/// <summary>
/// Diff two JSON objects.
///
/// The output is a JObject that contains enough information to represent the
/// delta between the two objects and to be able perform patch and reverse operations.
/// </summary>
/// <param name="left">The base JSON object</param>
/// <param name="right">The JSON object to compare against the base</param>
/// <returns>JSON Patch Document</returns>
public JToken Diff(JToken left, JToken right)
{
var objectHash = this._options.ObjectHash;
var itemMatch = new DefaultItemMatch(objectHash);
if (left == null)
{
left = new JValue("");
}
if (right == null)
{
right = new JValue("");
}
if (left.Type == JTokenType.Object && right.Type == JTokenType.Object)
{
return(ObjectDiff((JObject)left, (JObject)right));
}
if (_options.ArrayDiff == ArrayDiffMode.Efficient &&
left.Type == JTokenType.Array &&
right.Type == JTokenType.Array)
{
return(ArrayDiff((JArray)left, (JArray)right));
}
if (_options.TextDiff == TextDiffMode.Efficient &&
left.Type == JTokenType.String &&
right.Type == JTokenType.String &&
(left.ToString().Length > _options.MinEfficientTextDiffLength || right.ToString().Length > _options.MinEfficientTextDiffLength))
{
var dmp = new diff_match_patch();
List <Patch> patches = dmp.patch_make(left.ToObject <string>(), right.ToObject <string>());
return(patches.Any()
? new JArray(dmp.patch_toText(patches), 0, (int)DiffOperation.TextDiff)
: null);
}
if (!itemMatch.Match(left, right))
{
return(new JArray(left, right));
}
return(null);
}
private JObject ArrayDiff(JArray left, JArray right)
{
var objectHash = this._options.ObjectHash;
var itemMatch = new DefaultItemMatch(objectHash);
var result = JObject.Parse(@"{ ""_t"": ""a"" }");
int commonHead = 0;
int commonTail = 0;
if (itemMatch.Match(left, right))
{
return(null);
}
var childContext = new List <JToken>();
// Find common head
while (commonHead < left.Count &&
commonHead < right.Count &&
itemMatch.Match(left[commonHead], right[commonHead]))
{
var index = commonHead;
var child = Diff(left[index], right[index]);
if (child != null)
{
result[$"{index}"] = child;
}
commonHead++;
}
// Find common tail
while (commonTail + commonHead < left.Count &&
commonTail + commonHead < right.Count &&
itemMatch.Match(left[left.Count - 1 - commonTail], right[right.Count - 1 - commonTail]))
{
var index1 = left.Count - 1 - commonTail;
var index2 = right.Count - 1 - commonTail;
var child = Diff(left[index1], right[index2]);
if (child != null)
{
result[$"{index2}"] = child;
}
commonTail++;
}
if (commonHead + commonTail == left.Count)
{
// Trivial case, a block (1 or more consecutive items) was added
for (int index = commonHead; index < right.Count - commonTail; ++index)
{
result[$"{index}"] = new JArray(right[index]);
}
return(result);
}
if (commonHead + commonTail == right.Count)
{
// Trivial case, a block (1 or more consecutive items) was removed
for (int index = commonHead; index < left.Count - commonTail; ++index)
{
if (result.ContainsKey(index.ToString()))
{
result.Remove(index.ToString());
}
result[$"_{index}"] = new JArray(left[index], 0, (int)DiffOperation.Deleted);
}
return(result);
}
// Complex Diff, find the LCS (Longest Common Subsequence)
List <JToken> trimmedLeft = left.ToList().GetRange(commonHead, left.Count - commonTail - commonHead);
List <JToken> trimmedRight = right.ToList().GetRange(commonHead, right.Count - commonTail - commonHead);
Lcs lcs = Lcs.Get(trimmedLeft, trimmedRight, itemMatch);
for (int index = commonHead; index < left.Count - commonTail; ++index)
{
if (lcs.Indices1.IndexOf(index - commonHead) < 0)
{
// Removed
if (result.ContainsKey(index.ToString()))
{
result.Remove(index.ToString());
}
result[$"_{index}"] = new JArray(left[index], 0, (int)DiffOperation.Deleted);
}
}
for (int index = commonHead; index < right.Count - commonTail; index++)
{
int indexRight = lcs.Indices2.IndexOf(index - commonHead);
if (indexRight < 0)
{
// Added
result[$"{index}"] = new JArray(right[index]);
}
else
{
int li = lcs.Indices1[indexRight] + commonHead;
int ri = lcs.Indices2[indexRight] + commonHead;
JToken diff = Diff(left[li], right[ri]);
if (diff != null)
{
result[$"{index}"] = diff;
}
}
}
return(result);
}
