/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package dev.metaschema.schemagen;
   
   import java.util.Collection;
   import java.util.HashSet;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import dev.metaschema.core.model.IAssemblyDefinition;
  import dev.metaschema.core.model.IAssemblyInstance;
  import dev.metaschema.core.model.IChoiceInstance;
  import dev.metaschema.core.model.IDefinition;
  import dev.metaschema.core.model.IFieldDefinition;
  import dev.metaschema.core.model.IFieldInstance;
  import dev.metaschema.core.model.IFlagDefinition;
  import dev.metaschema.core.model.IFlagInstance;
  import dev.metaschema.core.model.IModule;
  import dev.metaschema.core.model.INamedInstance;
  import dev.metaschema.core.model.INamedModelInstance;
  import dev.metaschema.core.model.INamedModelInstanceGrouped;
  import dev.metaschema.core.model.ModelWalker;
  import dev.metaschema.core.util.ObjectUtils;
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  /**
   * Indexes definitions from a Metaschema module for use in schema generation.
   * <p>
   * This class maintains an ordered index of all definitions that are reachable
   * from root assembly definitions, tracking their reference counts, inline
   * status, and other usage patterns relevant to schema generation.
   */
  public class ModuleIndex {
    // needs to be ordered
    @SuppressWarnings("PMD.UseConcurrentHashMap")
    private final Map<IDefinition, DefinitionEntry> index = new LinkedHashMap<>();
  
    /**
     * Creates an index of all definitions reachable from the module's root assembly
     * definitions.
     *
     * @param module
     *          the Metaschema module to index
     * @param inlineStrategy
     *          the strategy for determining which definitions should be inlined
     * @return a new module index containing entries for all reachable definitions
     */
    @NonNull
    public static ModuleIndex indexDefinitions(@NonNull IModule module, @NonNull IInlineStrategy inlineStrategy) {
      Collection<? extends IAssemblyDefinition> definitions = module.getExportedRootAssemblyDefinitions();
      ModuleIndex index = new ModuleIndex();
      if (!definitions.isEmpty()) {
        IndexVisitor visitor = new IndexVisitor(index, inlineStrategy);
        for (IAssemblyDefinition definition : definitions) {
          assert definition != null;
  
          // // add the root definition to the index
          // index.getEntry(definition).incrementReferenceCount();
  
          // walk the definition
          visitor.walk(ObjectUtils.requireNonNull(definition));
        }
      }
      return index;
    }
  
    /**
     * Checks if an entry exists in this index for the specified definition.
     *
     * @param definition
     *          the definition to check
     * @return {@code true} if an entry exists for the definition, {@code false}
     *         otherwise
     */
    public boolean hasEntry(@NonNull IDefinition definition) {
      return index.containsKey(definition);
    }
  
    /**
     * Retrieves or creates the entry for the specified definition.
     * <p>
     * If no entry exists for the definition, a new entry is created and added to
     * the index.
     *
     * @param definition
     *          the definition to get an entry for
     * @return the existing or newly created entry for the definition
     */
    @NonNull
    public DefinitionEntry getEntry(@NonNull IDefinition definition) {
      return ObjectUtils.notNull(index.computeIfAbsent(
          definition,
          k -> new ModuleIndex.DefinitionEntry(ObjectUtils.notNull(k))));
    }
 
   /**
    * Retrieves all definition entries in this index.
    *
    * @return an unmodifiable collection of all definition entries, in insertion
    *         order
    */
   @NonNull
   public Collection<DefinitionEntry> getDefinitions() {
     return ObjectUtils.notNull(index.values());
   }
 
   private static class IndexVisitor
       extends ModelWalker<ModuleIndex> {
     @NonNull
     private final IInlineStrategy inlineStrategy;
     @NonNull
     private final ModuleIndex index;
 
     public IndexVisitor(@NonNull ModuleIndex index, @NonNull IInlineStrategy inlineStrategy) {
       this.index = index;
       this.inlineStrategy = inlineStrategy;
     }
 
     @Override
     protected ModuleIndex getDefaultData() {
       return index;
     }
 
     @Override
     protected boolean visit(IFlagInstance instance, ModuleIndex index) {
       handleInstance(instance);
       return true;
     }
 
     @Override
     protected boolean visit(IFieldInstance instance, ModuleIndex index) {
       handleInstance(instance);
       return true;
     }
 
     @Override
     protected boolean visit(IAssemblyInstance instance, ModuleIndex index) {
       handleInstance(instance);
       return true;
     }
 
     @Override
     protected void visit(IFlagDefinition def, ModuleIndex data) {
       handleDefinition(def);
     }
 
     // @Override
     // protected boolean visit(IAssemblyDefinition def, ModuleIndex data) {
     // // only walk if the definition hasn't already been visited
     // return !index.hasEntry(def);
     // }
 
     @Override
     protected boolean visit(IFieldDefinition def, ModuleIndex data) {
       return handleDefinition(def);
     }
 
     @Override
     protected boolean visit(IAssemblyDefinition def, ModuleIndex data) {
       return handleDefinition(def);
     }
 
     private boolean handleDefinition(@NonNull IDefinition definition) {
       DefinitionEntry entry = getDefaultData().getEntry(definition);
       boolean visited = entry.isVisited();
       if (!visited) {
         entry.markVisited();
 
         if (inlineStrategy.isInline(definition, index)) {
           entry.markInline();
         }
       }
       return !visited;
     }
 
     /**
      * Updates the index entry for the definition associated with the reference.
      *
      * @param instance
      *          the instance to process
      */
     @NonNull
     private DefinitionEntry handleInstance(INamedInstance instance) {
       IDefinition definition = instance.getDefinition();
       // check if this will be a new entry, which needs to be called before getEntry,
       // which will create it
       DefinitionEntry entry = getDefaultData().getEntry(definition);
       entry.addReference(instance);
 
       if (isChoice(instance)) {
         entry.markUsedAsChoice();
       }
 
       if (isChoiceSibling(instance)) {
         entry.markAsChoiceSibling();
       }
       return entry;
     }
 
     private static boolean isChoice(@NonNull INamedInstance instance) {
       return instance.getParentContainer() instanceof IChoiceInstance;
     }
 
     private static boolean isChoiceSibling(@NonNull INamedInstance instance) {
       IDefinition containingDefinition = instance.getContainingDefinition();
       return containingDefinition instanceof IAssemblyDefinition
           && !((IAssemblyDefinition) containingDefinition).getChoiceInstances().isEmpty();
     }
   }
 
   /**
    * Represents an entry in the module index for a single definition.
    * <p>
    * Each entry tracks usage information about a definition including its
    * references, inline status, and how it is used within choice groups.
    */
   public static class DefinitionEntry {
     @NonNull
     private final IDefinition definition;
     private final Set<INamedInstance> references = new HashSet<>();
     private final AtomicBoolean inline = new AtomicBoolean(); // false
     private final AtomicBoolean visited = new AtomicBoolean(); // false
     private final AtomicBoolean usedAsChoice = new AtomicBoolean(); // false
     private final AtomicBoolean choiceSibling = new AtomicBoolean(); // false
 
     /**
      * Constructs a new definition entry for the specified definition.
      *
      * @param definition
      *          the definition this entry represents
      */
     public DefinitionEntry(@NonNull IDefinition definition) {
       this.definition = definition;
     }
 
     /**
      * Retrieves the definition associated with this entry.
      *
      * @return the definition
      */
     @NonNull
     public IDefinition getDefinition() {
       return definition;
     }
 
     /**
      * Checks if this definition is a root assembly definition.
      *
      * @return {@code true} if the definition is a root assembly, {@code false}
      *         otherwise
      */
     public boolean isRoot() {
       return definition instanceof IAssemblyDefinition
           && ((IAssemblyDefinition) definition).isRoot();
     }
 
     /**
      * Checks if this definition is referenced by any instance or is a root
      * definition.
      *
      * @return {@code true} if the definition has references or is a root,
      *         {@code false} otherwise
      */
     public boolean isReferenced() {
       return !references.isEmpty()
           || isRoot();
     }
 
     /**
      * Retrieves all instances that reference this definition.
      *
      * @return a set of referencing instances
      */
     public Set<INamedInstance> getReferences() {
       return references;
     }
 
     /**
      * Adds a reference to this definition from the specified instance.
      *
      * @param reference
      *          the instance referencing this definition
      * @return {@code true} if the reference was added, {@code false} if it already
      *         existed
      */
     public boolean addReference(@NonNull INamedInstance reference) {
       return references.add(reference);
     }
 
     /**
      * Marks this definition as having been visited during indexing.
      */
     public void markVisited() {
       visited.compareAndSet(false, true);
     }
 
     /**
      * Checks if this definition has been visited during indexing.
      *
      * @return {@code true} if the definition was visited, {@code false} otherwise
      */
     public boolean isVisited() {
       return visited.get();
     }
 
     /**
      * Marks this definition as being inlined in the generated schema.
      */
     public void markInline() {
       inline.compareAndSet(false, true);
     }
 
     /**
      * Checks if this definition should be inlined in the generated schema.
      *
      * @return {@code true} if the definition is inlined, {@code false} otherwise
      */
     public boolean isInline() {
       return inline.get();
     }
 
     /**
      * Marks this definition as being used within a choice group.
      */
     public void markUsedAsChoice() {
       usedAsChoice.compareAndSet(false, true);
     }
 
     /**
      * Checks if this definition is used within a choice group.
      *
      * @return {@code true} if the definition is used as a choice, {@code false}
      *         otherwise
      */
     public boolean isUsedAsChoice() {
       return usedAsChoice.get();
     }
 
     /**
      * Marks this definition as having sibling elements in a choice group.
      */
     public void markAsChoiceSibling() {
       choiceSibling.compareAndSet(false, true);
     }
 
     /**
      * Checks if this definition has sibling elements in a choice group.
      *
      * @return {@code true} if the definition is a choice sibling, {@code false}
      *         otherwise
      */
     public boolean isChoiceSibling() {
       return choiceSibling.get();
     }
 
     /**
      * Checks if any reference to this definition uses a JSON key flag.
      *
      * @return {@code true} if any reference has a JSON key, {@code false} otherwise
      */
     public boolean isUsedAsJsonKey() {
       return references.stream()
           .anyMatch(ref -> ref instanceof INamedModelInstance
               && ((INamedModelInstance) ref).hasJsonKey());
     }
 
     /**
      * Checks if this definition is used without a JSON key flag or is a flag
      * definition.
      *
      * @return {@code true} if the definition is a flag or has any references
      *         without a JSON key, {@code false} otherwise
      */
     public boolean isUsedWithoutJsonKey() {
       return definition instanceof IFlagDefinition
           || references.isEmpty()
           || references.stream()
               .anyMatch(ref -> ref instanceof INamedModelInstance
                   && !((INamedModelInstance) ref).hasJsonKey());
     }
 
     /**
      * Checks if this definition is a member of a choice group.
      *
      * @return {@code true} if any reference is a grouped model instance,
      *         {@code false} otherwise
      */
     public boolean isChoiceGroupMember() {
       return references.stream()
           .anyMatch(INamedModelInstanceGrouped.class::isInstance);
     }
   }
 }