#include "buf.h"
#include <assert.h>
#include <math.h>
#include <stdbool.h>
#include <stdio.h>

/*
 * Inspired by Vedders bldc code.
 *
 * I stumbled upon this beautiful solution when reading the motor control firmware from the vesc project.
 * It effectively packs/serializes data into a buffer that could easily be sent over, say, uart. The original solution
 * also does fp magic in a seemingly portable way.
 *
 * For the original GPLv3 licensed source, see:
 *      https://github.com/vedderb/bldc/blob/master/util/buffer.c
 *
 * For a more permissive MIT licensed source, see:
 *      https://github.com/waas-rent/vesc_can_sdk/blob/main/vesc_buffer.c
 */

/* This buffer can live anywhere, make sure its long enough to hold your data! */
uint8_t buf[100];

/* Float comparison with error tolerance */
static inline bool float_eq(float a, float b, float epsilon) {
    return fabsf(a - b) < epsilon;
}

int main(void) {
    /* This index acts as a read/write pointer */
    size_t index = 0;

    /* Declare and define data to be serialized */
    uint8_t uint8bit = 8;
    int16_t int16bit = 16;
    int32_t int32bit = 32;
    float   float32bit = 1337.42;

    /* When appending the buffer, the index is passed along and incremented accordingly */
    buf_append_u8(buf, uint8bit, &index);
    assert(index == 1);
    buf_append_i16(buf, int16bit, &index);
    assert(index == 3);
    buf_append_i32(buf, int32bit, &index);
    assert(index == 7);
    buf_append_f32(buf, float32bit, &index);
    assert(index == 11);

    /*
     * Note that after we're done appending, the index value will hold the
     * length of the 'message', so, if you're piping this through uart or some
     * other medium, you dont have to send the entire buffer length, just send
     * up to the index.
     *
     * For bonus points for doing it vesc-style, prepend the message with the message type (a
     * byte-length enum shared by both sides, for example), as well as a message
     * length. You could also use the last two bytes of every message for a
     * crc16 checksum for error resilience.
     */

    /* Zero the original data */
    uint8bit = 0;
    int16bit = 0;
    int32bit = 0;
    float32bit = 0.f;

    /* Read from beginning */
    index = 0;

    /* Re-populate our original data */
    uint8bit = buf_read_u8(buf, &index);
    assert(index == 1);
    int16bit = buf_read_i16(buf, &index);
    assert(index == 3);
    int32bit = buf_read_i32(buf, &index);
    assert(index == 7);
    float32bit = buf_read_f32(buf, &index);
    assert(index == 11);

    /* Assert that it all worked out */
    assert(uint8bit == 8);
    assert(int16bit == 16);
    assert(int32bit == 32);
    assert(float_eq(float32bit, 1337.42, 0.01));

    printf("All asserts passed!\n");
}