import { useReducer } from 'react';
import type { AppState, AppAction } from '@/types';

const initialState: AppState = {
  phase: 'selecting',
  appMode: 'homework',
  topic: null,
  task: null,
  code: '',
  messages: [],
  classroomMessages: [],
  lessonContent: null,
  executionResult: null,
  streamingContent: '',
  isStreaming: false,
  error: null,
  responseMode: { hintMode: true, strict: false },
};

function reducer(state: AppState, action: AppAction): AppState {
  switch (action.type) {
    case 'SELECT_TOPIC':
      return {
        ...initialState,
        phase: 'loading_task',
        appMode: state.appMode,
        topic: action.payload,
        code: action.payload.starterCode,
        isStreaming: true,
        responseMode: state.responseMode,
      };

    case 'TASK_STREAM_START':
      return { ...state, phase: 'loading_task', isStreaming: true, streamingContent: '' };

    case 'TASK_STREAM_CHUNK':
      return { ...state, streamingContent: state.streamingContent + action.payload };

    case 'TASK_STREAM_DONE':
      return {
        ...state,
        phase: 'ready',
        task: action.payload,
        code: action.payload.starterCode || state.code,
        isStreaming: false,
        streamingContent: '',
        messages: [],
      };

    case 'CODE_CHANGE':
      return { ...state, code: action.payload };

    case 'EXECUTE_START':
      return { ...state, phase: 'executing', executionResult: null, error: null };

    case 'EXECUTE_DONE':
      return { ...state, phase: 'ready', executionResult: action.payload };

    case 'REVIEW_START':
      return {
        ...state,
        phase: 'reviewing',
        isStreaming: true,
        streamingContent: '',
        error: null,
      };

    case 'STREAM_CHUNK':
      return { ...state, streamingContent: state.streamingContent + action.payload };

    case 'STREAM_DONE':
      return {
        ...state,
        phase: 'ready',
        isStreaming: false,
        streamingContent: '',
        messages: [...state.messages, action.payload],
      };

    case 'SEND_USER_MESSAGE':
      return {
        ...state,
        isStreaming: true,
        streamingContent: '',
        messages: [
          ...state.messages,
          {
            id: crypto.randomUUID(),
            role: 'user',
            content: action.payload,
            timestamp: Date.now(),
            type: 'chat',
          },
        ],
      };

    case 'SET_APP_MODE':
      return { ...state, appMode: action.payload };

    case 'LESSON_STREAM_START':
      return { ...state, isStreaming: true, streamingContent: '', error: null };

    case 'LESSON_STREAM_DONE':
      return {
        ...state,
        isStreaming: false,
        streamingContent: '',
        lessonContent: action.payload,
      };

    case 'SEND_CLASSROOM_MESSAGE':
      return {
        ...state,
        isStreaming: true,
        streamingContent: '',
        classroomMessages: [
          ...state.classroomMessages,
          {
            id: crypto.randomUUID(),
            role: 'user',
            content: action.payload,
            timestamp: Date.now(),
            type: 'chat',
          },
        ],
      };

    case 'CLASSROOM_MESSAGE_DONE':
      return {
        ...state,
        isStreaming: false,
        streamingContent: '',
        classroomMessages: [...state.classroomMessages, action.payload],
      };

    case 'SET_ERROR':
      return { ...state, phase: 'ready', isStreaming: false, streamingContent: '', error: action.payload };

    case 'CLEAR_ERROR':
      return { ...state, error: null };

    case 'SET_RESPONSE_MODE':
      return { ...state, responseMode: { ...state.responseMode, ...action.payload } };

    case 'RESET':
      return {
        ...initialState,
        appMode: state.appMode,
        responseMode: state.responseMode,
      };

    case 'RESTORE_SESSION':
      return {
        ...initialState,
        phase: 'ready',
        appMode: state.appMode,
        topic: action.payload.topic,
        task: action.payload.task,
        code: action.payload.code,
        messages: action.payload.messages,
        executionResult: action.payload.executionResult,
        responseMode: state.responseMode,
      };

    default:
      return state;
  }
}

export function useAppState() {
  return useReducer(reducer, initialState);
}