suyu/src/core/file_sys/fs_path_utility.h

// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#include "common/assert.h"
#include "common/common_funcs.h"
#include "common/common_types.h"
#include "common/scope_exit.h"
#include "core/file_sys/fs_directory.h"
#include "core/file_sys/fs_memory_management.h"
#include "core/file_sys/fs_string_util.h"
#include "core/hle/result.h"

namespace FileSys {

constexpr inline size_t MountNameLengthMax = 15;

namespace StringTraits {

constexpr inline char DirectorySeparator = '/';
constexpr inline char DriveSeparator = ':';
constexpr inline char Dot = '.';
constexpr inline char NullTerminator = '\x00';

constexpr inline char AlternateDirectorySeparator = '\\';

constexpr inline const char InvalidCharacters[6] = {':', '*', '?', '<', '>', '|'};
constexpr inline const char InvalidCharactersForHostName[6] = {':', '*', '<', '>', '|', '$'};
constexpr inline const char InvalidCharactersForMountName[5] = {'*', '?', '<', '>', '|'};

namespace impl {

template <const char* InvalidCharacterSet, size_t NumInvalidCharacters>
consteval u64 MakeInvalidCharacterMask(size_t n) {
    u64 mask = 0;
    for (size_t i = 0; i < NumInvalidCharacters; ++i) {
        if ((static_cast<u64>(InvalidCharacterSet[i]) >> 6) == n) {
            mask |= static_cast<u64>(1) << (static_cast<u64>(InvalidCharacterSet[i]) & 0x3F);
        }
    }
    return mask;
}

template <const char* InvalidCharacterSet, size_t NumInvalidCharacters>
constexpr bool IsInvalidCharacterImpl(char c) {
    constexpr u64 Masks[4] = {
        MakeInvalidCharacterMask<InvalidCharacterSet, NumInvalidCharacters>(0),
        MakeInvalidCharacterMask<InvalidCharacterSet, NumInvalidCharacters>(1),
        MakeInvalidCharacterMask<InvalidCharacterSet, NumInvalidCharacters>(2),
        MakeInvalidCharacterMask<InvalidCharacterSet, NumInvalidCharacters>(3)};

    return (Masks[static_cast<u64>(c) >> 6] &
            (static_cast<u64>(1) << (static_cast<u64>(c) & 0x3F))) != 0;
}

} // namespace impl

constexpr bool IsInvalidCharacter(char c) {
    return impl::IsInvalidCharacterImpl<InvalidCharacters, Common::Size(InvalidCharacters)>(c);
}
constexpr bool IsInvalidCharacterForHostName(char c) {
    return impl::IsInvalidCharacterImpl<InvalidCharactersForHostName,
                                        Common::Size(InvalidCharactersForHostName)>(c);
}
constexpr bool IsInvalidCharacterForMountName(char c) {
    return impl::IsInvalidCharacterImpl<InvalidCharactersForMountName,
                                        Common::Size(InvalidCharactersForMountName)>(c);
}

} // namespace StringTraits

constexpr inline size_t WindowsDriveLength = 2;
constexpr inline size_t UncPathPrefixLength = 2;
constexpr inline size_t DosDevicePathPrefixLength = 4;

class PathFlags {
private:
    static constexpr u32 WindowsPathFlag = (1 << 0);
    static constexpr u32 RelativePathFlag = (1 << 1);
    static constexpr u32 EmptyPathFlag = (1 << 2);
    static constexpr u32 MountNameFlag = (1 << 3);
    static constexpr u32 BackslashFlag = (1 << 4);
    static constexpr u32 AllCharactersFlag = (1 << 5);

private:
    u32 m_value;

public:
    constexpr PathFlags() : m_value(0) { /* ... */
    }

#define DECLARE_PATH_FLAG_HANDLER(__WHICH__)                                                       \
    constexpr bool Is##__WHICH__##Allowed() const { return (m_value & __WHICH__##Flag) != 0; }     \
    constexpr void Allow##__WHICH__() { m_value |= __WHICH__##Flag; }

    DECLARE_PATH_FLAG_HANDLER(WindowsPath)
    DECLARE_PATH_FLAG_HANDLER(RelativePath)
    DECLARE_PATH_FLAG_HANDLER(EmptyPath)
    DECLARE_PATH_FLAG_HANDLER(MountName)
    DECLARE_PATH_FLAG_HANDLER(Backslash)
    DECLARE_PATH_FLAG_HANDLER(AllCharacters)

#undef DECLARE_PATH_FLAG_HANDLER
};

template <typename T>
    requires(std::same_as<T, char> || std::same_as<T, wchar_t>)
constexpr inline bool IsDosDevicePath(const T* path) {
    ASSERT(path != nullptr);

    using namespace StringTraits;

    return path[0] == AlternateDirectorySeparator && path[1] == AlternateDirectorySeparator &&
           (path[2] == Dot || path[2] == '?') &&
           (path[3] == DirectorySeparator || path[3] == AlternateDirectorySeparator);
}

template <typename T>
    requires(std::same_as<T, char> || std::same_as<T, wchar_t>)
constexpr inline bool IsUncPath(const T* path, bool allow_forward_slash = true,
                                bool allow_back_slash = true) {
    ASSERT(path != nullptr);

    using namespace StringTraits;

    return (allow_forward_slash && path[0] == DirectorySeparator &&
            path[1] == DirectorySeparator) ||
           (allow_back_slash && path[0] == AlternateDirectorySeparator &&
            path[1] == AlternateDirectorySeparator);
}

constexpr inline bool IsWindowsDrive(const char* path) {
    ASSERT(path != nullptr);

    return (('a' <= path[0] && path[0] <= 'z') || ('A' <= path[0] && path[0] <= 'Z')) &&
           path[1] == StringTraits::DriveSeparator;
}

constexpr inline bool IsWindowsPath(const char* path, bool allow_forward_slash_unc) {
    return IsWindowsDrive(path) || IsDosDevicePath(path) ||
           IsUncPath(path, allow_forward_slash_unc, true);
}

constexpr inline int GetWindowsSkipLength(const char* path) {
    if (IsDosDevicePath(path)) {
        return DosDevicePathPrefixLength;
    } else if (IsWindowsDrive(path)) {
        return WindowsDriveLength;
    } else if (IsUncPath(path)) {
        return UncPathPrefixLength;
    } else {
        return 0;
    }
}

constexpr inline bool IsPathAbsolute(const char* path) {
    return IsWindowsPath(path, false) || path[0] == StringTraits::DirectorySeparator;
}

constexpr inline bool IsPathRelative(const char* path) {
    return path[0] && !IsPathAbsolute(path);
}

constexpr inline bool IsCurrentDirectory(const char* path) {
    return path[0] == StringTraits::Dot &&
           (path[1] == StringTraits::NullTerminator || path[1] == StringTraits::DirectorySeparator);
}

constexpr inline bool IsParentDirectory(const char* path) {
    return path[0] == StringTraits::Dot && path[1] == StringTraits::Dot &&
           (path[2] == StringTraits::NullTerminator || path[2] == StringTraits::DirectorySeparator);
}

constexpr inline bool IsPathStartWithCurrentDirectory(const char* path) {
    return IsCurrentDirectory(path) || IsParentDirectory(path);
}

constexpr inline bool IsSubPath(const char* lhs, const char* rhs) {
    // Check pre-conditions
    ASSERT(lhs != nullptr);
    ASSERT(rhs != nullptr);

    // Import StringTraits names for current scope
    using namespace StringTraits;

    // Special case certain paths
    if (IsUncPath(lhs) && !IsUncPath(rhs)) {
        return false;
    }
    if (!IsUncPath(lhs) && IsUncPath(rhs)) {
        return false;
    }

    if (lhs[0] == DirectorySeparator && lhs[1] == NullTerminator && rhs[0] == DirectorySeparator &&
        rhs[1] != NullTerminator) {
        return true;
    }
    if (rhs[0] == DirectorySeparator && rhs[1] == NullTerminator && lhs[0] == DirectorySeparator &&
        lhs[1] != NullTerminator) {
        return true;
    }

    // Check subpath
    for (size_t i = 0; /* ... */; ++i) {
        if (lhs[i] == NullTerminator) {
            return rhs[i] == DirectorySeparator;
        } else if (rhs[i] == NullTerminator) {
            return lhs[i] == DirectorySeparator;
        } else if (lhs[i] != rhs[i]) {
            return false;
        }
    }
}

// Path utilities
constexpr inline void Replace(char* dst, size_t dst_size, char old_char, char new_char) {
    ASSERT(dst != nullptr);
    for (char* cur = dst; cur < dst + dst_size && *cur; ++cur) {
        if (*cur == old_char) {
            *cur = new_char;
        }
    }
}

constexpr inline Result CheckUtf8(const char* s) {
    // Check pre-conditions
    ASSERT(s != nullptr);

    // Iterate, checking for utf8-validity
    while (*s) {
        char utf8_buf[4] = {};

        const auto pick_res = PickOutCharacterFromUtf8String(utf8_buf, std::addressof(s));
        R_UNLESS(pick_res == CharacterEncodingResult_Success, ResultInvalidPathFormat);

        u32 dummy;
        const auto cvt_res = ConvertCharacterUtf8ToUtf32(std::addressof(dummy), utf8_buf);
        R_UNLESS(cvt_res == CharacterEncodingResult_Success, ResultInvalidPathFormat);
    }

    R_SUCCEED();
}

// Path formatting
class PathNormalizer {
private:
    enum class PathState {
        Start,
        Normal,
        FirstSeparator,
        Separator,
        CurrentDir,
        ParentDir,
    };

private:
    static constexpr void ReplaceParentDirectoryPath(char* dst, const char* src) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Start with a dir-separator
        dst[0] = DirectorySeparator;

        auto i = 1;
        while (src[i] != NullTerminator) {
            if ((src[i - 1] == DirectorySeparator || src[i - 1] == AlternateDirectorySeparator) &&
                src[i + 0] == Dot && src[i + 1] == Dot &&
                (src[i + 2] == DirectorySeparator || src[i + 2] == AlternateDirectorySeparator)) {
                dst[i - 1] = DirectorySeparator;
                dst[i + 0] = Dot;
                dst[i + 1] = Dot;
                dst[i + 2] = DirectorySeparator;
                i += 3;
            } else {
                if (src[i - 1] == AlternateDirectorySeparator && src[i + 0] == Dot &&
                    src[i + 1] == Dot && src[i + 2] == NullTerminator) {
                    dst[i - 1] = DirectorySeparator;
                    dst[i + 0] = Dot;
                    dst[i + 1] = Dot;
                    i += 2;
                    break;
                }

                dst[i] = src[i];
                ++i;
            }
        }

        dst[i] = StringTraits::NullTerminator;
    }

public:
    static constexpr bool IsParentDirectoryPathReplacementNeeded(const char* path) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        if (path[0] != DirectorySeparator && path[0] != AlternateDirectorySeparator) {
            return false;
        }

        // Check to find a parent reference using alternate separators
        if (path[0] != NullTerminator && path[1] != NullTerminator && path[2] != NullTerminator) {
            size_t i;
            for (i = 0; path[i + 3] != NullTerminator; ++path) {
                if (path[i + 1] != Dot || path[i + 2] != Dot) {
                    continue;
                }

                const char c0 = path[i + 0];
                const char c3 = path[i + 3];

                if (c0 == AlternateDirectorySeparator &&
                    (c3 == DirectorySeparator || c3 == AlternateDirectorySeparator ||
                     c3 == NullTerminator)) {
                    return true;
                }

                if (c3 == AlternateDirectorySeparator &&
                    (c0 == DirectorySeparator || c0 == AlternateDirectorySeparator)) {
                    return true;
                }
            }

            if (path[i + 0] == AlternateDirectorySeparator && path[i + 1] == Dot &&
                path[i + 2] == Dot /* && path[i + 3] == NullTerminator */) {
                return true;
            }
        }

        return false;
    }

    static constexpr Result IsNormalized(bool* out, size_t* out_len, const char* path,
                                         bool allow_all_characters = false) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Parse the path
        auto state = PathState::Start;
        size_t len = 0;
        while (path[len] != NullTerminator) {
            // Get the current character
            const char c = path[len++];

            // Check the current character is valid
            if (!allow_all_characters && state != PathState::Start) {
                R_UNLESS(!IsInvalidCharacter(c), ResultInvalidCharacter);
            }

            // Process depending on current state
            switch (state) {
                // Import the PathState enums for convenience
                using enum PathState;

            case Start:
                R_UNLESS(c == DirectorySeparator, ResultInvalidPathFormat);
                state = FirstSeparator;
                break;
            case Normal:
                if (c == DirectorySeparator) {
                    state = Separator;
                }
                break;
            case FirstSeparator:
            case Separator:
                if (c == DirectorySeparator) {
                    *out = false;
                    R_SUCCEED();
                }

                if (c == Dot) {
                    state = CurrentDir;
                } else {
                    state = Normal;
                }
                break;
            case CurrentDir:
                if (c == DirectorySeparator) {
                    *out = false;
                    R_SUCCEED();
                }

                if (c == Dot) {
                    state = ParentDir;
                } else {
                    state = Normal;
                }
                break;
            case ParentDir:
                if (c == DirectorySeparator) {
                    *out = false;
                    R_SUCCEED();
                }

                state = Normal;
                break;
            default:
                UNREACHABLE();
                break;
            }
        }

        // Check the final state
        switch (state) {
            // Import the PathState enums for convenience
            using enum PathState;
        case Start:
            R_THROW(ResultInvalidPathFormat);
        case Normal:
        case FirstSeparator:
            *out = true;
            break;
        case Separator:
        case CurrentDir:
        case ParentDir:
            *out = false;
            break;
        default:
            UNREACHABLE();
            break;
        }

        // Set the output length
        *out_len = len;
        R_SUCCEED();
    }

    static Result Normalize(char* dst, size_t* out_len, const char* path, size_t max_out_size,
                            bool is_windows_path, bool is_drive_relative_path,
                            bool allow_all_characters = false) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Prepare to iterate
        const char* cur_path = path;
        size_t total_len = 0;

        // If path begins with a separator, check that we're not drive relative
        if (cur_path[0] != DirectorySeparator) {
            R_UNLESS(is_drive_relative_path, ResultInvalidPathFormat);

            dst[total_len++] = DirectorySeparator;
        }

        // We're going to need to do path replacement, potentially
        char* replacement_path = nullptr;
        size_t replacement_path_size = 0;

        SCOPE_EXIT {
            if (replacement_path != nullptr) {
                if (std::is_constant_evaluated()) {
                    delete[] replacement_path;
                } else {
                    Deallocate(replacement_path, replacement_path_size);
                }
            }
        };

        // Perform path replacement, if necessary
        if (IsParentDirectoryPathReplacementNeeded(cur_path)) {
            if (std::is_constant_evaluated()) {
                replacement_path_size = EntryNameLengthMax + 1;
                replacement_path = new char[replacement_path_size];
            } else {
                replacement_path_size = EntryNameLengthMax + 1;
                replacement_path = static_cast<char*>(Allocate(replacement_path_size));
            }

            ReplaceParentDirectoryPath(replacement_path, cur_path);

            cur_path = replacement_path;
        }

        // Iterate, normalizing path components
        bool skip_next_sep = false;
        size_t i = 0;

        while (cur_path[i] != NullTerminator) {
            // Process a directory separator, if we run into one
            if (cur_path[i] == DirectorySeparator) {
                // Swallow separators
                do {
                    ++i;
                } while (cur_path[i] == DirectorySeparator);

                // Check if we hit end of string
                if (cur_path[i] == NullTerminator) {
                    break;
                }

                // If we aren't skipping the separator, write it, checking that we remain in bounds.
                if (!skip_next_sep) {
                    if (total_len + 1 == max_out_size) {
                        dst[total_len] = NullTerminator;
                        *out_len = total_len;
                        R_THROW(ResultTooLongPath);
                    }

                    dst[total_len++] = DirectorySeparator;
                }

                // Don't skip the next separator
                skip_next_sep = false;
            }

            // Get the length of the current directory component
            size_t dir_len = 0;
            while (cur_path[i + dir_len] != DirectorySeparator &&
                   cur_path[i + dir_len] != NullTerminator) {
                // Check for validity
                if (!allow_all_characters) {
                    R_UNLESS(!IsInvalidCharacter(cur_path[i + dir_len]), ResultInvalidCharacter);
                }

                ++dir_len;
            }

            // Handle the current dir component
            if (IsCurrentDirectory(cur_path + i)) {
                skip_next_sep = true;
            } else if (IsParentDirectory(cur_path + i)) {
                // We should have just written a separator
                ASSERT(dst[total_len - 1] == DirectorySeparator);

                // We should have started with a separator, for non-windows paths
                if (!is_windows_path) {
                    ASSERT(dst[0] == DirectorySeparator);
                }

                // Remove the previous component
                if (total_len == 1) {
                    R_UNLESS(is_windows_path, ResultDirectoryUnobtainable);

                    --total_len;
                } else {
                    total_len -= 2;

                    do {
                        if (dst[total_len] == DirectorySeparator) {
                            break;
                        }
                    } while ((--total_len) != 0);
                }

                // We should be pointing to a directory separator, for non-windows paths
                if (!is_windows_path) {
                    ASSERT(dst[total_len] == DirectorySeparator);
                }

                // We should remain in bounds
                ASSERT(total_len < max_out_size);
            } else {
                // Copy, possibly truncating
                if (total_len + dir_len + 1 > max_out_size) {
                    const size_t copy_len = max_out_size - (total_len + 1);

                    for (size_t j = 0; j < copy_len; ++j) {
                        dst[total_len++] = cur_path[i + j];
                    }

                    dst[total_len] = NullTerminator;
                    *out_len = total_len;
                    R_THROW(ResultTooLongPath);
                }

                for (size_t j = 0; j < dir_len; ++j) {
                    dst[total_len++] = cur_path[i + j];
                }
            }

            // Advance past the current directory component
            i += dir_len;
        }

        if (skip_next_sep) {
            --total_len;
        }

        if (total_len == 0 && max_out_size != 0) {
            total_len = 1;
            dst[0] = DirectorySeparator;
        }

        // NOTE: Probable nintendo bug, as max_out_size must be at least total_len + 1 for the null
        // terminator.
        R_UNLESS(max_out_size >= total_len - 1, ResultTooLongPath);

        dst[total_len] = NullTerminator;

        // Check that the result path is normalized
        bool is_normalized;
        size_t dummy;
        R_TRY(IsNormalized(std::addressof(is_normalized), std::addressof(dummy), dst,
                           allow_all_characters));

        // Assert that the result path is normalized
        ASSERT(is_normalized);

        // Set the output length
        *out_len = total_len;
        R_SUCCEED();
    }
};

class PathFormatter {
private:
    static constexpr Result CheckSharedName(const char* name, size_t len) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        if (len == 1) {
            R_UNLESS(name[0] != Dot, ResultInvalidPathFormat);
        } else if (len == 2) {
            R_UNLESS(name[0] != Dot || name[1] != Dot, ResultInvalidPathFormat);
        }

        for (size_t i = 0; i < len; ++i) {
            R_UNLESS(!IsInvalidCharacter(name[i]), ResultInvalidCharacter);
        }

        R_SUCCEED();
    }

    static constexpr Result CheckHostName(const char* name, size_t len) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        if (len == 2) {
            R_UNLESS(name[0] != Dot || name[1] != Dot, ResultInvalidPathFormat);
        }

        for (size_t i = 0; i < len; ++i) {
            R_UNLESS(!IsInvalidCharacterForHostName(name[i]), ResultInvalidCharacter);
        }

        R_SUCCEED();
    }

    static constexpr Result CheckInvalidBackslash(bool* out_contains_backslash, const char* path,
                                                  bool allow_backslash) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Default to no backslashes, so we can just write if we see one
        *out_contains_backslash = false;

        while (*path != NullTerminator) {
            if (*(path++) == AlternateDirectorySeparator) {
                *out_contains_backslash = true;

                R_UNLESS(allow_backslash, ResultInvalidCharacter);
            }
        }

        R_SUCCEED();
    }

public:
    static constexpr Result CheckPathFormat(const char* path, const PathFlags& flags) {
        bool normalized;
        size_t len;
        R_RETURN(IsNormalized(std::addressof(normalized), std::addressof(len), path, flags));
    }

    static constexpr Result SkipMountName(const char** out, size_t* out_len, const char* path) {
        R_RETURN(ParseMountName(out, out_len, nullptr, 0, path));
    }

    static constexpr Result ParseMountName(const char** out, size_t* out_len, char* out_mount_name,
                                           size_t out_mount_name_buffer_size, const char* path) {
        // Check pre-conditions
        ASSERT(path != nullptr);
        ASSERT(out_len != nullptr);
        ASSERT(out != nullptr);
        ASSERT((out_mount_name == nullptr) == (out_mount_name_buffer_size == 0));

        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Determine max mount length
        const auto max_mount_len =
            out_mount_name_buffer_size == 0
                ? MountNameLengthMax + 1
                : std::min(MountNameLengthMax + 1, out_mount_name_buffer_size);

        // Parse the path until we see a drive separator
        size_t mount_len = 0;
        for (/* ... */; mount_len < max_mount_len && path[mount_len]; ++mount_len) {
            const char c = path[mount_len];

            // If we see a drive separator, advance, then we're done with the pre-drive separator
            // part of the mount.
            if (c == DriveSeparator) {
                ++mount_len;
                break;
            }

            // If we see a directory separator, we're not in a mount name
            if (c == DirectorySeparator || c == AlternateDirectorySeparator) {
                *out = path;
                *out_len = 0;
                R_SUCCEED();
            }
        }

        // Check to be sure we're actually looking at a mount name
        if (mount_len <= 2 || path[mount_len - 1] != DriveSeparator) {
            *out = path;
            *out_len = 0;
            R_SUCCEED();
        }

        // Check that all characters in the mount name are allowable
        for (size_t i = 0; i < mount_len; ++i) {
            R_UNLESS(!IsInvalidCharacterForMountName(path[i]), ResultInvalidCharacter);
        }

        // Copy out the mount name
        if (out_mount_name_buffer_size > 0) {
            R_UNLESS(mount_len < out_mount_name_buffer_size, ResultTooLongPath);

            for (size_t i = 0; i < mount_len; ++i) {
                out_mount_name[i] = path[i];
            }
            out_mount_name[mount_len] = NullTerminator;
        }

        // Set the output
        *out = path + mount_len;
        *out_len = mount_len;
        R_SUCCEED();
    }

    static constexpr Result SkipRelativeDotPath(const char** out, size_t* out_len,
                                                const char* path) {
        R_RETURN(ParseRelativeDotPath(out, out_len, nullptr, 0, path));
    }

    static constexpr Result ParseRelativeDotPath(const char** out, size_t* out_len,
                                                 char* out_relative,
                                                 size_t out_relative_buffer_size,
                                                 const char* path) {
        // Check pre-conditions
        ASSERT(path != nullptr);
        ASSERT(out_len != nullptr);
        ASSERT(out != nullptr);
        ASSERT((out_relative == nullptr) == (out_relative_buffer_size == 0));

        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Initialize the output buffer, if we have one
        if (out_relative_buffer_size > 0) {
            out_relative[0] = NullTerminator;
        }

        // Check if the path is relative
        if (path[0] == Dot && (path[1] == NullTerminator || path[1] == DirectorySeparator ||
                               path[1] == AlternateDirectorySeparator)) {
            if (out_relative_buffer_size > 0) {
                R_UNLESS(out_relative_buffer_size >= 2, ResultTooLongPath);

                out_relative[0] = Dot;
                out_relative[1] = NullTerminator;
            }

            *out = path + 1;
            *out_len = 1;
            R_SUCCEED();
        }

        // Ensure the path isn't a parent directory
        R_UNLESS(!(path[0] == Dot && path[1] == Dot), ResultDirectoryUnobtainable);

        // There was no relative dot path
        *out = path;
        *out_len = 0;
        R_SUCCEED();
    }

    static constexpr Result SkipWindowsPath(const char** out, size_t* out_len, bool* out_normalized,
                                            const char* path, bool has_mount_name) {
        // We're normalized if and only if the parsing doesn't throw ResultNotNormalized()
        *out_normalized = true;

        R_TRY_CATCH(ParseWindowsPath(out, out_len, nullptr, 0, path, has_mount_name)) {
            R_CATCH(ResultNotNormalized) {
                *out_normalized = false;
            }
        }
        R_END_TRY_CATCH;
        ON_RESULT_INCLUDED(ResultNotNormalized) {
            *out_normalized = false;
        };

        R_SUCCEED();
    }

    static constexpr Result ParseWindowsPath(const char** out, size_t* out_len, char* out_win,
                                             size_t out_win_buffer_size, const char* path,
                                             bool has_mount_name) {
        // Check pre-conditions
        ASSERT(path != nullptr);
        ASSERT(out_len != nullptr);
        ASSERT(out != nullptr);
        ASSERT((out_win == nullptr) == (out_win_buffer_size == 0));

        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Initialize the output buffer, if we have one
        if (out_win_buffer_size > 0) {
            out_win[0] = NullTerminator;
        }

        // Handle path start
        const char* cur_path = path;
        if (has_mount_name && path[0] == DirectorySeparator) {
            if (path[1] == AlternateDirectorySeparator && path[2] == AlternateDirectorySeparator) {
                R_UNLESS(out_win_buffer_size > 0, ResultNotNormalized);

                ++cur_path;
            } else if (IsWindowsDrive(path + 1)) {
                R_UNLESS(out_win_buffer_size > 0, ResultNotNormalized);

                ++cur_path;
            }
        }

        // Handle windows drive
        if (IsWindowsDrive(cur_path)) {
            // Parse up to separator
            size_t win_path_len = WindowsDriveLength;
            for (/* ... */; cur_path[win_path_len] != NullTerminator; ++win_path_len) {
                R_UNLESS(!IsInvalidCharacter(cur_path[win_path_len]), ResultInvalidCharacter);

                if (cur_path[win_path_len] == DirectorySeparator ||
                    cur_path[win_path_len] == AlternateDirectorySeparator) {
                    break;
                }
            }

            // Ensure that we're normalized, if we're required to be
            if (out_win_buffer_size == 0) {
                for (size_t i = 0; i < win_path_len; ++i) {
                    R_UNLESS(cur_path[i] != AlternateDirectorySeparator, ResultNotNormalized);
                }
            } else {
                // Ensure we can copy into the normalized buffer
                R_UNLESS(win_path_len < out_win_buffer_size, ResultTooLongPath);

                for (size_t i = 0; i < win_path_len; ++i) {
                    out_win[i] = cur_path[i];
                }
                out_win[win_path_len] = NullTerminator;

                Replace(out_win, win_path_len, AlternateDirectorySeparator, DirectorySeparator);
            }

            *out = cur_path + win_path_len;
            *out_len = win_path_len;
            R_SUCCEED();
        }

        // Handle DOS device
        if (IsDosDevicePath(cur_path)) {
            size_t dos_prefix_len = DosDevicePathPrefixLength;

            if (IsWindowsDrive(cur_path + dos_prefix_len)) {
                dos_prefix_len += WindowsDriveLength;
            } else {
                --dos_prefix_len;
            }

            if (out_win_buffer_size > 0) {
                // Ensure we can copy into the normalized buffer
                R_UNLESS(dos_prefix_len < out_win_buffer_size, ResultTooLongPath);

                for (size_t i = 0; i < dos_prefix_len; ++i) {
                    out_win[i] = cur_path[i];
                }
                out_win[dos_prefix_len] = NullTerminator;

                Replace(out_win, dos_prefix_len, DirectorySeparator, AlternateDirectorySeparator);
            }

            *out = cur_path + dos_prefix_len;
            *out_len = dos_prefix_len;
            R_SUCCEED();
        }

        // Handle UNC path
        if (IsUncPath(cur_path, false, true)) {
            const char* final_path = cur_path;

            R_UNLESS(cur_path[UncPathPrefixLength] != DirectorySeparator, ResultInvalidPathFormat);
            R_UNLESS(cur_path[UncPathPrefixLength] != AlternateDirectorySeparator,
                     ResultInvalidPathFormat);

            size_t cur_component_offset = 0;
            size_t pos = UncPathPrefixLength;
            for (/* ... */; cur_path[pos] != NullTerminator; ++pos) {
                if (cur_path[pos] == DirectorySeparator ||
                    cur_path[pos] == AlternateDirectorySeparator) {
                    if (cur_component_offset != 0) {
                        R_TRY(CheckSharedName(cur_path + cur_component_offset,
                                              pos - cur_component_offset));

                        final_path = cur_path + pos;
                        break;
                    }

                    R_UNLESS(cur_path[pos + 1] != DirectorySeparator, ResultInvalidPathFormat);
                    R_UNLESS(cur_path[pos + 1] != AlternateDirectorySeparator,
                             ResultInvalidPathFormat);

                    R_TRY(CheckHostName(cur_path + 2, pos - 2));

                    cur_component_offset = pos + 1;
                }
            }

            R_UNLESS(cur_component_offset != pos, ResultInvalidPathFormat);

            if (cur_component_offset != 0 && final_path == cur_path) {
                R_TRY(CheckSharedName(cur_path + cur_component_offset, pos - cur_component_offset));

                final_path = cur_path + pos;
            }

            size_t unc_prefix_len = final_path - cur_path;

            // Ensure that we're normalized, if we're required to be
            if (out_win_buffer_size == 0) {
                for (size_t i = 0; i < unc_prefix_len; ++i) {
                    R_UNLESS(cur_path[i] != DirectorySeparator, ResultNotNormalized);
                }
            } else {
                // Ensure we can copy into the normalized buffer
                R_UNLESS(unc_prefix_len < out_win_buffer_size, ResultTooLongPath);

                for (size_t i = 0; i < unc_prefix_len; ++i) {
                    out_win[i] = cur_path[i];
                }
                out_win[unc_prefix_len] = NullTerminator;

                Replace(out_win, unc_prefix_len, DirectorySeparator, AlternateDirectorySeparator);
            }

            *out = cur_path + unc_prefix_len;
            *out_len = unc_prefix_len;
            R_SUCCEED();
        }

        // There's no windows path to parse
        *out = path;
        *out_len = 0;
        R_SUCCEED();
    }

    static constexpr Result IsNormalized(bool* out, size_t* out_len, const char* path,
                                         const PathFlags& flags = {}) {
        // Ensure nothing is null
        R_UNLESS(out != nullptr, ResultNullptrArgument);
        R_UNLESS(out_len != nullptr, ResultNullptrArgument);
        R_UNLESS(path != nullptr, ResultNullptrArgument);

        // Verify that the path is valid utf-8
        R_TRY(CheckUtf8(path));

        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Handle the case where the path is empty
        if (path[0] == NullTerminator) {
            R_UNLESS(flags.IsEmptyPathAllowed(), ResultInvalidPathFormat);

            *out = true;
            *out_len = 0;
            R_SUCCEED();
        }

        // All normalized paths start with a directory separator...unless they're windows paths,
        // relative paths, or have mount names.
        if (path[0] != DirectorySeparator) {
            R_UNLESS(flags.IsWindowsPathAllowed() || flags.IsRelativePathAllowed() ||
                         flags.IsMountNameAllowed(),
                     ResultInvalidPathFormat);
        }

        // Check that the path is allowed to be a windows path, if it is
        if (IsWindowsPath(path, false)) {
            R_UNLESS(flags.IsWindowsPathAllowed(), ResultInvalidPathFormat);
        }

        // Skip past the mount name, if one is present
        size_t total_len = 0;
        size_t mount_name_len = 0;
        R_TRY(SkipMountName(std::addressof(path), std::addressof(mount_name_len), path));

        // If we had a mount name, check that that was allowed
        if (mount_name_len > 0) {
            R_UNLESS(flags.IsMountNameAllowed(), ResultInvalidPathFormat);

            total_len += mount_name_len;
        }

        // Check that the path starts as a normalized path should
        if (path[0] != DirectorySeparator && !IsPathStartWithCurrentDirectory(path) &&
            !IsWindowsPath(path, false)) {
            R_UNLESS(flags.IsRelativePathAllowed(), ResultInvalidPathFormat);
            R_UNLESS(!IsInvalidCharacter(path[0]), ResultInvalidPathFormat);

            *out = false;
            R_SUCCEED();
        }

        // Process relative path
        size_t relative_len = 0;
        R_TRY(SkipRelativeDotPath(std::addressof(path), std::addressof(relative_len), path));

        // If we have a relative path, check that was allowed
        if (relative_len > 0) {
            R_UNLESS(flags.IsRelativePathAllowed(), ResultInvalidPathFormat);

            total_len += relative_len;

            if (path[0] == NullTerminator) {
                *out = true;
                *out_len = total_len;
                R_SUCCEED();
            }
        }

        // Process windows path
        size_t windows_len = 0;
        bool normalized_win = false;
        R_TRY(SkipWindowsPath(std::addressof(path), std::addressof(windows_len),
                              std::addressof(normalized_win), path, mount_name_len > 0));

        // If the windows path wasn't normalized, we're not normalized
        if (!normalized_win) {
            R_UNLESS(flags.IsWindowsPathAllowed(), ResultInvalidPathFormat);

            *out = false;
            R_SUCCEED();
        }

        // If we had a windows path, check that was allowed
        if (windows_len > 0) {
            R_UNLESS(flags.IsWindowsPathAllowed(), ResultInvalidPathFormat);

            total_len += windows_len;

            // We can't have both a relative path and a windows path
            R_UNLESS(relative_len == 0, ResultInvalidPathFormat);

            // A path ending in a windows path isn't normalized
            if (path[0] == NullTerminator) {
                *out = false;
                R_SUCCEED();
            }

            // Check that there are no windows directory separators in the path
            for (size_t i = 0; path[i] != NullTerminator; ++i) {
                if (path[i] == AlternateDirectorySeparator) {
                    *out = false;
                    R_SUCCEED();
                }
            }
        }

        // Check that parent directory replacement is not needed if backslashes are allowed
        if (flags.IsBackslashAllowed() &&
            PathNormalizer::IsParentDirectoryPathReplacementNeeded(path)) {
            *out = false;
            R_SUCCEED();
        }

        // Check that the backslash state is valid
        bool is_backslash_contained = false;
        R_TRY(CheckInvalidBackslash(std::addressof(is_backslash_contained), path,
                                    flags.IsWindowsPathAllowed() || flags.IsBackslashAllowed()));

        // Check that backslashes are contained only if allowed
        if (is_backslash_contained && !flags.IsBackslashAllowed()) {
            *out = false;
            R_SUCCEED();
        }

        // Check that the final result path is normalized
        size_t normal_len = 0;
        R_TRY(PathNormalizer::IsNormalized(out, std::addressof(normal_len), path,
                                           flags.IsAllCharactersAllowed()));

        // Add the normal length
        total_len += normal_len;

        // Set the output length
        *out_len = total_len;
        R_SUCCEED();
    }

    static constexpr Result Normalize(char* dst, size_t dst_size, const char* path, size_t path_len,
                                      const PathFlags& flags) {
        // Use StringTraits names for remainder of scope
        using namespace StringTraits;

        // Prepare to iterate
        const char* src = path;
        size_t cur_pos = 0;
        bool is_windows_path = false;

        // Check if the path is empty
        if (src[0] == NullTerminator) {
            if (dst_size != 0) {
                dst[0] = NullTerminator;
            }

            R_UNLESS(flags.IsEmptyPathAllowed(), ResultInvalidPathFormat);

            R_SUCCEED();
        }

        // Handle a mount name
        size_t mount_name_len = 0;
        if (flags.IsMountNameAllowed()) {
            R_TRY(ParseMountName(std::addressof(src), std::addressof(mount_name_len), dst + cur_pos,
                                 dst_size - cur_pos, src));

            cur_pos += mount_name_len;
        }

        // Handle a drive-relative prefix
        bool is_drive_relative = false;
        if (src[0] != DirectorySeparator && !IsPathStartWithCurrentDirectory(src) &&
            !IsWindowsPath(src, false)) {
            R_UNLESS(flags.IsRelativePathAllowed(), ResultInvalidPathFormat);
            R_UNLESS(!IsInvalidCharacter(src[0]), ResultInvalidPathFormat);

            dst[cur_pos++] = Dot;
            is_drive_relative = true;
        }

        size_t relative_len = 0;
        if (flags.IsRelativePathAllowed()) {
            R_UNLESS(cur_pos < dst_size, ResultTooLongPath);

            R_TRY(ParseRelativeDotPath(std::addressof(src), std::addressof(relative_len),
                                       dst + cur_pos, dst_size - cur_pos, src));

            cur_pos += relative_len;

            if (src[0] == NullTerminator) {
                R_UNLESS(cur_pos < dst_size, ResultTooLongPath);

                dst[cur_pos] = NullTerminator;
                R_SUCCEED();
            }
        }

        // Handle a windows path
        if (flags.IsWindowsPathAllowed()) {
            const char* const orig = src;

            R_UNLESS(cur_pos < dst_size, ResultTooLongPath);

            size_t windows_len = 0;
            R_TRY(ParseWindowsPath(std::addressof(src), std::addressof(windows_len), dst + cur_pos,
                                   dst_size - cur_pos, src, mount_name_len != 0));

            cur_pos += windows_len;

            if (src[0] == NullTerminator) {
                /* NOTE: Bug in original code here repeated, should be checking cur_pos + 2. */
                R_UNLESS(cur_pos + 1 < dst_size, ResultTooLongPath);

                dst[cur_pos + 0] = DirectorySeparator;
                dst[cur_pos + 1] = NullTerminator;
                R_SUCCEED();
            }

            if ((src - orig) > 0) {
                is_windows_path = true;
            }
        }

        // Check for invalid backslash
        bool backslash_contained = false;
        R_TRY(CheckInvalidBackslash(std::addressof(backslash_contained), src,
                                    flags.IsWindowsPathAllowed() || flags.IsBackslashAllowed()));

        // Handle backslash replacement as necessary
        if (backslash_contained && flags.IsWindowsPathAllowed()) {
            // Create a temporary buffer holding a slash-replaced version of the path.
            // NOTE: Nintendo unnecessarily allocates and replaces here a fully copy of the path,
            // despite having skipped some of it already.
            const size_t replaced_src_len = path_len - (src - path);

            char* replaced_src = nullptr;
            SCOPE_EXIT {
                if (replaced_src != nullptr) {
                    if (std::is_constant_evaluated()) {
                        delete[] replaced_src;
                    } else {
                        Deallocate(replaced_src, replaced_src_len);
                    }
                }
            };

            if (std::is_constant_evaluated()) {
                replaced_src = new char[replaced_src_len];
            } else {
                replaced_src = static_cast<char*>(Allocate(replaced_src_len));
            }

            Strlcpy<char>(replaced_src, src, replaced_src_len);

            Replace(replaced_src, replaced_src_len, AlternateDirectorySeparator,
                    DirectorySeparator);

            size_t dummy;
            R_TRY(PathNormalizer::Normalize(dst + cur_pos, std::addressof(dummy), replaced_src,
                                            dst_size - cur_pos, is_windows_path, is_drive_relative,
                                            flags.IsAllCharactersAllowed()));
        } else {
            // We can just do normalization
            size_t dummy;
            R_TRY(PathNormalizer::Normalize(dst + cur_pos, std::addressof(dummy), src,
                                            dst_size - cur_pos, is_windows_path, is_drive_relative,
                                            flags.IsAllCharactersAllowed()));
        }

        R_SUCCEED();
    }
};

} // namespace FileSys