/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
/** library to read/write internal flash (code)
 *  @file flash_internal.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016-2018
 *  @note peripherals used: none
 */
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general utilities

/* STM32 (including CM3) libraries */
#include <libopencm3/stm32/flash.h> // flash utilities
#include <libopencm3/stm32/desig.h> // device signature definitions
#include <libopencm3/stm32/dbgmcu.h> // debug definitions

#include "flash_internal.h" // flash storage library API
#include "global.h" // global definitions

/** verify if the data is in the internal flash area
 *  @param[in] address start address of the data to read
 *  @param[in] size how much data to read or write, in bytes
 *  @return if the data is in the internal flash area
 */
static bool flash_internal_range(uint32_t address, size_t size) {
	if (address>(UINT32_MAX-size)) { // on integer overflow will occur
		return false;
	}
	if (address<FLASH_BASE) { // start address is before the start of the internal flash
		return false;
	}
	if ((uint32_t)&__flash_end>=FLASH_BASE) { // check if the end for the internal flash is enforce by the linker script
		if ((address+size)>(uint32_t)&__flash_end) { // end address is after the end of the enforced internal flash
			return false;
		}
	} else {
		if ((address+size)>(FLASH_BASE+DESIG_FLASH_SIZE*1024)) { // end address is after the end of the advertised flash
			return false;
		}
	}
	return true;
}

bool flash_internal_read(uint32_t address, uint8_t *buffer, size_t size)
{
	// sanity checks
	if (buffer==NULL || size==0) {
		return false;
	}
	if (!flash_internal_range(address, size)) {
		return false;
	}

	// copy data byte per byte (a more efficient way would be to copy words, than the remaining bytes)
	for (size_t i=0; i<size; i++) {
		buffer[i] = *((uint8_t*)address+i);
	}

	return true;
}

int32_t flash_internal_write(uint32_t address, const uint8_t *buffer, size_t size, bool preserve)
{
	// sanity checks
	if (buffer == NULL || size == 0 || size % 2) {
		return -1;
	}
	if (!flash_internal_range(address, size)) {
		return -2;
	}

	// verify if it's in the flash area
	if (address < FLASH_BASE) {
		return -3;
	} else if ((uint32_t)&__flash_end >= FLASH_BASE && (address + size) > (uint32_t)&__flash_end) {
		return 4;
	} else if ((uint32_t)&__flash_end < FLASH_BASE && (address + size) > (FLASH_BASE+DESIG_FLASH_SIZE * 1024)) {
		return -5;
	}

	// get page size
	uint16_t page_size = 0;
	if ((0x410 == (DBGMCU_IDCODE&DBGMCU_IDCODE_DEV_ID_MASK)) || (0x412 == (DBGMCU_IDCODE&DBGMCU_IDCODE_DEV_ID_MASK))) { // low-density (16-32 KB flash) and medium-density (64-128 KB flash) devices have 1 KB flash pages
		page_size = 1024;
	} else if ((0x414 == (DBGMCU_IDCODE&DBGMCU_IDCODE_DEV_ID_MASK)) || (0x430 == (DBGMCU_IDCODE&DBGMCU_IDCODE_DEV_ID_MASK)) || (0x418==(DBGMCU_IDCODE&DBGMCU_IDCODE_DEV_ID_MASK))) { // high-density (256-512 KB flash), XL-density (768-1024 KB flash) devices and connectivity line have 2 KB flash pages
		page_size = 2048;
	} else { // unknown device type (or unreadable type, see errata), deduce page size from flash size
		if (DESIG_FLASH_SIZE < 256) {
			page_size = 1024;
		} else {
			page_size = 2048;
		}
	}

	uint32_t written = 0; // number of bytes written
	flash_unlock(); // unlock flash to be able to write it
	while (size) { // write page by page until all data has been written
		// verify of we need to erase the flash before writing it
		uint32_t page_start = address - (address % page_size); // get start of the current page
		bool erase = false; // verify if the flash to write is erased of if we need to erase the page
		for (uint32_t i = 0; i < size && (address + i) < (page_start + page_size); i += 2) { // verify if not bit need to be flipped to 1 again
			if (*(uint16_t*)(buffer + i) != 0x0000 && (*(uint16_t*)(address + i)) != 0xffff ) { // to write the flashed, it needs to be erased, or the data needs to be 0
				erase = true; // we need to erase the flash to flip the bit back to 1
			}
		}
		if (erase && preserve) { // erase before
			uint8_t page_data[page_size]; // a copy of the complete page before the erase it
			uint16_t page_i = 0; // index for page data
			// copy page before address
			for (uint32_t flash = page_start; flash < address && flash < (page_start + page_size) && page_i < page_size; flash++) {
				page_data[page_i++] = *(uint8_t*)(flash);
			}
			// copy data starting at address
			while (size > 0 && page_i < page_size) {
				page_data[page_i++] = *buffer;
				buffer++;
				address++;
				size--;
			}
			// copy data after buffer until end of page
			while (page_i < page_size) {
				page_data[page_i] = *(uint8_t*)(page_start+page_i);
				page_i++;
			}
			flash_erase_page(page_start); // erase current page
			if (flash_get_status_flags() != FLASH_SR_EOP) { // operation went wrong
				flash_lock(); // lock back flash to protect it
				return -6;
			}
			for (uint16_t i = 0; i < page_size; i += 2) { // write whole page
				flash_program_half_word(page_start + i, *((uint16_t*)(page_data + i)));
				if (flash_get_status_flags() != FLASH_SR_EOP) { // operation went wrong
					flash_lock(); // lock back flash to protect it
					return -7;
				}
				if (*((uint16_t*)(page_data + i)) != *((uint16_t*)(page_start + i))) { // verify the programmed data is right
					flash_lock(); // lock back flash to protect it
					return -8;
				}
				written += 2;
			}
		} else { // simply copy data until end of page (or end of data)
			if (erase) {
				flash_erase_page(page_start); // erase current page
				if (flash_get_status_flags() != FLASH_SR_EOP) { // operation went wrong
					flash_lock(); // lock back flash to protect it
					return -9;
				}
			}
			while (size > 0 && address < (page_start + page_size)) {
				flash_program_half_word(address, *((uint16_t*)(buffer)));
				if (flash_get_status_flags() != FLASH_SR_EOP) { // operation went wrong
					flash_lock(); // lock back flash to protect it
					return -10;
				}
				if (*((uint16_t*)address) != *((uint16_t*)buffer)) { // verify the programmed data is right
					flash_lock(); // lock back flash to protect it
					return -11;
				}
				written += 2;
				buffer += 2;
				address += 2;
				size -= 2;
			}
		}
	}
	flash_lock(); // lock back flash to protect it

	return written;
}