package appeng.items.parts;


import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import net.minecraft.util.ResourceLocation;

import appeng.api.parts.IPartModel;
import appeng.core.AELog;


/**
 * Helps with the reflection magic needed to gather all models for AE2 cable bus parts.
 */
class PartModelsHelper
{

	static List<ResourceLocation> createModels( Class<?> clazz )
	{
		List<ResourceLocation> locations = new ArrayList<>();

		// Check all static fields for used models
		Field[] fields = clazz.getDeclaredFields();
		for( Field field : fields )
		{
			if( field.getAnnotation( PartModels.class ) == null )
			{
				continue;
			}

			if( !Modifier.isStatic( field.getModifiers() ) )
			{
				AELog.error( "The @PartModels annotation can only be used on static fields or methods. Was seen on: " + field );
				continue;
			}

			Object value;
			try
			{
				field.setAccessible( true );
				value = field.get( null );
			}
			catch( IllegalAccessException e )
			{
				AELog.error( e, "Cannot access field annotated with @PartModels: " + field );
				continue;
			}

			convertAndAddLocation( field, value, locations );
		}

		// Check all static methods for the annotation
		for( Method method : clazz.getDeclaredMethods() )
		{
			if( method.getAnnotation( PartModels.class ) == null )
			{
				continue;
			}

			if( !Modifier.isStatic( method.getModifiers() ) )
			{
				AELog.error( "The @PartModels annotation can only be used on static fields or methods. Was seen on: " + method );
				continue;
			}

			// Check for parameter count
			if( method.getParameters().length != 0 )
			{
				AELog.error( "The @PartModels annotation can only be used on static methods without parameters. Was seen on: " + method );
				continue;
			}

			// Make sure we can handle the return type
			Class<?> returnType = method.getReturnType();
			if( !ResourceLocation.class.isAssignableFrom( returnType ) && !Collection.class.isAssignableFrom( returnType ) )
			{
				AELog.error(
						"The @PartModels annotation can only be used on static methods that return a ResourceLocation or Collection of " + "ResourceLocations. Was seen on: " + method );
				continue;
			}

			Object value = null;
			try
			{
				method.setAccessible( true );
				value = method.invoke( null );
			}
			catch( IllegalAccessException | InvocationTargetException e )
			{
				AELog.error( e, "Failed to invoke the @PartModels annotated method " + method );
				continue;
			}

			convertAndAddLocation( method, value, locations );
		}

		if( clazz.getSuperclass() != null )
		{
			locations.addAll( createModels( clazz.getSuperclass() ) );
		}

		return locations;
	}

	private static void convertAndAddLocation( Object source, Object value, List<ResourceLocation> locations )
	{
		if( value == null )
		{
			return;
		}

		if( value instanceof ResourceLocation )
		{
			locations.add( (ResourceLocation) value );
		}
		else if( value instanceof IPartModel )
		{
			locations.addAll( ( (IPartModel) value ).getModels() );
		}
		else if( value instanceof Collection )
		{
			// Check that each object is an IPartModel
			Collection values = (Collection) value;
			for( Object candidate : values )
			{
				if( !( candidate instanceof IPartModel ) )
				{
					AELog.error( "List of locations obtained from {} contains a non resource location: {}", source, candidate );
					continue;
				}

				locations.addAll( ( (IPartModel) candidate ).getModels() );
			}
		}
	}

}