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package prompto.graphql;

import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

import graphql.schema.FieldCoordinates;
import graphql.schema.GraphQLArgument;
import graphql.schema.GraphQLCodeRegistry;
import graphql.schema.GraphQLFieldDefinition;
import graphql.schema.GraphQLObjectType;
import graphql.schema.GraphQLSchema;
import prompto.code.ICodeStore;
import prompto.declaration.IDeclaration;
import prompto.declaration.IMethodDeclaration;
import prompto.param.IParameter;
import prompto.runtime.ApplicationContext;
import prompto.runtime.Context;
import prompto.type.IType;

public class GraphQLSchemaBuilder {

	static final String QUERIES_TYPE_NAME = "Queries";
	static final String MUTATIONS_TYPE_NAME = "Mutations";
	
	public GraphQLSchema build() {
		GraphQLCodeRegistry.Builder registry = GraphQLCodeRegistry.newCodeRegistry(); 
		return GraphQLSchema.newSchema()
				.query(buildQueries(registry))
				.mutation(buildMutations(registry))
				.codeRegistry(registry.build())
				.build();
	}

	
	private GraphQLObjectType buildQueries(GraphQLCodeRegistry.Builder registry) {
		return buildRootType(registry, "@GraphQLQuery", QUERIES_TYPE_NAME);
	}

	private GraphQLObjectType buildMutations(GraphQLCodeRegistry.Builder registry) {
		return buildRootType(registry, "@GraphQLMutation", MUTATIONS_TYPE_NAME);
	}
	
	
	private GraphQLObjectType buildRootType(GraphQLCodeRegistry.Builder registry, String annotation, String typeName) {
		Iterable queries = ICodeStore.getInstance().fetchDeclarationsWithAnnotations(Collections.singleton(annotation));
		List fields = StreamSupport.stream(queries.spliterator(), false)
				.filter(decl->decl instanceof IMethodDeclaration)
				.map(method->(IMethodDeclaration)method)
				.filter(method->method.getMemberOf()==null)
				.map(method->buildRootField(method, typeName, registry))
				.collect(Collectors.toList());
		if(fields.isEmpty())
			return null;
		else {
			return GraphQLObjectType.newObject()
					.name(typeName)
					.fields(fields)
					.build();
		}
	}

	private GraphQLFieldDefinition buildRootField(IMethodDeclaration method, String typeName, GraphQLCodeRegistry.Builder registry) {
		registry.dataFetcher(FieldCoordinates.coordinates(typeName, method.getName()), new GraphQLMethodFetcher(method));
		Context context = ApplicationContext.get().newLocalContext();
		method.getParameters().register(context);
		IType returnType = method.check(context);
		return GraphQLFieldDefinition.newFieldDefinition()
				.name(method.getName())
				.arguments(buildArguments(method, registry))
				.type(GraphQLType.buildOutputType(returnType, registry))
				.build();
	}


	private List buildArguments(IMethodDeclaration method, GraphQLCodeRegistry.Builder registry) {
		return method.getParameters().stream()
			.map(param->buildArgument(param, registry))
			.collect(Collectors.toList());
	}


	private GraphQLArgument buildArgument(IParameter param, GraphQLCodeRegistry.Builder registry) {
		return GraphQLArgument.newArgument()
				.name(param.getName())
				.type(GraphQLType.buildInputType(param.getType(ApplicationContext.get()), registry))
				.build();
	}




}