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namespace marlin.core.util;
using System.Text;
using System.Text.RegularExpressions;
public class VariableExpander
{
public static string Expand(string format, Dictionary<string, string> variables)
{
StringBuilder output = new();
for (int i = 0; i < format.Length; i++)
{
char c = format[i];
if (c == '{')
{
if (i + 1 >= format.Length)
throw new UnmatchedBraceException("Trailing expression '{'", i, format[i..]);
if (format[i + 1] == '{')
{
output.Append('{');
i++;
}
else
{
string expr = GetExpression(format, ref i);
string value = EvaluateExpression(expr, variables);
output.Append(value);
}
}
else if (c == '}')
{
if (i + 1 >= format.Length)
throw new UnmatchedBraceException("Uninitiated expression at '}'", i, format[i..]);
if (format[i + 1] == '}')
{
output.Append('}');
i++;
}
else
{
throw new UnmatchedBraceException("Uninitiated expression at '}'", i, format[i..]);
}
}
else
output.Append(c);
}
string result = output.ToString();
// Clean up extra spaces: collapse multiple consecutive spaces (but preserve other whitespace)
result = Regex.Replace(result, @" {2,}", " ");
result = result.Trim();
return result;
}
private static string GetExpression(string format, ref int pos)
{
StringBuilder part = new();
if (format[pos] != '{')
throw new InvalidExpressionException(format[pos..], "Expected '{' at start of expression");
pos++;
for (; pos < format.Length; pos++)
{
if (format[pos] == '}')
break;
part.Append(format[pos]);
}
if (pos >= format.Length || format[pos] != '}')
throw new UnmatchedBraceException($"Trailing expression {format[pos..]}", pos, format[pos..]);
return part.ToString();
}
private static string EvaluateExpression(string expr, Dictionary<string, string> variables)
{
Match match;
const string identifier = "[a-zA-Z0-9-_.]+";
// Variable value
match = Regex.Match(expr, $"^{identifier}$");
if (match.Success)
return GetVariableOrThrow(expr, variables);
// Conditional argument: only included if variable is set.
// --hello var
match = Regex.Match(expr, $"^(--?{identifier})\\s+({identifier})$");
if (match.Success)
{
if (variables.TryGetValue(match.Groups[2].Value, out var value))
return $"{match.Groups[1].Value} {value}";
else
return "";
}
// Default value, if value is unset, uses default
match = Regex.Match(expr, $@"^({identifier})\s*=\s*(.*)$");
if (match.Success)
{
if (variables.TryGetValue(match.Groups[1].Value, out var value))
return value;
else
return match.Groups[2].Value;
}
// Use value if set
match = Regex.Match(expr, $@"^({identifier})\?\s*(.*)$");
if (match.Success)
{
if (variables.TryGetValue(match.Groups[1].Value, out var value))
{
if (string.IsNullOrEmpty(value) || value == "null" || value == "false")
return "";
return match.Groups[2].Value;
}
else
return "";
}
throw new InvalidExpressionException(expr);
}
private static string GetVariableOrThrow(string variable, Dictionary<string, string> variables)
{
return variables.TryGetValue(variable, out var value)
? value
: throw new VariableNotFoundException(variable);
}
}
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