declare module 'shapeshifter' {
  declare export type SchemaMap = { [attribute: string]: Schema<> };

  declare export type DefineRelationMap = { [attribute: string]: Schema<> | Schema<>[] };

  declare export type PrimaryKey = string | string[];

  declare export type Relation = {
    attribute: string,
    collection: boolean,
    polymorph?: PolymorphRelation,
    relation: string,
    +schema: Schema<>,
  };

  declare export type PolymorphRelation = {
    keySuffix: string,
    type: string,
    typeSuffix: string,
  };

  declare export type MetadataField = {
    primaryKey?: string,
    resourceName?: string,
  };

  declare export default class Schema<T = any> {
    attributes: string[];
    metadata: MetadataField;
    primaryKey: PrimaryKey;
    relations: Relation[];
    relationTypes: { [key: string]: string };
    resourceName: string;
    static HAS_ONE: string;
    static HAS_MANY: string;
    static BELONGS_TO: string;
    static BELONGS_TO_MANY: string;
    static MORPH_TO: string;

    constructor(
      resourceName: string,
      primaryKey?: PrimaryKey | MetadataField,
      metadata?: MetadataField,
    ): void;
    addAttributes(attributes: string[]): this;
    addRelation(
      attribute: string,
      schema: Schema<>,
      relation: string,
      polymorph?: PolymorphRelation,
    ): this;
    addRelations(schemas: SchemaMap, relation: string): this;
    belongsTo(relations: SchemaMap): this;
    belongsToMany(relations: SchemaMap): this;
    define(relations: DefineRelationMap): this;
    hasOne(relations: SchemaMap): this;
    hasMany(relations: SchemaMap): this;
    morphTo(
      schemas: SchemaMap,
      attribute: string,
      typeSuffix?: string,
      keySuffix?: string,
    ): this;
  }
}