// Copyright 2017 Elias Kosunen
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// This file is a part of scnlib:
//     https://github.com/eliaskosunen/scnlib

#ifndef SCN_DETAIL_ERROR_H
#define SCN_DETAIL_ERROR_H

#include "fwd.h"

namespace scn {
    SCN_BEGIN_NAMESPACE

    /**
     * Error class.
     * Used as a return value for functions without a success value.
     */
    class SCN_TRIVIAL_ABI error {
    public:
        /// Error code
        enum code : char {
            /// No error
            good = 0,
            /// EOF
            end_of_range,
            /// Format string was invalid
            invalid_format_string,
            /// Scanned value was invalid for given type.
            /// e.g. a period '.' when scanning for an int
            invalid_scanned_value,
            /// Stream does not support the performed operation
            invalid_operation,
            /// Scanned value was out of range for the desired type.
            /// (e.g. `>2^32` for an `uint32_t`)
            value_out_of_range,
            /// Invalid argument given to operation
            invalid_argument,
            /// Source range has invalid (utf-8 or utf-16) encoding
            invalid_encoding,
            /// This operation is only possible with exceptions enabled
            exceptions_required,
            /// The source range emitted an error.
            source_error,
            /// The source range emitted an error that cannot be recovered
            /// from. The stream is now unusable.
            unrecoverable_source_error,

            unrecoverable_internal_error,

            max_error
        };

        struct success_tag_t {
        };
        static constexpr success_tag_t success_tag() noexcept
        {
            return {};
        }

        constexpr error() noexcept = default;
        constexpr error(success_tag_t) noexcept : error() {}
        constexpr error(enum code c, const char* m) noexcept
            : m_msg(m), m_code(c)
        {
        }

        /// Evaluated to true if there was no error
        constexpr explicit operator bool() const noexcept
        {
            return m_code == good;
        }
        constexpr bool operator!() const noexcept
        {
            return !(operator bool());
        }

        constexpr operator enum code() const noexcept { return m_code; }

        /// Get error code
        SCN_NODISCARD constexpr enum code code() const noexcept
        {
            return m_code;
        }
        SCN_NODISCARD constexpr const char* msg() const noexcept
        {
            return m_msg;
        }

        /// Returns `true` if, after this error, the state of the given input
        /// range is consistent, and thus, the range can be used for new
        /// scanning operations.
        SCN_NODISCARD constexpr bool is_recoverable() const noexcept
        {
            return !(m_code == unrecoverable_source_error ||
                     m_code == unrecoverable_internal_error);
        }

    private:
        const char* m_msg{nullptr};
        enum code m_code { good };
    };

    constexpr inline bool operator==(error a, error b) noexcept
    {
        return a.code() == b.code();
    }
    constexpr inline bool operator!=(error a, error b) noexcept
    {
        return !(a == b);
    }

    namespace detail {
        struct error_handler {
            constexpr error_handler() = default;

            void on_error(error e);
            void on_error(const char* msg);
        };
    }  // namespace detail

    SCN_END_NAMESPACE
}  // namespace scn

#endif