/**
 * @file DShotRMT.h
 * @brief DShot signal generation using ESP32 RMT with continuous repeat and pause between frames, including BiDirectional support
 * @author Wastl Kraus
 * @date 2025-06-11
 * @license MIT
 */

#pragma once

#include <Arduino.h>
#include <dshot_commands.h>
#include <driver/gpio.h>
#include <driver/rmt_tx.h>
#include <driver/rmt_rx.h>

static constexpr bool DSHOT_OK = 0;
static constexpr bool DSHOT_FAILED = 1;

// --- DShot Protocol Constants ---
static constexpr uint16_t DSHOT_THROTTLE_FAILSAVE = 0;
static constexpr uint16_t DSHOT_THROTTLE_MIN = 48;
static constexpr uint16_t DSHOT_THROTTLE_MAX = 2047;

// DShot Packet structure
typedef struct dshot_packet_s
{
    uint16_t throttle_value : 11;
    bool telemetric_request : 1;
    uint16_t checksum : 4;
} dshot_packet_t;

// --- DShot Mode Selection ---
typedef enum dshot_mode_s
{
    DSHOT_OFF,
    DSHOT150,
    DSHOT300,
    DSHOT600,
    DSHOT1200
} dshot_mode_t;

// --- DShot Timings ---
typedef struct dshot_timing_s
{
    uint16_t frameLength;
    uint16_t ticks_per_bit;
    uint16_t ticks_one_high;
    uint16_t ticks_zero_high;
    uint16_t ticks_zero_low;
    uint16_t ticks_one_low;
} dshot_timing_t;

// DShot Pulse Length Settings
const dshot_timing_t dshot_timings[] = {
    {0, 0, 0, 0, 0, 0},        // DSHOT_OFF
    {128, 64, 48, 24, 40, 16}, // DSHOT150
    {64, 32, 24, 12, 20, 8},   // DSHOT300
    {32, 16, 12, 6, 10, 4},    // DSHOT600
    {16, 8, 6, 3, 5, 2}        // DSHOT1200
};

//
// --- DShotRMT Class ---
class DShotRMT
{
public:
    // Constructor: initializes configuration state
    DShotRMT(gpio_num_t gpio, dshot_mode_t mode = DSHOT300, bool isBidirectional = false);

    // Initializes the RMT TX and RX channels
    void begin();

    // Sets a new throttle value (48-2047) and sends it
    void setThrottle(uint16_t throttle);

    // Receives and decodes the latest value from ESC, if available
    uint32_t getERPM();
    uint32_t getMotorRPM(uint8_t magnet_count);

    // Accessors for GPIO and DShot settings
    gpio_num_t getGPIO() const { return _gpio; }
    dshot_mode_t getDShotMode() const { return _mode; }

    // --- Configuration Parameters ---
    gpio_num_t _gpio = GPIO_NUM_NC;
    dshot_mode_t _mode = DSHOT_OFF;
    bool _isBidirectional = false;
    uint16_t _frame_time;
    const dshot_timing_t &dshot_times = dshot_timings[_mode];

private:
    static constexpr uint8_t DSHOT_BITS_PER_FRAME = 16;
    static constexpr uint8_t DSHOT_SWITCH_TIME = 42;

    static constexpr uint16_t DSHOT_NULL_PACKET = 0b000000000000000;
    static constexpr uint16_t DSHOT_FULL_PACKET = 0b111111111111111;
    static constexpr uint16_t NO_ERPM_SIGNAL = 0;

    // RMT configuration parameters
    static constexpr rmt_clock_source_t DSHOT_CLOCK_SRC_DEFAULT = RMT_CLK_SRC_DEFAULT;
    static constexpr uint32_t DSHOT_RMT_RESOLUTION = 10 * 1000 * 1000; // 10 MHz Clock

    static constexpr size_t TX_BUFFER_SIZE = DSHOT_BITS_PER_FRAME;
    static constexpr size_t RX_BUFFER_SIZE = 32;
    static constexpr size_t DSHOT_SYMBOLS_SIZE = 64;

    // Calculates the checksum for a DShot packet
    uint16_t calculateCRC(dshot_packet_t dshot_packet);

    // Parses the DShot packet (11 bit throttle + 1 bit telemetry request + 4 bit CRC)
    uint16_t parseDShotPacket(const dshot_packet_t dshot_packet);

    // Converts a 16-bit DShot packet into RMT symbols
    void encodeDShotTX(dshot_packet_t dshot_packet, rmt_symbol_word_t *symbols);

    // Decodes the ESC answer
    uint16_t decodeDShotRX(const rmt_symbol_word_t *symbols, uint32_t count);

    // --- DShot Packets Container ---
    uint16_t _rx_packet = DSHOT_NULL_PACKET;

    // --- RMT Channel Handles ---
    rmt_channel_handle_t _rmt_rx_channel = nullptr;
    rmt_channel_handle_t _rmt_tx_channel = nullptr;
    rmt_rx_channel_config_t _rmt_rx_channel_config = {};
    rmt_tx_channel_config_t _rmt_tx_channel_config = {};

    // --- DShot RMT Encoder ---
    rmt_encoder_handle_t _dshot_encoder = nullptr;

    // --- RMT Configuration ---
    rmt_receive_config_t _receive_config = {};
    rmt_transmit_config_t _transmit_config = {};

    // --- RMT Symbol Buffers ---
    rmt_symbol_word_t _rx_symbols[RX_BUFFER_SIZE] = {};

    // Stores the last valid eRPM received from the ESC
    uint16_t _last_erpm = NULL;
};