/**
 * @file relay_chn.c
 * 
 * @author
 * Ismail Sahillioglu <ismailsahillioglu@gmail.com>
 *
 * @date 2025.02.08
 * 
 * @ingroup relay_chn
 * 
 * @brief This file contains the implementation of the relay channel component.
 * @{
 */

#include <stdio.h>
#include "esp_err.h"
#include "esp_log.h"
#include "esp_task.h"
#include "driver/gpio.h"
#include "esp_timer.h"
#include "esp_event_base.h"
#include "esp_event.h"
#include "relay_chn.h"
#include "sdkconfig.h"

// TODO: on_state change API si ekle

#define RELAY_CHN_OPPOSITE_INERTIA_MS CONFIG_RELAY_CHN_OPPOSITE_INERTIA_MS
#define RELAY_CHN_COUNT CONFIG_RELAY_CHN_COUNT

const char* TAG = "relay_chn";

ESP_EVENT_DEFINE_BASE(RELAY_CHN_CMD_EVENT);


/**
 * @brief Enumeration for relay channel commands.
 */
enum relay_chn_cmd_enum {
    RELAY_CHN_CMD_NONE,     ///< No command.
    RELAY_CHN_CMD_STOP,     ///< Stop the relay channel.
    RELAY_CHN_CMD_FORWARD,  ///< Run the relay channel in the forward direction.
    RELAY_CHN_CMD_REVERSE,  ///< Run the relay channel in the reverse direction.
    RELAY_CHN_CMD_FLIP,     ///< Flip the direction of the relay channel.
    RELAY_CHN_CMD_FREE      ///< Free the relay channel.
};

/// @brief Alias for the enum type relay_chn_cmd_enum.
typedef enum relay_chn_cmd_enum relay_chn_cmd_t;

/**
 * @brief Structure to hold runtime information for a relay channel.
 */
typedef struct relay_chn_run_info_type {
    relay_chn_cmd_t last_run_cmd;   ///< The last run command issued on the relay channel; forward or reverse.
    uint32_t last_run_cmd_time_ms;  ///< The time in milliseconds when the last run command was issued.
} relay_chn_run_info_t;

/**
 * @brief Structure to hold the output configuration of a relay channel.
 */
typedef struct relay_chn_output_type {
    gpio_num_t forward_pin; ///< GPIO pin number for the forward direction.
    gpio_num_t reverse_pin; ///< GPIO pin number for the reverse direction.
    relay_chn_direction_t direction; ///< The current direction of the relay channel.
} relay_chn_output_t;

typedef struct relay_chn_type relay_chn_t; // Forward declaration

/**
 * @brief Function pointer type for relay channel command execution functions.
 * @param relay_chn Pointer to the relay channel to execute the command on.
 */
typedef void(*relay_chn_cmd_fn_t)(relay_chn_t*);

/**
 * @brief Structure to hold the state and configuration of a relay channel.
 */
typedef struct relay_chn_type {
    uint8_t id; ///< The ID of the relay channel.
    relay_chn_state_t state;        ///< The current state of the relay channel.
    relay_chn_run_info_t run_info;  ///< Runtime information of the relay channel.
    relay_chn_output_t output;      ///< Output configuration of the relay channel.
    relay_chn_cmd_t pending_cmd;    ///< The command that is pending to be issued
    esp_timer_handle_t timer;       ///< Timer to handle the opposite direction inertia time.
} relay_chn_t;


static relay_chn_t relay_channels[RELAY_CHN_COUNT];
static esp_event_loop_handle_t relay_chn_event_loop;


// Private function declarations
// Event handler for the relay channel command event
static void relay_chn_event_handler(void* handler_arg, esp_event_base_t event_base, int32_t event_id, void* event_data);

/**
 * @brief Check if the provided channel ID is valid.
 * 
 * @param chn_id Channel ID to check.
 * @return true Channel ID is valid.
 * @return false Channel ID is invalid.
 */
static bool relay_chn_is_channel_id_valid(uint8_t chn_id);

/**
 * @brief Dispatches a relay channel command to the event loop.
 * 
 * @param relay_chn The relay channel.
 * @param cmd The command to dispatch.
 */
static void relay_chn_dispatch_cmd(relay_chn_t *relay_chn, relay_chn_cmd_t cmd);

/**
 * @brief Returns the string representation of a relay channel command.
 * 
 * @param cmd The relay channel command.
 * @return char* The string representation of the command.
 */
static char *relay_chn_cmd_str(relay_chn_cmd_t cmd);

/**
 * @brief Timer callback function for relay channel direction change inertia.
 * 
 * This function is called when the opposite direction inertia timer expires. It checks if the channel
 * has a pending command and dispatches it if there is one.
 * 
 * @param arg The channel ID of the relay channel.
 */
static void relay_chn_timer_cb(void* arg)
{
    uint8_t chn_id = *(uint8_t*) arg;
    if (!relay_chn_is_channel_id_valid(chn_id)) {
        ESP_LOGE(TAG, "relay_chn_timer_cb: Invalid relay channel ID!");
        return;
    }
    relay_chn_t* relay_chn = &relay_channels[chn_id];
    // Does channel have a pending command?
    if (relay_chn->pending_cmd != RELAY_CHN_CMD_NONE) {
        relay_chn_dispatch_cmd(relay_chn, relay_chn->pending_cmd);
        relay_chn->pending_cmd = RELAY_CHN_CMD_NONE;
    }
    else {
        ESP_LOGE(TAG, "relay_chn_timer_cb: No pending cmd for relay channel %d!", chn_id);
    }
}

static esp_err_t relay_chn_init_timer(relay_chn_t *relay_chn)
{
    char timer_name[32];
    snprintf(timer_name, sizeof(timer_name), "relay_chn_%d_timer", relay_chn->id);
    esp_timer_create_args_t timer_args = {
        .callback = relay_chn_timer_cb,
        .arg = &relay_chn->id,
        .name = timer_name
    };
    return esp_timer_create(&timer_args, &relay_chn->timer);
}

/**
 * @brief Check if the provided GPIO pin number is valid for the current device.
 * 
 * @param gpio The GPIO pin number to check.
 * @return true GPIO pin number is valid.
 * @return false GPIO pin number is invalid.
 */
static bool relay_chn_is_gpio_valid(gpio_num_t gpio)
{
    return gpio >= 0 && gpio < GPIO_PIN_COUNT;
}

static esp_err_t relay_chn_create_event_loop()
{
    esp_event_loop_args_t loop_args = {
        .queue_size = 10,
        .task_name = "relay_chn_event_loop",
        .task_priority = ESP_TASKD_EVENT_PRIO - 1,
        .task_stack_size = 2048,
        .task_core_id = tskNO_AFFINITY
    };
    esp_err_t ret = esp_event_loop_create(&loop_args, &relay_chn_event_loop);
    ret |= esp_event_handler_register_with(relay_chn_event_loop,
                                            RELAY_CHN_CMD_EVENT,
                                            ESP_EVENT_ANY_ID,
                                            relay_chn_event_handler, NULL);
    return ret;
}

esp_err_t relay_chn_create(const gpio_num_t* gpio_map, uint8_t gpio_count)
{
    // Check if the device's GPIOs are enough for the number of channels
    if (RELAY_CHN_COUNT > (GPIO_PIN_COUNT / 2)) {
        ESP_LOGE(TAG, "Not enough GPIOs for the number of channels!");
        ESP_LOGE(TAG, "Max available num of channels: %d, requested channels: %d", GPIO_PIN_COUNT / 2, RELAY_CHN_COUNT);
        return ESP_ERR_INVALID_ARG;
    }

    // Check if the provided GPIOs correspond to the number of channels
    if (gpio_count != RELAY_CHN_COUNT * 2) {
        ESP_LOGE(TAG, "Invalid number of GPIOs provided: %d", gpio_count);
        ESP_LOGE(TAG, "Expected number of GPIOs: %d", RELAY_CHN_COUNT * 2);
        return ESP_ERR_INVALID_ARG;
    }

    esp_err_t ret;
    for (int i = 0; i < RELAY_CHN_COUNT; i++) {
        gpio_num_t forward_pin = gpio_map[i];
        gpio_num_t reverse_pin = gpio_map[i+1];
        // Check if the GPIOs are valid
        if (!relay_chn_is_gpio_valid(forward_pin)) {
            ESP_LOGE(TAG, "Invalid GPIO pin number: %d", forward_pin);
            return ESP_ERR_INVALID_ARG;
        }
        if (!relay_chn_is_gpio_valid(reverse_pin)) {
            ESP_LOGE(TAG, "Invalid GPIO pin number: %d", reverse_pin);
            return ESP_ERR_INVALID_ARG;
        }
        // Check if the GPIOs are valid

        // Initialize the GPIOs
        ret = gpio_reset_pin(forward_pin);
        ret |= gpio_set_direction(forward_pin, GPIO_MODE_OUTPUT);
        
        ret |= gpio_reset_pin(reverse_pin);
        ret |= gpio_set_direction(reverse_pin, GPIO_MODE_OUTPUT);
        if (ret != ESP_OK) {
            ESP_LOGE(TAG, "Failed to initialize GPIOs relay channel %d!", i);
            return ret;
        }
        // Initialize the GPIOs

        // Initialize the relay channel
        relay_chn_t* relay_chn = &relay_channels[i];
        relay_chn->id = i;
        relay_chn->output.forward_pin = forward_pin;
        relay_chn->output.reverse_pin = reverse_pin;
        relay_chn->output.direction = RELAY_CHN_DIRECTION_DEFAULT;
        relay_chn->state = RELAY_CHN_STATE_STOPPED;
        relay_chn->pending_cmd = RELAY_CHN_CMD_NONE;
        relay_chn->run_info.last_run_cmd = RELAY_CHN_CMD_NONE;
        ret |= relay_chn_init_timer(relay_chn);// Create direction change inertia timer
        if (ret != ESP_OK) {
            ESP_LOGE(TAG, "Failed to initialize relay channel %d!", i);
            return ret;
        }
    }

    // Create relay channel command event loop
    ret |= relay_chn_create_event_loop();

    return ret;
}

/**
 * @brief Check channel ID validity
 * 
 * @param chn_id Channel ID to check
 * @return true If channel is valid
 * @return false If channel is invalid
 */
static bool relay_chn_is_channel_id_valid(uint8_t chn_id)
{
    bool valid = chn_id >= 0 && chn_id < RELAY_CHN_COUNT;
    if (!valid) {
        ESP_LOGE(TAG, "Invalid channel ID: %d", chn_id);
    }
    return valid;
}


// Dispatch relay channel command to its event loop
static void relay_chn_dispatch_cmd(relay_chn_t *relay_chn, relay_chn_cmd_t cmd) {
    if (cmd == RELAY_CHN_CMD_NONE) {
        return;
    }
    esp_event_post_to(relay_chn_event_loop,
                        RELAY_CHN_CMD_EVENT,
                        cmd,
                        &relay_chn->id,
                        sizeof(relay_chn->id), portMAX_DELAY);
}

static esp_err_t relay_chn_invalidate_timer(relay_chn_t *relay_chn)
{
    if (esp_timer_is_active(relay_chn->timer)) {
        return esp_timer_stop(relay_chn->timer);
    }
    return ESP_OK;
}

static esp_err_t relay_chn_start_timer(relay_chn_t *relay_chn, uint32_t time_ms)
{
    // Invalidate the channel's timer if it is active
    relay_chn_invalidate_timer(relay_chn);
    return esp_timer_start_once(relay_chn->timer, time_ms * 1000);
}

/**
 * @brief The command issuer function.
 * 
 * This function is the deciding logic for issuing a command to a relay channel. It evaluates 
 * the current state of the channel before issuing the command. Then it decides whether to run
 * the command immediately or wait for the opposite inertia time.
 * 
 * The STOP command is an exception, it is always run immediately since it is safe in any case.
 * 
 * Another special consideration is the FLIP command. If the channel is running, the FLIP command
 * is issued after the channel is stopped. If the channel is stopped, the FLIP command is issued
 * immediately.
 * 
 * @param relay_chn The relay channel to issue the command to.
 * @param cmd The command to issue.
 */
static void relay_chn_issue_cmd(relay_chn_t* relay_chn, relay_chn_cmd_t cmd)
{
    if (cmd == RELAY_CHN_CMD_NONE) {
        return;
    }
    
    if (cmd == RELAY_CHN_CMD_STOP) {
        if (relay_chn->state == RELAY_CHN_STATE_STOPPED) {
            return; // Do nothing if already stopped
        }
        // If the command is STOP, issue it immediately
        relay_chn_dispatch_cmd(relay_chn, cmd);
        return;
    }

    // Evaluate the channel's next move depending on its status
    switch (relay_chn->state)
    {
        case RELAY_CHN_STATE_FREE:
            // If the channel is free, run the command immediately
            relay_chn_dispatch_cmd(relay_chn, cmd);
            break;
        
        case RELAY_CHN_STATE_FORWARD_PENDING:
        case RELAY_CHN_STATE_REVERSE_PENDING:
            // The channel is already waiting for the opposite inertia time,
            // so do nothing unless the command is STOP
            if (cmd == RELAY_CHN_CMD_STOP) {
                relay_chn_dispatch_cmd(relay_chn, cmd);
            }
            break;
        
        case RELAY_CHN_STATE_STOPPED:
            if (relay_chn->run_info.last_run_cmd == cmd) {
                // If the last run command is the same as the current command, run the command immediately
                relay_chn_dispatch_cmd(relay_chn, cmd);
            }
            else {
                // If the last run command is different from the current command, calculate the time passed 
                // since the last run command stopped and decide whether to run the command immediately or wait
                uint32_t inertia_time_passed_ms = (uint32_t) (esp_timer_get_time() / 1000) - relay_chn->run_info.last_run_cmd_time_ms;
                uint32_t inertia_time_ms = RELAY_CHN_OPPOSITE_INERTIA_MS - inertia_time_passed_ms;
                if (inertia_time_ms > 0) {
                    relay_chn->pending_cmd = cmd;
                    relay_chn->state = cmd == RELAY_CHN_CMD_FORWARD 
                                                ? RELAY_CHN_STATE_FORWARD_PENDING
                                                : RELAY_CHN_STATE_REVERSE_PENDING;
                    // If the time passed is less than the opposite inertia time, wait for the remaining time
                    relay_chn_start_timer(relay_chn, inertia_time_ms);
                }
                else {
                    // If the time passed is more than the opposite inertia time, run the command immediately
                    relay_chn_dispatch_cmd(relay_chn, cmd);
                }
            }
            break;
        
        case RELAY_CHN_STATE_FORWARD:
        case RELAY_CHN_STATE_REVERSE:
            if (cmd == RELAY_CHN_CMD_FLIP) {
                // If the command is FLIP, stop the running channel first, then issue the FLIP command
                relay_chn_dispatch_cmd(relay_chn, RELAY_CHN_CMD_STOP);
                relay_chn_dispatch_cmd(relay_chn, cmd);
                return;
            }

            if (relay_chn->run_info.last_run_cmd == cmd) {
                // If the last run command is the same as the current command, do nothing
                return;
            }

            // If the last run command is different from the current command, wait for the opposite inertia time
            relay_chn->pending_cmd = cmd;
            relay_chn->state = cmd == RELAY_CHN_CMD_FORWARD ? RELAY_CHN_STATE_FORWARD_PENDING : RELAY_CHN_STATE_REVERSE_PENDING;
            relay_chn_start_timer(relay_chn, RELAY_CHN_OPPOSITE_INERTIA_MS);
            break;

        default: ESP_LOGD(TAG, "relay_chn_evaluate: Unknown relay channel state!");
    }
}

/* relay_chn APIs */
relay_chn_state_t relay_chn_get_state(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) {
        return RELAY_CHN_STATE_STOPPED;
    }
    return relay_channels[chn_id].state;
}

char *relay_chn_get_state_str(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) {
        return "INVALID";
    }
    switch (relay_channels[chn_id].state) {
        case RELAY_CHN_STATE_FREE:
            return "FREE";
        case RELAY_CHN_STATE_STOPPED:
            return "STOPPED";
        case RELAY_CHN_STATE_FORWARD:
            return "FORWARD";
        case RELAY_CHN_STATE_REVERSE:
            return "REVERSE";
        case RELAY_CHN_STATE_FORWARD_PENDING:
            return "FORWARD_PENDING";
        case RELAY_CHN_STATE_REVERSE_PENDING:
            return "REVERSE_PENDING";
        default:
            return "UNKNOWN";
    }
}

void relay_chn_run_forward(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) return;

    relay_chn_t* relay_chn = &relay_channels[chn_id];
    relay_chn_issue_cmd(relay_chn, RELAY_CHN_CMD_FORWARD);
}

void relay_chn_run_reverse(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) return;

    relay_chn_t* relay_chn = &relay_channels[chn_id];
    relay_chn_issue_cmd(relay_chn, RELAY_CHN_CMD_REVERSE);
}

void relay_chn_stop(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) return;

    relay_chn_t* relay_chn = &relay_channels[chn_id];
    relay_chn_issue_cmd(relay_chn, RELAY_CHN_CMD_STOP);
}

void relay_chn_flip_direction(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) return;

    relay_chn_t* relay_chn = &relay_channels[chn_id];
    relay_chn_issue_cmd(relay_chn, RELAY_CHN_CMD_FLIP);    
}

relay_chn_direction_t relay_chn_get_direction(uint8_t chn_id)
{
    if (!relay_chn_is_channel_id_valid(chn_id)) {
        return RELAY_CHN_DIRECTION_DEFAULT;
    }
    return relay_channels[chn_id].output.direction;
}
/* relay_chn APIs */


static void relay_chn_execute_stop(relay_chn_t *relay_chn)
{
    gpio_set_level(relay_chn->output.forward_pin, 0);
    gpio_set_level(relay_chn->output.reverse_pin, 0);
    relay_chn->state = RELAY_CHN_STATE_STOPPED;
    
    // If there is any pending command, cancel it since the STOP command is issued right after it
    relay_chn->pending_cmd = RELAY_CHN_CMD_NONE;
    // Invalidate the channel's timer if it is active
    relay_chn_invalidate_timer(relay_chn);

    // If the channel was running, schedule a free command for the channel
    relay_chn_cmd_t last_run_cmd = relay_chn->run_info.last_run_cmd;
    if (last_run_cmd == RELAY_CHN_CMD_FORWARD || last_run_cmd == RELAY_CHN_CMD_REVERSE) {
        // Record the command's last run time
        relay_chn->run_info.last_run_cmd_time_ms = esp_timer_get_time() / 1000;
        // Schedule a free command for the channel
        relay_chn->pending_cmd = RELAY_CHN_CMD_FREE;
        relay_chn_start_timer(relay_chn, RELAY_CHN_OPPOSITE_INERTIA_MS);
    } else {
        // If the channel was not running, issue a free command immediately
        relay_chn_dispatch_cmd(relay_chn, RELAY_CHN_CMD_FREE);
    }
}

static void relay_chn_execute_forward(relay_chn_t *relay_chn)
{
    gpio_set_level(relay_chn->output.reverse_pin, 0);
    gpio_set_level(relay_chn->output.forward_pin, 1);
    relay_chn->state = RELAY_CHN_STATE_FORWARD;
    relay_chn->run_info.last_run_cmd = RELAY_CHN_CMD_FORWARD;
}

static void relay_chn_execute_reverse(relay_chn_t *relay_chn)
{
    gpio_set_level(relay_chn->output.forward_pin, 0);
    gpio_set_level(relay_chn->output.reverse_pin, 1);
    relay_chn->state = RELAY_CHN_STATE_REVERSE;
    relay_chn->run_info.last_run_cmd = RELAY_CHN_CMD_REVERSE;
}

static void relay_chn_execute_flip(relay_chn_t *relay_chn)
{
    // Flip the output GPIO pins
    gpio_num_t temp = relay_chn->output.forward_pin;
    relay_chn->output.forward_pin = relay_chn->output.reverse_pin;
    relay_chn->output.reverse_pin = temp;
    // Flip the direction
    relay_chn->output.direction = (relay_chn->output.direction == RELAY_CHN_DIRECTION_DEFAULT) 
                                    ? RELAY_CHN_DIRECTION_FLIPPED 
                                    : RELAY_CHN_DIRECTION_DEFAULT;
    // Set an inertia on the channel to prevent any immediate movement
    relay_chn->pending_cmd = RELAY_CHN_CMD_FREE;
    relay_chn_start_timer(relay_chn, RELAY_CHN_OPPOSITE_INERTIA_MS);
}

void relay_chn_execute_free(relay_chn_t *relay_chn)
{
    relay_chn->state = RELAY_CHN_STATE_FREE;
    relay_chn->pending_cmd = RELAY_CHN_CMD_NONE;
    // Invalidate the channel's timer if it is active
    relay_chn_invalidate_timer(relay_chn);
}

static void relay_chn_event_handler(void* handler_arg, esp_event_base_t event_base, int32_t event_id, void* event_data)
{
    uint8_t chn_id = *(uint8_t*) event_data;
    if (!relay_chn_is_channel_id_valid(chn_id)) {
        return;
    }
    relay_chn_t* relay_chn = &relay_channels[chn_id];
    ESP_LOGD(TAG, "relay_chn_event_handler: Channel %d, Command: %s", relay_chn->id, relay_chn_cmd_str(event_id));
    switch (event_id) {
        case RELAY_CHN_CMD_STOP:
            relay_chn_execute_stop(relay_chn);
            break;
        case RELAY_CHN_CMD_FORWARD:
            relay_chn_execute_forward(relay_chn);
            break;
        case RELAY_CHN_CMD_REVERSE:
            relay_chn_execute_reverse(relay_chn);
            break;
        case RELAY_CHN_CMD_FLIP:
            relay_chn_execute_flip(relay_chn);
            break;
        case RELAY_CHN_CMD_FREE:
            relay_chn_execute_free(relay_chn);
            break;
        default:
            ESP_LOGD(TAG, "Unknown relay channel command!");
    }
}

static char *relay_chn_cmd_str(relay_chn_cmd_t cmd)
{
    switch (cmd) {
        case RELAY_CHN_CMD_STOP:
            return "STOP";
        case RELAY_CHN_CMD_FORWARD:
            return "FORWARD";
        case RELAY_CHN_CMD_REVERSE:
            return "REVERSE";
        case RELAY_CHN_CMD_FLIP:
            return "FLIP";
        case RELAY_CHN_CMD_FREE:
            return "FREE";
        default:
            return "UNKNOWN";
    }
}

/// @}