/*
 * Исторический протокол основного контроллера ПМ67/TMS320F2812. Формирование команд и проверка
 * ответов находятся в общем ядре; адреса памяти C28x считаются словами, тогда как длины
 * передачи могут задаваться байтами.
 */

#include "tms2812.h"

#include <stdint.h>
#include <string.h>

#include "set_crc.h"

static void put_le32(uint8_t *output, uint32_t value)
{
    output[0] = (uint8_t)value;
    output[1] = (uint8_t)(value >> 8);
    output[2] = (uint8_t)(value >> 16);
    output[3] = (uint8_t)(value >> 24);
}

uint16_t tms2812_crc16(const uint8_t *data, size_t size)
{
    return set_crc16_modbus(data, size);
}

size_t tms2812_build_fixed_request(uint8_t controller, uint8_t command,
    const uint8_t *payload, size_t payload_size, uint8_t *output, size_t output_size)
{
    uint16_t crc;
    if (output == NULL || (payload == NULL && payload_size != 0U) ||
        payload_size > SIZE_MAX - 4U || output_size < payload_size + 4U) return 0U;
    output[0] = controller;
    output[1] = command;
    if (payload_size != 0U) memcpy(output + 2U, payload, payload_size);
    crc = tms2812_crc16(output, payload_size + 2U);
    output[payload_size + 2U] = (uint8_t)crc;
    output[payload_size + 3U] = (uint8_t)(crc >> 8);
    return payload_size + 4U;
}

size_t tms2812_build_memory_request(uint8_t controller, uint8_t command,
    uint32_t word_address, uint16_t value, uint8_t *output, size_t output_size)
{
    uint8_t payload[8];
    if (command == 0U) { command = TMS2812_CMD_PEEK; word_address = TMS2812_PING_ADDRESS; }
    if (command != TMS2812_CMD_PEEK && command != TMS2812_CMD_POKE) return 0U;
    put_le32(payload, word_address);
    put_le32(payload + 4U, value);
    return tms2812_build_fixed_request(controller, command, payload,
        command == TMS2812_CMD_PEEK ? 4U : 8U, output, output_size);
}

size_t tms2812_build_test_request(uint8_t controller, uint16_t duration,
    uint16_t pause, const uint8_t *digits, size_t digit_count,
    uint8_t *output, size_t output_size)
{
    uint8_t payload[16];
    if (digits == NULL || digit_count != 12U) return 0U;
    payload[0] = (uint8_t)duration; payload[1] = (uint8_t)(duration >> 8);
    payload[2] = (uint8_t)pause; payload[3] = (uint8_t)(pause >> 8);
    memcpy(payload + 4U, digits, 12U);
    return tms2812_build_fixed_request(controller, TMS2812_CMD_TEST_ALL,
        payload, sizeof payload, output, output_size);
}

int tms2812_validate_response(const uint8_t *data, size_t size,
    uint8_t controller, uint8_t command, size_t full_size, int allow_short_tail)
{
    size_t offset;
    uint16_t crc;
    if (data == NULL) return TMS2812_ERROR_ARGUMENT;
    if (full_size < 6U) return TMS2812_ERROR_ARGUMENT;
    if (size > full_size || size < full_size - (allow_short_tail ? 2U : 0U))
        return TMS2812_ERROR_LENGTH;
    if (data[0] != controller || data[1] != command) return TMS2812_ERROR_HEADER;
    offset = full_size - 4U;
    crc = (uint16_t)(data[offset] | ((uint16_t)data[offset + 1U] << 8));
    return crc == tms2812_crc16(data, offset) ? TMS2812_OK : TMS2812_ERROR_CRC;
}

size_t tms2812_build_upload_request(
    uint8_t controller, uint32_t word_address, uint32_t byte_count,
    uint8_t *output, size_t output_size)
{
    uint16_t crc;
    if ((output == NULL) || (output_size < TMS2812_UPLOAD_REQUEST_SIZE) ||
        (byte_count == 0U)) return 0U;
    output[0] = controller;
    output[1] = TMS2812_CMD_UPLOAD;
    put_le32(&output[2], word_address);
    put_le32(&output[6], byte_count);
    crc = tms2812_crc16(output, 10U);
    output[10] = (uint8_t)crc;
    output[11] = (uint8_t)(crc >> 8);
    return TMS2812_UPLOAD_REQUEST_SIZE;
}

size_t tms2812_expected_upload_response_size(uint32_t byte_count)
{
    if (byte_count == 0U ||
        (uint64_t)byte_count + TMS2812_UPLOAD_RESPONSE_OVERHEAD > SIZE_MAX) {
        return 0U;
    }
    return (size_t)byte_count + TMS2812_UPLOAD_RESPONSE_OVERHEAD;
}

int tms2812_validate_upload_response(
    const uint8_t *data, size_t size, uint8_t controller,
    uint32_t byte_count)
{
    size_t expected = tms2812_expected_upload_response_size(byte_count);
    size_t crc_offset;
    uint16_t expected_crc;
    uint16_t actual_crc;
    if (data == NULL) return TMS2812_ERROR_ARGUMENT;
    if (expected == 0U) return TMS2812_ERROR_RANGE;
    if (size != expected) return TMS2812_ERROR_LENGTH;
    if ((data[0] != controller) || (data[1] != TMS2812_CMD_UPLOAD))
        return TMS2812_ERROR_HEADER;
    crc_offset = (size_t)byte_count + 2U;
    expected_crc = tms2812_crc16(data, crc_offset);
    actual_crc = (uint16_t)(data[crc_offset] |
        ((uint16_t)data[crc_offset + 1U] << 8));
    return actual_crc == expected_crc ? TMS2812_OK : TMS2812_ERROR_CRC;
}

int tms2812_decode_upload_response(
    const uint8_t *data, size_t size, uint8_t controller,
    uint32_t byte_count, uint8_t *output, size_t output_size)
{
    int status = tms2812_validate_upload_response(
        data, size, controller, byte_count);
    if (status != TMS2812_OK) return status;
    if ((output == NULL) || (output_size < byte_count))
        return TMS2812_ERROR_CAPACITY;
    memcpy(output, &data[2], byte_count);
    return TMS2812_OK;
}