#include "message.h"
#include <assert.h>

uint16_t compute_crc16(const uint8_t *data, uint16_t len);
bool     is_type_valid(MessageType t);

/**
 * @brief Create a message
 *
 *      Use as: create_message(&m1, UI_VOLTAGE, (MessageData){.voltage = 6.3});
 *
 * @param m A pointer to the message struct
 * @param type The enum type of the message you want to send
 * @param data The data corresponding to the message type
 */
void message_create(Message *m, MessageType type, MessageData data) {
    m->type = type;
    m->data = data;
    m->crc = compute_crc16((const uint8_t *)m, offsetof(Message, crc));
}

bool message_validate(const Message *m) {
    return is_type_valid(m->type) && m->crc == compute_crc16((const uint8_t *)m, offsetof(Message, crc));
}

// Standard CRC-16-CCITT (poly 0x1021, init 0xFFFF)
uint16_t compute_crc16(const uint8_t *data, uint16_t len) {
    uint16_t crc = 0xFFFF;
    for (uint16_t i = 0; i < len; i++) {
        crc ^= (uint16_t)data[i] << 8;
        for (int j = 0; j < 8; j++) {
            if (crc & 0x8000)
                crc = (crc << 1) ^ 0x1021;
            else
                crc <<= 1;
        }
    }
    return crc;
}

bool is_type_valid(MessageType t) {
    return t >= UI_SPEED_MS && t <= UI_VOLTAGE;
}

int message_tests(void) {
    Message m;
    message_create(&m, UI_BATTERY, (MessageData){75});

    assert(message_validate(&m));

    return 0;
}