import _, { isArray } from 'lodash';
import compose from 'koa-compose';
import Resource from './resource';
import { requireModule, mergeFields } from './utils';
import { HandlerType } from './resourcer';
import Middleware, { MiddlewareType } from './middleware';

export type ActionType = string | HandlerType | ActionOptions;

export type DefaultActionType = 'list' | 'create' | 'get' | 'update' | 'destroy' | 'set' | 'add' | 'remove';

export type ActionName = DefaultActionType | Omit<String, DefaultActionType>;

export interface ActionContext {
  action?: Action;
  [key: string]: any;
}

export type FieldsOptions = string[] | {
  only?: string[];
  appends?: string[];
} | {
  except?: string[];
  appends?: string[];
};

export type FieldsOptionsFn = (ctx: ActionContext) => FieldsOptions | Promise<FieldsOptions>;

/**
 * 过滤参数
 * 
 * TODO：细节待定
 */
export interface FilterOptions {
  [key: string]: any;
}

export type FilterOptionsFn = (ctx: ActionContext) => FilterOptions | Promise<FieldsOptions>;

export type ParamsCallback = (ctx: ActionContext) => ActionParams | Promise<ActionParams>;

export interface ActionOptions {
  /**
   * 默认数据
   */
  defaultValues?: any;
  /**
   * 字段
   * 
   * 示例一：
   * ['col1', 'col2', 'relation.col1'];
   * 
   * 示例二：
   * {
   *  only: ['col1'],
   * }
   * 
   * 示例三：
   * {
   *  except: ['col1'],
   * }
   */
  fields?: FieldsOptions;
  /**
   * 过滤
   */
  filter?: FilterOptions;
  /**
   * 排序
   */
  sort?: string | string[];
  /**
   * 当前页码
   */
  page?: number;
  /**
   * 每页显示数量
   */
  perPage?: number;
  /**
   * 最大每页显示数量
   */
  maxPerPage?: number;
  /**
   * 中间件
   */
  middleware?: MiddlewareType;
  /**
   * 中间件
   * 
   * 与 middleware 用法相同
   */
  middlewares?: MiddlewareType;
  /**
   * 当前 Action 待执行的方法
   * 
   * 支持 Function 和 require 调用
   */
  handler?: HandlerType;
  /**
   * 其他扩展配置
   */
  [key: string]: any;
}

/**
 * action params 与 action options 略有不同
 * - options 的参数更灵活，主要用于开发配置
 * - params 是开发配置参数 + 客户端参数的结合体
 */
export interface ActionParams {
  /**
   * 输出哪些字段
   * 
   * 与 ActionOptions 的不同，这里的 fields 是 object，提供 only，except，appends 三种情况
   */
  fields?: {
    only?: string[];
    except?: string[];
    appends?: string[];
  };
  /**
   * 过滤
   */
  filter?: FilterOptions;
  /**
   * 排序
   * 
   * 与 ActionOptions 的不同，这里的 sort 只有一种 array 类型
   */
  sort?: string[];
  /**
   * 当前页码
   */
  page?: number;
  /**
   * 每页显示数量
   */
  perPage?: number;
  /**
   * 数据，默认为 options.defaultValues + request.body
   */
  values?: any;
  /**
   * 当前资源的主体，对应的表名或 Model 名称
   */
  resourceName?: string;
  /**
   * 资源标识符
   */
  resourceKey?: string;
  /**
   * 资源的从属关系
   */
  associatedName?: string;
  /**
   * 从属关系的标识符
   */
  associatedKey?: string;
  /**
   * 从属关系的当前实例
   */
  associated ?: any;
  /**
   * 资源提供哪些行为或方法
   */
  actionName?: string;
  /**
   * 其他扩展配置
   */
  [key: string]: any;
}

export const DEFAULT_PAGE = 1;
export const DEFAULT_PER_PAGE = 20;
export const MAX_PER_PAGE = 100;

export class Action {

  protected handler: any;

  protected resource: Resource;

  protected name: ActionName;

  protected options: ActionOptions;

  protected parameters: ActionParams = {};

  protected context: ActionContext = {};

  public readonly middlewares: Array<Middleware> = [];

  constructor(options: ActionOptions) {
    options = requireModule(options);
    if (typeof options === 'function') {
      options = { handler: options };
    }
    const { middleware, middlewares = [], handler } = options;
    this.middlewares = Middleware.toInstanceArray(middleware || middlewares);
    this.handler = handler;
    this.options = options;
  }

  get params(): ActionParams {
    return this.parameters;
  }

  clone() {
    const options = _.cloneDeep(this.options);
    delete options.middleware;
    delete options.middlewares;
    const action = new Action(options);
    action.setName(this.name);
    action.setResource(this.resource);
    action.middlewares.push(...this.middlewares);
    return action;
  }

  setContext(context: any) {
    this.context = context;
  }

  setParam(key: string, value: any) {
    if (/\[\]$/.test(key)) {
      key = key.substr(0, key.length - 2);
      let values = _.get(this.parameters, key);
      if (_.isArray(values)) {
        values.push(value);
      } else {
        values = [];
        values.push(value);
      }
      value = values;
    }
    _.set(this.parameters, key, value);
  }

  async mergeParams(params: ActionParams) {
    const {
      filter,
      fields,
      values,
      page: paramPage,
      perPage: paramPerPage,
      per_page,
      ...restPrams
    } = params;
    const {
      filter: optionsFilter,
      fields: optionsFields,
      page = DEFAULT_PAGE,
      perPage = DEFAULT_PER_PAGE,
      maxPerPage = MAX_PER_PAGE
    } = this.options;
    const options = _.omit(this.options, [
      'defaultValues',
      'filter',
      'fields',
      'maxPerPage',
      'page',
      'perPage',
      'handler',
      'middlewares',
      'middleware',
    ]);
    const data: ActionParams = {
      ...options,
      ...restPrams,
    };
    if (!_.isEmpty(this.options.defaultValues) || !_.isEmpty(values)) {
      data.values = _.merge(_.cloneDeep(this.options.defaultValues), values);
    }
    // TODO: to be unified by style funciton
    if (per_page || paramPerPage) {
      data.perPage = per_page || paramPerPage;
    }
    if (paramPage || data.perPage) {
      data.page = paramPage || page;
      data.perPage = data.perPage == -1 ? maxPerPage : Math.min(data.perPage || perPage, maxPerPage);
    }
    // if (typeof optionsFilter === 'function') {
    //   this.parameters = _.cloneDeep(data);
    //   optionsFilter = await optionsFilter(this.context);
    // }
    if (!_.isEmpty(optionsFilter) || !_.isEmpty(filter)) {
      const filterOptions = [_.cloneDeep(optionsFilter), filter].filter(Boolean);
      // TODO(feature): change 'and' to symbol
      data.filter = filterOptions.length > 1 ? { and: filterOptions } : filterOptions[0];
    }
    // if (typeof optionsFields === 'function') {
    //   this.parameters = _.cloneDeep(data);
    //   optionsFields = await optionsFields(this.context);
    // }
    if (!_.isEmpty(optionsFields) || !_.isEmpty(fields)) {
      data.fields = mergeFields(optionsFields, fields);
    }
    this.parameters = _.cloneDeep(data);
  }

  setResource(resource: Resource) {
    this.resource = resource;
    return this;
  }

  getResource() {
    return this.resource;
  }

  getOptions(): ActionOptions {
    return this.options;
  }

  setName(name: ActionName) {
    this.name = name;
    return this;
  }

  getName() {
    return this.name;
  }

  getMiddlewareHandlers() {
    return this.middlewares
      .filter(middleware => middleware.canAccess(this.name))
      .map(middleware => middleware.getHandler());
  }

  getHandler() {
    const handler = requireModule(this.handler || this.resource.resourcer.getRegisteredHandler(this.name));
    if (typeof handler !== 'function') {
      throw new Error('Handler must be a function!');
    }
    return handler;
  }

  getHandlers() {
    return [...this.resource.resourcer.getMiddlewares(),...this.getMiddlewareHandlers(), this.getHandler()].filter(Boolean);
  }

  async execute(context: any, next?: any) {
    return await compose(this.getHandlers())(context, next);
  }

  static toInstanceMap(actions: object, resource?: Resource) {
    return new Map(Object.entries(actions).map(([key, options]) => {
      let action: Action;
      if (options instanceof Action) {
        action = options;
      } else {
        action = new Action(options);
      }
      action.setName(key);
      action.setResource(resource);
      resource && action.middlewares.unshift(...resource.middlewares);
      return [key, action];
    }));
  }
}

export default Action;