/* @flow */

import { GraphQLObjectType, GraphQLSchema, getNamedType } from 'graphql';
import TypeComposer from './typeComposer';
import type Resolver from './resolver';

export default class ComposeStorage {
  types: { [typeName: string]: TypeComposer };

  constructor() {
    this.types = {};
  }

  has(typeName: string): boolean {
    return !!this.types[typeName];
  }

  add(typeComposer: TypeComposer): void {
    if (!(typeComposer instanceof TypeComposer)) {
      throw new Error('You must provide instance of TypeComposer');
    }

    this.types[typeComposer.getTypeName()] = typeComposer;
  }

  clear(): void {
    this.types = {};
  }

  get(typeName: string): TypeComposer {
    if (!this.has(typeName)) {
      this.types[typeName] = TypeComposer.create(typeName);
    }
    return this.types[typeName];
  }

  rootQuery(): TypeComposer {
    return this.get('Query');
  }

  rootMutation(): TypeComposer {
    return this.get('Mutation');
  }

  resolvers(typeName: string): Map<string, Resolver<*, *>> {
    return this.get(typeName).getResolvers();
  }

  resolver(typeName: string, resolverName: string): Resolver<*, *> | void {
    return this.get(typeName).getResolver(resolverName);
  }

  buildSchema() {
    const roots = {};

    const createdRelations = new Set();

    if (this.has('Query')) {
      const tc = this.get('Query');
      this.buildRelations(tc, createdRelations);
      this.removeEmptyTypes(tc, new Set());
      roots.query = tc.getType();
    }

    if (this.has('Mutation')) {
      const tc = this.get('Mutation');
      this.buildRelations(tc, createdRelations);
      this.removeEmptyTypes(tc, new Set());
      roots.mutation = tc.getType();
    }

    if (Object.keys(roots).length === 0) {
      throw new Error('Can not build schema. Must be initialized at least one '
      + 'of the following types: RootQuery, RootMutation.');
    }

    return new GraphQLSchema(roots);
  }

  buildRelations(
    typeComposer: TypeComposer,
    createdRelations: Set<string>
  ) {
    const relations = typeComposer.getRelations();
    const relationFieldNames = Object.keys(relations);

    relationFieldNames.forEach((relationFieldName) => {
      const typeAndField = `${typeComposer.getTypeName()}.${relationFieldName}`;

      const existedField = typeComposer.getField(relationFieldName);
      if (existedField && !existedField._gqcIsRelation) {
        if (!createdRelations.has(typeAndField)) {
          // eslint-disable-next-line
          console.log(`GQC: Skip building relation '${typeAndField}', `
                    + 'cause this type already has field with such name. '
                    + 'If you want create relation, you should remove this '
                    + 'field before run the schema build.');
        }
      } else {
        typeComposer.buildRelation(relationFieldName);
      }
    });

    const fields = typeComposer.getFields();
    Object.keys(fields).forEach((fieldName) => {
      const typeAndField = `${typeComposer.getTypeName()}.${fieldName}`;
      const fieldType = getNamedType(fields[fieldName].type);
      if (fieldType instanceof GraphQLObjectType && !createdRelations.has(typeAndField)) {
        createdRelations.add(typeAndField);
        this.buildRelations(new TypeComposer(fieldType), createdRelations);
      }
    });
  }

  removeEmptyTypes(
    typeComposer: TypeComposer,
    passedTypes: Set<string> = new Set()
  ) {
    const fields = typeComposer.getFields();
    Object.keys(fields).forEach((fieldName) => {
      const fieldType = fields[fieldName].type;
      if (fieldType instanceof GraphQLObjectType) {
        const typeName = fieldType.name;
        if (!passedTypes.has(typeName)) {
          passedTypes.add(typeName);
          const tc = new TypeComposer(fieldType);
          if (Object.keys(tc.getFields()).length > 0) {
            this.removeEmptyTypes(tc, passedTypes);
          } else {
            // eslint-disable-next-line
            console.log(`GQC: Delete field '${typeComposer.getTypeName()}.${fieldName}' `
                      + `with type '${tc.getTypeName()}', cause it does not have fields.`);
            delete fields[fieldName];
          }
        }
      }
    });
    typeComposer.setFields(fields);
  }
}