// $Id$
//
//  Copyright (c) 2010, Novartis Institutes for BioMedical Research Inc.
//  All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
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//       nor the names of its contributors may be used to endorse or promote
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//
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//
#include <postgres.h>
#include <fmgr.h>
#include <utils/memutils.h>

#include "rdkit.h"
#include "cache.h"

#define MAGICKNUMBER 0xBEEC0DED
/*
 * Deconstructed values cache
 */

typedef enum EntryKind { MolKind, BfpKind, SfpKind, ReactionKind } EntryKind;

typedef struct ValueCacheEntry {
  Datum toastedValue;
  EntryKind kind;

  union {
    struct {
      Mol *value;
      bytea *sign;
      CROMol mol;
    } mol;
    struct {
      Bfp *value;
      BfpSignature *sign;
      CBfp fp;
    } bfp;
    struct {
      Sfp *value;
      bytea *sign;
      CSfp fp;
    } sfp;
    struct {
      Reaction *value;
      bytea *sign;
      CChemicalReaction rxn;
    } reaction;
  } detoasted;

  struct ValueCacheEntry *prev;
  struct ValueCacheEntry *next;
} ValueCacheEntry;

#define NENTRIES (16)

typedef struct ValueCache {
  uint32 magickNumber;
  MemoryContext ctx;
  int32 nentries;
  ValueCacheEntry *head;
  ValueCacheEntry *tail;
  ValueCacheEntry *entries[NENTRIES];
} ValueCache;

/*********** Managing LRU **********/
/* move the most recently used value to the head */
static void moveFirst(ValueCache *ac, ValueCacheEntry *entry) {
  /*
   * unlink the entry from the list
   */
  Assert(entry != ac->head);

  if (entry == ac->tail) {
    Assert(entry->next == NULL);
    ac->tail = entry->prev;
    if (ac->tail) {
      ac->tail->next = NULL;
    } else {
      ac->head = NULL;
    }
  } else {
    entry->prev->next = entry->next;
    entry->next->prev = entry->prev;
  }

  /*
   * reinstall into head
   */

  Assert(ac->head != NULL);
  Assert(ac->tail != NULL);

  entry->next = ac->head;
  entry->prev = NULL;
  ac->head->prev = entry;
  ac->head = entry;
}

#define DATUMSIZE(d) VARSIZE_ANY(DatumGetPointer(d))

/*
 * define a comparison operator for the cached values.
 * generally applied to the toasted data, to verify the
 * equality of two values and to keep the cached entries
 * sorted (see cmpEntries below).
 */
static int cmpDatum(Datum a, Datum b) {
  int32 la = DATUMSIZE(a);
  int32 lb = DATUMSIZE(b);

  if (la == lb) {
    return memcmp(DatumGetPointer(a), DatumGetPointer(b), la);
  }
  return (la > lb) ? 1 : -1;
}

/*
 * free the memory allocated by a cache entry to hold the
 * toasted, detoasted and signature values (called when the
 * cache is destroyed or if the entry is reused for a new
 * value)
 */
static void cleanupData(ValueCacheEntry *entry) {
  pfree(DatumGetPointer(entry->toastedValue));

  switch (entry->kind) {
    case MolKind:
      if (entry->detoasted.mol.value) {
        pfree(entry->detoasted.mol.value);
      }
      if (entry->detoasted.mol.mol) {
        freeCROMol(entry->detoasted.mol.mol);
      }
      if (entry->detoasted.mol.sign) {
        pfree(entry->detoasted.mol.sign);
      }
      break;
    case BfpKind:
      if (entry->detoasted.bfp.value) {
        pfree(entry->detoasted.bfp.value);
      }
      if (entry->detoasted.bfp.fp) {
        freeCBfp(entry->detoasted.bfp.fp);
      }
      if (entry->detoasted.bfp.sign) {
        pfree(entry->detoasted.bfp.sign);
      }
      break;
    case SfpKind:
      if (entry->detoasted.sfp.value) {
        pfree(entry->detoasted.sfp.value);
      }
      if (entry->detoasted.sfp.fp) {
        freeCSfp(entry->detoasted.sfp.fp);
      }
      if (entry->detoasted.sfp.sign) {
        pfree(entry->detoasted.sfp.sign);
      }
      break;
    case ReactionKind:
      if (entry->detoasted.reaction.value) {
        pfree(entry->detoasted.reaction.value);
      }
      if (entry->detoasted.reaction.rxn) {
        freeChemReaction(entry->detoasted.reaction.rxn);
      }
      if (entry->detoasted.reaction.sign) {
        pfree(entry->detoasted.reaction.sign);
      }
      break;
    default:
      elog(ERROR, "Unknown kind: %d", entry->kind);
  }

  /* this function is called both when the memory context
   * is reset or destroyed, and all the cached entries are
   * discarded, but also when the least recently used value
   * in the cache is replaced, to make space for a new one.
   * to support this latter case, the prev/next pointers in
   * the entry are not zeroed by the call to memset here below.
   */
  memset(entry, 0, offsetof(ValueCacheEntry, prev));
}

/* assign a cache entry with the input toasted value and data kind */
static void makeEntry(ValueCache *ac, ValueCacheEntry *entry, Datum value,
                      EntryKind kind) {
  entry->toastedValue = (Datum)MemoryContextAlloc(ac->ctx, DATUMSIZE(value));
  entry->kind = kind;
  memcpy(DatumGetPointer(entry->toastedValue), DatumGetPointer(value),
         DATUMSIZE(value));
}

/* a comparison operator to sort the entries in ValueCache */
static int cmpEntry(const void *a, const void *b) {
  return cmpDatum((*(ValueCacheEntry **)a)->toastedValue,
                  (*(ValueCacheEntry **)b)->toastedValue);
}

/*********** Managing cache structure **********/

typedef struct CacheHolder {
  MemoryContext ctx;
  ValueCache *cache;
  struct CacheHolder *next;
} CacheHolder;

static CacheHolder *holder = NULL;

/*
 * A memory context callback. This function is registered to be
 * automatically called on a CacheHolder when the associated
 * memory context is reset or destroyed.
 */
static void cleanupRDKitCache(void *ptr) {
  CacheHolder *h = holder, *p = NULL;
  CacheHolder *holder_arg = (CacheHolder *)ptr;
  bool removed = false;

  /* cleanup the cached data */
  if (holder_arg->cache->magickNumber != MAGICKNUMBER) {
    elog(WARNING, "Something wrong in cleanupRDKitCache");
  } else {
    int i;

    for (i = 0; i < holder_arg->cache->nentries; i++) {
      cleanupData(holder_arg->cache->entries[i]);
    }
    holder_arg->cache->nentries = 0;
  }

  /* Find the holder and remove it from the list */
  while (h) {
    if (h != holder_arg) {
      p = h;
      h = h->next;
      continue;
    }

    /* h == holder_arg, remove from the list */
    if (p == NULL) {
      Assert(h == holder);
      holder = h->next;
      h = holder;
    } else {
      p->next = h->next;
      h = p->next;
    }

    /* done, exit */
    removed = true;
    break;
  }

  if (!removed) {
    elog(WARNING, "Deallocated cache holder not found in list");
  }
}

static ValueCache *createCache(void *cache, struct MemoryContextData *ctx) {
  ValueCache *ac;
  CacheHolder *newholder;
  MemoryContextCallback *ctxcb;

  if (cache != NULL) {
    ac = (ValueCache *)cache;
    if (ac->magickNumber != MAGICKNUMBER || ac->ctx != ctx) {
      elog(ERROR, "We can't use our approach with cache :(");
    }
  }

  /*
   * Try to connect to existing cache!
   */
  newholder = holder;
  while (newholder) {
    if (newholder->ctx == ctx) {
      /* Note: this reassigns the passed cache argument */
      cache = (void *)newholder->cache;
      break;
    }
    newholder = newholder->next;
  }

  if (!cache) {
    /*
     * did not found a cache in current context, make new one
     */
    cache = MemoryContextAllocZero(ctx, sizeof(ValueCache));

    /* init cache */
    ac = (ValueCache *)cache;
    ac->magickNumber = MAGICKNUMBER;
    ac->ctx = ctx;

    newholder = MemoryContextAllocZero(ctx, sizeof(CacheHolder));

    /* init holder */
    newholder->ctx = ctx;
    newholder->cache = ac;

    /* store holder */
    newholder->next = holder;
    holder = newholder;

    /*
     * register a context callback to cleanup this cache and
     * unlink the holder
     */
    ctxcb = MemoryContextAlloc(ctx, sizeof(MemoryContextCallback));
    ctxcb->func = cleanupRDKitCache;
    ctxcb->arg = newholder;
    MemoryContextRegisterResetCallback(ctx, ctxcb);
  }

  return (ValueCache *)cache;
}

/*********** SEARCHING **********/

/*
 * entry->kind == MolKind
 *      m, mol, fp, val
 * entry->kind == FpKind
 *      f, fp, val
 */

static void fetchData(ValueCache *ac, ValueCacheEntry *entry, void **detoasted,
                      void **internal, void **sign) {
  MemoryContext old;
  void *_tmp;

  switch (entry->kind) {
    case MolKind:
      if (detoasted) {
        if (entry->detoasted.mol.value == NULL) {
          Mol *detoastedMol;

          detoastedMol = DatumGetMolP(entry->toastedValue);
          entry->detoasted.mol.value =
              MemoryContextAlloc(ac->ctx, VARSIZE(detoastedMol));
          memcpy(entry->detoasted.mol.value, detoastedMol,
                 VARSIZE(detoastedMol));
        }
        *detoasted = entry->detoasted.mol.value;
      }

      if (internal) {
        if (entry->detoasted.mol.mol == NULL) {
          fetchData(ac, entry, &_tmp, NULL, NULL);
          entry->detoasted.mol.mol = constructROMol(entry->detoasted.mol.value);
        }
        *internal = entry->detoasted.mol.mol;
      }

      if (sign) {
        if (entry->detoasted.mol.sign == NULL) {
          fetchData(ac, entry, NULL, &_tmp, NULL);
          old = MemoryContextSwitchTo(ac->ctx);
          entry->detoasted.mol.sign =
              makeMolSignature(entry->detoasted.mol.mol);
          MemoryContextSwitchTo(old);
        }
        *sign = entry->detoasted.mol.sign;
      }
      break;
    case BfpKind:
      if (detoasted) {
        if (entry->detoasted.bfp.value == NULL) {
          Bfp *detoastedFP;

          detoastedFP = DatumGetBfpP(entry->toastedValue);
          entry->detoasted.bfp.value =
              MemoryContextAlloc(ac->ctx, VARSIZE(detoastedFP));
          memcpy(entry->detoasted.bfp.value, detoastedFP, VARSIZE(detoastedFP));
        }
        *detoasted = entry->detoasted.bfp.value;
      }

      if (internal) {
        if (entry->detoasted.bfp.fp == NULL) {
          fetchData(ac, entry, &_tmp, NULL, NULL);
          entry->detoasted.bfp.fp = constructCBfp(entry->detoasted.bfp.value);
        }
        *internal = entry->detoasted.bfp.fp;
      }

      if (sign) {
        if (entry->detoasted.bfp.sign == NULL) {
          fetchData(ac, entry, NULL, &_tmp, NULL);
          old = MemoryContextSwitchTo(ac->ctx);
          entry->detoasted.bfp.sign = makeBfpSignature(entry->detoasted.bfp.fp);
          MemoryContextSwitchTo(old);
        }
        *sign = entry->detoasted.bfp.sign;
      }
      break;
    case SfpKind:
      if (detoasted) {
        if (entry->detoasted.sfp.value == NULL) {
          Sfp *detoastedFP;

          detoastedFP = DatumGetSfpP(entry->toastedValue);
          entry->detoasted.sfp.value =
              MemoryContextAlloc(ac->ctx, VARSIZE(detoastedFP));
          memcpy(entry->detoasted.sfp.value, detoastedFP, VARSIZE(detoastedFP));
        }
        *detoasted = entry->detoasted.sfp.value;
      }

      if (internal) {
        if (entry->detoasted.sfp.fp == NULL) {
          fetchData(ac, entry, &_tmp, NULL, NULL);
          entry->detoasted.sfp.fp = constructCSfp(entry->detoasted.sfp.value);
        }
        *internal = entry->detoasted.sfp.fp;
      }

      if (sign) {
        if (entry->detoasted.sfp.sign == NULL) {
          fetchData(ac, entry, NULL, &_tmp, NULL);
          old = MemoryContextSwitchTo(ac->ctx);
          entry->detoasted.sfp.sign =
              makeSfpSignature(entry->detoasted.sfp.fp, NUMBITS);
          MemoryContextSwitchTo(old);
        }
        *sign = entry->detoasted.sfp.sign;
      }
      break;
    case ReactionKind:
      if (detoasted) {
        if (entry->detoasted.reaction.value == NULL) {
          Reaction *detoastedRxn;

          detoastedRxn = DatumGetReactionP(entry->toastedValue);
          entry->detoasted.reaction.value =
              MemoryContextAlloc(ac->ctx, VARSIZE(detoastedRxn));
          memcpy(entry->detoasted.reaction.value, detoastedRxn,
                 VARSIZE(detoastedRxn));
        }
        *detoasted = entry->detoasted.reaction.value;
      }

      if (internal) {
        if (entry->detoasted.reaction.rxn == NULL) {
          fetchData(ac, entry, &_tmp, NULL, NULL);
          entry->detoasted.reaction.rxn =
              constructChemReact(entry->detoasted.reaction.value);
        }
        *internal = entry->detoasted.reaction.rxn;
      }

      if (sign) {
        if (entry->detoasted.reaction.sign == NULL) {
          fetchData(ac, entry, NULL, &_tmp, NULL);
          old = MemoryContextSwitchTo(ac->ctx);
          entry->detoasted.reaction.sign =
              makeReactionSign(entry->detoasted.reaction.rxn);
          MemoryContextSwitchTo(old);
        }
        *sign = entry->detoasted.reaction.sign;
      }
      break;
    default:
      elog(ERROR, "Unknown kind: %d", entry->kind);
  }
}

static void *SearchValueCache(void *cache, struct MemoryContextData *ctx,
                              /*  in: */ Datum a, EntryKind kind,
                              /* out: */ void **detoasted, void **internal,
                              void **sign) {
  ValueCache *ac = createCache(cache, ctx);
  ValueCacheEntry *entry;

  /*
   * Fast check of most recently used value
   */
  if (ac->head && cmpDatum(ac->head->toastedValue, a) == 0) {
    Assert(ac->head->kind == kind);
    fetchData(ac, ac->head, detoasted, internal, sign);
    return cache;
  }

  /*
   * If the cache is empty, insert (and then return) the new value
   */
  if (ac->head == NULL) {
    ac->entries[0] = ac->head = ac->tail =
        MemoryContextAllocZero(ac->ctx, sizeof(ValueCacheEntry));
    ac->nentries = 1;
    makeEntry(ac, ac->head, a, kind);
    fetchData(ac, ac->head, detoasted, internal, sign);
    return cache;
  }

  /*
   * Do a binary search across the cached entries
   */
  do {
    ValueCacheEntry **StopLow = ac->entries;
    ValueCacheEntry **StopHigh = ac->entries + ac->nentries;
    ValueCacheEntry **StopMiddle;
    int cmp;

    while (StopLow < StopHigh) {
      StopMiddle = StopLow + ((StopHigh - StopLow) >> 1);
      entry = *StopMiddle;
      cmp = cmpDatum(entry->toastedValue, a);

      if (cmp == 0) {
        /*
         * If the value is found, move it to the head position
         * and return it
         */
        moveFirst(ac, entry);
        Assert(ac->head->kind == kind);
        fetchData(ac, ac->head, detoasted, internal, sign);
        return cache;
      } else if (cmp < 0) {
        StopLow = StopMiddle + 1;
      } else {
        StopHigh = StopMiddle;
      }
    }
  } while (0);

  /*
   * Not found
   */

  if (ac->nentries < NENTRIES) {
    /*
     * If the cache is not full, insert the new value in the head position
     */
    entry = ac->entries[ac->nentries] =
        MemoryContextAllocZero(ac->ctx, sizeof(ValueCacheEntry));

    /* install first */
    entry->next = ac->head;
    entry->prev = NULL;
    ac->head->prev = entry;
    ac->head = entry;

    ac->nentries++;

    makeEntry(ac, ac->head, a, kind);
    fetchData(ac, ac->head, detoasted, internal, sign);
  } else {
    /*
     * If the cache is full, clear the least recently used value (in tail
     * position) and reuse the entry to place the new value in the head
     */
    cleanupData(ac->tail);
    moveFirst(ac, ac->tail);
    makeEntry(ac, ac->head, a, kind);
    fetchData(ac, ac->head, detoasted, internal, sign);
  }

  /*
   * sort the entries in the array after values are added or removed.
   * this allows applying a binary search if the value is not found in
   * the head position.
   */
  qsort(ac->entries, ac->nentries, sizeof(ValueCacheEntry *), cmpEntry);
  return cache;
}

void *searchMolCache(void *cache, struct MemoryContextData *ctx, Datum a,
                     Mol **m, CROMol *mol, bytea **val) {
  return SearchValueCache(cache, ctx,
                          /*  in: */ a, MolKind,
                          /* out: */ (void **)m, (void **)mol, (void **)val);
}

void *searchBfpCache(void *cache, struct MemoryContextData *ctx, Datum a,
                     Bfp **f, CBfp *fp, BfpSignature **val) {
  return SearchValueCache(cache, ctx,
                          /*  in: */ a, BfpKind,
                          /* out: */ (void **)f, (void **)fp, (void **)val);
}

void *searchSfpCache(void *cache, struct MemoryContextData *ctx, Datum a,
                     Sfp **f, CSfp *fp, bytea **val) {
  return SearchValueCache(cache, ctx,
                          /*  in: */ a, SfpKind,
                          /* out: */ (void **)f, (void **)fp, (void **)val);
}

void *searchReactionCache(void *cache, struct MemoryContextData *ctx, Datum a,
                          Reaction **rxn, CChemicalReaction *crxn,
                          bytea **val) {
  return SearchValueCache(cache, ctx,
                          /*  in: */ a, ReactionKind,
                          /* out: */ (void **)rxn, (void **)crxn, (void **)val);
}