/*
   Copyright (c) 2018 James Ahlborn
   
   Licensed 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 com.healthmarketscience.jackcess.impl;
  
  import java.io.IOException;
  import java.math.BigDecimal;
  import java.text.DecimalFormat;
  import java.time.LocalDateTime;
  import java.time.ZoneId;
  import java.time.format.DateTimeFormatter;
  import java.util.Collection;
  import java.util.EnumMap;
  import java.util.Locale;
  import java.util.Map;
  import javax.script.Bindings;
  
  import com.healthmarketscience.jackcess.DataType;
  import com.healthmarketscience.jackcess.JackcessException;
  import com.healthmarketscience.jackcess.expr.EvalContext;
  import com.healthmarketscience.jackcess.expr.EvalException;
  import com.healthmarketscience.jackcess.expr.Expression;
  import com.healthmarketscience.jackcess.expr.Identifier;
  import com.healthmarketscience.jackcess.expr.LocaleContext;
  import com.healthmarketscience.jackcess.expr.NumericConfig;
  import com.healthmarketscience.jackcess.expr.TemporalConfig;
  import com.healthmarketscience.jackcess.expr.Value;
  import com.healthmarketscience.jackcess.impl.expr.Expressionator;
  import com.healthmarketscience.jackcess.impl.expr.ValueSupport;
  
  /**
   *
   * @author James Ahlborn
   */
  public abstract class BaseEvalContext implements EvalContext
  {
    /** map of all non-string data types */
    private static final Map<DataType,Value.Type> TYPE_MAP =
      new EnumMap<>(DataType.class);
  
    static {
      TYPE_MAP.put(DataType.BOOLEAN,Value.Type.LONG);
      TYPE_MAP.put(DataType.BYTE,Value.Type.LONG);
      TYPE_MAP.put(DataType.INT,Value.Type.LONG);
      TYPE_MAP.put(DataType.LONG,Value.Type.LONG);
      TYPE_MAP.put(DataType.MONEY,Value.Type.DOUBLE);
      TYPE_MAP.put(DataType.FLOAT,Value.Type.DOUBLE);
      TYPE_MAP.put(DataType.DOUBLE,Value.Type.DOUBLE);
      TYPE_MAP.put(DataType.SHORT_DATE_TIME,Value.Type.DATE_TIME);
      TYPE_MAP.put(DataType.NUMERIC,Value.Type.BIG_DEC);
      TYPE_MAP.put(DataType.BIG_INT,Value.Type.BIG_DEC);
    }
  
    private final DBEvalContext _dbCtx;
    private Expression _expr;
  
    protected BaseEvalContext(DBEvalContext dbCtx) {
      _dbCtx = dbCtx;
    }
  
    void setExpr(Expressionator.Type exprType, String exprStr) {
      _expr = new RawExpr(exprType, exprStr);
    }
  
    protected DatabaseImpl getDatabase() {
      return _dbCtx.getDatabase();
    }
  
    @Override
    public Locale getLocale() {
      return _dbCtx.getLocale();
    }
  
    @Override
    public TemporalConfig getTemporalConfig() {
      return _dbCtx.getTemporalConfig();
    }
  
    @Override
    public DateTimeFormatter createDateFormatter(String formatStr) {
      return _dbCtx.createDateFormatter(formatStr);
    }
  
    @Override
    public ZoneId getZoneId() {
      return _dbCtx.getZoneId();
   }
 
   @Override
   public NumericConfig getNumericConfig() {
     return _dbCtx.getNumericConfig();
   }
 
   @Override
   public DecimalFormat createDecimalFormat(String formatStr) {
     return _dbCtx.createDecimalFormat(formatStr);
   }
 
   @Override
   public float getRandom(Integer seed) {
     return _dbCtx.getRandom(seed);
   }
 
   @Override
   public Value.Type getResultType() {
     return null;
   }
 
   @Override
   public Value getThisColumnValue() {
     throw new UnsupportedOperationException();
   }
 
   @Override
   public Value getIdentifierValue(Identifier identifier) {
     throw new UnsupportedOperationException();
   }
 
   @Override
   public Bindings getBindings() {
     return _dbCtx.getBindings();
   }
 
   @Override
   public Object get(String key) {
     return _dbCtx.getBindings().get(key);
   }
 
   @Override
   public void put(String key, Object value) {
     _dbCtx.getBindings().put(key, value);
   }
 
   public Object eval() throws IOException {
     try {
       return _expr.eval(this);
     } catch(Exception e) {
       String msg = withErrorContext(e.getMessage());
       throw new JackcessException(msg, e);
     }
   }
 
   public void collectIdentifiers(Collection<Identifier> identifiers) {
     _expr.collectIdentifiers(identifiers);
   }
 
   @Override
   public String toString() {
     return _expr.toString();
   }
 
   protected Value toValue(Object val, DataType dType) {
     try {
       // expression engine always uses LocalDateTime, so force that date/time
       // type
       val = ColumnImpl.toInternalValue(dType, val, getDatabase(),
                                        ColumnImpl.LDT_DATE_TIME_FACTORY);
       if(val == null) {
         return ValueSupport.NULL_VAL;
       }
 
       Value.Type vType = toValueType(dType);
       switch(vType) {
       case STRING:
         return ValueSupport.toValue(val.toString());
       case DATE:
       case TIME:
       case DATE_TIME:
         return ValueSupport.toValue(vType, (LocalDateTime)val);
       case LONG:
         Integer i = ((val instanceof Integer) ? (Integer)val :
                      ((Number)val).intValue());
         return ValueSupport.toValue(i);
       case DOUBLE:
         Double d = ((val instanceof Double) ? (Double)val :
                     ((Number)val).doubleValue());
         return ValueSupport.toValue(d);
       case BIG_DEC:
         BigDecimal bd = ColumnImpl.toBigDecimal(val, getDatabase());
         return ValueSupport.toValue(bd);
       default:
         throw new RuntimeException("Unexpected type " + vType);
       }
     } catch(IOException e) {
       throw new EvalException("Failed converting value to type " + dType, e);
     }
   }
 
   /**
    * @return whether a default value which is not an expression may be taken
    *         as a literal here.  A column type with no Value.Type of its own,
    *         such as GUID, reads as a string, but it holds no free text
    */
   protected boolean allowLiteralDefaultValue() {
     return true;
   }
 
   public static Value.Type toValueType(DataType dType) {
     Value.Type type = TYPE_MAP.get(dType);
     return ((type == null) ? Value.Type.STRING : type);
   }
 
   protected abstract String withErrorContext(String msg);
 
   private class RawExpr implements Expression
   {
     private final Expressionator.Type _exprType;
     private final String _exprStr;
 
     private RawExpr(Expressionator.Type exprType, String exprStr) {
       _exprType = exprType;
       _exprStr = exprStr;
     }
 
     private Expression getExpr() {
       // when the expression is parsed we replace the raw version
       Expression expr = Expressionator.parse(
           _exprType, _exprStr, getResultType(), _dbCtx,
           allowLiteralDefaultValue());
       _expr = expr;
       return expr;
     }
 
     @Override
     public Object eval(EvalContext ctx) {
       return getExpr().eval(ctx);
     }
 
     @Override
     public String toDebugString(LocaleContext ctx) {
       return getExpr().toDebugString(ctx);
     }
 
     @Override
     public String toRawString() {
       return _exprStr;
     }
 
     @Override
     public String toCleanString(LocaleContext ctx) {
       return getExpr().toCleanString(ctx);
     }
 
     @Override
     public boolean isConstant() {
       return getExpr().isConstant();
     }
 
     @Override
     public void collectIdentifiers(Collection<Identifier> identifiers) {
       getExpr().collectIdentifiers(identifiers);
     }
 
     @Override
     public String toString() {
       return toRawString();
     }
   }
 }