/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.empire.dbms.sqlite;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;

import org.apache.empire.data.DataType;
import org.apache.empire.db.DBColumnExpr;
import org.apache.empire.db.DBCommand;
import org.apache.empire.db.DBDDLGenerator;
import org.apache.empire.db.DBDDLGenerator.DDLActionType;
import org.apache.empire.db.DBDatabase;
import org.apache.empire.db.DBJoinType;
import org.apache.empire.db.DBObject;
import org.apache.empire.db.DBSQLScript;
import org.apache.empire.db.DBTableColumn;
import org.apache.empire.db.expr.join.DBColumnJoinExpr;
import org.apache.empire.db.expr.join.DBJoinExpr;
import org.apache.empire.dbms.DBMSHandler;
import org.apache.empire.dbms.DBMSHandlerBase;
import org.apache.empire.dbms.DBMSFeature;
import org.apache.empire.dbms.DBSqlPhrase;
import org.apache.empire.exceptions.NotImplementedException;
import org.apache.empire.exceptions.NotSupportedException;
import org.apache.empire.exceptions.UnexpectedReturnValueException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class provides support for the SQLite database system.<br>
 * 
 */
public class DBMSHandlerSQLite extends DBMSHandlerBase
{
    // *Deprecated* private static final long serialVersionUID = 1L;
    private static final Logger log              = LoggerFactory.getLogger(DBMSHandlerSQLite.class);
    
    /**
     * Defines the SQLite command type.
     */
    public static class DBCommandSQLite extends DBCommand
    {
        // *Deprecated* private static final long serialVersionUID = 1L;
        
        /**
         * @param db
         *            the database
         * @see org.apache.empire.db.DBCommand
         */
        public DBCommandSQLite(boolean autoPrepareStmt)
        {
            super(autoPrepareStmt);
        }
        
        @Override
		public DBCommandSQLite join(DBJoinExpr join)
        {
            // http://www.sqlite.org/omitted.html
            if (join.getType() != DBJoinType.LEFT) {
                throw new NotImplementedException(join.getType(), join.getLeftTable().getName() + " join " + join.getRightTable().getName()); 
            }
            super.join(join);
            return this;
        }
        
        @Override
        public void addJoins(List<DBJoinExpr> joinExprList)
        {
            for (DBJoinExpr joinExpr : joinExprList)
            {
                if ((joinExpr instanceof DBColumnJoinExpr) && 
                    (joinExpr.getType() != DBJoinType.LEFT)) { 
                    DBColumnJoinExpr join = (DBColumnJoinExpr)joinExpr;
                    throw new NotImplementedException(joinExpr.getType(), join.getLeft() + " join " + join.getRight()); 
                }
            }
            /*
             * Iterator<DBJoinExpr> iterator = joinExprList.iterator(); for
             * (DBJoinExpr joinExpr = null; iterator.hasNext(); joinExpr =
             * iterator.next()) { if(joinExpr.getType() != DBJoinType.LEFT) {
             * iterator.remove(); } }
             */
            super.addJoins(joinExprList);
            
        }
        
    }
    
    private DBDDLGenerator<?> ddlGenerator = null; // lazy creation
                                                   
    /**
     * Constructor for the SQLite database dbms.
     */
    public DBMSHandlerSQLite()
    {
        setReservedKeywords();
    }
    
    private void addReservedKeyWord(final String keyWord)
    {
        boolean added = reservedSQLKeywords.add(keyWord.toLowerCase());
        if (!added)
        {
            log.debug("Existing keyWord added: " + keyWord);
        }
    }
    
    private void setReservedKeywords()
    {
        // list of reserved keywords
        // http://www.sqlite.org/lang_keywords.html
        addReservedKeyWord("ABORT".toLowerCase());
        addReservedKeyWord("ACTION".toLowerCase());
        addReservedKeyWord("ADD".toLowerCase());
        addReservedKeyWord("AFTER".toLowerCase());
        addReservedKeyWord("ALL".toLowerCase());
        addReservedKeyWord("ALTER".toLowerCase());
        addReservedKeyWord("ANALYZE".toLowerCase());
        addReservedKeyWord("AND".toLowerCase());
        addReservedKeyWord("AS".toLowerCase());
        addReservedKeyWord("ASC".toLowerCase());
        addReservedKeyWord("ATTACH".toLowerCase());
        addReservedKeyWord("AUTOINCREMENT".toLowerCase());
        addReservedKeyWord("BEFORE".toLowerCase());
        addReservedKeyWord("BEGIN".toLowerCase());
        addReservedKeyWord("BETWEEN".toLowerCase());
        addReservedKeyWord("BY".toLowerCase());
        addReservedKeyWord("CASCADE".toLowerCase());
        addReservedKeyWord("CASE".toLowerCase());
        addReservedKeyWord("CAST".toLowerCase());
        addReservedKeyWord("CHECK".toLowerCase());
        addReservedKeyWord("COLLATE".toLowerCase());
        addReservedKeyWord("COLUMN".toLowerCase());
        addReservedKeyWord("COMMIT".toLowerCase());
        addReservedKeyWord("CONFLICT".toLowerCase());
        addReservedKeyWord("CONSTRAINT".toLowerCase());
        
        addReservedKeyWord("CREATE".toLowerCase());
        addReservedKeyWord("CROSS".toLowerCase());
        addReservedKeyWord("CURRENT_DATE".toLowerCase());
        addReservedKeyWord("CURRENT_TIME".toLowerCase());
        addReservedKeyWord("CURRENT_DATETIME".toLowerCase());
        addReservedKeyWord("DATABASE".toLowerCase());
        addReservedKeyWord("DEFAULT".toLowerCase());
        addReservedKeyWord("DEFERRABLE".toLowerCase());
        addReservedKeyWord("DEFERRED".toLowerCase());
        addReservedKeyWord("DELETE".toLowerCase());
        addReservedKeyWord("DESC".toLowerCase());
        addReservedKeyWord("DETACH".toLowerCase());
        addReservedKeyWord("DISTINCT".toLowerCase());
        addReservedKeyWord("DROP".toLowerCase());
        addReservedKeyWord("EACH".toLowerCase());
        addReservedKeyWord("ELSE".toLowerCase());
        addReservedKeyWord("END".toLowerCase());
        addReservedKeyWord("ESCAPE".toLowerCase());
        addReservedKeyWord("EXCEPT".toLowerCase());
        addReservedKeyWord("EXCLUSIVE".toLowerCase());
        addReservedKeyWord("EXISTS".toLowerCase());
        addReservedKeyWord("EXPLAIN".toLowerCase());
        addReservedKeyWord("FAIL".toLowerCase());
        addReservedKeyWord("FOR".toLowerCase());
        addReservedKeyWord("FOREIGN".toLowerCase());
        
        addReservedKeyWord("FROM".toLowerCase());
        addReservedKeyWord("FULL".toLowerCase());
        addReservedKeyWord("GLOB".toLowerCase());
        addReservedKeyWord("GROUP".toLowerCase());
        addReservedKeyWord("HAVING".toLowerCase());
        addReservedKeyWord("IF".toLowerCase());
        addReservedKeyWord("IGNORE".toLowerCase());
        addReservedKeyWord("IMMEDIATE".toLowerCase());
        addReservedKeyWord("IN".toLowerCase());
        addReservedKeyWord("INDEX".toLowerCase());
        addReservedKeyWord("INDEXED".toLowerCase());
        addReservedKeyWord("INITIALLY".toLowerCase());
        addReservedKeyWord("INNER".toLowerCase());
        addReservedKeyWord("INSERT".toLowerCase());
        addReservedKeyWord("INSTEAD".toLowerCase());
        addReservedKeyWord("INTERSECT".toLowerCase());
        addReservedKeyWord("INTO".toLowerCase());
        addReservedKeyWord("IS".toLowerCase());
        addReservedKeyWord("ISNULL".toLowerCase());
        addReservedKeyWord("JOIN".toLowerCase());
        addReservedKeyWord("KEY".toLowerCase());
        addReservedKeyWord("LEFT".toLowerCase());
        addReservedKeyWord("LIKE".toLowerCase());
        addReservedKeyWord("LIMIT".toLowerCase());
        addReservedKeyWord("MATCH".toLowerCase());
        
        addReservedKeyWord("NATURAL".toLowerCase());
        addReservedKeyWord("NO".toLowerCase());
        addReservedKeyWord("NOT".toLowerCase());
        addReservedKeyWord("NOTNULL".toLowerCase());
        addReservedKeyWord("NULL".toLowerCase());
        addReservedKeyWord("OF".toLowerCase());
        addReservedKeyWord("OFFSET".toLowerCase());
        addReservedKeyWord("ON".toLowerCase());
        addReservedKeyWord("OR".toLowerCase());
        addReservedKeyWord("ORDER".toLowerCase());
        addReservedKeyWord("OUTER".toLowerCase());
        addReservedKeyWord("PLAN".toLowerCase());
        addReservedKeyWord("PRAGMA".toLowerCase());
        addReservedKeyWord("PRIMARY".toLowerCase());
        addReservedKeyWord("QUERY".toLowerCase());
        addReservedKeyWord("RAISE".toLowerCase());
        addReservedKeyWord("REFERENCES".toLowerCase());
        addReservedKeyWord("REGEXP".toLowerCase());
        addReservedKeyWord("REINDEX".toLowerCase());
        addReservedKeyWord("RELEASE".toLowerCase());
        addReservedKeyWord("RENAME".toLowerCase());
        addReservedKeyWord("REPLACE".toLowerCase());
        addReservedKeyWord("RESTRICT".toLowerCase());
        addReservedKeyWord("RIGHT".toLowerCase());
        addReservedKeyWord("ROLLBACK".toLowerCase());
        
        addReservedKeyWord("ROW".toLowerCase());
        addReservedKeyWord("SAVEPOINT".toLowerCase());
        addReservedKeyWord("SELECT".toLowerCase());
        addReservedKeyWord("SET".toLowerCase());
        addReservedKeyWord("TABLE".toLowerCase());
        addReservedKeyWord("TEMP".toLowerCase());
        addReservedKeyWord("TEMPORARY".toLowerCase());
        addReservedKeyWord("THEN".toLowerCase());
        addReservedKeyWord("TO".toLowerCase());
        addReservedKeyWord("TRANSACTION".toLowerCase());
        addReservedKeyWord("TRIGGER".toLowerCase());
        addReservedKeyWord("UNION".toLowerCase());
        addReservedKeyWord("UNIQUE".toLowerCase());
        addReservedKeyWord("UPDATE".toLowerCase());
        addReservedKeyWord("USING".toLowerCase());
        addReservedKeyWord("VACUUM".toLowerCase());
        addReservedKeyWord("VALUES".toLowerCase());
        addReservedKeyWord("VIEW".toLowerCase());
        addReservedKeyWord("VIRTUAL".toLowerCase());
        addReservedKeyWord("WHEN".toLowerCase());
        addReservedKeyWord("WHERE".toLowerCase());
    }
    
    /**
     * Creates a new SQLite command object.
     * 
     * @return the new DBCommandSQLite object
     */
    @Override
    public DBCommand createCommand(boolean autoPrepareStmt)
    {
        // create command object
        return new DBCommandSQLite(autoPrepareStmt);
    }
    
    /**
     * Returns whether or not a particular feature is supported by this dbms
     * 
     * @param type
     *            type of requested feature. @see DBMSFeature
     * @return true if the features is supported or false otherwise
     */
    @Override
    public boolean isSupported(DBMSFeature type)
    {
        switch (type)
        { // return support info
            case QUERY_LIMIT_ROWS:
                return true;
            case QUERY_SKIP_ROWS:
                return true;
            default:
                // All other features are not supported by default
                return false;
        }
    }
    
    /**
     * Gets an sql phrase template for this database system.<br>
     * 
     * @see DBMSHandler#getSQLPhrase(int)
     * @return the phrase template
     */
    @Override
    public String getSQLPhrase(DBSqlPhrase phrase)
    {
        switch (phrase)
        {
            // sql-phrases
            case SQL_NULL:            return "null";
            case SQL_PARAMETER:             return " ? ";
            case SQL_RENAME_TABLE:          return " ";
            case SQL_RENAME_COLUMN:         return " AS ";
            case SQL_DATABASE_LINK:         return "@";
            case SQL_QUOTES_OPEN:           return "`";
            case SQL_QUOTES_CLOSE:          return "`";
            case SQL_CONCAT_EXPR:           return "concat(?, {0})";
            // data types
            case SQL_BOOLEAN_TRUE:          return "1";
            case SQL_BOOLEAN_FALSE:         return "0";
            case SQL_CURRENT_DATE:          return "date('now','localtime');";
            case SQL_DATE_PATTERN:          return "yyyy-MM-dd";
            case SQL_DATE_TEMPLATE:         return "date('{0}')";
            case SQL_CURRENT_TIME:          return "time('now');";
            case SQL_TIME_TEMPLATE:         return "time('{0}')";
            case SQL_DATETIME_PATTERN:      return "yyyy-MM-dd hh:mm:ss.sss";
            case SQL_DATETIME_TEMPLATE:     return "'{0}'";
            case SQL_CURRENT_TIMESTAMP:     return "NOW()";
            case SQL_TIMESTAMP_PATTERN:     return "yyyy-MM-dd hh:mm:ss.sss";
            case SQL_TIMESTAMP_TEMPLATE:    return "'{0}'";
            // functions
            case SQL_FUNC_COALESCE:         return "coalesce(?, {0})";
            case SQL_FUNC_SUBSTRING:        return "substring(?, {0})";
            case SQL_FUNC_SUBSTRINGEX:      return "substring(?, {0}, {1})";
            case SQL_FUNC_REPLACE:          return "replace(?, {0}, {1})";
            case SQL_FUNC_REVERSE:          return "reverse(?)";
            case SQL_FUNC_STRINDEX:         return "instr(?, {0})";
            case SQL_FUNC_STRINDEXFROM:     return "locate({0}, ?, {1})";
            case SQL_FUNC_LENGTH:           return "length(?)";
            case SQL_FUNC_UPPER:            return "upper(?)";
            case SQL_FUNC_LOWER:            return "lcase(?)";
            case SQL_FUNC_TRIM:             return "trim(?)";
            case SQL_FUNC_LTRIM:            return "ltrim(?)";
            case SQL_FUNC_RTRIM:            return "rtrim(?)";
            case SQL_FUNC_ESCAPE:           return "? escape '{0}'";
            // Numeric
            case SQL_FUNC_ABS:              return "abs(?)";
            case SQL_FUNC_ROUND:            return "round(?,{0})";
            case SQL_FUNC_TRUNC:            return "truncate(?,{0})";
            case SQL_FUNC_CEILING:          return "ceiling(?)";
            case SQL_FUNC_FLOOR:            return "floor(?)";
            case SQL_FUNC_MOD:              return "mod(?,{0})";
            case SQL_FUNC_FORMAT:           return "printf({0:VARCHAR}, ?)";
            // Date
            case SQL_FUNC_DAY:              return "day(?)";
            case SQL_FUNC_MONTH:            return "month(?)";
            case SQL_FUNC_YEAR:             return "year(?)";
            // Aggregation
            case SQL_FUNC_SUM:              return "sum(?)";
            case SQL_FUNC_MAX:              return "max(?)";
            case SQL_FUNC_MIN:              return "min(?)";
            case SQL_FUNC_AVG:              return "avg(?)";
            // Others
            case SQL_FUNC_DECODE:           return "case ? {0} end";
            case SQL_FUNC_DECODE_SEP:       return " ";
            case SQL_FUNC_DECODE_PART:      return "when {0} then {1}";
            case SQL_FUNC_DECODE_ELSE:      return "else {0}";
            // Not defined
            default:
                // log.warn("SQL phrase " + phrase.name() + " is not defined!");
                return phrase.getSqlDefault();
        }
    }
    
    /**
     * @see DBMSHandler#getConvertPhrase(DataType, DataType, Object)
     */
    @Override
    public String getConvertPhrase(DataType destType, DataType srcType, Object format)
    {
        switch (destType)
        {
        // Convert to text
            case VARCHAR:
            case CHAR:
                if (format != null)
                { // Convert using a format string
                    if (srcType == DataType.INTEGER || srcType == DataType.AUTOINC)
                    {
                        log.error("getConvertPhrase: unknown type " + destType);
                        return "?";
                    }
                    else
                    {
                        return "to_char(?, '" + format.toString() + "')";
                    }
                }
                return "convert(?, CHAR)";
            case INTEGER:
            {
                return "convert(?, BIGINT)";
            }
            case DECIMAL:
            {
                return "convert(?, DECIMAL)";
            }
            case FLOAT:
            {
                return "convert(?, DOUBLE)";
            }
            // Unknown Type
            default:
                log.error("getConvertPhrase: unknown type (" + String.valueOf(destType));
                return "?";
        }
    }

    /**
     * Override since 
     *      conn.prepareStatement(sqlCmd, Statement.RETURN_GENERATED_KEYS) 
     * is not supported by SQLLite dbms
     */
    @Override
    public int executeSQL(String sqlCmd, Object[] sqlParams, Connection conn, DBSetGenKeys genKeys) throws SQLException
    {
        Statement stmt = null;
        int count = 0;
        try
        {
            if (sqlParams != null)
            { // Use a prepared statement
                PreparedStatement pstmt = conn.prepareStatement(sqlCmd);
                stmt = pstmt;
                prepareStatement(pstmt, sqlParams);
                count = pstmt.executeUpdate();
            }
            else
            { // Execute a simple statement
                stmt = conn.createStatement();
                count = stmt.executeUpdate(sqlCmd);
            }
            // Retrieve any auto-generated keys
            if (genKeys != null && count > 0)
            { // Return Keys
                ResultSet rs = stmt.getGeneratedKeys();
                try
                {   int rownum = 0;
                    while (rs.next())
                    {
                        genKeys.set(rownum++, rs.getObject(1));
                    }
                }
                finally
                {
                    rs.close();
                }
            }
        }
        finally
        {
            closeStatement(stmt);
        }
        return count;
    }
    
    
    @Override
    public Object getResultValue(ResultSet rset, int columnIndex, DataType dataType) throws SQLException
    {
        if (dataType == DataType.DATETIME || dataType == DataType.TIMESTAMP)
        {
            // SQLite does not have a Date type, or any kind of type :(
            String datePattern = getSQLPhrase(DBSqlPhrase.SQL_DATETIME_PATTERN);
            DateFormat dateFormat = new SimpleDateFormat(datePattern);
            try
            {
                Date timestamp = dateFormat.parse(rset.getString(columnIndex));
                return new java.sql.Timestamp(timestamp.getTime());
            }
            catch (ParseException e)
            {
                throw new UnexpectedReturnValueException(rset.getString(columnIndex), "getResultValue");
            }
        }
        else if (dataType == DataType.CLOB)
        {
            java.sql.Clob clob = rset.getClob(columnIndex);
            return ((clob != null) ? clob.getSubString(1, (int) clob.length()) : null);
        }
        else if (dataType == DataType.BLOB)
        { // Get bytes of a binary large object
            java.sql.Blob blob = rset.getBlob(columnIndex);
            return ((blob != null) ? blob.getBytes(1, (int) blob.length()) : null);
        }
        else
        {
            return rset.getObject(columnIndex);
        }
    }
    
    /**
     * Overridden. Returns a timestamp that is used for record updates created
     * by the database server.
     * 
     * @return the current date and time of the database server.
     */
    @Override
    public java.sql.Timestamp getUpdateTimestamp(Connection conn)
    {
        // Default implementation
        GregorianCalendar cal = new GregorianCalendar();
        return new java.sql.Timestamp(cal.getTimeInMillis());
    }
    
    /**
     * @see DBMSHandler#getDDLScript(DDLActionType, DBObject, DBSQLScript)
     */
    @Override
    public void getDDLScript(DDLActionType type, DBObject dbo, DBSQLScript script)
    {
        if (ddlGenerator == null)
            ddlGenerator = new SQLiteDDLGenerator(this);
        // forward request
        ddlGenerator.getDDLScript(type, dbo, script);
    }
    
    @Override
    public Object getNextSequenceValue(DBDatabase db, String SeqName, int minValue, Connection conn)
    {
        throw new NotImplementedException(db, " sequence values are assigned dynamicaly from sqlite ");
    }

    /**
     * @see DBMSHandler#getNextSequenceValueExpr(DBTableColumn col)
     */
    @Override
    public DBColumnExpr getNextSequenceValueExpr(DBTableColumn column)
    {
        throw new NotSupportedException(this, "getNextSequenceValueExpr");
    }
    
}