StringFormatter.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/Array.h"
#include "Containers/Map.h"
#include "Containers/UnrealString.h"
#include "CoreTypes.h"
#include "Misc/AssertionMacros.h"
#include "Misc/ExpressionParserTypes.h"
#include "Templates/UnrealTemplate.h"
#include "Templates/ValueOrError.h"
 
struct FStringFormatArg;
template<typename KeyType,typename ValueType,typename SetAllocator ,typename KeyFuncs > class TMap;
 
/** A string formatter is responsible for formatting string patterns using a set of named, or ordered arguments */
class FStringFormatter
{
public:
 
    FStringFormatter();
 
    /**
     * Format the specified string using the specified arguments. Replaces instances of { Argument } with keys in the map matching 'Argument'
     * @param InExpression      A string representing the format expression
     * @param InArgs            A map of named arguments that match the tokens specified in InExpression
     * @return A string containing the formatted text
     */
    FString Format(const TCHAR* InExpression, const TMap<FString, FStringFormatArg>& InArgs) const
    {
        auto Result = FormatInternal(InExpression, InArgs, false);
        if (ensure(Result.IsValid()))
        {
            return MoveTemp(Result.GetValue());
        }
 
        return InExpression;
    }
 
    /**
     * Format the specified string using the specified arguments. Replaces instances of {0} with indices from the given array matching the index specified in the token
     * @param InExpression      A string representing the format expression
     * @param InArgs            An array of ordered arguments that match the tokens specified in InExpression
     * @return A string containing the formatted text
     */
    FString Format(const TCHAR* InExpression, const TArray<FStringFormatArg>& InArgs) const
    {
        auto Result = FormatInternal(InExpression, InArgs, false);
        if (ensure(Result.IsValid()))
        {
            return MoveTemp(Result.GetValue());
        }
 
        return InExpression;
    }
 
    /**
     * Format the specified string using the specified arguments. Replaces instances of { Argument } with keys in the map matching 'Argument'
     * @param InExpression      A string representing the format expression
     * @param InArgs            A map of named arguments that match the tokens specified in InExpression
     * @return A string containing the formatted text, or an error where InExpression is ill-formed, or contains undefined arguments
    */
    TValueOrError<FString, FExpressionError> FormatStrict(const TCHAR* InExpression, const TMap<FString, FStringFormatArg>& InArgs) const
    {
        return FormatInternal(InExpression, InArgs, true);
    }
 
    /**
     * Format the specified string using the specified arguments. Replaces instances of {0} with indices from the given array matching the index specified in the token
     * @param InExpression      A string representing the format expression
     * @param InArgs            An array of ordered arguments that match the tokens specified in InExpression
     * @return A string containing the formatted text, or an error where InExpression is ill-formed, or contains undefined arguments
     */
    TValueOrError<FString, FExpressionError> FormatStrict(const TCHAR* InExpression, const TArray<FStringFormatArg>& InArgs) const
    {
        return FormatInternal(InExpression, InArgs, true);
    }
 
private:
 
    /** Internal formatting logic */
    TValueOrError<FString, FExpressionError> FormatInternal(const TCHAR* InExpression, const TMap<FString, FStringFormatArg>& InArgs, bool bStrict) const;
    TValueOrError<FString, FExpressionError> FormatInternal(const TCHAR* InExpression, const TArray<FStringFormatArg>& InArgs, bool bStrict) const;
 
    /** Token definitions for lenient lexers */
    FTokenDefinitions NamedDefinitions;
    FTokenDefinitions OrderedDefinitions;
 
    /** Token definitions for strict lexers */
    FTokenDefinitions StrictNamedDefinitions;
    FTokenDefinitions StrictOrderedDefinitions;
};