/*
 * spiffs_cache.c
 *
 *  Created on: Jun 23, 2013
 *      Author: petera
 */

#include "spiffs.h"
#include "spiffs_nucleus.h"
#include <string.h>

#if SPIFFS_CACHE

// returns cached page for give page index, or null if no such cached page
static spiffs_cache_page *spiffs_cache_page_get(spiffs *fs, spiffs_page_ix pix) {
  spiffs_cache *cache = spiffs_get_cache(fs);
  if ((cache->cpage_use_map & cache->cpage_use_mask) == 0) return 0;
  int i;
  for (i = 0; i < cache->cpage_count; i++) {
    spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
    if ((cache->cpage_use_map & (1<<i)) &&
        (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) == 0 &&
        cp->pix == pix ) {
      SPIFFS_CACHE_DBG("CACHE_GET: have cache page %i for %04x\n", i, pix);
      cp->last_access = cache->last_access;
      return cp;
    }
  }
  //SPIFFS_CACHE_DBG("CACHE_GET: no cache for %04x\n", pix);
  return 0;
}

// frees cached page
static s32_t spiffs_cache_page_free(spiffs *fs, int ix, u8_t write_back) {
  s32_t res = SPIFFS_OK;
  spiffs_cache *cache = spiffs_get_cache(fs);
  spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, ix);
  if (cache->cpage_use_map & (1<<ix)) {
    if (write_back &&
        (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) == 0 &&
        (cp->flags & SPIFFS_CACHE_FLAG_DIRTY)) {
      u8_t *mem =  spiffs_get_cache_page(fs, cache, ix);
      res = SPIFFS_HAL_WRITE(fs, SPIFFS_PAGE_TO_PADDR(fs, cp->pix), SPIFFS_CFG_LOG_PAGE_SZ(fs), mem);
    }

    cp->flags = 0;
    cache->cpage_use_map &= ~(1 << ix);

    if (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) {
      SPIFFS_CACHE_DBG("CACHE_FREE: free cache page %i objid %04x\n", ix, cp->obj_id);
    } else {
      SPIFFS_CACHE_DBG("CACHE_FREE: free cache page %i pix %04x\n", ix, cp->pix);
    }
  }

  return res;
}

// removes the oldest accessed cached page
static s32_t spiffs_cache_page_remove_oldest(spiffs *fs, u8_t flag_mask, u8_t flags) {
  s32_t res = SPIFFS_OK;
  spiffs_cache *cache = spiffs_get_cache(fs);

  if ((cache->cpage_use_map & cache->cpage_use_mask) != cache->cpage_use_mask) {
    // at least one free cpage
    return SPIFFS_OK;
  }

  // all busy, scan thru all to find the cpage which has oldest access
  int i;
  int cand_ix = -1;
  u32_t oldest_val = 0;
  for (i = 0; i < cache->cpage_count; i++) {
    spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
    if ((cache->last_access - cp->last_access) > oldest_val &&
        (cp->flags & flag_mask) == flags) {
      oldest_val = cache->last_access - cp->last_access;
      cand_ix = i;
    }
  }

  if (cand_ix >= 0) {
    res = spiffs_cache_page_free(fs, cand_ix, 1);
  }

  return res;
}

// allocates a new cached page and returns it, or null if all cache pages are busy
static spiffs_cache_page *spiffs_cache_page_allocate(spiffs *fs) {
  spiffs_cache *cache = spiffs_get_cache(fs);
  if (cache->cpage_use_map == 0xffffffff) {
    // out of cache memory
    return 0;
  }
  int i;
  for (i = 0; i < cache->cpage_count; i++) {
    if ((cache->cpage_use_map & (1<<i)) == 0) {
      spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
      cache->cpage_use_map |= (1<<i);
      cp->last_access = cache->last_access;
      SPIFFS_CACHE_DBG("CACHE_ALLO: allocated cache page %i\n", i);
      return cp;
    }
  }
  // out of cache entries
  return 0;
}

// drops the cache page for give page index
void spiffs_cache_drop_page(spiffs *fs, spiffs_page_ix pix) {
  spiffs_cache_page *cp =  spiffs_cache_page_get(fs, pix);
  if (cp) {
    spiffs_cache_page_free(fs, cp->ix, 0);
  }
}

// ------------------------------

// reads from spi flash or the cache
s32_t spiffs_phys_rd(
    spiffs *fs,
    u8_t op,
    spiffs_file fh,
    u32_t addr,
    u32_t len,
    u8_t *dst) {
  (void)fh;
  s32_t res = SPIFFS_OK;
  spiffs_cache *cache = spiffs_get_cache(fs);
  spiffs_cache_page *cp =  spiffs_cache_page_get(fs, SPIFFS_PADDR_TO_PAGE(fs, addr));
  cache->last_access++;
  if (cp) {
#if SPIFFS_CACHE_STATS
    fs->cache_hits++;
#endif
    cp->last_access = cache->last_access;
  } else {
    if ((op & SPIFFS_OP_TYPE_MASK) == SPIFFS_OP_T_OBJ_LU2) {
      // for second layer lookup functions, we do not cache in order to prevent shredding
      return SPIFFS_HAL_READ(fs, addr, len, dst);
    }
#if SPIFFS_CACHE_STATS
    fs->cache_misses++;
#endif
    res = spiffs_cache_page_remove_oldest(fs, SPIFFS_CACHE_FLAG_TYPE_WR, 0);
    cp = spiffs_cache_page_allocate(fs);
    if (cp) {
      cp->flags = SPIFFS_CACHE_FLAG_WRTHRU;
      cp->pix = SPIFFS_PADDR_TO_PAGE(fs, addr);
    }
    s32_t res2 = SPIFFS_HAL_READ(fs,
        addr - SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr),
        SPIFFS_CFG_LOG_PAGE_SZ(fs),
        spiffs_get_cache_page(fs, cache, cp->ix));
    if (res2 != SPIFFS_OK) {
      res = res2;
    }
  }
  u8_t *mem =  spiffs_get_cache_page(fs, cache, cp->ix);
  memcpy(dst, &mem[SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr)], len);
  return res;
}

// writes to spi flash and/or the cache
s32_t spiffs_phys_wr(
    spiffs *fs,
    u8_t op,
    spiffs_file fh,
    u32_t addr,
    u32_t len,
    u8_t *src) {
  (void)fh;
  spiffs_page_ix pix = SPIFFS_PADDR_TO_PAGE(fs, addr);
  spiffs_cache *cache = spiffs_get_cache(fs);
  spiffs_cache_page *cp =  spiffs_cache_page_get(fs, pix);

  if (cp && (op & SPIFFS_OP_COM_MASK) != SPIFFS_OP_C_WRTHRU) {
    // have a cache page
    // copy in data to cache page

    if ((op & SPIFFS_OP_COM_MASK) == SPIFFS_OP_C_DELE &&
        (op & SPIFFS_OP_TYPE_MASK) != SPIFFS_OP_T_OBJ_LU) {
      // page is being deleted, wipe from cache - unless it is a lookup page
      spiffs_cache_page_free(fs, cp->ix, 0);
      return SPIFFS_HAL_WRITE(fs, addr, len, src);
    }

    u8_t *mem =  spiffs_get_cache_page(fs, cache, cp->ix);
    memcpy(&mem[SPIFFS_PADDR_TO_PAGE_OFFSET(fs, addr)], src, len);

    cache->last_access++;
    cp->last_access = cache->last_access;

    if (cp->flags & SPIFFS_CACHE_FLAG_WRTHRU) {
      // page is being updated, no write-cache, just pass thru
      return SPIFFS_HAL_WRITE(fs, addr, len, src);
    } else {
      return SPIFFS_OK;
    }
  } else {
    // no cache page, no write cache - just write thru
    return SPIFFS_HAL_WRITE(fs, addr, len, src);
  }
}

#if SPIFFS_CACHE_WR
// returns the cache page that this fd refers, or null if no cache page
spiffs_cache_page *spiffs_cache_page_get_by_fd(spiffs *fs, spiffs_fd *fd) {
  spiffs_cache *cache = spiffs_get_cache(fs);

  if ((cache->cpage_use_map & cache->cpage_use_mask) == 0) {
    // all cpages free, no cpage cannot be assigned to obj_id
    return 0;
  }

  int i;
  for (i = 0; i < cache->cpage_count; i++) {
    spiffs_cache_page *cp = spiffs_get_cache_page_hdr(fs, cache, i);
    if ((cache->cpage_use_map & (1<<i)) &&
        (cp->flags & SPIFFS_CACHE_FLAG_TYPE_WR) &&
        cp->obj_id == fd->obj_id) {
      return cp;
    }
  }

  return 0;
}

// allocates a new cache page and refers this to given fd - flushes an old cache
// page if all cache is busy
spiffs_cache_page *spiffs_cache_page_allocate_by_fd(spiffs *fs, spiffs_fd *fd) {
  // before this function is called, it is ensured that there is no already existing
  // cache page with same object id
  spiffs_cache_page_remove_oldest(fs, SPIFFS_CACHE_FLAG_TYPE_WR, 0);
  spiffs_cache_page *cp = spiffs_cache_page_allocate(fs);
  if (cp == 0) {
    // could not get cache page
    return 0;
  }

  cp->flags = SPIFFS_CACHE_FLAG_TYPE_WR;
  cp->obj_id = fd->obj_id;
  fd->cache_page = cp;
  return cp;
}

// unrefers all fds that this cache page refers to and releases the cache page
void spiffs_cache_fd_release(spiffs *fs, spiffs_cache_page *cp) {
  if (cp == 0) return;
  u32_t i;
  spiffs_fd *fds = (spiffs_fd *)fs->fd_space;
  for (i = 0; i < fs->fd_count; i++) {
    spiffs_fd *cur_fd = &fds[i];
    if (cur_fd->file_nbr != 0 && cur_fd->cache_page == cp) {
      cur_fd->cache_page = 0;
    }
  }
  spiffs_cache_page_free(fs, cp->ix, 0);

  cp->obj_id = 0;
}

#endif

// initializes the cache
void spiffs_cache_init(spiffs *fs) {
  if (fs->cache == 0) return;
  u32_t sz = fs->cache_size;
  u32_t cache_mask = 0;
  int i;
  int cache_entries =
      (sz - sizeof(spiffs_cache)) / (SPIFFS_CACHE_PAGE_SIZE(fs));
  if (cache_entries <= 0) return;

  for (i = 0; i < cache_entries; i++) {
    cache_mask <<= 1;
    cache_mask |= 1;
  }

  spiffs_cache cache;
  memset(&cache, 0, sizeof(spiffs_cache));
  cache.cpage_count = cache_entries;
  cache.cpages = (u8_t *)((u8_t *)fs->cache + sizeof(spiffs_cache));

  cache.cpage_use_map = 0xffffffff;
  cache.cpage_use_mask = cache_mask;
  memcpy(fs->cache, &cache, sizeof(spiffs_cache));

  spiffs_cache *c = spiffs_get_cache(fs);

  memset(c->cpages, 0, c->cpage_count * SPIFFS_CACHE_PAGE_SIZE(fs));

  c->cpage_use_map &= ~(c->cpage_use_mask);
  for (i = 0; i < cache.cpage_count; i++) {
    spiffs_get_cache_page_hdr(fs, c, i)->ix = i;
  }
}

#endif // SPIFFS_CACHE
