/// <summary>
/// Compute the tree edit distance
/// </summary>
/// <returns>Returns a tuple. The first item is the cost. The second item is the
/// sequence of edit operations</returns>
public EditDistance Compute()
{
GenerateNodes(PreviousTree, CurrentTree);
_l1 = ComputeL(T1, A);
_l2 = ComputeL(T2, B);
_k1 = ComputeK(T1, _l1);
_k2 = ComputeK(T2, _l2);
_treedists = new EditDistance[T1.Length + 1, T2.Length + 1];
_treedists[0, 0] = new EditDistance()
{
Distance = 0
};
foreach (var x in _k1)
{
foreach (var y in _k2)
{
Treedists(x, y);
}
}
return(_treedists[T1.Length, T2.Length]);
}
private void Treedists(int i, int j)
{
var m = i - _l1[i] + 2;
var n = j - _l2[j] + 2;
var fd = new EditDistance[m, n];
fd[0, 0] = new EditDistance()
{
Distance = 0
};
var ioff = _l1[i] - 1;
var joff = _l2[j] - 1;
for (int x = 1; x < m; x++)
{
var edits = new List <Edit>(fd[x - 1, 0].Edits);
var pythonNode = A[x + ioff - 1];
edits.Add(new Delete(pythonNode, pythonNode.Parent));
fd[x, 0] = new EditDistance()
{
Distance = fd[x - 1, 0].Distance + 1, Edits = edits, Mapping = new Dictionary <PythonNode, PythonNode>(fd[x - 1, 0].Mapping)
};
}
for (int y = 1; y < n; y++)
{
var node = B[y - 1 + joff];
var edits = new List <Edit>(fd[0, y - 1].Edits);
edits.Add(new Insert(node, node.Parent));
fd[0, y] = new EditDistance()
{
Distance = fd[0, y - 1].Distance + 1, Edits = edits, Mapping = new Dictionary <PythonNode, PythonNode>(fd[0, y - 1].Mapping)
};
}
for (int x = 1; x < m; x++)
{
for (int y = 1; y < n; y++)
{
if (_l1[i] == _l1[x + ioff] && _l2[j] == _l2[y + joff])
{
var value = Math.Min(Math.Min(fd[x - 1, y].Distance + 1, //cost to remove is 1
fd[x, y - 1].Distance + 1), //cost to insert is 1
fd[x - 1, y - 1].Distance + CostUpdate(A[x + ioff - 1], B[y + joff - 1])); //cost to Edit depends
List <Edit> edits;
Dictionary <PythonNode, PythonNode> mapping;
if (value == fd[x - 1, y].Distance + 1)
{
var node = A[x - 1 + ioff];
edits = new List <Edit>(fd[x - 1, y].Edits)
{
new Delete(node, node.Parent)
};
mapping = new Dictionary <PythonNode, PythonNode>(fd[x - 1, y].Mapping);
}
else if (value == fd[x, y - 1].Distance + 1)
{
var node = B[y - 1 + joff];
edits = new List <Edit>(fd[x, y - 1].Edits)
{
new Insert(node, node.Parent)
};
mapping = new Dictionary <PythonNode, PythonNode>(fd[x, y - 1].Mapping);
}
else
{
edits = new List <Edit>(fd[x - 1, y - 1].Edits);
var oldNode = A[x + ioff - 1];
var newNode = B[y + joff - 1];
if (CostUpdate(oldNode, newNode) > 0)
{
edits.Add(new Update(newNode, oldNode));
}
mapping = new Dictionary <PythonNode, PythonNode>(fd[x - 1, y - 1].Mapping);
if (mapping.ContainsKey(newNode))
{
mapping.Remove(newNode);
}
mapping.Add(newNode, oldNode);
}
fd[x, y] = new EditDistance()
{
Distance = value, Edits = edits, Mapping = mapping
};
_treedists[x + ioff, y + joff] = fd[x, y];
}
else
{
var p = _l1[x + ioff] - 1 - ioff;
var q = _l2[y + joff] - 1 - joff;
var value = Math.Min(fd[p, q].Distance + _treedists[x + ioff, y + joff].Distance,
Math.Min(fd[x - 1, y].Distance + 1, fd[x, y - 1].Distance + 1));
List <Edit> edits;
Dictionary <PythonNode, PythonNode> mapping;
if (value == fd[p, q].Distance + _treedists[x + ioff, y + joff].Distance)
{
edits = new List <Edit>(fd[p, q].Edits);
edits.AddRange(_treedists[x + ioff, y + joff].Edits);
mapping = new Dictionary <PythonNode, PythonNode>(fd[p, q].Mapping);
foreach (var keyValuePair in _treedists[x + ioff, y + joff].Mapping)
{
//todo there is problem a bug here
//it should check whether the maps come from each one of them.
if (mapping.ContainsKey(keyValuePair.Key))
{
mapping.Remove(keyValuePair.Key);
}
PythonNode key = null;
foreach (var keyValue in mapping)
{
if (keyValue.Value.Equals(keyValuePair.Value))
{
key = keyValue.Key;
}
}
if (key != null)
{
mapping.Remove(key);
}
mapping.Add(keyValuePair.Key, keyValuePair.Value);
}
}
else if (value == fd[x - 1, y].Distance + 1)
{
edits = new List <Edit>(fd[x - 1, y].Edits);
var pythonNode = A[x - 1 + ioff];
edits.Add(new Delete(pythonNode, pythonNode.Parent));
mapping = new Dictionary <PythonNode, PythonNode>(fd[x - 1, y].Mapping);
}
else
{
edits = new List <Edit>(fd[x, y - 1].Edits);
var pythonNode = B[y - 1 + joff];
edits.Add(new Insert(pythonNode, pythonNode.Parent));
mapping = new Dictionary <PythonNode, PythonNode>(fd[x, y - 1].Mapping);
}
fd[x, y] = new EditDistance()
{
Distance = value, Edits = edits, Mapping = mapping
};
}
}
}
}
