/*
 * nvram.c
 *
 *  Created on: 4 Jun 2017
 *      Author: Mike
 */

/* Includes ------------------------------------------------------------------*/
#include "stm32l1xx_hal.h"

#include "nvram.h"

// NVRAM hardware erases to all 0x
nvram_info_t const HARDWARE_ERASED = {.u32 = 0UL};
// Marked as erased change to all 1
nvram_info_t const MARKED_ERASED = {.u32 = ~0UL};
// marked as unusable  change pattern to something in between
nvram_info_t const MARKED_UNUSABLE = {.u32 = 0x55555555UL};

nvram_info_t NVRAM_Base[NVRAM_WORDS] __attribute__((section(".NVRAM_Data"))); // set by linker

static void
WriteNVRAM(nvram_info_t *Address, nvram_info_t data)
{
  HAL_FLASHEx_DATAEEPROM_Unlock();
  HAL_FLASHEx_DATAEEPROM_Program(FLASH_TYPEPROGRAMDATA_WORD, (uint32_t)Address, data.u32);
  HAL_FLASHEx_DATAEEPROM_Lock();
}

static void
EraseNVRAM(nvram_info_t *Address)
{
  HAL_FLASHEx_DATAEEPROM_Unlock();
  HAL_FLASHEx_DATAEEPROM_Erase(FLASH_TYPEERASEDATA_WORD, (uint32_t)Address);
  HAL_FLASHEx_DATAEEPROM_Lock();
}

void write_nvram_data(nvram_info_t data)
{
  int base = 0;

  /* search blank */
  for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
  {
    // erase the entry just found
    if (NVRAM_Base[ptr].data.tag == data.data.tag)
    {
      // erase previous data
      WriteNVRAM(&NVRAM_Base[ptr], MARKED_ERASED);
      base = ptr;
      break;
    }
  }
  // search forward for next erased or empty element, use it
  for (int offset = 1; offset < NVRAM_WORDS + 1; offset++)
  {
    int index = (base + offset) % NVRAM_WORDS;
    if (NVRAM_Base[index].u32 == MARKED_ERASED.u32 || NVRAM_Base[index].u32 == HARDWARE_ERASED.u32)
    {
      if (NVRAM_Base[index].u32 != HARDWARE_ERASED.u32)
        EraseNVRAM(&NVRAM_Base[index]);
      WriteNVRAM(&NVRAM_Base[index], data);
      // now check to see if it actually went
      if (NVRAM_Base[index].u32 != data.u32)
      {
        WriteNVRAM(&NVRAM_Base[index], MARKED_UNUSABLE); // mark as neither unused or used
        continue;
      }
      return;
    }
  }
}

nvram_info_t *find_nvram_data(uint8_t searchTag)
{
  for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
  {
    if (NVRAM_Base[ptr].data.tag == searchTag)
      return &NVRAM_Base[ptr];
  }
  return NULL;
}