/*
 * 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.lucene.expressions;

import static org.apache.lucene.expressions.js.VariableContext.Type.INT_INDEX;
import static org.apache.lucene.expressions.js.VariableContext.Type.MEMBER;
import static org.apache.lucene.expressions.js.VariableContext.Type.STR_INDEX;

import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.NumericDocValuesField;
import org.apache.lucene.expressions.js.JavascriptCompiler;
import org.apache.lucene.expressions.js.VariableContext;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.DoubleValuesSource;
import org.apache.lucene.search.FieldDoc;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopFieldDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.tests.index.RandomIndexWriter;
import org.apache.lucene.tests.util.LuceneTestCase;

/** simple demo of using expressions */
public class TestDemoExpressions extends LuceneTestCase {
  IndexSearcher searcher;
  DirectoryReader reader;
  Directory dir;

  @Override
  public void setUp() throws Exception {
    super.setUp();
    dir = newDirectory();
    RandomIndexWriter iw = new RandomIndexWriter(random(), dir);

    Document doc = new Document();
    doc.add(newStringField("id", "1", Field.Store.YES));
    doc.add(newTextField("body", "some contents and more contents", Field.Store.NO));
    doc.add(new NumericDocValuesField("popularity", 5));
    doc.add(new NumericDocValuesField("latitude", Double.doubleToRawLongBits(40.759011)));
    doc.add(new NumericDocValuesField("longitude", Double.doubleToRawLongBits(-73.9844722)));
    iw.addDocument(doc);

    doc = new Document();
    doc.add(newStringField("id", "2", Field.Store.YES));
    doc.add(newTextField("body", "another document with different contents", Field.Store.NO));
    doc.add(new NumericDocValuesField("popularity", 20));
    doc.add(new NumericDocValuesField("latitude", Double.doubleToRawLongBits(40.718266)));
    doc.add(new NumericDocValuesField("longitude", Double.doubleToRawLongBits(-74.007819)));
    iw.addDocument(doc);

    doc = new Document();
    doc.add(newStringField("id", "3", Field.Store.YES));
    doc.add(newTextField("body", "crappy contents", Field.Store.NO));
    doc.add(new NumericDocValuesField("popularity", 2));
    doc.add(new NumericDocValuesField("latitude", Double.doubleToRawLongBits(40.7051157)));
    doc.add(new NumericDocValuesField("longitude", Double.doubleToRawLongBits(-74.0088305)));
    iw.addDocument(doc);

    reader = iw.getReader();
    searcher = new IndexSearcher(reader);
    iw.close();
  }

  @Override
  public void tearDown() throws Exception {
    reader.close();
    dir.close();
    super.tearDown();
  }

  /** an example of how to rank by an expression */
  public void test() throws Exception {
    // compile an expression:
    Expression expr = JavascriptCompiler.compile("sqrt(_score) + ln(popularity)");

    // we use SimpleBindings: which just maps variables to DoubleValuesSource instances
    SimpleBindings bindings = new SimpleBindings();
    bindings.add("_score", DoubleValuesSource.SCORES);
    bindings.add("popularity", DoubleValuesSource.fromIntField("popularity"));

    // create a sort field and sort by it (reverse order)
    Sort sort = new Sort(expr.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    searcher.search(query, 3, sort);
  }

  /** tests the returned sort values are correct */
  public void testSortValues() throws Exception {
    Expression expr = JavascriptCompiler.compile("sqrt(_score)");

    SimpleBindings bindings = new SimpleBindings();
    bindings.add("_score", DoubleValuesSource.SCORES);

    Sort sort = new Sort(expr.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    TopFieldDocs td = searcher.search(query, 3, sort, true);
    for (int i = 0; i < 3; i++) {
      FieldDoc d = (FieldDoc) td.scoreDocs[i];
      float expected = (float) Math.sqrt(d.score);
      float actual = ((Double) d.fields[0]).floatValue();
      assertEquals(expected, actual, 0d);
    }
  }

  /** tests same binding used more than once in an expression */
  public void testTwoOfSameBinding() throws Exception {
    Expression expr = JavascriptCompiler.compile("_score + _score");

    SimpleBindings bindings = new SimpleBindings();
    bindings.add("_score", DoubleValuesSource.SCORES);

    Sort sort = new Sort(expr.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    TopFieldDocs td = searcher.search(query, 3, sort, true);
    for (int i = 0; i < 3; i++) {
      FieldDoc d = (FieldDoc) td.scoreDocs[i];
      float expected = 2 * d.score;
      float actual = ((Double) d.fields[0]).floatValue();
      assertEquals(expected, actual, 0d);
    }
  }

  /** Uses variables with $ */
  public void testDollarVariable() throws Exception {
    Expression expr = JavascriptCompiler.compile("$0+$score");

    SimpleBindings bindings = new SimpleBindings();
    bindings.add("$0", DoubleValuesSource.SCORES);
    bindings.add("$score", DoubleValuesSource.SCORES);

    Sort sort = new Sort(expr.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    TopFieldDocs td = searcher.search(query, 3, sort, true);
    for (int i = 0; i < 3; i++) {
      FieldDoc d = (FieldDoc) td.scoreDocs[i];
      float expected = 2 * d.score;
      float actual = ((Double) d.fields[0]).floatValue();
      assertEquals(expected, actual, 0d);
    }
  }

  /** tests expression referring to another expression */
  public void testExpressionRefersToExpression() throws Exception {
    Expression expr1 = JavascriptCompiler.compile("_score");
    Expression expr2 = JavascriptCompiler.compile("2*expr1");

    SimpleBindings bindings = new SimpleBindings();
    bindings.add("_score", DoubleValuesSource.SCORES);
    bindings.add("expr1", expr1);

    Sort sort = new Sort(expr2.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    TopFieldDocs td = searcher.search(query, 3, sort, true);
    for (int i = 0; i < 3; i++) {
      FieldDoc d = (FieldDoc) td.scoreDocs[i];
      float expected = 2 * d.score;
      float actual = ((Double) d.fields[0]).floatValue();
      assertEquals(expected, actual, 0d);
    }
  }

  /** tests huge amounts of variables in the expression */
  public void testLotsOfBindings() throws Exception {
    doTestLotsOfBindings(Byte.MAX_VALUE - 1);
    doTestLotsOfBindings(Byte.MAX_VALUE);
    doTestLotsOfBindings(Byte.MAX_VALUE + 1);
    // TODO: ideally we'd test > Short.MAX_VALUE too, but compilation is currently recursive.
    // so if we want to test such huge expressions, we need to instead change parser to use an
    // explicit Stack
  }

  private void doTestLotsOfBindings(int n) throws Exception {
    SimpleBindings bindings = new SimpleBindings();
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < n; i++) {
      if (i > 0) {
        sb.append("+");
      }
      sb.append("x" + i);
      bindings.add("x" + i, DoubleValuesSource.SCORES);
    }

    Expression expr = JavascriptCompiler.compile(sb.toString());
    Sort sort = new Sort(expr.getSortField(bindings, true));
    Query query = new TermQuery(new Term("body", "contents"));
    TopFieldDocs td = searcher.search(query, 3, sort, true);
    for (int i = 0; i < 3; i++) {
      FieldDoc d = (FieldDoc) td.scoreDocs[i];
      float expected = n * d.score;
      float actual = ((Double) d.fields[0]).floatValue();
      assertEquals(expected, actual, 0d);
    }
  }

  public void testDistanceSort() throws Exception {
    Expression distance =
        JavascriptCompiler.compile("haversin(40.7143528,-74.0059731,latitude,longitude)");
    SimpleBindings bindings = new SimpleBindings();
    bindings.add("latitude", DoubleValuesSource.fromDoubleField("latitude"));
    bindings.add("longitude", DoubleValuesSource.fromDoubleField("longitude"));
    Sort sort = new Sort(distance.getSortField(bindings, false));
    TopFieldDocs td = searcher.search(MatchAllDocsQuery.INSTANCE, 3, sort);

    FieldDoc d = (FieldDoc) td.scoreDocs[0];
    assertEquals(0.4621D, (Double) d.fields[0], 1E-1);

    d = (FieldDoc) td.scoreDocs[1];
    assertEquals(1.055, (Double) d.fields[0], 1E-1);

    d = (FieldDoc) td.scoreDocs[2];
    assertEquals(5.2859D, (Double) d.fields[0], 1E-1);
  }

  public void testHaversinMetersDistanceSort() throws Exception {
    Expression distance =
        JavascriptCompiler.compile("haversinMeters(40.7143528,-74.0059731,latitude,longitude)");
    SimpleBindings bindings = new SimpleBindings();
    bindings.add("latitude", DoubleValuesSource.fromDoubleField("latitude"));
    bindings.add("longitude", DoubleValuesSource.fromDoubleField("longitude"));
    Sort sort = new Sort(distance.getSortField(bindings, false));
    TopFieldDocs td = searcher.search(MatchAllDocsQuery.INSTANCE, 3, sort);

    FieldDoc d = (FieldDoc) td.scoreDocs[0];
    assertEquals(462.1D, (Double) d.fields[0], 1E-1);

    d = (FieldDoc) td.scoreDocs[1];
    assertEquals(1055, (Double) d.fields[0], 1E-1);

    d = (FieldDoc) td.scoreDocs[2];
    assertEquals(5285.9D, (Double) d.fields[0], 1E-1);
  }

  public void testStaticExtendedVariableExample() throws Exception {
    Expression popularity = JavascriptCompiler.compile("doc[\"popularity\"].value");
    SimpleBindings bindings = new SimpleBindings();
    bindings.add("doc['popularity'].value", DoubleValuesSource.fromIntField("popularity"));
    Sort sort = new Sort(popularity.getSortField(bindings, true));
    TopFieldDocs td = searcher.search(MatchAllDocsQuery.INSTANCE, 3, sort);

    FieldDoc d = (FieldDoc) td.scoreDocs[0];
    assertEquals(20D, (Double) d.fields[0], 1E-4);

    d = (FieldDoc) td.scoreDocs[1];
    assertEquals(5D, (Double) d.fields[0], 1E-4);

    d = (FieldDoc) td.scoreDocs[2];
    assertEquals(2D, (Double) d.fields[0], 1E-4);
  }

  public void testDynamicExtendedVariableExample() throws Exception {
    Expression popularity =
        JavascriptCompiler.compile("doc['popularity'].value + magicarray[0] + fourtytwo");

    // The following is an example of how to write bindings which parse the variable name into
    // pieces.
    // Note, however, that this requires a lot of error checking.  Each "error case" below should be
    // filled in with proper error messages for a real use case.
    Bindings bindings =
        new Bindings() {
          @Override
          public DoubleValuesSource getDoubleValuesSource(String name) {
            VariableContext[] var = VariableContext.parse(name);
            assert var[0].type == MEMBER;
            String base = var[0].text;
            if (base.equals("doc")) {
              if (var.length > 1 && var[1].type == STR_INDEX) {
                String field = var[1].text;
                if (var.length > 2 && var[2].type == MEMBER && var[2].text.equals("value")) {
                  return DoubleValuesSource.fromIntField(field);
                } else {
                  fail("member: " + var[2].text); // error case, non/missing "value" member access
                }
              } else {
                fail(); // error case, doc should be a str indexed array
              }
            } else if (base.equals("magicarray")) {
              if (var.length > 1 && var[1].type == INT_INDEX) {
                return DoubleValuesSource.constant(2048);
              } else {
                fail(); // error case, magic array isn't an array
              }
            } else if (base.equals("fourtytwo")) {
              return DoubleValuesSource.constant(42);
            } else {
              fail(); // error case (variable doesn't exist)
            }
            throw new IllegalArgumentException("Illegal reference '" + name + "'");
          }
        };
    Sort sort = new Sort(popularity.getSortField(bindings, false));
    TopFieldDocs td = searcher.search(MatchAllDocsQuery.INSTANCE, 3, sort);

    FieldDoc d = (FieldDoc) td.scoreDocs[0];
    assertEquals(2092D, (Double) d.fields[0], 1E-4);

    d = (FieldDoc) td.scoreDocs[1];
    assertEquals(2095D, (Double) d.fields[0], 1E-4);

    d = (FieldDoc) td.scoreDocs[2];
    assertEquals(2110D, (Double) d.fields[0], 1E-4);
  }
}
