InitialValue);
      StmtBuilder.Add(Bpl.Cmd.SimpleAssign(tok, new Bpl.IdentifierExpr(tok, loc), e));
      return;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <remarks>(mschaef) not implemented</remarks>
    /// <param name="returnStatement"></param>
    public override void Visit(IReturnStatement returnStatement) {
      Bpl.IToken tok = returnStatement.Token();

      if (returnStatement.Expression != null) {
        ExpressionTraverser etrav = this.factory.MakeExpressionTraverser(this.sink, this);
        etrav.Visit(returnStatement.Expression);

        if (this.sink.RetVariable == null || etrav.TranslatedExpressions.Count < 1) {
          throw new TranslationException(String.Format("{0} returns a value that is not supported by the function", returnStatement.ToString()));
        }

        StmtBuilder.Add(Bpl.Cmd.SimpleAssign(tok,
            new Bpl.IdentifierExpr(tok, this.sink.RetVariable), etrav.TranslatedExpressions.Pop()));
      }
      StmtBuilder.Add(new Bpl.ReturnCmd(returnStatement.Token()));
    }
    #endregion

    #region Goto and Labels

    /// <summary>
    /// 
    /// </summary>
    /// <remarks> STUB </remarks>
    /// <param name="gotoStatement"></param>
    public override void Visit(IGotoStatement gotoStatement) {
      String[] target = new String[1] { gotoStatement.TargetStatement.Label.Value };

      Bpl.GotoCmd gotocmd = new Microsoft.Boogie.GotoCmd(gotoStatement.Token(), new Bpl.StringSeq(target));

      StmtBuilder.Add(gotocmd);
    }

    /// <summary>
    /// 
    /// </summary>
    /// <remarks> (mschaef) not sure if there is more work to do</remarks>
    /// <param name="labeledStatement"></param>
    public override void Visit(ILabeledStatement labeledStatement) {
      StmtBuilder.AddLabelCmd(labeledStatement.Label.Value);
      base.Visit(labeledStatement.Statement);
    }

    #endregion

    #region Looping Statements

    public override void Visit(IWhileDoStatement whileDoStatement) {
      throw new NotImplementedException("While Statements are not implemented");
    }



    #endregion

  }

}