/*
 * 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 = 0x555555FFUL};

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

static void
WriteNVRAM(int offset, nvram_info_t data)
{
  HAL_FLASHEx_DATAEEPROM_Unlock();
  HAL_FLASHEx_DATAEEPROM_Program(FLASH_TYPEPROGRAMDATA_WORD, (uint32_t)(&NVRAM_Base[offset]), data.u32);
  HAL_FLASHEx_DATAEEPROM_Lock();
}

static void
EraseNVRAM(int offset)
{
  HAL_FLASHEx_DATAEEPROM_Unlock();
  HAL_FLASHEx_DATAEEPROM_Erase(FLASH_TYPEERASEDATA_WORD, (uint32_t)(&NVRAM_Base[offset]));
  HAL_FLASHEx_DATAEEPROM_Lock();
}

void write_nvram_data(nvram_info_t data)
{
#if defined SEMIHOSTING
  printf("write\n");
#endif

  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, delete any entries that have a matching tag
#if defined SEMIHOSTING
      printf("marked erased %d\n", ptr);
#endif
      WriteNVRAM(ptr, MARKED_ERASED);

      base = ptr;
    }
  }

  // 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)
      {
   #if defined SEMIHOSTING
       printf("erase %d\n", index);
#endif

        EraseNVRAM(index);
      }
        #if defined SEMIHOSTING
printf("write %d=%d\n", index, data.data.pos);
#endif
      WriteNVRAM(index, data);
      // now check to see if it actually went
      if (NVRAM_Base[index].u32 != data.u32)
      {
          #if defined SEMIHOSTING
        printf("unusable %d\n", index);
#endif
        WriteNVRAM(index, MARKED_UNUSABLE); // mark as neither unused or used
        continue;
      }
      return;
    }
  }
}

nvram_info_t *find_nvram_data(uint8_t searchTag)
{  
  #if defined SEMIHOSTING
  printf("find\n");
#endif
  for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
  {
    if (NVRAM_Base[ptr].data.tag == searchTag)
    {
        #if defined SEMIHOSTING
      printf("found %d=%d\n", ptr, NVRAM_Base[ptr].data.pos);
#endif
      return &NVRAM_Base[ptr];
    }
  }
  return NULL;
}

void erase_nvram()
{
    #if defined SEMIHOSTING
  printf("erase all\n");
#endif
  for (int ptr = 0; ptr < NVRAM_WORDS; ptr++)
    EraseNVRAM(ptr);
}