/** global definitions and methods
 *  @file
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @copyright SPDX-License-Identifier: GPL-3.0-or-later
 *  @date 2016-2020
 */
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general utilities
#include <string.h> // memory utilities

/* STM32 (including CM3) libraries */
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencm3/cm3/systick.h> // SysTick library
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/exti.h> // external interrupt defines
#include <libopencm3/stm32/syscfg.h> // system definitions
#include <libopencm3/usb/dwc/otg_fs.h> // USB OTG utilities

#include "global.h" // common methods

volatile bool button_flag = false;
volatile bool user_input_available = false;

static volatile uint8_t user_input_buffer[64] = {0}; /**< ring buffer for received data */
static volatile uint8_t user_input_i = 0; /**< current position of read received data */
static volatile uint8_t user_input_used = 0; /**< how much data has been received and not red */

static volatile uint32_t sleep_duration = 0; /**< sleep duration count down (in SysTick interrupts) */

uint8_t addu8_safe(uint8_t a, uint8_t b)
{
	if (a > UINT8_MAX - b) {
		return UINT8_MAX;
	} else {
		return a + b;
	}
}

uint16_t addu16_safe(uint16_t a, uint16_t b)
{
	if (a > UINT16_MAX - b) {
		return UINT16_MAX;
	} else {
		return a + b;
	}
}

uint32_t addu32_safe(uint32_t a, uint32_t b)
{
	if (a > UINT32_MAX - b) {
		return UINT32_MAX;
	} else {
		return a + b;
	}
}

int8_t adds8_safe(int8_t a, int8_t b)
{
	if (b > 0) {
		if (a > INT8_MAX - b) {
			return INT8_MAX;
		} else {
			return a + b;
		}
	} else {
		if (a <  INT8_MIN + b) {
			return INT8_MIN;
		} else {
			return a + b;
		}
	}
}

int16_t adds16_safe(int16_t a, int16_t b)
{
	if (b > 0) {
		if (a > INT16_MAX - b) {
			return INT16_MAX;
		} else {
			return a + b;
		}
	} else {
		if (a <  INT16_MIN + b) {
			return INT16_MIN;
		} else {
			return a + b;
		}
	}
}

int32_t adds32_safe(int32_t a, int32_t b)
{
	if (b > 0) {
		if (a > INT32_MAX - b) {
			return INT32_MAX;
		} else {
			return a + b;
		}
	} else {
		if (a <  INT32_MIN + b) {
			return INT32_MIN;
		} else {
			return a + b;
		}
	}
}

char* b2s(uint64_t binary, uint8_t rjust)
{
	static char string[64 + 1] = {0}; // the string representation to return
	uint8_t bit = LENGTH(string) - 1; // the index of the bit to print
	string[bit--] = '\0'; // terminate string

	while (binary) {
		if (binary & 1) {
			string[bit--] = '1';
		} else {
			string[bit--] = '0';
		}
		binary >>= 1;
	}

	while (64 - bit - 1 < rjust && bit > 0) {
		string[bit--] = '0';
	}

	return string;
}

/** switch on board LED */
inline void led_on(void)
{
#if defined(LED_PIN)
#if defined(LED_ON) && LED_ON
	gpio_set(GPIO_PORT(LED_PIN), GPIO_PIN(LED_PIN));
#else
	gpio_clear(GPIO_PORT(LED_PIN), GPIO_PIN(LED_PIN));
#endif // LED_ON
#endif // LED_PIN
}

/** switch off board LED */
inline void led_off(void)
{
#if defined(LED_PIN)
#if defined(LED_ON) && LED_ON
	gpio_clear(GPIO_PORT(LED_PIN), GPIO_PIN(LED_PIN));
#else
	gpio_set(GPIO_PORT(LED_PIN), GPIO_PIN(LED_PIN));
#endif // LED_ON
#endif // LED_PIN
}

/** toggle board LED */
inline void led_toggle(void)
{
#if defined(LED_PIN)
	gpio_toggle(GPIO_PORT(LED_PIN), GPIO_PIN(LED_PIN));
#endif // LED_PIN
}

void sleep_us(uint32_t duration)
{
	if (duration <= 4) { // less than the setup time
		for (volatile uint32_t nop = 0; nop < 5 * duration; nop++); // busy loop, approximate
		return;
	}

	duration -= 4; // subtract setup time
	systick_counter_disable(); // disable SysTick to reconfigure it
	if (!systick_set_frequency(1000000, rcc_ahb_frequency)) { // set SysTick frequency to microseconds
		 while (true); // unhandled error
	}
	systick_clear(); // reset SysTick
	systick_interrupt_enable(); // enable interrupt to count duration
	sleep_duration = duration; // save sleep duration for count down
	systick_counter_enable(); // start counting
	while (sleep_duration > 0) { // wait for count down to complete
		__WFI(); // go to sleep
	}
}

void sleep_ms(uint32_t duration)
{
	if (0 == duration) {
		return;
	}

	systick_counter_disable(); // disable SysTick to reconfigure it
	if (!systick_set_frequency(1000, rcc_ahb_frequency)) { // set SysTick frequency to milliseconds
		while (true); // unhandled error
	}
	systick_clear(); // reset SysTick
	systick_interrupt_enable(); // enable interrupt to count duration
	sleep_duration = duration; // save sleep duration for count down
	systick_counter_enable(); // start counting
	while (sleep_duration > 0) { // wait for count down to complete
		__WFI(); // go to sleep
	}
}

/** SysTick interrupt handler */
void sys_tick_handler(void)
{
	if (sleep_duration > 0) {
		sleep_duration--; // decrement duration
	}
	if (0 == sleep_duration) { // sleep complete
		systick_counter_disable(); // stop systick
		systick_interrupt_disable(); // stop interrupting
		sleep_duration = 0; // ensure it still is at 0
	}
}

char user_input_get(void)
{
	while (0 == user_input_used) { // wait for user input to be available (don't trust user_input_available since it user modifiable)
		__WFI(); // go to sleep
	}
	volatile char to_return = user_input_buffer[user_input_i]; // get the next available character
	user_input_i = (user_input_i + 1) % LENGTH(user_input_buffer); // update used buffer
	user_input_used--; // update used buffer
	user_input_available = (user_input_used != 0); // update available data
	return to_return;
}

void user_input_store(char c)
{
	// only save data if there is space in the buffer
	if (user_input_used >= LENGTH(user_input_buffer)) { // if buffer is full
		user_input_i = (user_input_i + 1) % LENGTH(user_input_buffer); // drop oldest data
		user_input_used--; // update used buffer information
	}
	user_input_buffer[(user_input_i + user_input_used) % LENGTH(user_input_buffer)] = c; // put character in buffer
	user_input_used++; // update used buffer
	user_input_available = true; // update available data
}

void board_setup(void)
{
	// setup main clock
#if defined(MINIF401)
	rcc_clock_setup_pll(&rcc_hse_25mhz_3v3[RCC_CLOCK_3V3_84MHZ]); // the MINIF401 uses an STM32F401 which can go up to 84 MHz, and the board has a 25 MHz crystal
#else
	rcc_clock_setup_pll(&rcc_hsi_configs[RCC_CLOCK_3V3_84MHZ]); // use HSI which is present on all boards, and limit to 84MHz (supported by all STM32F4
#endif

#if defined(LED_PIN) && defined(LED_ON)
	// setup LED
	rcc_periph_clock_enable(GPIO_RCC(LED_PIN)); // enable clock for LED
	gpio_mode_setup(GPIO_PORT(LED_PIN), GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO_PIN(LED_PIN)); // set LED pin as output
#if LED_ON // LED is on when sourcing
	gpio_set_output_options(GPIO_PORT(LED_PIN), GPIO_OTYPE_PP, GPIO_OSPEED_2MHZ, GPIO_PIN(LED_PIN)); // set LED pin output as push-pull
#else // LED is on when sinking
	gpio_set_output_options(GPIO_PORT(LED_PIN), GPIO_OTYPE_OD, GPIO_OSPEED_2MHZ, GPIO_PIN(LED_PIN)); // set LED pin output as open-drain
#endif
	led_off(); // switch off LED per default
#endif // LED_PIN

/*
	// setup button
#if defined(BUTTON_PIN) && defined(BUTTON_PRESSED)
	rcc_periph_clock_enable(GPIO_RCC(BUTTON_PIN)); // enable clock for button
	exti_select_source(GPIO_EXTI(BUTTON_PIN), GPIO_PORT(BUTTON_PIN)); // mask external interrupt of this pin only for this port
#if BUTTON_PRESSED // level goes high when pressed
	gpio_mode_setup(GPIO_PORT(BUTTON_PIN), GPIO_MODE_INPUT, GPIO_PUPD_PULLDOWN, GPIO_PIN(BUTTON_PIN)); // set GPIO to input and pull down
	exti_set_trigger(GPIO_EXTI(BUTTON_PIN), EXTI_TRIGGER_RISING); // trigger when button is pressed
#else // level goes low when pressed
	gpio_mode_setup(GPIO_PORT(BUTTON_PIN), GPIO_MODE_INPUT, GPIO_PUPD_PULLUP, GPIO_PIN(BUTTON_PIN)); // set GPIO to input and pull up
	exti_set_trigger(GPIO_EXTI(BUTTON_PIN), EXTI_TRIGGER_FALLING); // trigger when button is pressed
#endif
	exti_enable_request(GPIO_EXTI(BUTTON_PIN)); // enable external interrupt
	nvic_enable_irq(GPIO_NVIC_EXTI_IRQ(BUTTON_PIN)); // enable interrupt
#endif
*/

	// reset user input buffer
	user_input_available = false;
	user_input_i = 0;
	user_input_used = 0;
}

/** disconnect USB by sending a reset condition */
static void usb_disconnect(void)
{
	if (OTG_FS_GUSBCFG & OTG_GUSBCFG_FDMOD) { // USB configured as device
		// pull USB D+ low for a short while
		OTG_FS_DCTL |= OTG_DCTL_SDIS; // disconnect DP pull-up to simulate a disconnect
		// in case there is an external pull-up resistor, pull DP low
		// I have no idea why, but once USB is configured, I can't use PA12/DP back as GPIO
		gpio_mode_setup(GPIOA, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO12); // be sure the D+ pin can be used as GPIO output
		gpio_set_output_options(GPIOA, GPIO_OTYPE_PP, GPIO_OSPEED_2MHZ, GPIO12); // use push-pull output
		gpio_clear(GPIOA, GPIO12); // pull D+ low
		for (volatile uint32_t i = 0; i < 0x2000; i++); // USB disconnected must be at least 10 ms long, at most 100 ms
	}
}

void system_memory(void)
{
	usb_disconnect(); // disconnect from USB (if necessary)

	// for more details, see https://stm32f4-discovery.net/2017/04/tutorial-jump-system-memory-software-stm32/

	// deinit RCC (according to STM32CubeF4 source code)
	RCC_CR |= RCC_CR_HSION; // enable high speed internal clock
	while (!(RCC_CR & RCC_CR_HSIRDY)); // wait until clock is ready
	RCC_CR |= (0x10U << RCC_CR_HSITRIM_SHIFT); // set HSITRIM[4:0] bits to the reset value
	RCC_CFGR = 0;// reset CFGR register
	while (((RCC_CFGR >> RCC_CFGR_SWS_SHIFT) & RCC_CFGR_SWS_MASK) != RCC_CFGR_SWS_HSI); // wait it till clock switch is ready
	RCC_CR &= ~(RCC_CR_HSEON | RCC_CR_HSEBYP | RCC_CR_CSSON); // clear HSEON, HSEBYP and CSSON bits
	while (RCC_CR & RCC_CR_HSERDY); // wait till HSE is disabled
	RCC_CR &= ~RCC_CR_PLLON; // Clear PLLON bit
	while (RCC_CR & RCC_CR_PLLRDY); // wait till PLL is disabled
	//RCC_PLLCFGR = 0x24003010; // reset PLLCFGR register to default value (value for STM32F401)
	RCC_CIR &= ~(RCC_CIR_LSIRDYIE | RCC_CIR_LSERDYIE | RCC_CIR_HSIRDYIE | RCC_CIR_HSERDYIE | RCC_CIR_PLLRDYIE); // disable all interrupts
	RCC_CIR |= (RCC_CIR_LSIRDYC | RCC_CIR_LSERDYC | RCC_CIR_HSIRDYC | RCC_CIR_HSERDYC | RCC_CIR_PLLRDYC | RCC_CIR_CSSC); // clear all interrupt flags
	RCC_CR &= ~RCC_CSR_LSION; // clear LSION bit
	RCC_CSR |= RCC_CSR_RMVF; // reset all CSR flags

	// switch to system memory
	RCC_APB2ENR = RCC_APB2ENR_SYSCFGEN; // enable system configure clock (all others are not required)
	cm_disable_interrupts(); // disable all interrupts
	SYSCFG_MEMRM = 1; // map system memory to 0x0000 0000 (this bypasses the BOOT0 pin)
	const uint32_t address = 0x1FFF0000; // system memory address
	__asm__ volatile ("MSR msp,%0" : :"r"(*(uint32_t*)address)); // set stack pointer to address provided in the beginning of the bootloader (loaded into a register first)
	(*(void(**)(void))((uint32_t)address + 4))(); // start system memory (by jumping to the reset function which address is stored as second entry of the vector table)
	// we should not reach this point
}

void dfu_bootloader(void)
{
	usb_disconnect(); // disconnect from USB (if necessary)

	// set DFU magic to specific RAM location
	__dfu_magic[0] = 'D';
	__dfu_magic[1] = 'F';
	__dfu_magic[2] = 'U';
	__dfu_magic[3] = '!';
	scb_reset_system(); // reset system (core and peripherals)
	while (true); // wait for the reset to happen
}

#if defined(BUTTON_PIN)
/** interrupt service routine called when button is pressed */
void GPIO_EXTI_ISR(BUTTON_PIN)(void)
{
	exti_reset_request(GPIO_EXTI(BUTTON_PIN)); // reset interrupt
	button_flag = true; // perform button action
}
#endif