using System;
using System.Diagnostics;
using i16 = System.Int16;
using u16 = System.UInt16;
using u8 = System.Byte;

namespace Community.CsharpSqlite
{
	public partial class Sqlite3
	{
		/*
		** 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.
		*************************************************************************
		**  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
		**  C#-SQLite is an independent reimplementation of the SQLite software library
		**
		**  SQLITE_SOURCE_ID: 2011-05-19 13:26:54 ed1da510a239ea767a01dc332b667119fa3c908e
		**
		*************************************************************************
		*/

		//#include "sqliteInt.h"

		/*
		** Invoke the 'collation needed' callback to request a collation sequence
		** in the encoding enc of name zName, length nName.
		*/

		private static void callCollNeeded(sqlite3 db, int enc, string zName)
		{
			Debug.Assert(db.xCollNeeded == null || db.xCollNeeded16 == null);
			if (db.xCollNeeded != null)
			{
				string zExternal = zName;// sqlite3DbStrDup(db, zName);
				if (zExternal == null)
					return;
				db.xCollNeeded(db.pCollNeededArg, db, enc, zExternal);
				sqlite3DbFree(db, ref zExternal);
			}
#if !SQLITE_OMIT_UTF16
if( db.xCollNeeded16!=null ){
string 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, db.aDbStatic[0].pSchema.enc, zExternal );//(int)ENC(db), zExternal);
}
sqlite3ValueFree(ref 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.
		*/

		private static int synthCollSeq(sqlite3 db, CollSeq pColl)
		{
			CollSeq pColl2;
			string z = pColl.zName;
			int i;
			byte[] aEnc = { SQLITE_UTF16BE, SQLITE_UTF16LE, SQLITE_UTF8 };
			for (i = 0; i < 3; i++)
			{
				pColl2 = sqlite3FindCollSeq(db, aEnc[i], z, 0);
				if (pColl2.xCmp != null)
				{
					pColl = pColl2.Copy(); //memcpy(pColl, pColl2, sizeof(CollSeq));
					pColl.xDel = null;         /* Do not copy the destructor */
					return SQLITE_OK;
				}
			}
			return SQLITE_ERROR;
		}

		/*
		** 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.
		**
		** See also: sqlite3LocateCollSeq(), sqlite3FindCollSeq()
		*/

		private static CollSeq sqlite3GetCollSeq(
		sqlite3 db,         /* The database connection */
		u8 enc,             /* The desired encoding for the collating sequence */
		CollSeq pColl,      /* Collating sequence with native encoding, or NULL */
		string zName        /* Collating sequence name */
		)
		{
			CollSeq p;

			p = pColl;
			if (p == null)
			{
				p = sqlite3FindCollSeq(db, enc, zName, 0);
			}
			if (p == null || p.xCmp == null)
			{
				/* 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 != null && p.xCmp == null && synthCollSeq(db, p) != 0)
			{
				p = null;
			}
			Debug.Assert(p == null || p.xCmp != null);
			return p;
		}

		/*
		** 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.
		*/

		private static int sqlite3CheckCollSeq(Parse pParse, CollSeq pColl)
		{
			if (pColl != null)
			{
				string zName = pColl.zName;
				sqlite3 db = pParse.db;
				CollSeq p = sqlite3GetCollSeq(db, ENC(db), pColl, zName);
				if (null == p)
				{
					sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
					pParse.nErr++;
					return SQLITE_ERROR;
				}
				//
				//Debug.Assert(p == pColl);
				if (p != pColl) // Had to lookup appropriate sequence
				{
					pColl.enc = p.enc;
					pColl.pUser = p.pUser;
					pColl.type = p.type;
					pColl.xCmp = p.xCmp;
					pColl.xDel = p.xDel;
				}
			}
			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
		** prefferred 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.
		*/

		private static CollSeq[] findCollSeqEntry(
		sqlite3 db,         /* Database connection */
		string zName,       /* Name of the collating sequence */
		int create          /* Create a new entry if true */
		)
		{
			CollSeq[] pColl;
			int nName = sqlite3Strlen30(zName);
			pColl = sqlite3HashFind(db.aCollSeq, zName, nName, (CollSeq[])null);

			if ((null == pColl) && create != 0)
			{
				pColl = new CollSeq[3]; //sqlite3DbMallocZero(db, 3*sizeof(*pColl) + nName + 1 );
				if (pColl != null)
				{
					CollSeq pDel = null;
					pColl[0] = new CollSeq();
					pColl[0].zName = zName;
					pColl[0].enc = SQLITE_UTF8;
					pColl[1] = new CollSeq();
					pColl[1].zName = zName;
					pColl[1].enc = SQLITE_UTF16LE;
					pColl[2] = new CollSeq();
					pColl[2].zName = zName;
					pColl[2].enc = SQLITE_UTF16BE;
					//memcpy(pColl[0].zName, zName, nName);
					//pColl[0].zName[nName] = 0;
					CollSeq[] pDelArray = sqlite3HashInsert(ref db.aCollSeq, pColl[0].zName, nName, pColl);
					if (pDelArray != null)
						pDel = pDelArray[0];
					/* 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).
					*/
					Debug.Assert(pDel == null || pDel == pColl[0]);
					if (pDel != null)
					{
						////        db.mallocFailed = 1;
						pDel = null; //was  sqlite3DbFree(db,ref  pDel);
						pColl = null;
					}
				}
			}
			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()
		*/

		private static CollSeq sqlite3FindCollSeq(
		sqlite3 db,
		u8 enc,
		string zName,
		u8 create
		)
		{
			CollSeq[] pColl;
			if (zName != null)
			{
				pColl = findCollSeqEntry(db, zName, create);
			}
			else
			{
				pColl = new CollSeq[enc];
				pColl[enc - 1] = db.pDfltColl;
			}
			Debug.Assert(SQLITE_UTF8 == 1 && SQLITE_UTF16LE == 2 && SQLITE_UTF16BE == 3);
			Debug.Assert(enc >= SQLITE_UTF8 && enc <= SQLITE_UTF16BE);
			if (pColl != null)
			{
				enc -= 1; // if (pColl != null) pColl += enc - 1;
				return pColl[enc];
			}
			else
				return null;
		}

		/* 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.
		**
		** The returned value is always between 0 and 6, as follows:
		**
		** 0: Not a match, or if nArg<0 and the function is has no implementation.
		** 1: A variable arguments function that prefers UTF-8 when a UTF-16
		**    encoding is requested, or vice versa.
		** 2: A variable arguments function that uses UTF-16BE when UTF-16LE is
		**    requested, or vice versa.
		** 3: A variable arguments function using the same text encoding.
		** 4: A function with the exact number of arguments requested that
		**    prefers UTF-8 when a UTF-16 encoding is requested, or vice versa.
		** 5: A function with the exact number of arguments requested that
		**    prefers UTF-16LE when UTF-16BE is requested, or vice versa.
		** 6: An exact match.
		**
		*/

		private static int matchQuality(FuncDef p, int nArg, int enc)
		{
			int match = 0;
			if (p.nArg == -1 || p.nArg == nArg
			|| (nArg == -1 && (p.xFunc != null || p.xStep != null))
			)
			{
				match = 1;
				if (p.nArg == nArg || nArg == -1)
				{
					match = 4;
				}
				if (enc == p.iPrefEnc)
				{
					match += 2;
				}
				else if ((enc == SQLITE_UTF16LE && p.iPrefEnc == SQLITE_UTF16BE) ||
				(enc == SQLITE_UTF16BE && p.iPrefEnc == SQLITE_UTF16LE))
				{
					match += 1;
				}
			}
			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.
		*/

		private static FuncDef functionSearch(
		FuncDefHash pHash,  /* Hash table to search */
		int h,              /* Hash of the name */
		string zFunc,       /* Name of function */
		int nFunc           /* Number of bytes in zFunc */
		)
		{
			FuncDef p;
			for (p = pHash.a[h]; p != null; p = p.pHash)
			{
				if (p.zName.Length == nFunc && p.zName.StartsWith(zFunc, StringComparison.OrdinalIgnoreCase))
				{
					return p;
				}
			}
			return null;
		}

		/*
		** Insert a new FuncDef into a FuncDefHash hash table.
		*/

		private static void sqlite3FuncDefInsert(
		FuncDefHash pHash,  /* The hash table into which to insert */
		FuncDef pDef        /* The function definition to insert */
		)
		{
			FuncDef pOther;
			int nName = sqlite3Strlen30(pDef.zName);
			u8 c1 = (u8)pDef.zName[0];
			int h = (sqlite3UpperToLower[c1] + nName) % ArraySize(pHash.a);
			pOther = functionSearch(pHash, h, pDef.zName, nName);
			if (pOther != null)
			{
				Debug.Assert(pOther != pDef && pOther.pNext != pDef);
				pDef.pNext = pOther.pNext;
				pOther.pNext = pDef;
			}
			else
			{
				pDef.pNext = null;
				pDef.pHash = pHash.a[h];
				pHash.a[h] = pDef;
			}
		}

		/*
		** 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.  When createFlag is true
		** and the nArg parameter is -1, then only a function that accepts
		** any number of arguments will be returned.
		**
		** If createFlag is false and nArg is -1, then the first valid
		** function found is returned.  A function is valid if either xFunc
		** or xStep is non-zero.
		**
		** 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.
		*/

		private static FuncDef sqlite3FindFunction(
		sqlite3 db,           /* An open database */
		string zName,         /* Name of the function.  Not null-terminated */
		int nName,            /* Number of characters in the name */
		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 = null; /* Best match found so far */
			int bestScore = 0;
			int h;              /* Hash value */

			Debug.Assert(enc == SQLITE_UTF8 || enc == SQLITE_UTF16LE || enc == SQLITE_UTF16BE);
			h = (sqlite3UpperToLower[(u8)zName[0]] + nName) % ArraySize(db.aFunc.a);

			/* First search for a match amongst the application-defined functions.
			*/
			p = functionSearch(db.aFunc, h, zName, nName);
			while (p != null)
			{
				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 SQLITE_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 (0 == createFlag && (pBest == null || (db.flags & SQLITE_PreferBuiltin) != 0))
			{
#if SQLITE_OMIT_WSD
FuncDefHash pHash = GLOBAL( FuncDefHash, sqlite3GlobalFunctions );
#else
				FuncDefHash pHash = sqlite3GlobalFunctions;
#endif
				bestScore = 0;
				p = functionSearch(pHash, h, zName, nName);
				while (p != null)
				{
					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 != 0 && (bestScore < 6 || pBest.nArg != nArg) &&
			(pBest = new FuncDef()) != null)
			{ //sqlite3DbMallocZero(db, sizeof(*pBest)+nName+1))!=0 ){
				//pBest.zName = (char *)&pBest[1];
				pBest.nArg = (i16)nArg;
				pBest.iPrefEnc = enc;
				pBest.zName = zName; //memcpy(pBest.zName, zName, nName);
				//pBest.zName[nName] = 0;
				sqlite3FuncDefInsert(db.aFunc, pBest);
			}

			if (pBest != null && (pBest.xStep != null || pBest.xFunc != null || createFlag != 0))
			{
				return pBest;
			}
			return null;
		}

		/*
		** 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.
		*/

		private static void sqlite3SchemaClear(Schema p)
		{
			Hash temp1;
			Hash temp2;
			HashElem pElem;
			Schema pSchema = p;

			temp1 = pSchema.tblHash;
			temp2 = pSchema.trigHash;
			sqlite3HashInit(pSchema.trigHash);
			sqlite3HashClear(pSchema.idxHash);
			for (pElem = sqliteHashFirst(temp2); pElem != null; pElem = sqliteHashNext(pElem))
			{
				Trigger pTrigger = (Trigger)sqliteHashData(pElem);
				sqlite3DeleteTrigger(null, ref pTrigger);
			}
			sqlite3HashClear(temp2);
			sqlite3HashInit(pSchema.trigHash);
			for (pElem = temp1.first; pElem != null; pElem = pElem.next)//sqliteHashFirst(&temp1); pElem; pElem = sqliteHashNext(pElem))
			{
				Table pTab = (Table)pElem.data; //sqliteHashData(pElem);
				sqlite3DeleteTable(null, ref pTab);
			}
			sqlite3HashClear(temp1);
			sqlite3HashClear(pSchema.fkeyHash);
			pSchema.pSeqTab = null;
			if ((pSchema.flags & DB_SchemaLoaded) != 0)
			{
				pSchema.iGeneration++;
				pSchema.flags = (u16)(pSchema.flags & (~DB_SchemaLoaded));
			}
			p.Clear();
		}

		/*
		** Find and return the schema associated with a BTree.  Create
		** a new one if necessary.
		*/

		private static Schema sqlite3SchemaGet(sqlite3 db, Btree pBt)
		{
			Schema p;
			if (pBt != null)
			{
				p = sqlite3BtreeSchema(pBt, -1, (dxFreeSchema)sqlite3SchemaClear);//Schema.Length, sqlite3SchemaFree);
			}
			else
			{
				p = new Schema(); // (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
			}
			if (p == null)
			{
				////        db.mallocFailed = 1;
			}
			else if (0 == p.file_format)
			{
				sqlite3HashInit(p.tblHash);
				sqlite3HashInit(p.idxHash);
				sqlite3HashInit(p.trigHash);
				sqlite3HashInit(p.fkeyHash);
				p.enc = SQLITE_UTF8;
			}
			return p;
		}
	}
}