import { model } from '@modern-js-reduck/react';

export enum VisibilityFilters {
  SHOW_ALL = 'SHOW_ALL',
  SHOW_COMPLETED = 'SHOW_COMPLETED',
  SHOW_ACTIVE = 'SHOW_ACTIVE',
}

let nextTodoId = 0;

export interface Todo {
  id: number;
  text: string;
  completed: boolean;
}

interface State {
  data: Todo[];
  visibilityFilter: VisibilityFilters;
}

const todos = model<State>('todos').define({
  state: {
    data: [],
    visibilityFilter: VisibilityFilters.SHOW_ALL,
  },
  computed: {
    visibleTodos: state => {
      const { data, visibilityFilter } = state;
      switch (visibilityFilter) {
        case VisibilityFilters.SHOW_ALL:
          return data;
        case VisibilityFilters.SHOW_COMPLETED:
          return data.filter(t => t.completed);
        case VisibilityFilters.SHOW_ACTIVE:
          return data.filter(t => !t.completed);
        default:
          throw new Error('Unknown filter: ' + visibilityFilter);
      }
    },
    completedTodoCount: state =>
      state.data.reduce(
        (count, todo) => (todo.completed ? count + 1 : count),
        0,
      ),
  },
  actions: {
    addTodo: (state, text: string) => {
      state.data.push({ id: nextTodoId++, text, completed: false });
    },
    toggleTodo: (state, id: number) => {
      state.data.forEach(todo =>
        todo.id === id ? (todo.completed = !todo.completed) : todo,
      );
    },
    setVisibilityFilter: (state, filter: VisibilityFilters) => {
      state.visibilityFilter = filter;
    },
  },
});

export default todos;