public void Source_NextPhrase(
string text,
int offSet,
SourceNextPhraseDelegate predicate,
string expectedOutput,
int expectedCursorPosition)
{
var source = new SourceText(text.AsMemory(), offSet);
var result = source.NextPhrase(predicate);
Assert.AreEqual(expectedOutput, result.ToString());
Assert.AreEqual(expectedCursorPosition, source.Cursor);
}
/// <summary>
/// Begins processing characters, building a span of text until the predicate condition is not met
/// at which point the characters are returned and the cursor advanced to the character that did not meet the condition.
/// The predicate will recieve the entire set of characters in the phrase on each iteration. The predicate should inspect
/// the phrase then return true when it matches an expected condition. This will cause the phraser to
/// cease processing and return the phrase that was created while advancing the cursor.
/// </summary>
/// <param name="predicate">The predicate which recieves the entire set of characters to be returned so far.</param>
/// <returns>System.ReadOnlySpan<System.Char>.</returns>
public ReadOnlySpan <char> NextPhrase(SourceNextPhraseDelegate predicate)
{
var length = 1;
var isProcessing = true;
while (isProcessing && this.Cursor + length <= _sourceText.Length)
{
var result = predicate(this.Slice(this.Cursor, length));
switch (result)
{
// keep adding characters to the phrase
case NextPhraseResult.Continue:
break;
// we're done, exit out and extract the string
case NextPhraseResult.Complete:
isProcessing = false;
break;
// we're done but the previous iteration was correct
case NextPhraseResult.CompleteOnPrevious:
length = length >= 1 ? length - 1 : 0;
isProcessing = false;
break;
default:
throw new ArgumentOutOfRangeException($"{typeof(NextPhraseResult).Name} value not supported ('{result}')");
}
length += isProcessing ? 1 : 0;
}
// if while loop was exited because the end of the text is
// reached, length will be one beyond where it should be
length += isProcessing ? -1 : 0;
var slice = this.Slice(this.Cursor, length);
this.Cursor += length;
return(slice);
}
