/// <summary>
/// Initializes a new instance of the <see cref="StringDifferences" /> class.
/// </summary>
/// <param name="a">The 'A' string.</param>
/// <param name="offsetA">The offset to the start of a window in the first string.</param>
/// <param name="lengthA">The length of the window in the first string.</param>
/// <param name="b">The 'B' string.</param>
/// <param name="offsetB">The offset to the start of a window in the second string.</param>
/// <param name="lengthB">The length of the window in the second string.</param>
/// <param name="textOptions">The text options.</param>
/// <param name="comparer">The character comparer.</param>
/// <exception cref="ArgumentNullException"><paramref name="a" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="b" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="comparer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentOutOfRangeException">The <paramref name="offsetA" /> is out of range.</exception>
/// <exception cref="ArgumentOutOfRangeException">The <paramref name="lengthA" /> is out of range.</exception>
/// <exception cref="ArgumentOutOfRangeException">The <paramref name="offsetB" /> is out of range.</exception>
/// <exception cref="ArgumentOutOfRangeException">The <paramref name="lengthB" /> is out of range.</exception>
/// <exception cref="Exception">The <paramref name="comparer" /> throws an exception.</exception>
internal StringDifferences(
[NotNull] string a,
int offsetA,
int lengthA,
[NotNull] string b,
int offsetB,
int lengthB,
TextOptions textOptions,
[NotNull] Func <char, char, bool> comparer)
{
if (a == null)
{
throw new ArgumentNullException(nameof(a));
}
if (b == null)
{
throw new ArgumentNullException(nameof(b));
}
if (comparer == null)
{
throw new ArgumentNullException(nameof(comparer));
}
A = a;
B = b;
if (textOptions != TextOptions.None)
{
// Wrap the comparer with an additional check to handle special characters.
Func <char, char, bool> oc = comparer;
if (textOptions.HasFlag(TextOptions.IgnoreWhiteSpace))
{
// Ignore white space - treat all whitespace as the same (note this will handle line endings too).
comparer = (x, y) => char.IsWhiteSpace(x) ? char.IsWhiteSpace(y) : oc(x, y);
}
else if (textOptions.HasFlag(TextOptions.NormalizeLineEndings))
{
// Just normalize line endings - treat '\r' and '\n\ as the same
comparer = (x, y) => x == '\r' || x == '\n' ? y == '\r' || y == '\n' : oc(x, y);
}
}
// Map strings based on text options
StringMap aMap = a.ToMapped(textOptions);
StringMap bMap = b.ToMapped(textOptions);
// Perform diff on mapped string
Differences <char> chunks = aMap.Diff(bMap, comparer);
// Special case simple equality
if (chunks.Count < 2)
{
Chunk <char> chunk = chunks.Single();
// ReSharper disable once PossibleNullReferenceException
_chunks = new[] { new StringChunk(chunk.AreEqual, a, 0, b, 0) };
return;
}
// To reverse the mapping we first calculate the split points in the original strings, and find
// the last reference to the original strings in each chunk.
int[] aEnds = new int[chunks.Count];
int[] bEnds = new int[chunks.Count];
int lastA = 0;
int lastB = 0;
for (int i = 0; i < chunks.Count; i++)
{
Chunk <char> chunk = chunks[i];
ReadOnlyWindow <char> chunkA = chunk.A;
ReadOnlyWindow <char> chunkB = chunk.B;
if (chunk.A != null)
{
aEnds[i] = aMap.GetOriginalIndex(chunkA.Offset + chunkA.Count - 1) + 1;
lastA = i;
}
else
{
aEnds[i] = -1;
}
if (chunk.B != null)
{
bEnds[i] = bMap.GetOriginalIndex(chunkB.Offset + chunkB.Count - 1) + 1;
lastB = i;
}
else
{
bEnds[i] = -1;
}
}
// Now we're ready to build up a new chunk array based on the original strings
StringChunk[] stringChunks = new StringChunk[chunks.Count];
int aStart = 0;
int bStart = 0;
for (int i = 0; i < chunks.Count; i++)
{
int aEnd = i == lastA ? aMap.OriginalCount : aEnds[i];
int bEnd = i == lastB ? bMap.OriginalCount : bEnds[i];
string ac = aEnd > -1 ? a.Substring(aStart, aEnd - aStart) : null;
string bc = bEnd > -1 ? b.Substring(bStart, bEnd - bStart) : null;
stringChunks[i] = new StringChunk(chunks[i].AreEqual, ac, aEnd > -1 ? aStart : -1, bc, bEnd > -1 ? bStart : -1);
if (aEnd > -1)
{
aStart = aEnd;
}
if (bEnd > -1)
{
bStart = bEnd;
}
}
_chunks = stringChunks;
}
