const todo = (state, action) => {
  switch (action.type) {
    case 'ADD_TODO':
      return {
        id: action.id,
        text: action.text,
        completed: false
      };
    case 'TOGGLE_TODO':
      if (state.id !== action.id) {
        return state;
      }

      return {
        ...state,
        completed: !state.completed
      };
    default:
      return state;
  }
};

const todos = (state = [], action) => {
  switch (action.type) {
    case 'ADD_TODO':
      return [
        ...state,
        todo(undefined, action)
      ];
    case 'TOGGLE_TODO':
      return state.map(t =>
        todo(t, action)
      );
    default:
      return state;
  }
};

const visibilityFilter = (
  state = 'SHOW_ALL',
  action
) => {
  switch (action.type) {
    case 'SET_VISIBILITY_FILTER':
      return action.filter;
    default:
      return state;
  }
};

const { combineReducers } = Redux;
const todoApp = combineReducers({
  todos,
  visibilityFilter
});

let nextTodoId = 0;
const addTodo = (text) => {
  return {
    type: 'ADD_TODO',
    id: nextTodoId++,
    text: text
  }
}
const setVisibilityFilter = (filter) => {
  return {
    type: 'SET_VISIBILITY_FILTER',
    filter: filter
  }
}
const toggleTodo = (id) => {
  return {
    type: 'TOGGLE_TODO',
    id
  }
}

const { Component } = React;
const { connect } = ReactRedux;

const Link = ({
  active,
  children,
  onClick
}) => {
  if (active) {
    return <span>{children}</span>;
  }

  return (
    <a href='#'
       onClick={e => {
         e.preventDefault();
         onClick();
       }}
    >
      {children}
    </a>
  );
};

const mapStateToLinkProps = (state, ownProps) => {
  return {
    active: (ownProps.filter === state.visibilityFilter)
  }
}
const mapDispatchToLinkProps = (dispatch, ownProps) => {
  return {
    onClick: () => {
      dispatch(
        setVisibilityFilter(ownProps.filter)
      )
    }
  }
}
const FilterLink = connect(
  mapStateToLinkProps,
  mapDispatchToLinkProps
)(Link)

const Footer = () => (
  <p>
    Show:
    {' '}
    <FilterLink filter='SHOW_ALL'>
      All
    </FilterLink>
    {', '}
    <FilterLink filter='SHOW_ACTIVE'>
      Active
    </FilterLink>
    {', '}
    <FilterLink filter='SHOW_COMPLETED'>
      Completed
    </FilterLink>
  </p>
);

const Todo = ({
  onClick,
  completed,
  text
}) => (
  <li
    onClick={onClick}
    style={{
      textDecoration:
        completed ?
          'line-through' :
          'none'
    }}
  >
    {text}
  </li>
);

const TodoList = ({
  todos,
  onTodoClick
}) => (
  <ul>
    {todos.map(todo =>
      <Todo
        key={todo.id}
        {...todo}
        onClick={() => onTodoClick(todo.id)}
      />
    )}
  </ul>
);

let AddTodo = ({ dispatch }) => {
  let input;

  return (
    <div>
      <input ref={node => {
        input = node;
      }} />
      <button onClick={() => {
        dispatch(addTodo(input.value))
        input.value = '';
      }}>
        Add Todo
      </button>
    </div>
  );
};
AddTodo = connect()(AddTodo)


const getVisibleTodos = (
  todos,
  filter
) => {
  switch (filter) {
    case 'SHOW_ALL':
      return todos;
    case 'SHOW_COMPLETED':
      return todos.filter(
        t => t.completed
      );
    case 'SHOW_ACTIVE':
      return todos.filter(
        t => !t.completed
      );
  }
}
const mapStateToTodoListProps = (state) => {
  return {
    todos: getVisibleTodos(
      state.todos,
      state.visibilityFilter
    )
  }
}
const mapDispatchToTodoListProps = (dispatch) => {
  return {
    onTodoClick: (id) => {
      dispatch(
        toggleTodo(id)
      )
    }
  }
}
const VisibleTodoList = connect(
  mapStateToTodoListProps,
  mapDispatchToTodoListProps
)(TodoList)


const TodoApp = () => (
  <div>
    <AddTodo />
    <VisibleTodoList />
    <Footer />
  </div>
);

const { Provider } = ReactRedux;
const { createStore } = Redux;

ReactDOM.render(
  <Provider store={createStore(todoApp)}>
    <TodoApp />
  </Provider>,
  document.getElementById('root')
);