#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>

#include <tabby/link.h>
#include <tabby/printer.h>

#define PACKET_RECV_ERROR_THRESHOLD 30

static uint16_t checksum(tabby_printer_packet *header, void *body) {
    uint16_t checksum = header->data[2]
                      + header->data[3]
                      + header->data[4]
                      + header->data[5];

    size_t i;

    for (i=0; i<header->size; i++) {
        checksum += ((uint8_t *)body)[i];
    }

    return checksum;
}

int tabby_printer_packet_recv(int fd,
                              tabby_printer_packet *header,
                              void *body) {
    ssize_t len;

    size_t i = 0,
           b = 0;

    uint8_t value;

    uint16_t sum = 0;

    memset(header, '\0', sizeof(*header));

    while ((len = read(fd, &value, 1)) >= 0) {
        if (i == 0) {
            if (value == TABBY_PRINTER_SYNC_1) {
                header->preamble[0] = value;
                i++;
            } else {
                continue;
            }
        } else if (i == 1) {
            if (value == TABBY_PRINTER_SYNC_2) {
                header->preamble[1] = value;
                i++;
            } else {
                i = 0;
                continue;
            }
        } else if (i == 2) {
            header->type = value;
            i++;
        } else if (i == 3) {
            header->compression = value;
            i++;
        } else if (i == 4) {
            header->size = value;
            i++;
        } else if (i == 5) {
            header->size |= value << 8;
            i++;

            b = 0;
        } else if (b < header->size) {
            ((uint8_t *)body)[b++] = value;
        } else if (b == header->size) {
            sum = value;
            b++;
        } else if (b == header->size + 1) {
            sum |= value << 8;

            if (checksum(header, body) != sum) {
                errno = EIO;

                goto error_io;
            }

            return errno = 0;
        }
    }

error_io:
    return -errno;
}

static inline int resend(tabby_printer_response *response) {
    if (response->device != TABBY_PRINTER_DEVICE_ID) {
        return 1;
    }

    if (response->status & (TABBY_PRINTER_ER0 | TABBY_PRINTER_SUM)) {
        return 1;
    }

    return 0;
}

int tabby_printer_packet_send(int fd,
                              tabby_printer_packet *header,
                              void *body,
                              tabby_printer_response *response) {
    uint16_t sum = checksum(header, body);

    if (write(fd, header, sizeof(*header)) < 0) {
        goto error_io;
    }

    if (header->size) {
        if (write(fd, body, header->size) < 0) {
            goto error_io;
        }
    }

    if (write(fd, &sum, sizeof(sum)) < 0) {
        goto error_io;
    }

    if (read(fd, response, sizeof(*response)) < 0) {
        goto error_io;
    }

    return 0;

error_io:
    return -1;
}

static void init_header(tabby_printer_packet *header,
                        tabby_printer_packet_type type, size_t size) {
    header->preamble[0] = TABBY_PRINTER_SYNC_1;
    header->preamble[1] = TABBY_PRINTER_SYNC_2;
    header->type        = type;
    header->compression = TABBY_PRINTER_COMPRESSION_NONE;
    header->size        = (uint16_t)size;
}

int tabby_printer_init(int fd,
                       tabby_printer_response *response) {
    tabby_printer_packet header;

    init_header(&header, TABBY_PRINTER_PACKET_INIT, 0);

    return tabby_printer_packet_send(fd, &header, NULL, response);
}

int tabby_printer_send_inquiry(int fd,
                               tabby_printer_response *response) {
    tabby_printer_packet header;

    init_header(&header, TABBY_PRINTER_PACKET_INQUIRY, 0);

    return tabby_printer_packet_send(fd, &header, NULL, response);
}

int tabby_printer_job_start(int fd, uint8_t sheets,
                                    uint8_t linefeeds,
                                    uint8_t palette,
                                    uint8_t density,
                                    tabby_printer_response *response) {
    tabby_printer_packet header;

    uint8_t body[4] = {
        sheets, linefeeds, palette, density
    };

    init_header(&header, TABBY_PRINTER_PACKET_JOB, sizeof(body));

    return tabby_printer_packet_send(fd, &header, &body, response);
}

int tabby_printer_job_cancel(int fd,
                             tabby_printer_response *response) {
    tabby_printer_packet header;

    init_header(&header, TABBY_PRINTER_PACKET_CANCEL, 0);

    return tabby_printer_packet_send(fd, &header, NULL, response);
}

int tabby_printer_send_sheet(int fd, void *data,
                                     tabby_printer_response *response) {
    int i;
    size_t offset = 0;

    tabby_printer_packet header;

    for (i=0; i<TABBY_PRINTER_SHEET_BANDS; i++) {
        tabby_printer_response current;

        init_header(&header,
                    TABBY_PRINTER_PACKET_DATA,
                    TABBY_PRINTER_BAND_SIZE);

        if (tabby_printer_packet_send(fd, &header,
                                          ((uint8_t *)data) + offset,
                                          &current) < 0) {
            goto error_packet_send;
        }

        if (resend(&current)) {
            tabby_printer_init(fd, &current);
            i = -1;

            continue;
        }

        offset += TABBY_PRINTER_BAND_SIZE;
    }

    init_header(&header, TABBY_PRINTER_PACKET_DATA, 0);

    return tabby_printer_packet_send(fd, &header, NULL, response);

error_packet_send:
    return -1;
}