#define _LUNA_SYSTEM_ERROR_EXTENSIONS
#include <bits/errno-return.h>
#include <fcntl.h>
#include <luna/Format.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>
#include <unistd.h>

FILE* stderr = nullptr;
FILE* stdout = nullptr;

static int fopen_parse_mode(const char* mode)
{
    int result = 0;
    switch (*mode)
    {
    case 'r': result |= O_RDONLY; break;
    case 'w': result |= (O_WRONLY | O_CREAT | O_TRUNC); break;
    case 'a': result |= (O_WRONLY | O_CREAT | O_APPEND); break;

    default: errno = EINVAL; return -1;
    }

    if (strchr(mode, '+')) result |= O_RDWR;

    return result;
}

extern "C"
{
    FILE* fopen(const char* path, const char* mode)
    {
        int flags;

        if ((flags = fopen_parse_mode(mode)) < 0) return nullptr;

        FILE* f = (FILE*)malloc(sizeof(FILE));
        if (!f) { return nullptr; }

        int fd = open(path, flags, 0666);
        if (fd < 0)
        {
            free(f);
            return nullptr;
        }

        f->_fd = fd;
        clearerr(f);

        return f;
    }

    FILE* fdopen(int fd, const char* mode)
    {
        int flags;

        if ((flags = fopen_parse_mode(mode)) < 0) return nullptr;

        // FIXME: We do verify that fd is valid, but not that the mode is compatible.
        long rc = lseek(fd, 0, SEEK_CUR);
        if (rc < 0) return nullptr;

        FILE* f = (FILE*)malloc(sizeof(FILE));
        if (!f) { return nullptr; }

        f->_fd = fd;
        clearerr(f);

        return f;
    }

    int fclose(FILE* stream)
    {
        if (close(stream->_fd) < 0) return EOF;

        free(stream);

        return 0;
    }

    int fileno(FILE* stream)
    {
        return stream->_fd;
    }

    size_t fread(void* buf, size_t size, size_t nmemb, FILE* stream)
    {
        if (size * nmemb == 0) return 0;

        ssize_t nread = read(stream->_fd, buf, size * nmemb);

        if (nread < 0)
        {
            stream->_err = 1;
            return 0;
        }
        else if (nread == 0)
        {
            stream->_eof = 1;
            return 0;
        }
        else
            return (size_t)nread / size;
    }

    size_t fwrite(const void* buf, size_t size, size_t nmemb, FILE* stream)
    {
        if (size * nmemb == 0) return 0;

        ssize_t nwrite = write(stream->_fd, buf, size * nmemb);

        return (size_t)nwrite / size;
    }

    int fseek(FILE* stream, long offset, int whence)
    {
        long result = lseek(stream->_fd, offset, whence);
        if (result < 0) return -1;

        // man fseek(3): A successful call to the fseek() function clears the end-of-file indicator for the stream.
        stream->_eof = 0;

        return 0;
    }

    long ftell(FILE* stream)
    {
        return lseek(stream->_fd, 0, SEEK_CUR);
    }

    void rewind(FILE* stream)
    {
        lseek(stream->_fd, 0, SEEK_SET);

        clearerr(stream);
    }

    int fgetpos(FILE* stream, fpos_t* pos)
    {
        long offset = ftell(stream);
        if (offset < 0) return -1;

        *pos = offset;

        return 0;
    }

    int fsetpos(FILE* stream, const fpos_t* pos)
    {
        return fseek(stream, *pos, SEEK_SET);
    }

    int ferror(FILE* stream)
    {
        return stream->_err;
    }

    int feof(FILE* stream)
    {
        return stream->_eof;
    }

    int fputc(int c, FILE* stream)
    {
        u8 value = (u8)c;
        ssize_t rc = write(stream->_fd, &value, 1);
        if (rc <= 0) return EOF;
        return c;
    }

    int putc(int c, FILE* stream)
    {
        return fputc(c, stream);
    }

    int putchar(int c)
    {
        return fputc(c, stdout);
    }

    int fputs(const char* str, FILE* stream)
    {
        ssize_t rc = write(stream->_fd, str, strlen(str));
        return (rc < 0) ? -1 : 0;
    }

    void clearerr(FILE* stream)
    {
        stream->_eof = stream->_err = 0;
    }

    int vsnprintf(char* buf, size_t max, const char* format, va_list ap)
    {
        return (int)vstring_format(buf, max, format, ap);
    }

    int snprintf(char* buf, size_t max, const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);

        int rc = vsnprintf(buf, max, format, ap);

        va_end(ap);

        return rc;
    }

    int vsprintf(char* buf, const char* format, va_list ap)
    {
        return vsnprintf(buf, (size_t)-1, format, ap);
    }

    int sprintf(char* buf, const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);

        int rc = vsnprintf(buf, (size_t)-1, format, ap);

        va_end(ap);

        return rc;
    }

    int vfprintf(FILE* stream, const char* format, va_list ap)
    {
        usize rc = cstyle_format(
                       format,
                       [](char c, void* f) -> Result<void> {
                           int rc = fputc(c, (FILE*)f);
                           if (rc == EOF) return err(errno);
                           return {};
                       },
                       stream, ap)
                       .value_or(-1);

        if (rc == (usize)-1) return -1;

        return (int)rc;
    }

    int fprintf(FILE* stream, const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);

        int rc = vfprintf(stream, format, ap);

        va_end(ap);

        return rc;
    }

    int vprintf(const char* format, va_list ap)
    {
        return vfprintf(stdout, format, ap);
    }

    int printf(const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);

        int rc = vfprintf(stdout, format, ap);

        va_end(ap);

        return rc;
    }

    int puts(const char* s)
    {
        if (fputs(s, stdout) < 0) return -1;
        if (putchar('\n') == EOF) return -1;

        return 0;
    }

    void perror(const char* s)
    {
        int err = errno;
        if (s && *s) fprintf(stderr, "%s: ", s);
        fprintf(stderr, "%s\n", strerror(err));
    }
}

void debug_log_impl(const char* format, va_list ap)
{
    vfprintf(stderr, format, ap);
    fputc('\n', stderr);
}