// POSIX compatibility support for byte-stream file I/O.

#include <stddef.h>
#include <string.h>
#include <intrin.h>
#include <ntlite/syscall.h>
#include <ntlite/console_service.h>
#include <ntlite/path.h>
#include "posix_internal.h"
#include "posix_fd.h"
#include "posix_path.h"

// Returns whether one open description permits reading.
static bool PosixDescriptionReadable(const POSIX_OPEN_DESCRIPTION* description) {
    return description && (PosixFdGetStatusFlags(description) & O_ACCMODE) != O_WRONLY;
}

// Returns whether one open description permits writing.
static bool PosixDescriptionWritable(const POSIX_OPEN_DESCRIPTION* description) {
    return description && (PosixFdGetStatusFlags(description) & O_ACCMODE) != O_RDONLY;
}

// Returns the server-owned shared ring behind one pipe open description.
static SYS_PIPE_SHARED_STATE* PosixPipeShared(POSIX_OPEN_DESCRIPTION* description) {
    if (!description || !description->Shared || description->Shared->SharedObjectData == 0) {
        errno = EIO;
        return (SYS_PIPE_SHARED_STATE*)0;
    }
    SYS_PIPE_SHARED_STATE* shared =
        (SYS_PIPE_SHARED_STATE*)(uintptr_t)description->Shared->SharedObjectData;
    if (shared->Magic != SYS_PIPE_SHARED_MAGIC || shared->Version != SYS_PIPE_SHARED_VERSION ||
        shared->Capacity != SYS_PIPE_BUFFER_CAPACITY ||
        shared->HeaderBytes != SYS_PIPE_SHARED_HEADER_BYTES) {
        errno = EIO;
        return (SYS_PIPE_SHARED_STATE*)0;
    }
    return shared;
}

// Acquires one shared pipe-side serialization lock without entering the kernel.
static void PosixPipeLock(volatile long* lock) {
    while (_InterlockedCompareExchange(lock, 1, 0) != 0)
        _mm_pause();
    _ReadWriteBarrier();
}

// Releases one shared pipe-side serialization lock.
static void PosixPipeUnlock(volatile long* lock) {
    _ReadWriteBarrier();
    _InterlockedExchange(lock, 0);
}

// Returns buffered bytes, rejecting corrupted shared counters.
static int PosixPipeUsed(SYS_PIPE_SHARED_STATE* shared, uint64_t* usedOut) {
    uint64_t readPosition = shared->ReadPosition;
    _ReadWriteBarrier();
    uint64_t writePosition = shared->WritePosition;
    uint64_t used = writePosition - readPosition;
    if (used > SYS_PIPE_BUFFER_CAPACITY) {
        errno = EIO;
        return -1;
    }
    *usedOut = used;
    return 0;
}

// Copies bytes out of the shared circular pipe buffer.
static void PosixPipeCopyOut(SYS_PIPE_SHARED_STATE* shared, uint64_t readPosition,
                             void* buffer, size_t length) {
    size_t offset = (size_t)(readPosition % SYS_PIPE_BUFFER_CAPACITY);
    size_t first = SYS_PIPE_BUFFER_CAPACITY - offset;
    if (first > length) first = length;
    memcpy(buffer, shared->Buffer + offset, first);
    if (first < length)
        memcpy((uint8_t*)buffer + first, shared->Buffer, length - first);
}

// Copies bytes into the shared circular pipe buffer.
static void PosixPipeCopyIn(SYS_PIPE_SHARED_STATE* shared, uint64_t writePosition,
                            const void* buffer, size_t length) {
    size_t offset = (size_t)(writePosition % SYS_PIPE_BUFFER_CAPACITY);
    size_t first = SYS_PIPE_BUFFER_CAPACITY - offset;
    if (first > length) first = length;
    memcpy(shared->Buffer + offset, buffer, first);
    if (first < length)
        memcpy(shared->Buffer, (const uint8_t*)buffer + first, length - first);
}

// Reads one pipe entirely through the shared user mapping except when blocking.
static ssize_t PosixPipeRead(POSIX_OPEN_DESCRIPTION* description, void* buffer, size_t length) {
    SYS_PIPE_SHARED_STATE* shared = PosixPipeShared(description);
    if (!shared) return -1;

    for (;;) {
        PosixPipeLock(&shared->ReadLock);
        uint64_t used = 0;
        if (PosixPipeUsed(shared, &used) != 0) {
            PosixPipeUnlock(&shared->ReadLock);
            return -1;
        }
        if (used != 0) {
            size_t transfer = length < used ? length : (size_t)used;
            uint64_t readPosition = shared->ReadPosition;
            PosixPipeCopyOut(shared, readPosition, buffer, transfer);
            _ReadWriteBarrier();
            shared->ReadPosition = readPosition + transfer;
            _ReadWriteBarrier();
            long writeWaiters = shared->WriteWaiters;
            PosixPipeUnlock(&shared->ReadLock);
            if (writeWaiters != 0)
                (void)SysNotifyPipe(description->KHandle);
            return (ssize_t)transfer;
        }
        if (shared->WriterOpen == 0) {
            PosixPipeUnlock(&shared->ReadLock);
            return 0;
        }
        if (PosixFdGetStatusFlags(description) & O_NONBLOCK) {
            PosixPipeUnlock(&shared->ReadLock);
            errno = EAGAIN;
            return -1;
        }
        PosixPipeUnlock(&shared->ReadLock);

        uint32_t status = SysWait(description->KHandle, SYS_WAIT_FLAG_NONE);
        if (status != NTLSTATUS_SUCCESS) {
            errno = PosixStatusToErrno(status);
            return -1;
        }
    }
}

// Writes one pipe entirely through the shared user mapping except when blocking/waking.
static ssize_t PosixPipeWrite(POSIX_OPEN_DESCRIPTION* description, const void* buffer, size_t length) {
    SYS_PIPE_SHARED_STATE* shared = PosixPipeShared(description);
    if (!shared) return -1;

    for (;;) {
        PosixPipeLock(&shared->WriteLock);
        if (shared->ReaderOpen == 0) {
            PosixPipeUnlock(&shared->WriteLock);
            errno = EPIPE;
            return -1;
        }

        uint64_t used = 0;
        if (PosixPipeUsed(shared, &used) != 0) {
            PosixPipeUnlock(&shared->WriteLock);
            return -1;
        }
        size_t available = SYS_PIPE_BUFFER_CAPACITY - (size_t)used;
        size_t transfer = 0;
        if (length <= SYS_PIPE_ATOMIC_WRITE_MAX) {
            if (available >= length)
                transfer = length;
        } else if (available != 0) {
            transfer = length < available ? length : available;
        }

        if (transfer != 0) {
            uint64_t writePosition = shared->WritePosition;
            PosixPipeCopyIn(shared, writePosition, buffer, transfer);
            _ReadWriteBarrier();
            shared->WritePosition = writePosition + transfer;
            _ReadWriteBarrier();
            long readWaiters = shared->ReadWaiters;
            PosixPipeUnlock(&shared->WriteLock);
            if (readWaiters != 0)
                (void)SysNotifyPipe(description->KHandle);
            return (ssize_t)transfer;
        }

        if (PosixFdGetStatusFlags(description) & O_NONBLOCK) {
            PosixPipeUnlock(&shared->WriteLock);
            errno = EAGAIN;
            return -1;
        }
        PosixPipeUnlock(&shared->WriteLock);

        uint32_t status = SysWait(description->KHandle, SYS_WAIT_FLAG_NONE);
        if (status != NTLSTATUS_SUCCESS) {
            errno = PosixStatusToErrno(status);
            return -1;
        }
    }
}

// Clears the native console display.
__declspec(dllexport) void clearscreen(void) {
    (void)NtlConsoleClear(SYS_HANDLE_INVALID, 0x012456);
}

// Flushes pending native console keyboard input.
__declspec(dllexport) void clearkeyboard(void) {
    (void)NtlConsoleFlushInput(SYS_HANDLE_INVALID);
}

// Opens one native file or synthetic POSIX device and returns a process-local descriptor.
__declspec(dllexport) int open(const char* path, int flags, ...) {
    if (!path || (flags & O_ACCMODE) == O_ACCMODE) {
        errno = EINVAL;
        return -1;
    }

    char native[512];
    const char* p = PosixTranslatePath(path, native, sizeof(native));

    int statusFlags = flags & (O_ACCMODE | O_APPEND | O_NONBLOCK);
    if (strcmp(p, SYNTH_DEVNULL) == 0)
        return PosixFdCreate(PosixFdDevNull, SYS_HANDLE_INVALID, statusFlags);
    if (strcmp(p, SYNTH_DEVZERO) == 0)
        return PosixFdCreate(PosixFdDevZero, SYS_HANDLE_INVALID, statusFlags);

    uint32_t kh = SYS_HANDLE_INVALID;
    uint32_t access = SYS_FILE_ACCESS_QUERY | SYS_FILE_ACCESS_LOCK;
    uint32_t disposition = SYS_FILE_OPEN_EXISTING;

    if ((flags & O_ACCMODE) == O_RDWR)
        access |= SYS_FILE_ACCESS_READ | SYS_FILE_ACCESS_WRITE;
    else if ((flags & O_ACCMODE) == O_WRONLY)
        access |= SYS_FILE_ACCESS_WRITE;
    else
        access |= SYS_FILE_ACCESS_READ;

    if (flags & O_APPEND)
        access |= SYS_FILE_ACCESS_APPEND;

    if ((flags & O_CREAT) && (flags & O_TRUNC))
        disposition = SYS_FILE_CREATE_ALWAYS;
    else if (flags & O_CREAT)
        disposition = SYS_FILE_OPEN_ALWAYS;
    else if (flags & O_TRUNC)
        disposition = SYS_FILE_TRUNCATE_EXISTING;

    uint32_t status = NtlOpenFile(SysSvFromCstr(p), access, disposition,
                                  SYS_FILE_FLAG_NONE, &kh);
    if (status != NTLSTATUS_SUCCESS) {
        errno = PosixStatusToErrno(status);
        return -1;
    }

    int fd = PosixFdCreate(PosixFdFile, kh, statusFlags);
    if (fd < 0)
        SysCloseHandle(kh);
    return fd;
}

// Reads bytes from one descriptor through its stable open-description reference.
__declspec(dllexport) ssize_t read(int fd, void* buf, size_t count) {
    if (count == 0)
        return 0;
    if (!buf) {
        errno = EINVAL;
        return -1;
    }

    POSIX_OPEN_DESCRIPTION* description = PosixFdAcquire(fd);
    if (!description)
        return -1;
    if (!PosixDescriptionReadable(description)) {
        PosixFdRelease(description);
        errno = EBADF;
        return -1;
    }

    ssize_t result = -1;
    switch (description->Type) {
        case PosixFdConsoleRead: {
            char* dst = (char*)buf;
            result = (ssize_t)count;
            for (size_t i = 0; i < count; i++) {
                uint32_t status = NtlConsoleReadCharacter(SYS_HANDLE_INVALID, &dst[i]);
                if (status != NTLSTATUS_SUCCESS) {
                    errno = PosixStatusToErrno(status);
                    result = -1;
                    break;
                }
                if (dst[i] == '\n' || dst[i] == '\r') {
                    result = (ssize_t)(i + 1u);
                    break;
                }
            }
            break;
        }
        case PosixFdDevNull:
            result = 0;
            break;
        case PosixFdDevZero:
            memset(buf, 0, count);
            result = (ssize_t)count;
            break;
        case PosixFdFile: {
            size_t got = 0;
            SYS_FILE_IO_REQUEST request =
                SysMakeFileIoRequest(description->KHandle, buf, count, &got);
            uint32_t status = SysReadFile(&request);
            if (status != NTLSTATUS_SUCCESS && got == 0)
                errno = PosixStatusToErrno(status);
            else
                result = (ssize_t)got;
            break;
        }
        case PosixFdPipeRead:
            result = PosixPipeRead(description, buf, count);
            break;
        case PosixFdSocket: {
            size_t got = 0;
            SYS_SOCKET_RECV_REQUEST request = {
                sizeof(SYS_SOCKET_RECV_REQUEST), description->KHandle, 0,
                buf, count, &got
            };
            uint32_t status = SysRecvSocket(&request);
            if (status != NTLSTATUS_SUCCESS)
                errno = PosixStatusToErrno(status);
            else
                result = (ssize_t)got;
            break;
        }
        default:
            errno = EBADF;
            break;
    }

    PosixFdRelease(description);
    return result;
}

// Writes bytes through one descriptor's shared open description.
__declspec(dllexport) ssize_t write(int fd, const void* buf, size_t count) {
    if (count == 0)
        return 0;
    if (!buf) {
        errno = EINVAL;
        return -1;
    }

    POSIX_OPEN_DESCRIPTION* description = PosixFdAcquire(fd);
    if (!description)
        return -1;
    if (!PosixDescriptionWritable(description)) {
        PosixFdRelease(description);
        errno = EBADF;
        return -1;
    }

    ssize_t result = -1;
    switch (description->Type) {
        case PosixFdConsoleWrite: {
            size_t written = 0;
            uint32_t status = NtlConsoleWrite(SYS_HANDLE_INVALID, buf, count, &written);
            if (status != NTLSTATUS_SUCCESS && written == 0)
                errno = PosixStatusToErrno(status);
            else
                result = (ssize_t)written;
            break;
        }
        case PosixFdDevNull:
        case PosixFdDevZero:
            result = (ssize_t)count;
            break;
        case PosixFdFile: {
            size_t written = 0;
            SYS_FILE_IO_REQUEST request =
                SysMakeFileIoRequest(description->KHandle, (void*)buf, count, &written);
            uint32_t status = SysWriteFile(&request);
            if (status != NTLSTATUS_SUCCESS && written == 0)
                errno = PosixStatusToErrno(status);
            else
                result = (ssize_t)written;
            break;
        }
        case PosixFdPipeWrite:
            result = PosixPipeWrite(description, buf, count);
            break;
        case PosixFdSocket: {
            size_t sent = 0;
            SYS_SOCKET_SEND_REQUEST request = {
                sizeof(SYS_SOCKET_SEND_REQUEST), description->KHandle, 0,
                buf, count, &sent
            };
            uint32_t status = SysSendSocket(&request);
            if (status != NTLSTATUS_SUCCESS)
                errno = PosixStatusToErrno(status);
            else
                result = (ssize_t)sent;
            break;
        }
        default:
            errno = EBADF;
            break;
    }

    PosixFdRelease(description);
    return result;
}

// Closes one descriptor without invalidating concurrent open-description users.
__declspec(dllexport) int close(int fd) {
    return PosixFdClose(fd);
}

// Creates one anonymous pipe whose backing and master endpoint capabilities are owned by posixsrv.
__declspec(dllexport) int pipe(int pipefd[2]) {
    if (!pipefd) {
        errno = EINVAL;
        return -1;
    }

    NTL_POSIX_REQUEST request;
    memset(&request, 0, sizeof(request));
    request.Size = sizeof(request);
    request.Version = NTL_POSIX_PROTOCOL_VERSION;
    request.Operation = NTL_POSIX_OP_CREATE_PIPE;
    request.Flags = NTL_POSIX_REQUEST_FLAG_NONE;

    SYS_HANDLE handles[2] = { SYS_HANDLE_INVALID, SYS_HANDLE_INVALID };
    NTL_POSIX_REPLY reply;
    KSTATUS status = PosixRuntimeCallServerExchange(
        &request, (const SYS_PORT_HANDLE_TRANSFER*)0, 0, handles, 2u, 2u, &reply);
    if (!KSUCCESS(status) || !KSUCCESS(reply.Status)) {
        for (uint32_t i = 0; i < 2u; ++i) {
            if (handles[i] != SYS_HANDLE_INVALID)
                (void)SysCloseHandle(handles[i]);
        }
        errno = PosixStatusToErrno(KSUCCESS(status) ? reply.Status : status);
        return -1;
    }

    NTL_POSIX_SHARED_OPEN_DESCRIPTION* readShared =
        (NTL_POSIX_SHARED_OPEN_DESCRIPTION*)(uintptr_t)reply.SharedOpenDescription;
    NTL_POSIX_SHARED_OPEN_DESCRIPTION* writeShared =
        (NTL_POSIX_SHARED_OPEN_DESCRIPTION*)(uintptr_t)reply.SharedOpenDescription2;
    SYS_PIPE_SHARED_STATE* pipeShared = readShared ?
        (SYS_PIPE_SHARED_STATE*)(uintptr_t)readShared->SharedObjectData :
        (SYS_PIPE_SHARED_STATE*)0;
    int valid = handles[0] != SYS_HANDLE_INVALID && handles[1] != SYS_HANDLE_INVALID &&
        reply.OpenDescriptionId != 0 && reply.OpenDescriptionId2 != 0 &&
        reply.OpenDescriptionId != reply.OpenDescriptionId2 &&
        reply.OpenDescriptionType == NTL_POSIX_OPEN_TYPE_PIPE_READ &&
        reply.OpenDescriptionType2 == NTL_POSIX_OPEN_TYPE_PIPE_WRITE &&
        reply.OpenStatusFlags == NTL_POSIX_OPEN_STATUS_RDONLY &&
        reply.OpenStatusFlags2 == NTL_POSIX_OPEN_STATUS_WRONLY &&
        readShared && writeShared &&
        readShared->Magic == NTL_POSIX_SHARED_OPEN_MAGIC &&
        writeShared->Magic == NTL_POSIX_SHARED_OPEN_MAGIC &&
        readShared->Version == NTL_POSIX_SHARED_OPEN_VERSION &&
        writeShared->Version == NTL_POSIX_SHARED_OPEN_VERSION &&
        readShared->Type == NTL_POSIX_OPEN_TYPE_PIPE_READ &&
        writeShared->Type == NTL_POSIX_OPEN_TYPE_PIPE_WRITE &&
        readShared->DescriptionId == reply.OpenDescriptionId &&
        writeShared->DescriptionId == reply.OpenDescriptionId2 &&
        readShared->Reserved == 0 && writeShared->Reserved == 0 &&
        readShared->Reserved2 == 0 && writeShared->Reserved2 == 0 &&
        readShared->SharedObjectData != 0 &&
        readShared->SharedObjectData == writeShared->SharedObjectData &&
        pipeShared && pipeShared->Magic == SYS_PIPE_SHARED_MAGIC &&
        pipeShared->Version == SYS_PIPE_SHARED_VERSION &&
        pipeShared->Capacity == SYS_PIPE_BUFFER_CAPACITY &&
        pipeShared->HeaderBytes == SYS_PIPE_SHARED_HEADER_BYTES;
    if (!valid) {
        (void)SysCloseHandle(handles[0]);
        (void)SysCloseHandle(handles[1]);
        PosixFdReleaseServerDescription(reply.OpenDescriptionId);
        PosixFdReleaseServerDescription(reply.OpenDescriptionId2);
        errno = EIO;
        return -1;
    }

    int readFd = PosixFdImport(PosixFdPipeRead, handles[0], reply.OpenDescriptionId,
                               readShared, 0);
    handles[0] = SYS_HANDLE_INVALID;
    if (readFd < 0) {
        (void)SysCloseHandle(handles[1]);
        PosixFdReleaseServerDescription(reply.OpenDescriptionId2);
        return -1;
    }

    int writeFd = PosixFdImport(PosixFdPipeWrite, handles[1], reply.OpenDescriptionId2,
                                writeShared, 0);
    handles[1] = SYS_HANDLE_INVALID;
    if (writeFd < 0) {
        (void)PosixFdClose(readFd);
        return -1;
    }

    pipefd[0] = readFd;
    pipefd[1] = writeFd;
    return 0;
}

// Deletes one translated native path.
__declspec(dllexport) int unlink(const char* path) {
    if (!path) { errno = EINVAL; return -1; }

    char native[512];
    const char* p = PosixTranslatePath(path, native, sizeof(native));
    if (strcmp(p, SYNTH_DEVNULL) == 0 || strcmp(p, SYNTH_DEVZERO) == 0) {
        errno = EINVAL;
        return -1;
    }

    uint32_t status = NtlDeleteFile(SysSvFromCstr(p));
    if (status != NTLSTATUS_SUCCESS) {
        errno = PosixStatusToErrno(status);
        return -1;
    }
    return 0;
}

// Repositions the shared file offset owned by an open description.
__declspec(dllexport) off_t lseek(int fd, off_t offset, int whence) {
    POSIX_OPEN_DESCRIPTION* description = PosixFdAcquire(fd);
    if (!description)
        return -1;
    if (description->Type != PosixFdFile) {
        PosixFdRelease(description);
        errno = ESPIPE;
        return -1;
    }

    int64_t target = 0;
    uint32_t status = NTLSTATUS_SUCCESS;
    if (whence == SEEK_SET) {
        target = (int64_t)offset;
    } else if (whence == SEEK_CUR) {
        uint64_t current = 0;
        status = SysGetFilePos(description->KHandle, &current);
        if (status == NTLSTATUS_SUCCESS && current <= 0x7FFFFFFFULL)
            target = (int64_t)current + (int64_t)offset;
        else if (status == NTLSTATUS_SUCCESS)
            status = NTLSTATUS_INVALID_PARAMETER;
    } else if (whence == SEEK_END) {
        uint64_t size = 0;
        status = SysGetFileSize(description->KHandle, &size);
        if (status == NTLSTATUS_SUCCESS && size <= 0x7FFFFFFFULL)
            target = (int64_t)size + (int64_t)offset;
        else if (status == NTLSTATUS_SUCCESS)
            status = NTLSTATUS_INVALID_PARAMETER;
    } else {
        status = NTLSTATUS_INVALID_PARAMETER;
    }

    if (status == NTLSTATUS_SUCCESS && (target < 0 || target > 0x7FFFFFFFLL))
        status = NTLSTATUS_INVALID_PARAMETER;
    if (status == NTLSTATUS_SUCCESS)
        status = SysSeekFile(description->KHandle, (uint64_t)target);

    PosixFdRelease(description);
    if (status != NTLSTATUS_SUCCESS) {
        errno = PosixStatusToErrno(status);
        return -1;
    }
    return (off_t)target;
}