#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>

#include <patty/ax25.h>
#include <patty/kiss.h>

#include "config.h"

enum state_flags {
    STATE_NONE    = 0,
    STATE_FRAME   = 1 << 0,
    STATE_COMMAND = 1 << 1,
    STATE_ESCAPE  = 1 << 2
};

enum tnc_opts {
    TNC_NONE             = 0,
    TNC_CLOSE_ON_DESTROY = 1 << 0
};

struct _patty_kiss_tnc {
    struct termios attrs,
                   attrs_old;

    int fd,
        opts;

    void *buf,
         *frame;

    size_t bufsz,
           offset,
           dropped;

    ssize_t readlen;
};

patty_kiss_tnc *patty_kiss_tnc_new(patty_kiss_tnc_info *info) {
    patty_kiss_tnc *tnc;

    if ((tnc = malloc(sizeof(*tnc))) == NULL) {
        goto error_malloc_tnc;
    }

    if ((tnc->buf = malloc(PATTY_KISS_TNC_BUFSZ)) == NULL) {
        goto error_malloc_buf;
    }

    if (info->flags & PATTY_KISS_TNC_DEVICE) {
        struct stat st;

        if (strcmp(info->device, "/dev/ptmx") == 0) {
            int ptysub;

            if (openpty(&tnc->fd, &ptysub, NULL, NULL, NULL) < 0) {
                goto error_open;
            }
        } else if (stat(info->device, &st) < 0) {
            goto error_stat;
        } else if ((st.st_mode & S_IFMT) == S_IFSOCK) {
            struct sockaddr_un addr;

            if (strlen(info->device) > sizeof(addr.sun_path)) {
                errno = EOVERFLOW;

                goto error_overflow;
            }

            if ((tnc->fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
                goto error_socket;
            }

            memset(&addr, '\0', sizeof(addr));
            addr.sun_family = AF_UNIX;
            strncpy(addr.sun_path, info->device, sizeof(addr.sun_path)-1);

            if (connect(tnc->fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
                goto error_connect;
            }
        } else {
            if ((tnc->fd = open(info->device, O_RDWR | O_NOCTTY)) < 0) {
                goto error_open;
            }
        }

        tnc->opts |= TNC_CLOSE_ON_DESTROY;
    } else if (info->flags & PATTY_KISS_TNC_FD) {
        tnc->fd = info->fd;
    } else {
        errno = EINVAL;

        goto error_no_fd;
    }

    if (isatty(tnc->fd) && ptsname(tnc->fd) == NULL) {
        if (tcgetattr(tnc->fd, &tnc->attrs) < 0) {
            goto error_tcgetattr;
        }

        memcpy(&tnc->attrs_old, &tnc->attrs, sizeof(tnc->attrs_old));

        cfmakeraw(&tnc->attrs);

        if (info->flags & PATTY_KISS_TNC_BAUD) {
            cfsetspeed(&tnc->attrs, info->baud);
        }

        if (info->flags & PATTY_KISS_TNC_FLOW) {
            switch (info->flow) {
                case PATTY_KISS_TNC_FLOW_NONE:
                    break;

                case PATTY_KISS_TNC_FLOW_CRTSCTS:
                    tnc->attrs.c_cflag |= CRTSCTS;

                    break;

                case PATTY_KISS_TNC_FLOW_XONXOFF:
                    tnc->attrs.c_iflag |= IXON | IXOFF;

                    break;
            }
        }

        if (tcflush(tnc->fd, TCIOFLUSH) < 0) {
            goto error_tcflush;
        }

        if (tcsetattr(tnc->fd, TCSANOW, &tnc->attrs) < 0) {
            goto error_tcsetattr;
        }
    } else {
        errno = 0;
    }

    tnc->opts    =  TNC_NONE;
    tnc->bufsz   =  PATTY_KISS_TNC_BUFSZ;
    tnc->offset  =  0;
    tnc->dropped =  0;
    tnc->readlen = -1;

    return tnc;

error_tcflush:
error_tcsetattr:
error_tcgetattr:
error_connect:
    if (info->flags & PATTY_KISS_TNC_DEVICE) {
        (void)close(tnc->fd);
    }

error_open:
error_no_fd:
error_socket:
error_overflow:
error_stat:
    free(tnc->buf);

error_malloc_buf:
    free(tnc);

error_malloc_tnc:
    return NULL;
}

void patty_kiss_tnc_destroy(patty_kiss_tnc *tnc) {
    if (isatty(tnc->fd) && ptsname(tnc->fd) == NULL) {
        (void)tcsetattr(tnc->fd, TCSANOW, &tnc->attrs_old);
    }

    if (tnc->opts & TNC_CLOSE_ON_DESTROY) {
        (void)close(tnc->fd);
    }

    free(tnc->buf);
    free(tnc);
}

int patty_kiss_tnc_fd(patty_kiss_tnc *tnc) {
    return tnc->fd;
}

static void tnc_drop(patty_kiss_tnc *tnc) {
    tnc->offset  =  0;
    tnc->readlen = -1;
    tnc->dropped++;
}

size_t patty_kiss_tnc_dropped(patty_kiss_tnc *tnc) {
    return tnc->dropped;
}

ssize_t patty_kiss_tnc_pending(patty_kiss_tnc *tnc) {
    if (tnc->readlen < 0) {
        return -1;
    }

    if (tnc->offset == 0) {
        return 0;
    }

    return tnc->readlen - tnc->offset;
}

ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
                            void *buf,
                            size_t len) {
    size_t w = 0; /* Number of bytes written to buf */

    int flags = STATE_NONE;

    if (tnc->offset == tnc->readlen) {
        errno = 0;

        return 0;
    }

    while (1) {
        uint8_t c;

        if (w == len) {
            tnc_drop(tnc);

            flags &= ~STATE_FRAME;
                w  = 0;
        }

        if (tnc->offset == 0) {
            if ((tnc->readlen = read(tnc->fd, tnc->buf, tnc->bufsz)) < 0) {
                goto error_io;
            } else if (tnc->readlen == 0) {
                goto done;
            }
        }

        c = ((uint8_t *)tnc->buf)[tnc->offset++];

        if (tnc->offset == tnc->readlen) {
            tnc->offset = 0;
        }

        if (!(flags & STATE_FRAME)) {
            if (c == PATTY_KISS_FEND) {
                flags = STATE_FRAME;

                continue;
            } else {
                errno = EIO;

                goto error_io;
            }
        } else {
            if (c == PATTY_KISS_FEND) {
                flags = STATE_NONE;

                if (w > 0) {
                    goto done;
                }

                continue;
            }
        }

        if (!(flags & STATE_COMMAND)) {
            if (PATTY_KISS_COMMAND(c) != PATTY_KISS_DATA) {
                errno = EIO;

                goto error_io;
            }

            flags |= STATE_COMMAND;

            continue;
        }

        if (!(flags & STATE_ESCAPE)) {
            if (c == PATTY_KISS_FESC) {
                flags |= STATE_ESCAPE;

                continue;
            }
        } else {
            switch (c) {
                case PATTY_KISS_TFEND:
                    ((uint8_t *)buf)[w++] = PATTY_KISS_FEND;
                    flags &= ~STATE_ESCAPE;
                    continue;

                case PATTY_KISS_TFESC:
                    ((uint8_t *)buf)[w++] = PATTY_KISS_FESC;
                    flags &= ~STATE_ESCAPE;
                    continue;

                default:
                    errno = EIO;

                    goto error_io;
            }
        }

        ((uint8_t *)buf)[w++] = c;
    }

done:
    if (flags & STATE_FRAME) {
        tnc_drop(tnc);

        errno = 0;

        return 0;
    }

    return (ssize_t)w;

error_io:
    return -1;
}

ssize_t patty_kiss_tnc_send(patty_kiss_tnc *tnc,
                            const void *buf,
                            size_t len) {
    return patty_kiss_frame_send(tnc->fd, buf, len, PATTY_KISS_TNC_PORT);
}

patty_ax25_if_driver *patty_kiss_tnc_driver() {
    static patty_ax25_if_driver driver = {
        .destroy = (patty_ax25_if_driver_destroy *)patty_kiss_tnc_destroy,
        .fd      = (patty_ax25_if_driver_fd *)patty_kiss_tnc_fd,
        .pending = (patty_ax25_if_driver_pending *)patty_kiss_tnc_pending,
        .recv    = (patty_ax25_if_driver_recv *)patty_kiss_tnc_recv,
        .send    = (patty_ax25_if_driver_send *)patty_kiss_tnc_send
    };

    return &driver;
}