/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package dev.metaschema.databind.io.json;
   
   import com.fasterxml.jackson.core.JsonGenerator;
   
  import org.eclipse.jdt.annotation.NotOwning;
  
  import java.io.IOException;
  import java.util.List;
  
  import dev.metaschema.core.model.IBoundObject;
  import dev.metaschema.core.model.JsonGroupAsBehavior;
  import dev.metaschema.databind.model.IBoundDefinitionModelAssembly;
  import dev.metaschema.databind.model.IBoundDefinitionModelComplex;
  import dev.metaschema.databind.model.IBoundDefinitionModelFieldComplex;
  import dev.metaschema.databind.model.IBoundFieldValue;
  import dev.metaschema.databind.model.IBoundInstance;
  import dev.metaschema.databind.model.IBoundInstanceFlag;
  import dev.metaschema.databind.model.IBoundInstanceModel;
  import dev.metaschema.databind.model.IBoundInstanceModelAssembly;
  import dev.metaschema.databind.model.IBoundInstanceModelChoiceGroup;
  import dev.metaschema.databind.model.IBoundInstanceModelFieldComplex;
  import dev.metaschema.databind.model.IBoundInstanceModelFieldScalar;
  import dev.metaschema.databind.model.IBoundInstanceModelGroupedAssembly;
  import dev.metaschema.databind.model.IBoundInstanceModelGroupedField;
  import dev.metaschema.databind.model.IBoundInstanceModelGroupedNamed;
  import dev.metaschema.databind.model.IBoundProperty;
  import dev.metaschema.databind.model.info.AbstractModelInstanceWriteHandler;
  import dev.metaschema.databind.model.info.IFeatureComplexItemValueHandler;
  import dev.metaschema.databind.model.info.IFeatureScalarItemValueHandler;
  import dev.metaschema.databind.model.info.IItemWriteHandler;
  import dev.metaschema.databind.model.info.IModelInstanceCollectionInfo;
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  /**
   * Provides support for writing Metaschema-bound Java objects to JSON format.
   * <p>
   * This class implements the {@link IItemWriteHandler} interface to serialize
   * bound objects to JSON using Jackson's {@link JsonGenerator}. It handles
   * flags, fields, assemblies, and choice groups according to the Metaschema JSON
   * serialization rules.
   *
   * @see IJsonWritingContext
   * @see JsonGenerator
   */
  @SuppressWarnings("PMD.CouplingBetweenObjects")
  public class MetaschemaJsonWriter implements IJsonWritingContext, IItemWriteHandler {
    @NonNull
    @NotOwning
    private final JsonGenerator generator;
  
    /**
     * Construct a new Module-aware JSON writer.
     *
     * @param generator
     *          the JSON generator to write with. The caller retains ownership of
     *          this generator and is responsible for closing it.
     * @see DefaultJsonProblemHandler
     */
    public MetaschemaJsonWriter(@NonNull @NotOwning JsonGenerator generator) {
      this.generator = generator;
    }
  
    @Override
    public JsonGenerator getWriter() {
      return generator;
    }
  
    // =====================================
    // Entry point for top-level-definitions
    // =====================================
  
    @Override
    public void write(
        @NonNull IBoundDefinitionModelComplex definition,
        @NonNull IBoundObject item) throws IOException {
      definition.writeItem(item, this);
    }
  
    // ================
    // Instance writers
    // ================
  
    private <T> void writeInstance(
        @NonNull IBoundProperty<T> instance,
        @NonNull IBoundObject parentItem) throws IOException {
      @SuppressWarnings("unchecked")
      T value = (T) instance.getValue(parentItem);
      if (value != null && !value.equals(instance.getResolvedDefaultValue())) {
        generator.writeFieldName(instance.getJsonName());
        instance.writeItem(value, this);
      }
    }
  
    private <T> void writeModelInstance(
       @NonNull IBoundInstanceModel<T> instance,
       @NonNull Object parentItem) throws IOException {
     Object value = instance.getValue(parentItem);
     if (value != null) {
       // this if is not strictly needed, since isEmpty will return false on a null
       // value
       // checking null here potentially avoids the expensive operation of instatiating
       IModelInstanceCollectionInfo<T> collectionInfo = instance.getCollectionInfo();
       if (!collectionInfo.isEmpty(value)) {
         generator.writeFieldName(instance.getJsonName());
         collectionInfo.writeItems(new ModelInstanceWriteHandler<>(instance), value);
       }
     }
   }
 
   @SuppressWarnings("PMD.NullAssignment")
   private void writeFieldValue(@NonNull IBoundFieldValue fieldValue, @NonNull Object parentItem) throws IOException {
     Object item = fieldValue.getValue(parentItem);
 
     // handle json value key
     IBoundInstanceFlag jsonValueKey = fieldValue.getParentFieldDefinition().getJsonValueKeyFlagInstance();
     if (item == null) {
       if (jsonValueKey != null) {
         item = fieldValue.getDefaultValue();
       }
     } else if (item.equals(fieldValue.getResolvedDefaultValue())) {
       // same as default
       item = null;
     }
 
     if (item != null) {
       // There are two modes:
       // 1) use of a JSON value key, or
       // 2) a simple value named "value"
 
       String valueKeyName;
       if (jsonValueKey != null) {
         Object keyValue = jsonValueKey.getValue(parentItem);
         if (keyValue == null) {
           throw new IOException(String.format("Null value for json-value-key for definition '%s'",
               jsonValueKey.getContainingDefinition().toCoordinates()));
         }
         try {
           // this is the JSON value key case
           valueKeyName = jsonValueKey.getJavaTypeAdapter().asString(keyValue);
         } catch (IllegalArgumentException ex) {
           throw new IOException(
               String.format("Invalid value '%s' for json-value-key for definition '%s'",
                   keyValue,
                   jsonValueKey.getContainingDefinition().toCoordinates()),
               ex);
         }
       } else {
         valueKeyName = fieldValue.getParentFieldDefinition().getEffectiveJsonValueKeyName();
       }
       generator.writeFieldName(valueKeyName);
       // LOGGER.info("FIELD: {}", valueKeyName);
 
       writeItemFieldValue(item, fieldValue);
     }
   }
 
   @Override
   public void writeItemFlag(Object item, IBoundInstanceFlag instance) throws IOException {
     writeScalarItem(item, instance);
   }
 
   @Override
   public void writeItemField(Object item, IBoundInstanceModelFieldScalar instance) throws IOException {
     writeScalarItem(item, instance);
   }
 
   @Override
   public void writeItemField(IBoundObject item, IBoundInstanceModelFieldComplex instance) throws IOException {
     writeModelObject(
         instance,
         item,
         this::writeObjectProperties);
   }
 
   @Override
   public void writeItemField(IBoundObject item, IBoundInstanceModelGroupedField instance) throws IOException {
     writeGroupedModelObject(
         instance,
         item,
         (parent, handler) -> {
           writeDiscriminatorProperty(handler);
           writeObjectProperties(parent, handler);
         });
   }
 
   @Override
   public void writeItemField(IBoundObject item, IBoundDefinitionModelFieldComplex definition) throws IOException {
     writeDefinitionObject(
         definition,
         item,
         (ObjectWriter<IBoundDefinitionModelFieldComplex>) this::writeObjectProperties);
   }
 
   @Override
   public void writeItemFieldValue(Object item, IBoundFieldValue fieldValue) throws IOException {
     fieldValue.getJavaTypeAdapter().writeJsonValue(item, generator);
   }
 
   @Override
   public void writeItemAssembly(IBoundObject item, IBoundInstanceModelAssembly instance) throws IOException {
     writeModelObject(instance, item, this::writeObjectProperties);
   }
 
   @Override
   public void writeItemAssembly(IBoundObject item, IBoundInstanceModelGroupedAssembly instance) throws IOException {
     writeGroupedModelObject(
         instance,
         item,
         (parent, handler) -> {
           writeDiscriminatorProperty(handler);
           writeObjectProperties(parent, handler);
         });
   }
 
   @Override
   public void writeItemAssembly(IBoundObject item, IBoundDefinitionModelAssembly definition) throws IOException {
     writeDefinitionObject(definition, item, this::writeObjectProperties);
   }
 
   @Override
   public void writeChoiceGroupItem(IBoundObject item, IBoundInstanceModelChoiceGroup instance) throws IOException {
     IBoundInstanceModelGroupedNamed actualInstance = instance.getItemInstance(item);
     assert actualInstance != null;
     actualInstance.writeItem(item, this);
   }
 
   /**
    * Writes a scalar item.
    *
    * @param item
    *          the item to write
    * @param handler
    *          the value handler
    * @throws IOException
    *           if an error occurred while writing the scalar value
    */
   private void writeScalarItem(@NonNull Object item, @NonNull IFeatureScalarItemValueHandler handler)
       throws IOException {
     handler.getJavaTypeAdapter().writeJsonValue(item, generator);
   }
 
   private <T extends IBoundInstanceModelGroupedNamed> void writeDiscriminatorProperty(
       @NonNull T instance) throws IOException {
 
     IBoundInstanceModelChoiceGroup choiceGroup = instance.getParentContainer();
 
     // write JSON object discriminator
     String discriminatorProperty = choiceGroup.getJsonDiscriminatorProperty();
     String discriminatorValue = instance.getEffectiveDisciminatorValue();
 
     generator.writeStringField(discriminatorProperty, discriminatorValue);
   }
 
   private <T extends IFeatureComplexItemValueHandler> void writeObjectProperties(
       @NonNull IBoundObject parent,
       @NonNull T handler) throws IOException {
     for (IBoundProperty<?> property : handler.getJsonProperties().values()) {
       assert property != null;
 
       if (property instanceof IBoundInstanceModel) {
         writeModelInstance((IBoundInstanceModel<?>) property, parent);
       } else if (property instanceof IBoundInstance) {
         writeInstance(property, parent);
       } else { // IBoundFieldValue
         writeFieldValue((IBoundFieldValue) property, parent);
       }
     }
   }
 
   private <T extends IFeatureComplexItemValueHandler> void writeDefinitionObject(
       @NonNull T handler,
       @NonNull IBoundObject parent,
       @NonNull ObjectWriter<T> propertyWriter) throws IOException {
     generator.writeStartObject();
 
     propertyWriter.accept(parent, handler);
     generator.writeEndObject();
   }
 
   private <T extends IFeatureComplexItemValueHandler & IBoundInstanceModel<IBoundObject>>
       void writeModelObject(
           @NonNull T handler,
           @NonNull IBoundObject parent,
           @NonNull ObjectWriter<T> propertyWriter) throws IOException {
     generator.writeStartObject();
 
     IBoundInstanceFlag jsonKey = handler.getItemJsonKey(parent);
     if (jsonKey != null) {
       Object keyValue = jsonKey.getValue(parent);
       if (keyValue == null) {
         throw new IOException(
             String.format("Null value for json-key for definition '%s'",
                 jsonKey.getContainingDefinition().toCoordinates()));
       }
 
       // the field will be the JSON key value
       String key;
       try {
         key = jsonKey.getJavaTypeAdapter().asString(keyValue);
       } catch (IllegalArgumentException ex) {
         throw new IOException(
             String.format("Illegal value '%s' for json-key for definition '%s'",
                 keyValue,
                 jsonKey.getContainingDefinition().toCoordinates()),
             ex);
       }
       generator.writeFieldName(key);
 
       // next the value will be a start object
       generator.writeStartObject();
     }
 
     propertyWriter.accept(parent, handler);
 
     if (jsonKey != null) {
       // next the value will be a start object
       generator.writeEndObject();
     }
     generator.writeEndObject();
   }
 
   private <T extends IFeatureComplexItemValueHandler & IBoundInstanceModelGroupedNamed> void writeGroupedModelObject(
       @NonNull T handler,
       @NonNull IBoundObject parent,
       @NonNull ObjectWriter<T> propertyWriter) throws IOException {
     generator.writeStartObject();
 
     IBoundInstanceModelChoiceGroup choiceGroup = handler.getParentContainer();
     IBoundInstanceFlag jsonKey = choiceGroup.getItemJsonKey(parent);
     if (jsonKey != null) {
       Object keyValue = jsonKey.getValue(parent);
       if (keyValue == null) {
         throw new IOException(String.format("Null value for json-key for definition '%s'",
             jsonKey.getContainingDefinition().toCoordinates()));
       }
 
       // the field will be the JSON key value
       String key;
       try {
         key = jsonKey.getJavaTypeAdapter().asString(keyValue);
       } catch (IllegalArgumentException ex) {
         throw new IOException(
             String.format("Invalid value '%s' for json-key for definition '%s'",
                 keyValue,
                 jsonKey.getContainingDefinition().toCoordinates()),
             ex);
       }
       generator.writeFieldName(key);
 
       // next the value will be a start object
       generator.writeStartObject();
     }
 
     propertyWriter.accept(parent, handler);
 
     if (jsonKey != null) {
       // next the value will be a start object
       generator.writeEndObject();
     }
     generator.writeEndObject();
   }
 
   /**
    * Supports writing items that are {@link IBoundInstanceModel}-based.
    *
    * @param <ITEM>
    *          the Java type of the item
    */
   private class ModelInstanceWriteHandler<ITEM>
       extends AbstractModelInstanceWriteHandler<ITEM> {
     public ModelInstanceWriteHandler(
         @NonNull IBoundInstanceModel<ITEM> instance) {
       super(instance);
     }
 
     @Override
     public void writeList(List<ITEM> items) throws IOException {
       IBoundInstanceModel<ITEM> instance = getCollectionInfo().getInstance();
 
       boolean writeArray = false;
       if (JsonGroupAsBehavior.LIST.equals(instance.getJsonGroupAsBehavior())
           || JsonGroupAsBehavior.SINGLETON_OR_LIST.equals(instance.getJsonGroupAsBehavior())
               && items.size() > 1) {
         // write array, then items
         writeArray = true;
         generator.writeStartArray();
       } // only other option is a singleton value, write item
 
       super.writeList(items);
 
       if (writeArray) {
         // write the end array
         generator.writeEndArray();
       }
     }
 
     @Override
     public void writeItem(ITEM item) throws IOException {
       IBoundInstanceModel<ITEM> instance = getInstance();
       instance.writeItem(item, MetaschemaJsonWriter.this);
     }
   }
 }