/*
Copyright (c) 2016 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.expr;

import java.io.BufferedReader;
import java.io.FileReader;
import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import javax.script.Bindings;
import javax.script.SimpleBindings;

import com.healthmarketscience.jackcess.DataType;
import com.healthmarketscience.jackcess.TestUtil;
import com.healthmarketscience.jackcess.expr.EvalContext;
import com.healthmarketscience.jackcess.expr.Expression;
import com.healthmarketscience.jackcess.expr.FunctionLookup;
import com.healthmarketscience.jackcess.expr.Identifier;
import com.healthmarketscience.jackcess.expr.NumericConfig;
import com.healthmarketscience.jackcess.expr.ParseException;
import com.healthmarketscience.jackcess.expr.TemporalConfig;
import com.healthmarketscience.jackcess.expr.Value;
import com.healthmarketscience.jackcess.impl.BaseEvalContext;
import junit.framework.TestCase;

/**
 *
 * @author James Ahlborn
 */
public class ExpressionatorTest extends TestCase
{
  private static final double[] DBLS = {
    -10.3d,-9.0d,-8.234d,-7.11111d,-6.99999d,-5.5d,-4.0d,-3.4159265d,-2.84d,
    -1.0000002d,-1.0d,-0.0002013d,0.0d, 0.9234d,1.0d,1.954d,2.200032d,3.001d,
    4.9321d,5.0d,6.66666d,7.396d,8.1d,9.20456200d,10.325d};

  private static final int TRUE_NUM = -1;
  private static final int FALSE_NUM = 0;

  public ExpressionatorTest(String name) {
    super(name);
  }


  public void testParseSimpleExprs() throws Exception
  {
    validateExpr("\"A\"", "<ELiteralValue>{\"A\"}");

    validateExpr("13", "<ELiteralValue>{13}");

    validateExpr("-42", "<EUnaryOp>{- <ELiteralValue>{42}}");

    validateExpr("(+37)", "<EParen>{(<EUnaryOp>{+ <ELiteralValue>{37}})}");

    doTestSimpleBinOp("EBinaryOp", "+", "-", "*", "/", "\\", "^", "&", "Mod");
    doTestSimpleBinOp("ECompOp", "<", "<=", ">", ">=", "=", "<>");
    doTestSimpleBinOp("ELogicalOp", "And", "Or", "Eqv", "Xor", "Imp");

    for(String constStr : new String[]{"True", "False", "Null"}) {
      validateExpr(constStr, "<EConstValue>{" + constStr + "}");
    }

    validateExpr("[Field1]", "<EObjValue>{[Field1]}");

    validateExpr("[Table2].[Field3]", "<EObjValue>{[Table2].[Field3]}");

    validateExpr("Not \"A\"", "<EUnaryOp>{Not <ELiteralValue>{\"A\"}}");

    validateExpr("-[Field1]", "<EUnaryOp>{- <EObjValue>{[Field1]}}");

    validateExpr("\"A\" Is Null", "<ENullOp>{<ELiteralValue>{\"A\"} Is Null}");

    validateExpr("\"A\" In (1,2,3)", "<EInOp>{<ELiteralValue>{\"A\"} In (<ELiteralValue>{1},<ELiteralValue>{2},<ELiteralValue>{3})}");

    validateExpr("\"A\" Not Between 3 And 7", "<EBetweenOp>{<ELiteralValue>{\"A\"} Not Between <ELiteralValue>{3} And <ELiteralValue>{7}}");

    validateExpr("(\"A\" Or \"B\")", "<EParen>{(<ELogicalOp>{<ELiteralValue>{\"A\"} Or <ELiteralValue>{\"B\"}})}");

    validateExpr("IIf(\"A\",42,False)", "<EFunc>{IIf(<ELiteralValue>{\"A\"},<ELiteralValue>{42},<EConstValue>{False})}");

    validateExpr("\"A\" Like \"a*b\"", "<ELikeOp>{<ELiteralValue>{\"A\"} Like \"a*b\"(a.*b)}");

    validateExpr("' \"A\" '", "<ELiteralValue>{\" \"\"A\"\" \"}",
                 "\" \"\"A\"\" \"");

    validateExpr("<=1 And >=0", "<ELogicalOp>{<ECompOp>{<EThisValue>{<THIS_COL>} <= <ELiteralValue>{1}} And <ECompOp>{<EThisValue>{<THIS_COL>} >= <ELiteralValue>{0}}}", "<= 1 And >= 0");
  }

  private static void doTestSimpleBinOp(String opName, String... ops) throws Exception
  {
    for(String op : ops) {
      validateExpr("\"A\" " + op + " \"B\"",
                   "<" + opName + ">{<ELiteralValue>{\"A\"} " + op +
                   " <ELiteralValue>{\"B\"}}");
    }
  }

  public void testOrderOfOperations() throws Exception
  {
    validateExpr("\"A\" Eqv \"B\"",
                 "<ELogicalOp>{<ELiteralValue>{\"A\"} Eqv <ELiteralValue>{\"B\"}}");

    validateExpr("\"A\" Eqv \"B\" Xor \"C\"",
                 "<ELogicalOp>{<ELiteralValue>{\"A\"} Eqv <ELogicalOp>{<ELiteralValue>{\"B\"} Xor <ELiteralValue>{\"C\"}}}");

    validateExpr("\"A\" Eqv \"B\" Xor \"C\" Or \"D\"",
                 "<ELogicalOp>{<ELiteralValue>{\"A\"} Eqv <ELogicalOp>{<ELiteralValue>{\"B\"} Xor <ELogicalOp>{<ELiteralValue>{\"C\"} Or <ELiteralValue>{\"D\"}}}}");

    validateExpr("\"A\" Eqv \"B\" Xor \"C\" Or \"D\" And \"E\"",
                 "<ELogicalOp>{<ELiteralValue>{\"A\"} Eqv <ELogicalOp>{<ELiteralValue>{\"B\"} Xor <ELogicalOp>{<ELiteralValue>{\"C\"} Or <ELogicalOp>{<ELiteralValue>{\"D\"} And <ELiteralValue>{\"E\"}}}}}");

    validateExpr("\"A\" Or \"B\" Or \"C\"",
                 "<ELogicalOp>{<ELogicalOp>{<ELiteralValue>{\"A\"} Or <ELiteralValue>{\"B\"}} Or <ELiteralValue>{\"C\"}}");

    validateExpr("\"A\" & \"B\" Is Null",
                 "<ENullOp>{<EBinaryOp>{<ELiteralValue>{\"A\"} & <ELiteralValue>{\"B\"}} Is Null}");

    validateExpr("\"A\" Or \"B\" Is Null",
                 "<ELogicalOp>{<ELiteralValue>{\"A\"} Or <ENullOp>{<ELiteralValue>{\"B\"} Is Null}}");

    validateExpr("Not \"A\" & \"B\"",
                 "<EUnaryOp>{Not <EBinaryOp>{<ELiteralValue>{\"A\"} & <ELiteralValue>{\"B\"}}}");

    validateExpr("Not \"A\" Or \"B\"",
                 "<ELogicalOp>{<EUnaryOp>{Not <ELiteralValue>{\"A\"}} Or <ELiteralValue>{\"B\"}}");

    validateExpr("\"A\" + \"B\" Not Between 37 - 15 And 52 / 4",
                 "<EBetweenOp>{<EBinaryOp>{<ELiteralValue>{\"A\"} + <ELiteralValue>{\"B\"}} Not Between <EBinaryOp>{<ELiteralValue>{37} - <ELiteralValue>{15}} And <EBinaryOp>{<ELiteralValue>{52} / <ELiteralValue>{4}}}");

    validateExpr("\"A\" + (\"B\" Not Between 37 - 15 And 52) / 4",
                 "<EBinaryOp>{<ELiteralValue>{\"A\"} + <EBinaryOp>{<EParen>{(<EBetweenOp>{<ELiteralValue>{\"B\"} Not Between <EBinaryOp>{<ELiteralValue>{37} - <ELiteralValue>{15}} And <ELiteralValue>{52}})} / <ELiteralValue>{4}}}");


  }

  public void testSimpleMathExpressions() throws Exception
  {
    for(int i = -10; i <= 10; ++i) {
      assertEquals(-i, eval("=-(" + i + ")"));
    }

    for(int i = -10; i <= 10; ++i) {
      assertEquals(i, eval("=+(" + i + ")"));
    }

    for(double i : DBLS) {
      assertEquals(toBD(-i), eval("=-(" + i + ")"));
    }

    for(double i : DBLS) {
      assertEquals(toBD(i), eval("=+(" + i + ")"));
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        assertEquals((i + j), eval("=" + i + " + " + j));
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        assertEquals(toBD(toBD(i).add(toBD(j))), eval("=" + i + " + " + j));
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        assertEquals((i - j), eval("=" + i + " - " + j));
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        assertEquals(toBD(toBD(i).subtract(toBD(j))), eval("=" + i + " - " + j));
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        assertEquals((i * j), eval("=" + i + " * " + j));
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        assertEquals(toBD(toBD(i).multiply(toBD(j))), eval("=" + i + " * " + j));
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        if(j == 0L) {
          evalFail("=" + i + " \\ " + j, ArithmeticException.class);
        } else {
          assertEquals((i / j), eval("=" + i + " \\ " + j));
        }
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        if(roundToLongInt(j) == 0) {
          evalFail("=" + i + " \\ " + j, ArithmeticException.class);
        } else {
          assertEquals((roundToLongInt(i) / roundToLongInt(j)),
                       eval("=" + i + " \\ " + j));
        }
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        if(j == 0) {
          evalFail("=" + i + " Mod " + j, ArithmeticException.class);
        } else {
          assertEquals((i % j), eval("=" + i + " Mod " + j));
        }
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        if(roundToLongInt(j) == 0) {
          evalFail("=" + i + " Mod " + j, ArithmeticException.class);
        } else {
          assertEquals((roundToLongInt(i) % roundToLongInt(j)),
                       eval("=" + i + " Mod " + j));
        }
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        if(j == 0) {
          evalFail("=" + i + " / " + j, ArithmeticException.class);
        } else {
          double result = (double)i / (double)j;
          if((int)result == result) {
            assertEquals((int)result, eval("=" + i + " / " + j));
          } else {
            assertEquals(result, eval("=" + i + " / " + j));
          }
        }
      }
    }

    for(double i : DBLS) {
      for(double j : DBLS) {
        if(j == 0.0d) {
          evalFail("=" + i + " / " + j, ArithmeticException.class);
        } else {
          assertEquals(toBD(BuiltinOperators.divide(toBD(i), toBD(j))),
                       eval("=" + i + " / " + j));
        }
      }
    }

    for(int i = -10; i <= 10; ++i) {
      for(int j = -10; j <= 10; ++j) {
        double result = Math.pow(i, j);
        if((int)result == result) {
          assertEquals((int)result, eval("=" + i + " ^ " + j));
        } else {
          assertEquals(result, eval("=" + i + " ^ " + j));
        }
      }
    }
  }

  public void testComparison() throws Exception
  {
    assertEquals(TRUE_NUM, eval("='blah'<'fuzz'"));
    assertEquals(FALSE_NUM, eval("=23>56"));
    assertEquals(FALSE_NUM, eval("=23>=56"));
    assertEquals(TRUE_NUM, eval("=13.2<=45.8"));
    assertEquals(FALSE_NUM, eval("='blah'='fuzz'"));
    assertEquals(TRUE_NUM, eval("='blah'<>'fuzz'"));
    assertEquals(TRUE_NUM, eval("=CDbl(13.2)<=CDbl(45.8)"));

    assertEquals(FALSE_NUM, eval("='blah' Is Null"));
    assertEquals(TRUE_NUM, eval("='blah' Is Not Null"));

    assertEquals(TRUE_NUM, eval("=Null Is Null"));
    assertEquals(FALSE_NUM, eval("=Null Is Not Null"));

    assertEquals(TRUE_NUM, eval("='blah' Between 'a' And 'z'"));
    assertEquals(TRUE_NUM, eval("='blah' Between 'z' And 'a'"));
    assertEquals(FALSE_NUM, eval("='blah' Not Between 'a' And 'z'"));

    assertEquals(TRUE_NUM, eval("='blah' In ('foo','bar','blah')"));
    assertEquals(FALSE_NUM, eval("='blah' Not In ('foo','bar','blah')"));

    assertEquals(TRUE_NUM, eval("=True Xor False"));
    assertEquals(TRUE_NUM, eval("=True Or False"));
    assertEquals(TRUE_NUM, eval("=False Or True"));
    assertEquals(FALSE_NUM, eval("=True Imp False"));
    assertEquals(FALSE_NUM, eval("=True Eqv False"));
    assertEquals(TRUE_NUM, eval("=Not(True Eqv False)"));
  }

  public void testDateArith() throws Exception
  {
    assertEquals(LocalDateTime.of(2003,1,2,7,0), eval("=#01/02/2003# + #7:00:00 AM#"));
    assertEquals(LocalDateTime.of(2003,1,1,17,0), eval("=#01/02/2003# - #7:00:00 AM#"));
    assertEquals(LocalDateTime.of(2003,2,8,0,0), eval("=#01/02/2003# + '37'"));
    assertEquals(LocalDateTime.of(2003,2,8,0,0), eval("='37' + #01/02/2003#"));
    assertEquals(LocalDateTime.of(2003,1,2,7,0), eval("=#01/02/2003 7:00:00 AM#"));

    assertEquals("2/8/2003", eval("=CStr(#01/02/2003# + '37')"));
    assertEquals("9:24:00 AM", eval("=CStr(#7:00:00 AM# + 0.1)"));
    assertEquals("1/2/2003 1:10:00 PM", eval("=CStr(#01/02/2003# + #13:10:00#)"));
  }

  public void testNull() throws Exception
  {
    assertNull(eval("=37 + Null"));
    assertNull(eval("=37 - Null"));
    assertNull(eval("=37 / Null"));
    assertNull(eval("=37 * Null"));
    assertNull(eval("=37 ^ Null"));
    assertEquals("37", eval("=37 & Null"));
    assertEquals("37", eval("=Null & 37"));
    assertNull(eval("=37 Mod Null"));
    assertNull(eval("=37 \\ Null"));
    assertNull(eval("=-(Null)"));
    assertNull(eval("=+(Null)"));
    assertNull(eval("=Not Null"));
    assertEquals(TRUE_NUM, eval("=37 Or Null"));
    assertNull(eval("=Null Or 37"));
    assertNull(eval("=37 And Null"));
    assertNull(eval("=Null And 37"));
    assertNull(eval("=37 Xor Null"));
    assertNull(eval("=37 Imp Null"));
    assertNull(eval("=Null Imp Null"));
    assertEquals(TRUE_NUM, eval("=Null Imp 37"));
    assertNull(eval("=37 Eqv Null"));
    assertNull(eval("=37 < Null"));
    assertNull(eval("=37 > Null"));
    assertNull(eval("=37 = Null"));
    assertNull(eval("=37 <> Null"));
    assertNull(eval("=37 <= Null"));
    assertNull(eval("=37 >= Null"));

    assertNull(eval("=37 Between Null And 54"));
    assertEquals(FALSE_NUM, eval("=37 In (23, Null, 45)"));
    assertNull(eval("=Null In (23, Null, 45)"));
  }

  public void testTrickyMathExpressions() throws Exception
  {
    assertEquals(37, eval("=30+7"));
    assertEquals(23, eval("=30+-7"));
    assertEquals(23, eval("=30-+7"));
    assertEquals(37, eval("=30--7"));
    assertEquals(23, eval("=30-7"));

    assertEquals(100, eval("=-10^2"));
    assertEquals(-100, eval("=-(10)^2"));
    assertEquals(-100d, eval("=-\"10\"^2"));
    assertEquals(toBD(-98.9d), eval("=1.1+(-\"10\"^2)"));

    assertEquals(toBD(99d), eval("=-10E-1+10e+1"));
    assertEquals(toBD(-101d), eval("=-10E-1-10e+1"));
  }

  public void testTypeCoercion() throws Exception
  {
    assertEquals("foobar", eval("=\"foo\" + \"bar\""));

    assertEquals("12foo", eval("=12 + \"foo\""));
    assertEquals("foo12", eval("=\"foo\" + 12"));

    assertEquals(37d, eval("=\"25\" + 12"));
    assertEquals(37d, eval("=12 + \"25\""));
    assertEquals(37d, eval("=\" 25 \" + 12"));
    assertEquals(37d, eval("=\" &h1A \" + 11"));
    assertEquals(37d, eval("=\" &h1a \" + 11"));
    assertEquals(37d, eval("=\" &O32 \" + 11"));
    assertEquals(1037d, eval("=\"1,025\" + 12"));

    evalFail(("=12 - \"foo\""), RuntimeException.class);
    evalFail(("=\"foo\" - 12"), RuntimeException.class);

    assertEquals("foo1225", eval("=\"foo\" + 12 + 25"));
    assertEquals("37foo", eval("=12 + 25 + \"foo\""));
    assertEquals("foo37", eval("=\"foo\" + (12 + 25)"));
    assertEquals("25foo12", eval("=\"25foo\" + 12"));

    assertEquals(LocalDateTime.of(2017,1,28,0,0), eval("=#1/1/2017# + 27"));
    assertEquals(128208, eval("=#1/1/2017# * 3"));
  }

  public void testLikeExpression() throws Exception
  {
    validateExpr("Like \"[abc]*\"", "<ELikeOp>{<EThisValue>{<THIS_COL>} Like \"[abc]*\"([abc].*)}",
                 "Like \"[abc]*\"");
    assertTrue(evalCondition("Like \"[abc]*\"", "afcd"));
    assertFalse(evalCondition("Like \"[abc]*\"", "fcd"));

    validateExpr("Like  \"[abc*\"", "<ELikeOp>{<EThisValue>{<THIS_COL>} Like \"[abc*\"((?!))}",
                 "Like \"[abc*\"");
    assertFalse(evalCondition("Like \"[abc*\"", "afcd"));
    assertFalse(evalCondition("Like \"[abc*\"", "fcd"));
    assertTrue(evalCondition("Not Like \"[abc*\"", "fcd"));
    assertFalse(evalCondition("Like \"[abc*\"", ""));
  }

  public void testLiteralDefaultValue() throws Exception
  {
    assertEquals("-28 blah ", eval("=CDbl(9)-37 & \" blah \"",
                                     Value.Type.STRING));
    assertEquals("CDbl(9)-37 & \" blah \"",
                 eval("CDbl(9)-37 & \" blah \"", Value.Type.STRING));

    assertEquals(-28d, eval("=CDbl(9)-37", Value.Type.DOUBLE));
    assertEquals(-28d, eval("CDbl(9)-37", Value.Type.DOUBLE));
  }

  public void testParseSomeExprs() throws Exception
  {
    BufferedReader br = new BufferedReader(new FileReader("src/test/resources/test_exprs.txt"));

    TestContext tc = new TestContext() {
      @Override
      public Value getThisColumnValue() {
        return ValueSupport.toValue(23.0);
      }

      @Override
      public Value getIdentifierValue(Identifier identifier) {
        return ValueSupport.toValue(23.0);
      }
    };

    String line = null;
    while((line = br.readLine()) != null) {
      line = line.trim();
      if(line.isEmpty()) {
        continue;
      }

      String[] parts = line.split(";", 3);
      Expressionator.Type type = Expressionator.Type.valueOf(parts[0]);
      DataType dType =
        (("null".equals(parts[1])) ? null : DataType.valueOf(parts[1]));
      String exprStr = parts[2];

      Value.Type resultType = ((dType != null) ?
                               BaseEvalContext.toValueType(dType) : null);

      Expression expr = Expressionator.parse(
          type, exprStr, resultType, tc);

      expr.eval(tc);
    }

    br.close();
  }

  public void testInvalidExpressions() throws Exception
  {
    doTestEvalFail("", "empty");
    doTestEvalFail("=", "found?");
    doTestEvalFail("=(34 + 5", "closing");
    doTestEvalFail("=(34 + )", "found?");
    doTestEvalFail("=(34 + [A].[B].[C].[D])", "object reference");
    doTestEvalFail("=34 + 5,", "delimiter");
    doTestEvalFail("=Foo()", "find function");
    doTestEvalFail("=(/37)", "left expression");
    doTestEvalFail("=(>37)", "left expression");
    doTestEvalFail("=(And 37)", "left expression");
    doTestEvalFail("=37 In 42", "'In' expression");
    doTestEvalFail("=37 Between 42", "'Between' expression");
    doTestEvalFail("=(3 + 5) Rnd()", "multiple expressions");
  }

  private static void doTestEvalFail(String exprStr, String msgStr) {
    try {
      eval(exprStr);
      fail("ParseException should have been thrown");
    } catch(ParseException pe) {
      // success
      assertTrue(pe.getMessage().contains(msgStr));
    }
  }

  private static void validateExpr(String exprStr, String debugStr) {
    validateExpr(exprStr, debugStr, exprStr);
  }

  private static void validateExpr(String exprStr, String debugStr,
                                   String cleanStr) {
    TestContext ctx = new TestContext();
    Expression expr = Expressionator.parse(
        Expressionator.Type.FIELD_VALIDATOR, exprStr, null, ctx);
    String foundDebugStr = expr.toDebugString(ctx);
    if(foundDebugStr.startsWith("<EImplicitCompOp>")) {
      assertEquals("<EImplicitCompOp>{<EThisValue>{<THIS_COL>} = " +
                   debugStr + "}", foundDebugStr);
    } else {
      assertEquals(debugStr, foundDebugStr);
    }
    assertEquals(cleanStr, expr.toCleanString(ctx));
    assertEquals(exprStr, expr.toRawString());
  }

  static Object eval(String exprStr) {
    return eval(exprStr, null);
  }

  static Object eval(String exprStr, Value.Type resultType) {
    TestContext tc = new TestContext();
    Expression expr = Expressionator.parse(
        Expressionator.Type.DEFAULT_VALUE, exprStr, resultType, tc);
    return expr.eval(tc);
  }

  private static void evalFail(
      String exprStr, Class<? extends Exception> failure)
  {
    TestContext tc = new TestContext();
    Expression expr = Expressionator.parse(
        Expressionator.Type.DEFAULT_VALUE, exprStr, null, tc);
    try {
      expr.eval(tc);
      fail(failure + " should have been thrown");
    } catch(Exception e) {
      assertTrue(failure.isInstance(e));
    }
  }

  private static Boolean evalCondition(String exprStr, String thisVal) {
    TestContext tc = new TestContext(ValueSupport.toValue(thisVal));
    Expression expr = Expressionator.parse(
        Expressionator.Type.FIELD_VALIDATOR, exprStr, null, tc);
    return (Boolean)expr.eval(tc);
  }

  static int roundToLongInt(double d) {
    return new BigDecimal(d).setScale(0, NumberFormatter.ROUND_MODE)
      .intValueExact();
  }

  static BigDecimal toBD(double d) {
    return toBD(BigDecimal.valueOf(d));
  }

  static BigDecimal toBD(BigDecimal bd) {
    return ValueSupport.normalize(bd);
  }

  private static class TestContext
    implements Expressionator.ParseContext, EvalContext
  {
    private final Value _thisVal;
    private final RandomContext _rndCtx = new RandomContext();
    private final Bindings _bindings = new SimpleBindings();

    private TestContext() {
      this(null);
    }

    private TestContext(Value thisVal) {
      _thisVal = thisVal;
    }

    @Override
    public Value.Type getResultType() {
      return null;
    }

    @Override
    public TemporalConfig getTemporalConfig() {
      return TemporalConfig.US_TEMPORAL_CONFIG;
    }

    @Override
    public DateTimeFormatter createDateFormatter(String formatStr) {
      DateTimeFormatter dtf = DateTimeFormatter.ofPattern(
          formatStr, TemporalConfig.US_TEMPORAL_CONFIG.getLocale());
      return dtf;
    }

    @Override
    public ZoneId getZoneId() {
      return TestUtil.TEST_TZ.toZoneId();
    }

    @Override
    public NumericConfig getNumericConfig() {
      return NumericConfig.US_NUMERIC_CONFIG;
    }

    @Override
    public DecimalFormat createDecimalFormat(String formatStr) {
      return new DecimalFormat(
          formatStr, NumericConfig.US_NUMERIC_CONFIG.getDecimalFormatSymbols());
    }

    @Override
    public FunctionLookup getFunctionLookup() {
      return DefaultFunctions.LOOKUP;
    }

    @Override
    public Value getThisColumnValue() {
      if(_thisVal == null) {
        throw new UnsupportedOperationException();
      }
      return _thisVal;
    }

    @Override
    public Value getIdentifierValue(Identifier identifier) {
      throw new UnsupportedOperationException();
    }

    @Override
    public float getRandom(Integer seed) {
      return _rndCtx.getRandom(seed);
    }

    @Override
    public Bindings getBindings() {
      return _bindings;
    }

    @Override
    public Object get(String key) {
      return _bindings.get(key);
    }

    @Override
    public void put(String key, Object value) {
      _bindings.put(key, value);
    }
  }
}