/*
    * Portions of this software was developed by employees of the National Institute
    * of Standards and Technology (NIST), an agency of the Federal Government and is
    * being made available as a public service. Pursuant to title 17 United States
    * Code Section 105, works of NIST employees are not subject to copyright
    * protection in the United States. This software may be subject to foreign
    * copyright. Permission in the United States and in foreign countries, to the
    * extent that NIST may hold copyright, to use, copy, modify, create derivative
    * works, and distribute this software and its documentation without fee is hereby
   * granted on a non-exclusive basis, provided that this notice and disclaimer
   * of warranty appears in all copies.
   *
   * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
   * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
   * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
   * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
   * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
   * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
   * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
   * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
   * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
   * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
   * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
   */
  
  package gov.nist.secauto.metaschema.core.metapath;
  
  import gov.nist.secauto.metaschema.core.metapath.antlr.metapath10Lexer;
  import gov.nist.secauto.metaschema.core.metapath.antlr.metapath10Parser;
  import gov.nist.secauto.metaschema.core.metapath.function.FunctionUtils;
  import gov.nist.secauto.metaschema.core.metapath.function.library.FnBoolean;
  import gov.nist.secauto.metaschema.core.metapath.function.library.FnData;
  import gov.nist.secauto.metaschema.core.metapath.item.IItem;
  import gov.nist.secauto.metaschema.core.metapath.item.atomic.IAnyAtomicItem;
  import gov.nist.secauto.metaschema.core.metapath.item.atomic.IDecimalItem;
  import gov.nist.secauto.metaschema.core.metapath.item.atomic.INumericItem;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import org.antlr.v4.runtime.CharStreams;
  import org.antlr.v4.runtime.CommonTokenStream;
  import org.antlr.v4.runtime.misc.ParseCancellationException;
  import org.antlr.v4.runtime.tree.ParseTree;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.PrintStream;
  import java.nio.charset.StandardCharsets;
  import java.util.Arrays;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public class MetapathExpression {
  
    public enum ResultType {
      NUMBER,
      STRING,
      BOOLEAN,
      SEQUENCE,
      NODE;
    }
  
    private static final Logger LOGGER = LogManager.getLogger(MetapathExpression.class);
  
    @NonNull
    public static final MetapathExpression CONTEXT_NODE = new MetapathExpression(".", ContextItem.instance());
  
    private final String path;
    @NonNull
    private final IExpression node;
  
    /**
     * Compiles a Metapath expression string.
     *
     * @param path
     *          the metapath expression
     * @return the compiled expression object
     * @throws MetapathException
     *           if an error occurred while compiling the Metapath expression
     */
    @NonNull
    public static MetapathExpression compile(@NonNull String path) {
      @NonNull MetapathExpression retval;
      if (".".equals(path)) {
        retval = CONTEXT_NODE;
      } else {
        try {
          metapath10Lexer lexer = new metapath10Lexer(CharStreams.fromString(path));
          CommonTokenStream tokens = new CommonTokenStream(lexer);
          metapath10Parser parser = new metapath10Parser(tokens);
          parser.removeErrorListeners();
          parser.addErrorListener(new FailingErrorListener());
  
          ParseTree tree = ObjectUtils.notNull(parser.expr());
  
          if (LOGGER.isDebugEnabled()) {
           try (ByteArrayOutputStream os = new ByteArrayOutputStream()) {
             try (PrintStream ps = new PrintStream(os, true, StandardCharsets.UTF_8)) {
               CSTPrinter printer = new CSTPrinter(ps);
               printer.print(tree, Arrays.asList(metapath10Parser.ruleNames));
               ps.flush();
             }
             LOGGER.atDebug().log(String.format("Metapath CST:%n%s", os.toString(StandardCharsets.UTF_8)));
           } catch (IOException ex) {
             LOGGER.atError().withThrowable(ex).log("An unexpected error occured while closing the steam.");
           }
         }
 
         IExpression expr = new BuildAstVisitor().visit(tree);
 
         if (LOGGER.isDebugEnabled()) {
           LOGGER.atDebug().log(String.format("Metapath AST:%n%s", ASTPrinter.instance().visit(expr)));
         }
         retval = new MetapathExpression(path, expr);
       } catch (MetapathException | ParseCancellationException ex) {
         String msg = String.format("Unable to compile Metapath '%s'", path);
         LOGGER.atError().withThrowable(ex).log(msg);
         throw new MetapathException(msg, ex);
       }
     }
     return retval;
   }
 
   /**
    * Construct a new Metapath expression.
    *
    * @param path
    *          the Metapath as a string
    * @param expr
    *          the Metapath as a compiled abstract syntax tree (AST)
    */
   protected MetapathExpression(@NonNull String path, @NonNull IExpression expr) {
     this.path = path;
     this.node = expr;
   }
 
   /**
    * Get the original Metapath expression as a string.
    *
    * @return the expression
    */
   public String getPath() {
     return path;
   }
 
   /**
    * Get the compiled abstract syntax tree (AST) representation of the Metapath.
    *
    * @return the Metapath AST
    */
   @NonNull
   protected IExpression getASTNode() {
     return node;
   }
 
   @Override
   public String toString() {
     return ASTPrinter.instance().visit(getASTNode());
   }
 
   /**
    * Evaluate this Metapath expression without a specific focus. The required
    * result type will be determined by the {@code resultType} argument.
    *
    * @param <T>
    *          the expected result type
    * @param resultType
    *          the type of result to produce
    * @return the converted result
    * @throws TypeMetapathException
    *           if the provided sequence is incompatible with the requested result
    *           type
    * @throws MetapathException
    *           if an error occurred during evaluation
    * @see #toResultType(ISequence, ResultType)
    */
   @Nullable
   public <T> T evaluateAs(@NonNull ResultType resultType) {
     return evaluateAs(null, resultType);
   }
 
   /**
    * Evaluate this Metapath expression using the provided {@code focus} as the
    * initial evaluation context. The required result type will be determined by
    * the {@code resultType} argument.
    *
    * @param <T>
    *          the expected result type
    * @param focus
    *          the outer focus of the expression
    * @param resultType
    *          the type of result to produce
    * @return the converted result
    * @throws TypeMetapathException
    *           if the provided sequence is incompatible with the requested result
    *           type
    * @throws MetapathException
    *           if an error occurred during evaluation
    * @see #toResultType(ISequence, ResultType)
    */
   @Nullable
   public <T> T evaluateAs(
       @Nullable IItem focus,
       @NonNull ResultType resultType) {
     ISequence<?> result = evaluate(focus);
     return toResultType(result, resultType);
   }
 
   /**
    * Evaluate this Metapath expression using the provided {@code focus} as the
    * initial evaluation context. The specific result type will be determined by
    * the {@code resultType} argument.
    * <p>
    * This variant allow for reuse of a provided {@code dynamicContext}.
    *
    * @param <T>
    *          the expected result type
    * @param focus
    *          the outer focus of the expression
    * @param resultType
    *          the type of result to produce
    * @param dynamicContext
    *          the dynamic context to use for evaluation
    * @return the converted result
    * @throws TypeMetapathException
    *           if the provided sequence is incompatible with the requested result
    *           type
    * @throws MetapathException
    *           if an error occurred during evaluation
    * @see #toResultType(ISequence, ResultType)
    */
   @Nullable
   public <T> T evaluateAs(
       @NonNull IItem focus,
       @NonNull ResultType resultType,
       @NonNull DynamicContext dynamicContext) {
     ISequence<?> result = evaluate(focus, dynamicContext);
     return toResultType(result, resultType);
   }
 
   /**
    * Converts the provided {@code sequence} to the requested {@code resultType}.
    * <p>
    * The {@code resultType} determines the returned result, which is derived from
    * the evaluation result sequence, as follows:
    * <ul>
    * <li>BOOLEAN - the effective boolean result is produced using
    * {@link FnBoolean#fnBoolean(ISequence)}.</li>
    * <li>NODE - the first result item in the sequence is returned.</li>
    * <li>NUMBER - the sequence is cast to a number using
    * {@link IDecimalItem#cast(IAnyAtomicItem)}.</li>
    * <li>SEQUENCE - the evaluation result sequence.</li>
    * <li>STRING - the string value of the first result item in the sequence.</li>
    * </ul>
    *
    * @param <T>
    *          the requested return value
    * @param sequence
    *          the sequence to convert
    * @param resultType
    *          the type of result to produce
    * @return the converted result
    * @throws TypeMetapathException
    *           if the provided sequence is incompatible with the requested result
    *           type
    */
   @SuppressWarnings("PMD.NullAssignment") // for readability
   @Nullable
   protected <T> T toResultType(@NonNull ISequence<?> sequence, @NonNull ResultType resultType) {
     Object result;
     switch (resultType) {
     case BOOLEAN:
       result = FnBoolean.fnBoolean(sequence).toBoolean();
       break;
     case NODE:
       result = FunctionUtils.getFirstItem(sequence, true);
       break;
     case NUMBER:
       INumericItem numeric = FunctionUtils.toNumeric(sequence, true);
       result = numeric == null ? null : numeric.asDecimal();
       break;
     case SEQUENCE:
       result = sequence;
       break;
     case STRING:
       IItem item = FunctionUtils.getFirstItem(sequence, true);
       result = item == null ? "" : FnData.fnDataItem(item).asString();
       break;
     default:
       throw new InvalidTypeMetapathException(null, String.format("unsupported result type '%s'", resultType.name()));
     }
 
     @SuppressWarnings("unchecked") T retval = (T) result;
     return retval;
   }
 
   /**
    * Evaluate this Metapath expression without a specific focus.
    *
    * @param <T>
    *          the type of items contained in the resulting sequence
    * @return a sequence of Metapath items representing the result of the
    *         evaluation
    * @throws MetapathException
    *           if an error occurred during evaluation
    */
   @NonNull
   public <T extends IItem> ISequence<T> evaluate() {
     return evaluate(null);
   }
 
   /**
    * Evaluate this Metapath expression using the provided {@code focus} as the
    * initial evaluation context.
    *
    * @param <T>
    *          the type of items contained in the resulting sequence
    * @param focus
    *          the outer focus of the expression
    * @return a sequence of Metapath items representing the result of the
    *         evaluation
    * @throws MetapathException
    *           if an error occurred during evaluation
    */
   @SuppressWarnings("unchecked")
   @NonNull
   public <T extends IItem> ISequence<T> evaluate(
       @Nullable IItem focus) {
     return (ISequence<T>) evaluate(
         focus,
         StaticContext.builder()
             .build().newDynamicContext());
   }
 
   /**
    * Evaluate this Metapath expression using the provided {@code focus} as the
    * initial evaluation context.
    * <p>
    * This variant allow for reuse of a provided {@code dynamicContext}.
    *
    * @param <T>
    *          the type of items contained in the resulting sequence
    * @param focus
    *          the outer focus of the expression
    * @param dynamicContext
    *          the dynamic context to use for evaluation
    * @return a sequence of Metapath items representing the result of the
    *         evaluation
    * @throws MetapathException
    *           if an error occurred during evaluation
    */
   @SuppressWarnings("unchecked")
   @NonNull
   public <T extends IItem> ISequence<T> evaluate(
       @Nullable IItem focus,
       @NonNull DynamicContext dynamicContext) {
     try {
       return (ISequence<T>) getASTNode().accept(dynamicContext, ISequence.of(focus));
     } catch (MetapathException ex) { // NOPMD - intentional
       throw new MetapathException(
           String.format("An error occurred while evaluating the expression '%s'.", getPath()), ex);
     }
   }
 }