New slash command parser

Source/Integration/SlashCommand.cpp

@@ -0,0 +1,157 @@
+#include "SlashCommand.h"
+#include "CoreMinimal.h"
+#include "Containers/StringView.h"
+#include "Misc/Char.h"
+#include "Misc/DefaultValueHelper.h"
+
+//////////////////////////////////////////////////////////////
+//
+// SlashCommand
+//
+// A command line plus a cursor, exposed to blueprint.
+//
+//////////////////////////////////////////////////////////////
+
+
+UlxSlashCommand* UlxSlashCommand::MakeSlashCommand(const FString& CommandLine)
+{
+	UlxSlashCommand* Result = NewObject<UlxSlashCommand>();
+	Result->CommandLine = CommandLine;
+	return Result;
+}
+
+
+bool UlxSlashCommand::IsSlashCommand(const FString& Command)
+{
+	if (Command.Len() < 2 || Command[0] != TEXT('/'))
+	{
+		return false;
+	}
+
+	// Every character after the slash must be alphanumeric.
+	for (int32 i = 1; i < Command.Len(); i++)
+	{
+		if (!FChar::IsAlnum(Command[i]))
+		{
+			return false;
+		}
+	}
+
+	return true;
+}
+
+
+FStringView UlxSlashCommand::FetchToken()
+{
+	const TCHAR* Data = *CommandLine;
+	int32 Len = CommandLine.Len();
+
+	// Skip leading whitespace.
+	while (Cursor < Len && FChar::IsWhitespace(Data[Cursor]))
+	{
+		Cursor++;
+	}
+
+	// Read characters up to the next whitespace.
+	int32 Start = Cursor;
+	while (Cursor < Len && !FChar::IsWhitespace(Data[Cursor]))
+	{
+		Cursor++;
+	}
+
+	return FStringView(Data + Start, Cursor - Start);
+}
+
+ElxSuccessOrError UlxSlashCommand::CheckCommand(const FString& Literal, const FString& Prototype)
+{
+	KnownCommands.Add(Literal);
+
+	// Checking the command always starts a fresh parse.
+	Cursor = 0;
+	FStringView Token = FetchToken();
+	if (Token.Equals(Literal, ESearchCase::IgnoreCase))
+	{
+		MatchingPrototypes.Add(Prototype);
+		return ElxSuccessOrError::Success;
+	}
+
+	return ElxSuccessOrError::Error;
+}
+
+ElxSuccessOrError UlxSlashCommand::ReadToken(FString& Result)
+{
+	FStringView Token = FetchToken();
+	if (Token.IsEmpty())
+	{
+		Result.Empty();
+		return ElxSuccessOrError::Error;
+	}
+
+	Result = FString(Token);
+	return ElxSuccessOrError::Success;
+}
+
+
+ElxSuccessOrError UlxSlashCommand::ReadInteger(int32& Result)
+{
+	// ParseInt validates the whole token and converts it, so "12abc"
+	// is rejected rather than read as a partial number.
+	FStringView Token = FetchToken();
+	if (!FDefaultValueHelper::ParseInt(FString(Token), Result))
+	{
+		Result = 0;
+		return ElxSuccessOrError::Error;
+	}
+
+	return ElxSuccessOrError::Success;
+}
+
+
+ElxSuccessOrError UlxSlashCommand::ReadFloat(double& Result)
+{
+	// ParseDouble validates the whole token and converts it, so
+	// "12abc" is rejected rather than read as a partial number.
+	FStringView Token = FetchToken();
+	if (!FDefaultValueHelper::ParseDouble(FString(Token), Result))
+	{
+		Result = 0.0;
+		return ElxSuccessOrError::Error;
+	}
+
+	return ElxSuccessOrError::Success;
+}
+
+
+ElxSuccessOrError UlxSlashCommand::ReadRest(FString& Result)
+{
+	const TCHAR* Data = *CommandLine;
+	int32 Len = CommandLine.Len();
+
+	// Everything from the cursor to the end of the line, trimmed.
+	Result = FString(FStringView(Data + Cursor, Len - Cursor));
+	Result.TrimStartAndEndInline();
+	Cursor = Len;
+	return ElxSuccessOrError::Success;
+}
+
+FString UlxSlashCommand::GetErrorMessage() const
+{
+	if (MatchingPrototypes.Num() == 0)
+	{
+		TArray<FString> Commands;
+		for (const FString& Command : KnownCommands)
+		{
+			Commands.Add(Command);
+		}
+		Commands.Sort();
+		return FString(TEXT("No such slash command.  Valid slash commands: ")) + FString::Join(Commands, TEXT(", "));
+	}
+
+	FString Result = TEXT("Invalid parameters.  Valid parameters:\n");
+	for (const FString& Prototype : MatchingPrototypes)
+	{
+		Result += Prototype;
+		Result += TEXT("\n");
+	}
+	return Result;
+}