/// <summary>
/// Processes a list of format tokens into a string
/// </summary>
/// <param name="tokens">List of tokens to turn into a string</param>
/// <param name="replacements">An <see cref="IDictionary"/> with keys and values to inject into the formatted result</param>
/// <param name="missingKeyBehaviour">The behaviour to use when the format string contains a parameter that is not present in the lookup dictionary</param>
/// <param name="fallbackReplacementValue">When the <see cref="MissingKeyBehaviour.ReplaceWithFallback"/> is specified, this string is used as a fallback replacement value when the parameter is present in the lookup dictionary.</param>
/// <returns>The processed result of joining the tokens with the replacement dictionary.</returns>
public static string ProcessTokens(
IEnumerable <FormatToken> tokens,
Func <string, ReplacementResult> handler,
MissingKeyBehaviour missingKeyBehaviour,
object fallbackReplacementValue,
int outputLengthHint)
{
// create a StringBuilder to hold the resultant output string
// use the input hint as the initial size
StringBuilder resultBuilder = new StringBuilder(outputLengthHint);
foreach (FormatToken thisToken in tokens)
{
if (thisToken.TokenType == TokenType.Text)
{
// token is a text token
// add the token to the result string builder
resultBuilder.Append(thisToken.SourceString, thisToken.StartIndex, thisToken.Length);
}
else if (thisToken.TokenType == TokenType.Parameter)
{
// token is a parameter token
// perform parameter logic now.
// append the replacement for this parameter
ReplacementResult replacementResult = handler(thisToken.Value);
if (replacementResult.Success)
{
// the key exists, add the replacement value
// this does nothing if replacement value is null
resultBuilder.Append(replacementResult.Value);
}
else
{
// the key does not exist, handle this using the missing key behaviour specified.
switch (missingKeyBehaviour)
{
case MissingKeyBehaviour.ThrowException:
// the key was not found as a possible replacement, throw exception
throw new KeyNotFoundException($"The parameter \"{thisToken.Value}\" was not present in the lookup dictionary");
case MissingKeyBehaviour.ReplaceWithFallback:
resultBuilder.Append(fallbackReplacementValue);
break;
case MissingKeyBehaviour.Ignore:
// the replacement value is the input key as a parameter.
// use source string and start/length directly with append rather than
// parameter.ParameterKey to avoid allocating an extra string
resultBuilder.Append(thisToken.SourceString, thisToken.StartIndex, thisToken.Length);
break;
}
}
}
}
// return the resultant string
return(resultBuilder.ToString());
}
/// <summary>
/// Processes a list of format tokens into a string
/// </summary>
/// <param name="tokens">List of tokens to turn into a string</param>
/// <param name="replacements">An <see cref="IDictionary"/> with keys and values to inject into the formatted result</param>
/// <param name="missingKeyBehaviour">The behaviour to use when the format string contains a parameter that is not present in the lookup dictionary</param>
/// <param name="fallbackReplacementValue">When the <see cref="MissingKeyBehaviour.ReplaceWithFallback"/> is specified, this string is used as a fallback replacement value when the parameter is present in the lookup dictionary.</param>
/// <returns>The processed result of joining the tokens with the replacement dictionary.</returns>
public static FormattableString ProcessTokensIntoFormattableString(
IEnumerable <FormatToken> tokens,
Func <string, ReplacementResult> handler,
MissingKeyBehaviour missingKeyBehaviour,
object fallbackReplacementValue,
int outputLengthHint)
{
List <object> replacementParams = new List <object>();
// create a StringBuilder to hold the resultant output string
// use the input hint as the initial size
StringBuilder resultBuilder = new StringBuilder(outputLengthHint);
// this is the index of the current placeholder in the composite format string
int placeholderIndex = 0;
foreach (FormatToken thisToken in tokens)
{
if (thisToken.TokenType == TokenType.Text)
{
// token is a text token.
// add the token to the result string builder.
// because this text is going into a standard composite format string,
// any instaces of { or } must be escaped with {{ and }}
resultBuilder.AppendWithEscapedBrackets(thisToken.SourceString, thisToken.StartIndex, thisToken.Length);
}
else if (thisToken.TokenType == TokenType.Parameter)
{
// token is a parameter token
// perform parameter logic now.
var tokenKey = thisToken.Value;
string format = null;
var separatorIdx = tokenKey.IndexOf(":", StringComparison.Ordinal);
if (separatorIdx > -1)
{
tokenKey = thisToken.Value.Substring(0, separatorIdx);
format = thisToken.Value.Substring(separatorIdx + 1);
}
// append the replacement for this parameter
ReplacementResult replacementResult = handler(tokenKey);
string IndexAndFormat()
{
if (string.IsNullOrWhiteSpace(format))
{
return("{" + placeholderIndex + "}");
}
return("{" + placeholderIndex + ":" + format + "}");
}
// append the replacement for this parameter
if (replacementResult.Success)
{
// Instead of appending the replacement value directly as before,
// append the next placeholder with the current placeholder index.
// Add the actual replacement format item into the replacement values.
resultBuilder.Append(IndexAndFormat());
placeholderIndex++;
replacementParams.Add(replacementResult.Value);
}
else
{
// the key does not exist, handle this using the missing key behaviour specified.
switch (missingKeyBehaviour)
{
case MissingKeyBehaviour.ThrowException:
// the key was not found as a possible replacement, throw exception
throw new KeyNotFoundException($"The parameter \"{thisToken.Value}\" was not present in the lookup dictionary");
case MissingKeyBehaviour.ReplaceWithFallback:
// Instead of appending the replacement value directly as before,
// append the next placeholder with the current placeholder index.
// Add the actual replacement format item into the replacement values.
resultBuilder.Append(IndexAndFormat());
placeholderIndex++;
replacementParams.Add(fallbackReplacementValue);
break;
case MissingKeyBehaviour.Ignore:
resultBuilder.AppendWithEscapedBrackets(thisToken.SourceString, thisToken.StartIndex, thisToken.Length);
break;
}
}
}
}
// return the resultant string
return(FormattableStringFactory.Create(resultBuilder.ToString(), replacementParams.ToArray()));
}
