'use strict';

const Utils = require('./../utils');
const Helpers = require('./helpers');
const _ = require('lodash');
const Association = require('./base');
const Op = require('../operators');

/**
 * One-to-one association
 *
 * In the API reference below, add the name of the association to the method, e.g. for `User.belongsTo(Project)` the getter will be `user.getProject()`.
 *
 * @see {@link Model.belongsTo}
 */
class BelongsTo extends Association {
  constructor(source, target, options) {
    super(source, target, options);

    this.associationType = 'BelongsTo';
    this.isSingleAssociation = true;
    this.foreignKeyAttribute = {};

    if (this.as) {
      this.isAliased = true;
      this.options.name = {
        singular: this.as
      };
    } else {
      this.as = this.target.options.name.singular;
      this.options.name = this.target.options.name;
    }

    if (_.isObject(this.options.foreignKey)) {
      this.foreignKeyAttribute = this.options.foreignKey;
      this.foreignKey = this.foreignKeyAttribute.name || this.foreignKeyAttribute.fieldName;
    } else if (this.options.foreignKey) {
      this.foreignKey = this.options.foreignKey;
    }

    if (!this.foreignKey) {
      this.foreignKey = Utils.camelize(
        [
          this.as,
          this.target.primaryKeyAttribute
        ].join('_')
      );
    }

    this.identifier = this.foreignKey;
    if (this.source.rawAttributes[this.identifier]) {
      this.identifierField = this.source.rawAttributes[this.identifier].field || this.identifier;
    }

    if (
      this.options.targetKey
      && !this.target.rawAttributes[this.options.targetKey]
    ) {
      throw new Error(`Unknown attribute "${this.options.targetKey}" passed as targetKey, define this attribute on model "${this.target.name}" first`);
    }

    this.targetKey = this.options.targetKey || this.target.primaryKeyAttribute;
    this.targetKeyField = this.target.rawAttributes[this.targetKey].field || this.targetKey;
    this.targetKeyIsPrimary = this.targetKey === this.target.primaryKeyAttribute;
    this.targetIdentifier = this.targetKey;

    this.associationAccessor = this.as;
    this.options.useHooks = options.useHooks;

    // Get singular name, trying to uppercase the first letter, unless the model forbids it
    const singular = _.upperFirst(this.options.name.singular);

    this.accessors = {
      get: `get${singular}`,
      set: `set${singular}`,
      create: `create${singular}`
    };
  }

  // the id is in the source table
  _injectAttributes() {
    const newAttributes = {};

    newAttributes[this.foreignKey] = _.defaults({}, this.foreignKeyAttribute, {
      type: this.options.keyType || this.target.rawAttributes[this.targetKey].type,
      allowNull: true
    });

    if (this.options.constraints !== false) {
      const source = this.source.rawAttributes[this.foreignKey] || newAttributes[this.foreignKey];
      this.options.onDelete = this.options.onDelete || (source.allowNull ? 'SET NULL' : 'NO ACTION');
      this.options.onUpdate = this.options.onUpdate || 'CASCADE';
    }

    Helpers.addForeignKeyConstraints(newAttributes[this.foreignKey], this.target, this.source, this.options, this.targetKeyField);
    Utils.mergeDefaults(this.source.rawAttributes, newAttributes);

    this.source.refreshAttributes();

    this.identifierField = this.source.rawAttributes[this.foreignKey].field || this.foreignKey;

    Helpers.checkNamingCollision(this);

    return this;
  }

  mixin(obj) {
    const methods = ['get', 'set', 'create'];

    Helpers.mixinMethods(this, obj, methods);
  }

  /**
   * Get the associated instance.
   *
   * @param {Model|Array<Model>} instances source instances
   * @param {Object}         [options] find options
   * @param {string|boolean} [options.scope]  Apply a scope on the related model, or remove its default scope by passing false.
   * @param {string}         [options.schema] Apply a schema on the related model
   *
   * @see
   * {@link Model.findOne} for a full explanation of options
   *
   * @returns {Promise<Model>}
   */
  get(instances, options) {
    const where = {};
    let Target = this.target;
    let instance;

    options = Utils.cloneDeep(options);

    if (Object.prototype.hasOwnProperty.call(options, 'scope')) {
      if (!options.scope) {
        Target = Target.unscoped();
      } else {
        Target = Target.scope(options.scope);
      }
    }

    if (Object.prototype.hasOwnProperty.call(options, 'schema')) {
      Target = Target.schema(options.schema, options.schemaDelimiter);
    }

    if (!Array.isArray(instances)) {
      instance = instances;
      instances = undefined;
    }

    if (instances) {
      where[this.targetKey] = {
        [Op.in]: instances.map(instance => instance.get(this.foreignKey))
      };
    } else {
      if (this.targetKeyIsPrimary && !options.where) {
        return Target.findByPk(instance.get(this.foreignKey), options);
      }
      where[this.targetKey] = instance.get(this.foreignKey);
      options.limit = null;
    }

    options.where = options.where ?
      { [Op.and]: [where, options.where] } :
      where;

    if (instances) {
      return Target.findAll(options).then(results => {
        const result = {};
        for (const instance of instances) {
          result[instance.get(this.foreignKey, { raw: true })] = null;
        }

        for (const instance of results) {
          result[instance.get(this.targetKey, { raw: true })] = instance;
        }

        return result;
      });
    }

    return Target.findOne(options);
  }

  /**
   * Set the associated model.
   *
   * @param {Model} sourceInstance the source instance
   * @param {?<Model>|string|number} [associatedInstance] An persisted instance or the primary key of an instance to associate with this. Pass `null` or `undefined` to remove the association.
   * @param {Object} [options={}] options passed to `this.save`
   * @param {boolean} [options.save=true] Skip saving this after setting the foreign key if false.
   *
   *  @returns {Promise}
   */
  set(sourceInstance, associatedInstance, options = {}) {
    let value = associatedInstance;

    if (associatedInstance instanceof this.target) {
      value = associatedInstance[this.targetKey];
    }

    sourceInstance.set(this.foreignKey, value);

    if (options.save === false) return;

    options = Object.assign({
      fields: [this.foreignKey],
      allowNull: [this.foreignKey],
      association: true
    }, options);

    // passes the changed field to save, so only that field get updated.
    return sourceInstance.save(options);
  }

  /**
   * Create a new instance of the associated model and associate it with this.
   *
   * @param {Model} sourceInstance the source instance
   * @param {Object} [values={}] values to create associated model instance with
   * @param {Object} [options={}] Options passed to `target.create` and setAssociation.
   *
   * @see
   * {@link Model#create}  for a full explanation of options
   *
   * @returns {Promise<Model>} The created target model
   */
  create(sourceInstance, values, options) {
    values = values || {};
    options = options || {};

    return this.target.create(values, options)
      .then(newAssociatedObject => sourceInstance[this.accessors.set](newAssociatedObject, options)
        .then(() => newAssociatedObject)
      );
  }

  verifyAssociationAlias(alias) {
    if (typeof alias === 'string') {
      return this.as === alias;
    }

    if (alias && alias.singular) {
      return this.as === alias.singular;
    }

    return !this.isAliased;
  }
}

module.exports = BelongsTo;
module.exports.BelongsTo = BelongsTo;
module.exports.default = BelongsTo;
