/*
** 2005 May 23 
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains functions used to access the internal hash tables
** of user defined functions and collation sequences.
*/

#include "sqliteInt.h"

/*
** Invoke the 'collation needed' callback to request a collation sequence
** in the encoding enc of name zName, length nName.
*/
static void callCollNeeded(sqlite3 *db, int enc, const char *zName){
 assert( !db->xCollNeeded || !db->xCollNeeded16 );
 if( db->xCollNeeded ){
 char *zExternal = sqlite3DbStrDup(db, zName);
 if( !zExternal ) return;
 db->xCollNeeded(db->pCollNeededArg, db, enc, zExternal);
 sqlite3DbFree(db, zExternal);
 }
#ifndef SQLITE_OMIT_UTF16
 if( db->xCollNeeded16 ){
 char const *zExternal;
 sqlite3_value *pTmp = sqlite3ValueNew(db);
 sqlite3ValueSetStr(pTmp, -1, zName, SQLITE_UTF8, SQLITE_STATIC);
 zExternal = sqlite3ValueText(pTmp, SQLITE_UTF16NATIVE);
 if( zExternal ){
 db->xCollNeeded16(db->pCollNeededArg, db, (int)ENC(db), zExternal);
 }
 sqlite3ValueFree(pTmp);
 }
#endif
}

/*
** This routine is called if the collation factory fails to deliver a
** collation function in the best encoding but there may be other versions
** of this collation function (for other text encodings) available. Use one
** of these instead if they exist. Avoid a UTF-8 <-> UTF-16 conversion if
** possible.
*/
static int synthCollSeq(sqlite3 *db, CollSeq *pColl){
 CollSeq *pColl2;
 char *z = pColl->zName;
 int i;
 static const u8 aEnc[] = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
 for(i=0; i<3; i++){
 pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, 0);
 if( pColl2->xCmp!=0 ){
 memcpy(pColl, pColl2, sizeof(CollSeq));
 pColl->xDel = 0; /* Do not copy the destructor */
 return SQLITE_OK;
 }
 }
 return SQLITE_ERROR;
}

/*
** This routine is called on a collation sequence before it is used to
** check that it is defined. An undefined collation sequence exists when
** a database is loaded that contains references to collation sequences
** that have not been defined by sqlite3_create_collation() etc.
**
** If required, this routine calls the 'collation needed' callback to
** request a definition of the collating sequence. If this doesn't work, 
** an equivalent collating sequence that uses a text encoding different
** from the main database is substituted, if one is available.
*/
int sqlite3CheckCollSeq(Parse *pParse, CollSeq *pColl){
 if( pColl && pColl->xCmp==0 ){
 const char *zName = pColl->zName;
 sqlite3 *db = pParse->db;
 CollSeq *p = sqlite3GetCollSeq(pParse, ENC(db), pColl, zName);
 if( !p ){
 return SQLITE_ERROR;
 }
 assert( p==pColl );
 }
 return SQLITE_OK;
}



/*
** Locate and return an entry from the db.aCollSeq hash table. If the entry
** specified by zName and nName is not found and parameter 'create' is
** true, then create a new entry. Otherwise return NULL.
**
** Each pointer stored in the sqlite3.aCollSeq hash table contains an
** array of three CollSeq structures. The first is the collation sequence
** preferred for UTF-8, the second UTF-16le, and the third UTF-16be.
**
** Stored immediately after the three collation sequences is a copy of
** the collation sequence name. A pointer to this string is stored in
** each collation sequence structure.
*/
static CollSeq *findCollSeqEntry(
 sqlite3 *db, /* Database connection */
 const char *zName, /* Name of the collating sequence */
 int create /* Create a new entry if true */
){
 CollSeq *pColl;
 pColl = sqlite3HashFind(&db->aCollSeq, zName);

 if( 0==pColl && create ){
 int nName = sqlite3Strlen30(zName) + 1;
 pColl = sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName);
 if( pColl ){
 CollSeq *pDel = 0;
 pColl[0].zName = (char*)&pColl[3];
 pColl[0].enc = SQLITE_UTF8;
 pColl[1].zName = (char*)&pColl[3];
 pColl[1].enc = SQLITE_UTF16LE;
 pColl[2].zName = (char*)&pColl[3];
 pColl[2].enc = SQLITE_UTF16BE;
 memcpy(pColl[0].zName, zName, nName);
 pDel = sqlite3HashInsert(&db->aCollSeq, pColl[0].zName, pColl);

 /* If a malloc() failure occurred in sqlite3HashInsert(), it will 
 ** return the pColl pointer to be deleted (because it wasn't added
 ** to the hash table).
 */
 assert( pDel==0 || pDel==pColl );
 if( pDel!=0 ){
 sqlite3OomFault(db);
 sqlite3DbFree(db, pDel);
 pColl = 0;
 }
 }
 }
 return pColl;
}

/*
** Parameter zName points to a UTF-8 encoded string nName bytes long.
** Return the CollSeq* pointer for the collation sequence named zName
** for the encoding 'enc' from the database 'db'.
**
** If the entry specified is not found and 'create' is true, then create a
** new entry. Otherwise return NULL.
**
** A separate function sqlite3LocateCollSeq() is a wrapper around
** this routine. sqlite3LocateCollSeq() invokes the collation factory
** if necessary and generates an error message if the collating sequence
** cannot be found.
**
** See also: sqlite3LocateCollSeq(), sqlite3GetCollSeq()
*/
CollSeq *sqlite3FindCollSeq(
 sqlite3 *db, /* Database connection to search */
 u8 enc, /* Desired text encoding */
 const char *zName, /* Name of the collating sequence. Might be NULL */
 int create /* True to create CollSeq if doesn't already exist */
){
 CollSeq *pColl;
 assert( SQLITE_UTF8==1 && SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
 assert( enc>=SQLITE_UTF8 && enc<=SQLITE_UTF16BE );
 if( zName ){
 pColl = findCollSeqEntry(db, zName, create);
 if( pColl ) pColl += enc-1;
 }else{
 pColl = db->pDfltColl;
 }
 return pColl;
}

/*
** Change the text encoding for a database connection. This means that
** the pDfltColl must change as well.
*/
void sqlite3SetTextEncoding(sqlite3 *db, u8 enc){
 assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
 db->enc = enc;
 /* EVIDENCE-OF: R-08308-17224 The default collating function for all
 ** strings is BINARY. 
 */
 db->pDfltColl = sqlite3FindCollSeq(db, enc, sqlite3StrBINARY, 0);
 sqlite3ExpirePreparedStatements(db, 1);
}

/*
** This function is responsible for invoking the collation factory callback
** or substituting a collation sequence of a different encoding when the
** requested collation sequence is not available in the desired encoding.
** 
** If it is not NULL, then pColl must point to the database native encoding 
** collation sequence with name zName, length nName.
**
** The return value is either the collation sequence to be used in database
** db for collation type name zName, length nName, or NULL, if no collation
** sequence can be found. If no collation is found, leave an error message.
**
** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
*/
CollSeq *sqlite3GetCollSeq(
 Parse *pParse, /* Parsing context */
 u8 enc, /* The desired encoding for the collating sequence */
 CollSeq *pColl, /* Collating sequence with native encoding, or NULL */
 const char *zName /* Collating sequence name */
){
 CollSeq *p;
 sqlite3 *db = pParse->db;

 p = pColl;
 if( !p ){
 p = sqlite3FindCollSeq(db, enc, zName, 0);
 }
 if( !p || !p->xCmp ){
 /* No collation sequence of this type for this encoding is registered.
 ** Call the collation factory to see if it can supply us with one.
 */
 callCollNeeded(db, enc, zName);
 p = sqlite3FindCollSeq(db, enc, zName, 0);
 }
 if( p && !p->xCmp && synthCollSeq(db, p) ){
 p = 0;
 }
 assert( !p || p->xCmp );
 if( p==0 ){
 sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
 pParse->rc = SQLITE_ERROR_MISSING_COLLSEQ;
 }
 return p;
}

/*
** This function returns the collation sequence for database native text
** encoding identified by the string zName.
**
** If the requested collation sequence is not available, or not available
** in the database native encoding, the collation factory is invoked to
** request it. If the collation factory does not supply such a sequence,
** and the sequence is available in another text encoding, then that is
** returned instead.
**
** If no versions of the requested collations sequence are available, or
** another error occurs, NULL is returned and an error message written into
** pParse.
**
** This routine is a wrapper around sqlite3FindCollSeq(). This routine
** invokes the collation factory if the named collation cannot be found
** and generates an error message.
**
** See also: sqlite3FindCollSeq(), sqlite3GetCollSeq()
*/
CollSeq *sqlite3LocateCollSeq(Parse *pParse, const char *zName){
 sqlite3 *db = pParse->db;
 u8 enc = ENC(db);
 u8 initbusy = db->init.busy;
 CollSeq *pColl;

 pColl = sqlite3FindCollSeq(db, enc, zName, initbusy);
 if( !initbusy && (!pColl || !pColl->xCmp) ){
 pColl = sqlite3GetCollSeq(pParse, enc, pColl, zName);
 }

 return pColl;
}

/* During the search for the best function definition, this procedure
** is called to test how well the function passed as the first argument
** matches the request for a function with nArg arguments in a system
** that uses encoding enc. The value returned indicates how well the
** request is matched. A higher value indicates a better match.
**
** If nArg is -1 that means to only return a match (non-zero) if p->nArg
** is also -1. In other words, we are searching for a function that
** takes a variable number of arguments.
**
** If nArg is -2 that means that we are searching for any function 
** regardless of the number of arguments it uses, so return a positive
** match score for any
**
** The returned value is always between 0 and 6, as follows:
**
** 0: Not a match.
** 1: UTF8/16 conversion required and function takes any number of arguments.
** 2: UTF16 byte order change required and function takes any number of args.
** 3: encoding matches and function takes any number of arguments
** 4: UTF8/16 conversion required - argument count matches exactly
** 5: UTF16 byte order conversion required - argument count matches exactly
** 6: Perfect match: encoding and argument count match exactly.
**
** If nArg==(-2) then any function with a non-null xSFunc is
** a perfect match and any function with xSFunc NULL is
** a non-match.
*/
#define FUNC_PERFECT_MATCH 6 /* The score for a perfect match */
static int matchQuality(
 FuncDef *p, /* The function we are evaluating for match quality */
 int nArg, /* Desired number of arguments. (-1)==any */
 u8 enc /* Desired text encoding */
){
 int match;
 assert( p->nArg>=-1 );

 /* Wrong number of arguments means "no match" */
 if( p->nArg!=nArg ){
 if( nArg==(-2) ) return (p->xSFunc==0) ? 0 : FUNC_PERFECT_MATCH;
 if( p->nArg>=0 ) return 0;
 }

 /* Give a better score to a function with a specific number of arguments
 ** than to function that accepts any number of arguments. */
 if( p->nArg==nArg ){
 match = 4;
 }else{
 match = 1;
 }

 /* Bonus points if the text encoding matches */
 if( enc==(p->funcFlags & SQLITE_FUNC_ENCMASK) ){
 match += 2; /* Exact encoding match */
 }else if( (enc & p->funcFlags & 2)!=0 ){
 match += 1; /* Both are UTF16, but with different byte orders */
 }

 return match;
}

/*
** Search a FuncDefHash for a function with the given name. Return
** a pointer to the matching FuncDef if found, or 0 if there is no match.
*/
FuncDef *sqlite3FunctionSearch(
 int h, /* Hash of the name */
 const char *zFunc /* Name of function */
){
 FuncDef *p;
 for(p=sqlite3BuiltinFunctions.a[h]; p; p=p->u.pHash){
 assert( p->funcFlags & SQLITE_FUNC_BUILTIN );
 if( sqlite3StrICmp(p->zName, zFunc)==0 ){
 return p;
 }
 }
 return 0;
}

/*
** Insert a new FuncDef into a FuncDefHash hash table.
*/
void sqlite3InsertBuiltinFuncs(
 FuncDef *aDef, /* List of global functions to be inserted */
 int nDef /* Length of the apDef[] list */
){
 int i;
 for(i=0; i<nDef; i++){
 FuncDef *pOther;
 const char *zName = aDef[i].zName;
 int nName = sqlite3Strlen30(zName);
 int h = SQLITE_FUNC_HASH(zName[0], nName);
 assert( aDef[i].funcFlags & SQLITE_FUNC_BUILTIN );
 pOther = sqlite3FunctionSearch(h, zName);
 if( pOther ){
 assert( pOther!=&aDef[i] && pOther->pNext!=&aDef[i] );
 aDef[i].pNext = pOther->pNext;
 pOther->pNext = &aDef[i];
 }else{
 aDef[i].pNext = 0;
 aDef[i].u.pHash = sqlite3BuiltinFunctions.a[h];
 sqlite3BuiltinFunctions.a[h] = &aDef[i];
 }
 }
}
 
 

/*
** Locate a user function given a name, a number of arguments and a flag
** indicating whether the function prefers UTF-16 over UTF-8. Return a
** pointer to the FuncDef structure that defines that function, or return
** NULL if the function does not exist.
**
** If the createFlag argument is true, then a new (blank) FuncDef
** structure is created and liked into the "db" structure if a
** no matching function previously existed.
**
** If nArg is -2, then the first valid function found is returned. A
** function is valid if xSFunc is non-zero. The nArg==(-2)
** case is used to see if zName is a valid function name for some number
** of arguments. If nArg is -2, then createFlag must be 0.
**
** If createFlag is false, then a function with the required name and
** number of arguments may be returned even if the eTextRep flag does not
** match that requested.
*/
FuncDef *sqlite3FindFunction(
 sqlite3 *db, /* An open database */
 const char *zName, /* Name of the function. zero-terminated */
 int nArg, /* Number of arguments. -1 means any number */
 u8 enc, /* Preferred text encoding */
 u8 createFlag /* Create new entry if true and does not otherwise exist */
){
 FuncDef *p; /* Iterator variable */
 FuncDef *pBest = 0; /* Best match found so far */
 int bestScore = 0; /* Score of best match */
 int h; /* Hash value */
 int nName; /* Length of the name */

 assert( nArg>=(-2) );
 assert( nArg>=(-1) || createFlag==0 );
 nName = sqlite3Strlen30(zName);

 /* First search for a match amongst the application-defined functions.
 */
 p = (FuncDef*)sqlite3HashFind(&db->aFunc, zName);
 while( p ){
 int score = matchQuality(p, nArg, enc);
 if( score>bestScore ){
 pBest = p;
 bestScore = score;
 }
 p = p->pNext;
 }

 /* If no match is found, search the built-in functions.
 **
 ** If the DBFLAG_PreferBuiltin flag is set, then search the built-in
 ** functions even if a prior app-defined function was found. And give
 ** priority to built-in functions.
 **
 ** Except, if createFlag is true, that means that we are trying to
 ** install a new function. Whatever FuncDef structure is returned it will
 ** have fields overwritten with new information appropriate for the
 ** new function. But the FuncDefs for built-in functions are read-only.
 ** So we must not search for built-ins when creating a new function.
 */ 
 if( !createFlag && (pBest==0 || (db->mDbFlags & DBFLAG_PreferBuiltin)!=0) ){
 bestScore = 0;
 h = SQLITE_FUNC_HASH(sqlite3UpperToLower[(u8)zName[0]], nName);
 p = sqlite3FunctionSearch(h, zName);
 while( p ){
 int score = matchQuality(p, nArg, enc);
 if( score>bestScore ){
 pBest = p;
 bestScore = score;
 }
 p = p->pNext;
 }
 }

 /* If the createFlag parameter is true and the search did not reveal an
 ** exact match for the name, number of arguments and encoding, then add a
 ** new entry to the hash table and return it.
 */
 if( createFlag && bestScore<FUNC_PERFECT_MATCH && 
 (pBest = sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
 FuncDef *pOther;
 u8 *z;
 pBest->zName = (const char*)&pBest[1];
 pBest->nArg = (u16)nArg;
 pBest->funcFlags = enc;
 memcpy((char*)&pBest[1], zName, nName+1);
 for(z=(u8*)pBest->zName; *z; z++) *z = sqlite3UpperToLower[*z];
 pOther = (FuncDef*)sqlite3HashInsert(&db->aFunc, pBest->zName, pBest);
 if( pOther==pBest ){
 sqlite3DbFree(db, pBest);
 sqlite3OomFault(db);
 return 0;
 }else{
 pBest->pNext = pOther;
 }
 }

 if( pBest && (pBest->xSFunc || createFlag) ){
 return pBest;
 }
 return 0;
}

/*
** Free all resources held by the schema structure. The void* argument points
** at a Schema struct. This function does not call sqlite3DbFree(db, ) on the 
** pointer itself, it just cleans up subsidiary resources (i.e. the contents
** of the schema hash tables).
**
** The Schema.cache_size variable is not cleared.
*/
void sqlite3SchemaClear(void *p){
 Hash temp1;
 Hash temp2;
 HashElem *pElem;
 Schema *pSchema = (Schema *)p;
 sqlite3 xdb;

 memset(&xdb, 0, sizeof(xdb));
 temp1 = pSchema->tblHash;
 temp2 = pSchema->trigHash;
 sqlite3HashInit(&pSchema->trigHash);
 sqlite3HashClear(&pSchema->idxHash);
 for(pElem=sqliteHashFirst(&temp2); pElem; pElem=sqliteHashNext(pElem)){
 sqlite3DeleteTrigger(&xdb, (Trigger*)sqliteHashData(pElem));
 }
 sqlite3HashClear(&temp2);
 sqlite3HashInit(&pSchema->tblHash);
 for(pElem=sqliteHashFirst(&temp1); pElem; pElem=sqliteHashNext(pElem)){
 Table *pTab = sqliteHashData(pElem);
 sqlite3DeleteTable(&xdb, pTab);
 }
 sqlite3HashClear(&temp1);
 sqlite3HashClear(&pSchema->fkeyHash);
 pSchema->pSeqTab = 0;
 if( pSchema->schemaFlags & DB_SchemaLoaded ){
 pSchema->iGeneration++;
 }
 pSchema->schemaFlags &= ~(DB_SchemaLoaded|DB_ResetWanted);
}

/*
** Find and return the schema associated with a BTree. Create
** a new one if necessary.
*/
Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
 Schema * p;
 if( pBt ){
 p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
 }else{
 p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
 }
 if( !p ){
 sqlite3OomFault(db);
 }else if ( 0==p->file_format ){
 sqlite3HashInit(&p->tblHash);
 sqlite3HashInit(&p->idxHash);
 sqlite3HashInit(&p->trigHash);
 sqlite3HashInit(&p->fkeyHash);
 p->enc = SQLITE_UTF8;
 }
 return p;
}