#include <zephyr/kernel.h>
#include "modbus_server.h"
#include <zephyr/modbus/modbus.h>
#include <zephyr/logging/log.h>
#include <zephyr/settings/settings.h>
#include <zephyr/sys/reboot.h>
#include "valve.h"
#include "fwu.h"

LOG_MODULE_REGISTER(modbus_server, LOG_LEVEL_INF);


/**
 * @brief Modbus Input Register Addresses.
 */
enum {
	/* Valve Control & Status */
	REG_INPUT_VALVE_STATE_MOVEMENT        = 0x0000,
	REG_INPUT_MOTOR_CURRENT_MA            = 0x0001,
	/* Digital Inputs */
	REG_INPUT_DIGITAL_INPUTS_STATE        = 0x0020,
	REG_INPUT_BUTTON_EVENTS               = 0x0021,
	/* System Config & Status */
	REG_INPUT_FIRMWARE_VERSION_MAJOR_MINOR = 0x00F0,
	REG_INPUT_FIRMWARE_VERSION_PATCH      = 0x00F1,
	REG_INPUT_DEVICE_STATUS               = 0x00F2,
	REG_INPUT_UPTIME_SECONDS_LOW          = 0x00F3,
	REG_INPUT_UPTIME_SECONDS_HIGH         = 0x00F4,
	/* Firmware Update */
	REG_INPUT_FWU_LAST_CHUNK_CRC          = 0x0100,
};

/**
 * @brief Modbus Holding Register Addresses.
 */
enum {
	/* Valve Control */
	REG_HOLDING_VALVE_COMMAND             = 0x0000,
	REG_HOLDING_MAX_OPENING_TIME_S        = 0x0001,
	REG_HOLDING_MAX_CLOSING_TIME_S        = 0x0002,
	/* Digital Outputs */
	REG_HOLDING_DIGITAL_OUTPUTS_STATE     = 0x0010,
	/* System Config */
	REG_HOLDING_WATCHDOG_TIMEOUT_S        = 0x00F0,
	/* Firmware Update */
	REG_HOLDING_FWU_COMMAND               = 0x0100,
	REG_HOLDING_FWU_CHUNK_OFFSET_LOW      = 0x0101,
	REG_HOLDING_FWU_CHUNK_OFFSET_HIGH     = 0x0102,
	REG_HOLDING_FWU_CHUNK_SIZE            = 0x0103,
	REG_HOLDING_FWU_DATA_BUFFER           = 0x0180,
};

static int modbus_iface;
static struct modbus_iface_param server_param = {
	.mode = MODBUS_MODE_RTU,
	.server = { .user_cb = NULL, .unit_id = 1 },
	.serial = { .baud = 19200, .parity = UART_CFG_PARITY_NONE },
};

static uint16_t watchdog_timeout_s = 0;
static struct k_timer watchdog_timer;

static void watchdog_timer_handler(struct k_timer *timer_id)
{
	LOG_WRN("Modbus watchdog expired! Closing valve as a fail-safe.");
	valve_close();
}

static inline void reset_watchdog(void)
{
	if (watchdog_timeout_s > 0) {
		k_timer_start(&watchdog_timer, K_SECONDS(watchdog_timeout_s), K_NO_WAIT);
	}
}

static int holding_reg_rd(uint16_t addr, uint16_t *reg)
{
	reset_watchdog();
	switch (addr) {
	case REG_HOLDING_MAX_OPENING_TIME_S: *reg = valve_get_max_open_time(); break;
	case REG_HOLDING_MAX_CLOSING_TIME_S: *reg = valve_get_max_close_time(); break;
	case REG_HOLDING_WATCHDOG_TIMEOUT_S: *reg = watchdog_timeout_s; break;
	default: *reg = 0; break;
	}
	return 0;
}

static int holding_reg_wr(uint16_t addr, uint16_t reg)
{
	reset_watchdog();
	switch (addr) {
	case REG_HOLDING_VALVE_COMMAND:
		if (reg == 1) { valve_open(); }
		else if (reg == 2) { valve_close(); }
		else if (reg == 0) { valve_stop(); }
		break;
	case REG_HOLDING_MAX_OPENING_TIME_S:
		valve_set_max_open_time(reg);
		break;
	case REG_HOLDING_MAX_CLOSING_TIME_S:
		valve_set_max_close_time(reg);
		break;
	case REG_HOLDING_WATCHDOG_TIMEOUT_S:
		watchdog_timeout_s = reg;
		if (watchdog_timeout_s > 0) {
			LOG_INF("Watchdog enabled with %u s timeout.", watchdog_timeout_s);
			reset_watchdog();
		} else {
			LOG_INF("Watchdog disabled.");
			k_timer_stop(&watchdog_timer);
		}
		break;
    default:
        fwu_handler(addr, reg);
        break;
	}
	return 0;
}

static int input_reg_rd(uint16_t addr, uint16_t *reg)
{
	reset_watchdog();
	uint32_t uptime_s = k_uptime_get_32() / 1000;
	switch (addr) {
	case REG_INPUT_VALVE_STATE_MOVEMENT: *reg = (valve_get_movement() << 8) | (valve_get_state() & 0xFF); break;
	case REG_INPUT_MOTOR_CURRENT_MA: *reg = valve_get_motor_current(); break;
	case REG_INPUT_UPTIME_SECONDS_LOW: *reg = (uint16_t)(uptime_s & 0xFFFF); break;
	case REG_INPUT_UPTIME_SECONDS_HIGH: *reg = (uint16_t)(uptime_s >> 16); break;
	case REG_INPUT_FWU_LAST_CHUNK_CRC: *reg = fwu_get_last_chunk_crc(); break;
	default: *reg = 0; break;
	}
	return 0;
}

static struct modbus_user_callbacks mbs_cbs = {
	.holding_reg_rd = holding_reg_rd,
	.holding_reg_wr = holding_reg_wr,
	.input_reg_rd = input_reg_rd,
};

#define MODBUS_NODE DT_COMPAT_GET_ANY_STATUS_OKAY(zephyr_modbus_serial)

int modbus_server_init(void)
{
	k_timer_init(&watchdog_timer, watchdog_timer_handler, NULL);
	const char iface_name[] = {DEVICE_DT_NAME(MODBUS_NODE)};
	modbus_iface = modbus_iface_get_by_name(iface_name);
	if (modbus_iface < 0) { return modbus_iface; }
	server_param.server.user_cb = &mbs_cbs;
	return modbus_init_server(modbus_iface, server_param);
}

int modbus_reconfigure(uint32_t baudrate, uint8_t unit_id)
{
	server_param.serial.baud = baudrate;
	server_param.server.unit_id = unit_id;

	int ret = modbus_init_server(modbus_iface, server_param);

    if (ret == 0) {
        settings_save_one("modbus/baudrate", &baudrate, sizeof(baudrate));
        settings_save_one("modbus/unit_id", &unit_id, sizeof(unit_id));
    }

    return ret;
}

uint32_t modbus_get_baudrate(void) { return server_param.serial.baud; }
uint8_t modbus_get_unit_id(void) { return server_param.server.unit_id; }