import { createAsyncThunk, createSlice, PayloadAction } from '@reduxjs/toolkit';
import { fetchCount } from '../utils/counter-api';
import { RootState } from '..';
import { IncrementByAmountPayload } from './types';

export interface CounterState {
  value: number;
  status: 'idle' | 'loading' | 'failed';
}

const initialState: CounterState = {
  value: 0,
  status: 'idle',
};

// The function below is called a thunk and allows us to perform async logic. It
// can be dispatched like a regular action: `dispatch(incrementAsync(10))`. This
// will call the thunk with the `dispatch` function as the first argument. Async
// code can then be executed and other actions can be dispatched
export const incrementAsync = createAsyncThunk<
  number,
  number,
  { state: { counter: CounterState } }
>('counter/fetchCount', async (amount: number, { getState }) => {
  const { value } = getState().counter;
  const response = await fetchCount(value, amount);
  return response.data;
});

export const counterSlice = createSlice({
  name: 'counter',
  initialState,
  reducers: {
    increment: state => {
      // Redux Toolkit allows us to write "mutating" logic in reducers. It
      // doesn't actually mutate the state because it uses the Immer library,
      // which detects changes to a "draft state" and produces a brand new
      // immutable state based off those changes
      state.value += 1;
    },
    decrement: state => {
      state.value -= 1;
    },
    // Use the PayloadAction type to declare the contents of `action.payload`
    incrementByAmount: (
      state,
      action: PayloadAction<IncrementByAmountPayload>,
    ) => {
      state.value += action.payload.amount;
    },
  },
  extraReducers: builder => {
    builder
      .addCase(incrementAsync.pending, state => {
        state.status = 'loading';
      })
      .addCase(incrementAsync.fulfilled, (state, action) => {
        state.status = 'idle';
        state.value = action.payload;
      });
  },
});

export const { increment, decrement, incrementByAmount } = counterSlice.actions;

// The function below is called a selector and allows us to select a value from
// the state. Selectors can also be defined inline where they're used instead of
// in the slice file. For example: `useSelector((state: RootState) => state.counter.value)`
export const selectCount = (state: RootState) => state.counter.value;

export const counterReducer = counterSlice.reducer;