#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* stdin = nullptr;
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;
}

static int fdopen_check_compatible_mode(int fd, int new_flags)
{
    int old_flags = fcntl(fd, F_GETFL);
    if (old_flags < 0) return -1;

    int old_mode = old_flags & O_ACCMODE;
    int new_mode = new_flags & O_ACCMODE;
    if ((old_mode & new_mode) != new_mode)
    {
        errno = EINVAL;
        return -1;
    }

    return 0;
}

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;

        if (fdopen_check_compatible_mode(fd, flags) < 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;
    }

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

    int getc(FILE* stream)
    {
        return fgetc(stream);
    }

    int getchar()
    {
        return fgetc(stdin);
    }

    char* fgets(char* buf, size_t size, FILE* stream)
    {
        size_t i = 0;
        while (i + 1 < size)
        {
            int c = fgetc(stream);
            if (c == EOF) break;
            buf[i++] = (char)c;
            if (c == '\n') break;
        }

        if (i == 0) return NULL;

        buf[i] = 0;

        return buf;
    }

    ssize_t getline(char** linep, size_t* n, FILE* stream)
    {
        return getdelim(linep, n, '\n', stream);
    }

    ssize_t getdelim(char** linep, size_t* n, int delim, FILE* stream)
    {
        if (!n || !linep)
        {
            errno = EINVAL;
            return -1;
        }

        char* buf = *linep;
        size_t size = *n;
        size_t len = 0;

        if (!buf)
        {
            buf = (char*)malloc(BUFSIZ);
            size = BUFSIZ;
            if (!buf) return -1;
            *linep = buf;
            *n = size;
        }

        while (1)
        {
            int c = fgetc(stream);
            if (c == EOF) break;

            if (len == size)
            {
                buf = (char*)realloc(buf, size + 64);
                size += 64;
                if (!buf) return -1;
                *linep = buf;
                *n = size;
            }

            buf[len++] = (char)c;
            if (c == delim) break;
        }

        if (len == 0) return -1;

        if (len == size)
        {
            buf = (char*)realloc(buf, size + 16);
            size += 16;
            if (!buf) return -1;
            *linep = buf;
            *n = size;
        }

        buf[len] = '\0';

        return (ssize_t)len;
    }

    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 count = 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 (count == (usize)-1) return -1;

        return (int)count;
    }

    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 sscanf(const char* str, const char* format, ...)
    {
        va_list ap;
        va_start(ap, format);

        int rc = vsscanf(str, format, ap);

        va_end(ap);

        return rc;
    }

    int vfscanf(FILE* stream, const char* format, va_list ap)
    {
        char buf[BUFSIZ];
        if (!fgets(buf, sizeof(buf), stream)) return EOF;
        return vsscanf(buf, format, ap);
    }

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

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

        va_end(ap);

        return rc;
    }

    int vscanf(const char* format, va_list ap)
    {
        return vfscanf(stdin, format, ap);
    }

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

        int rc = vfscanf(stdin, 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));
    }

    int remove(const char* path)
    {
        // On Luna, unlink() allows removal of directories.
        return unlink(path);
    }

    FILE* tmpfile()
    {
        // FIXME: use /tmp as the directory when the tmpfs is mounted only there.
        int fd = open("/", O_RDWR | O_TMPFILE, 0600);
        if (fd < 0) return nullptr;

        FILE* f = fdopen(fd, "w+b");
        if (!f) close(fd);
        return f;
    }
}