// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

namespace scope_exit_support
{
    /**
     * Not meant for direct consumption : use ON_SCOPE_EXIT instead.
     *
     * RAII class that calls a lambda when it is destroyed.
     */
    template <typename FuncType>
    class scope_guard
    {
        scope_guard(scope_guard&&) = delete;
        scope_guard(const scope_guard&) = delete;
        scope_guard& operator=(scope_guard&&) = delete;
        scope_guard& operator=(const scope_guard&) = delete;

    public:
        // Given a lambda, constructs an RAII scope guard.
        explicit scope_guard(FuncType&& InFunc)
            : func_((FuncType&&)InFunc)
        {
        }

        // Causes the lambda to be executed.
        ~scope_guard()
        {
            func_();
        }

    private:
        // The lambda to be executed when this guard goes out of scope.
        FuncType func_;
    };

    struct scope_guard_syntax_support
    {
        template <typename FuncType>
        scope_guard<FuncType> operator+(FuncType&& in_func)
        {
            return scope_guard<FuncType>((FuncType&&)in_func);
        }
    };
}

#define UE_PRIVATE_SCOPE_EXIT_JOIN_INNER(A, B) A##B
#define UE_PRIVATE_SCOPE_EXIT_JOIN(A, B) UE_PRIVATE_SCOPE_EXIT_JOIN_INNER(A, B)

/**
 * Enables a lambda to be executed on scope exit.
 *
 * Example:
 *    {
 *      FileHandle* Handle = GetFileHandle();
 *      ON_SCOPE_EXIT
 *      {
 *          CloseFile(Handle);
 *      };
 *
 *      DoSomethingWithFile( Handle );
 *
 *      // File will be closed automatically no matter how the scope is exited, e.g.:
 *      // * Any return statement.
 *      // * break or continue (if the scope is a loop body).
 *      // * An exception is thrown outside the block.
 *      // * Execution reaches the end of the block.
 *    }
 */
#define ON_SCOPE_EXIT const auto UE_PRIVATE_SCOPE_EXIT_JOIN(ScopeGuard_, __LINE__) = ::scope_exit_support::scope_guard_syntax_support() + [&]()