/**************************************************************************
    *
    * Copyright (c) 2017-2020 Yawg project contributors.
    *
    **************************************************************************/
   
   package com.varmateo.yawg.spi;
   
   import java.nio.file.Path;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.function.Function;
  
  
  /**
   * A builder of <code>PageContext</code> instances.
   */
  public final class PageContextBuilder {
  
  
      private String _dirUrl;
      private Function<Path, Optional<Template>> _templateFetcher;
      private String _rootRelativeUrl;
      private PageVarsBuilder _pageVarsBuilder;
      private String _bakeId;
  
  
      /**
       *
       */
      private PageContextBuilder() {
  
          _dirUrl = null;
          _templateFetcher = (path -> Optional.empty());
          _rootRelativeUrl = null;
          _pageVarsBuilder = PageVarsBuilder.create();
          _bakeId = null;
      }
  
  
      /**
       *
       */
      private PageContextBuilder(final PageContext data) {
  
          _dirUrl = data.dirUrl();
          _templateFetcher = data::templateFor;
          _rootRelativeUrl = data.rootRelativeUrl();
          _pageVarsBuilder = PageVarsBuilder.create(data.pageVars());
          _bakeId = data.bakeId();
      }
  
  
      /**
       * Creates a new empty <code>PageContextBuilder</code> instance.
       *
       * @return A new empty builder object.
       */
      public static PageContextBuilder create() {
  
          return new PageContextBuilder();
      }
  
  
      /**
       * Creates a new <code>PageContextBuilder</code> instance
       * initialized with the data from the given
       * <code>PageContext</code>.
       *
       * @param initialData Provides the data used for initializing the
       * returned builder.
       *
       * @return A new builder object initialized with the given data.
       */
      public static PageContextBuilder create(final PageContext initialData) {
  
          return new PageContextBuilder(initialData);
      }
  
  
      /**
       * @return A reference to this builder.
       */
      public PageContextBuilder dirUrl(final String dirUrl) {
  
          _dirUrl = dirUrl;
          return this;
      }
  
  
      /**
       * @param templateFetcher Function that can be used to retrieve
       * the template to be applied to a given path.
       *
       * @return A reference to this builder.
       */
      public PageContextBuilder templateFetcher(
              final Function<Path, Optional<Template>> templateFetcher) {
  
         _templateFetcher = templateFetcher;
         return this;
     }
 
 
     /**
      * @return A reference to this builder.
      */
     public PageContextBuilder rootRelativeUrl(final String rootRelativeUrl) {
 
         _rootRelativeUrl = rootRelativeUrl;
         return this;
     }
 
 
     /**
      * @return A reference to this builder.
      */
     public PageContextBuilder pageVars(final PageVars pageVars) {
 
         _pageVarsBuilder = PageVarsBuilder.create(pageVars);
         return this;
     }
 
 
     /**
      * Merges the given set of page variables into the set of page
      * variables currently hold by this builder. Page variables
      * currently in this builder with the same name will be superseded
      * by the new provided page variables.
      *
      * @param pageVars The set of page variables to add to the set of
      * page variables hold by this builder.
      *
      * @return A reference to this builder.
      */
     public PageContextBuilder addPageVars(final PageVars pageVars) {
 
         _pageVarsBuilder.addPageVars(pageVars);
         return this;
     }
 
 
     /**
      * Adds one page variable to this builder. An existing page
      * variable in this builder with the same name will be superseded
      * by the given page variable.
      *
      * @param varName The name of the page variable to be added.
      *
      * @param varValue The value of the page variable to be added.
      *
      * @return A reference to this builder.
      */
     public PageContextBuilder addVar(
             final String varName,
             final Object varValue) {
 
         _pageVarsBuilder.addVar(varName, varValue);
         return this;
     }
 
 
     /**
      *
      */
     public PageContextBuilder bakeId(final String bakeId) {
 
         _bakeId = bakeId;
         return this;
     }
 
 
     /**
      * Creates a new <code>PageContext</code> instance initialized
      * with the current values in this builder.
      *
      * @return A newly created <code>PageContext</code> instance.
      */
     public PageContext build() {
 
         return new PageContextImpl(this);
     }
 
 
     /**
      *
      */
     private static final class PageContextImpl
             implements PageContext {
 
 
         private final String _dirUrl;
         private final Function<Path, Optional<Template>> _templateFetcher;
         private final PageVars _pageVars;
         private final String _rootRelativeUrl;
         private final String _bakeId;
 
 
         /**
          *
          */
         /* default */ PageContextImpl(final PageContextBuilder builder) {
 
             _dirUrl = Objects.requireNonNull(builder._dirUrl);
             _templateFetcher = builder._templateFetcher;
             _rootRelativeUrl = Objects.requireNonNull(builder._rootRelativeUrl);
             _pageVars = builder._pageVarsBuilder.build();
             _bakeId = Objects.requireNonNull(builder._bakeId);
         }
 
 
         /**
          * {@inheritDoc}
          */
         @Override
         public String dirUrl() {
             return _dirUrl;
         }
 
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Optional<Template> templateFor(final Path path) {
             return _templateFetcher.apply(path);
         }
 
 
         /**
          * {@inheritDoc}
          */
         @Override
         public PageVars pageVars() {
             return _pageVars;
         }
 
 
         /**
          * {@inheritDoc}
          */
         @Override
         public String rootRelativeUrl() {
             return _rootRelativeUrl;
         }
 
 
         /**
          * {@inheritDoc}
          */
         @Override
         public String bakeId() {
             return _bakeId;
         }
 
     }
 
 }