import { createContext } from "preact";
import { useContext, useMemo, useReducer } from "preact/hooks";

// ─── Types ────────────────────────────────────────────────────────────────────

export interface Story {
    id: string;
    title: string;
    text: string;
}

// ─── State ───────────────────────────────────────────────────────────────────

interface IState {
    stories: Story[];
    currentStoryId: string | null;
}

// ─── Actions ─────────────────────────────────────────────────────────────────

type Action =
    | { type: 'CREATE_STORY'; title: string }
    | { type: 'RENAME_STORY'; id: string; title: string }
    | { type: 'EDIT_STORY'; id: string; text: string }
    | { type: 'DELETE_STORY'; id: string }
    | { type: 'SELECT_STORY'; id: string };

// ─── Initial State ───────────────────────────────────────────────────────────

const DEFAULT_STATE: IState = {
    stories: [],
    currentStoryId: null,
};

// ─── Reducer ─────────────────────────────────────────────────────────────────

function reducer(state: IState, action: Action): IState {
    switch (action.type) {
        case 'CREATE_STORY': {
            const story: Story = {
                id: crypto.randomUUID(),
                title: action.title,
                text: '',
            };
            return {
                ...state,
                stories: [...state.stories, story],
                currentStoryId: story.id,
            };
        }
        case 'RENAME_STORY': {
            return {
                ...state,
                stories: state.stories.map(s =>
                    s.id === action.id ? { ...s, title: action.title } : s
                ),
            };
        }
        case 'EDIT_STORY': {
            return {
                ...state,
                stories: state.stories.map(s =>
                    s.id === action.id ? { ...s, text: action.text } : s
                ),
            };
        }
        case 'DELETE_STORY': {
            const remaining = state.stories.filter(s => s.id !== action.id);
            const deletingCurrent = state.currentStoryId === action.id;
            return {
                ...state,
                stories: remaining,
                currentStoryId: deletingCurrent ? null : state.currentStoryId,
            };
        }
        case 'SELECT_STORY': {
            return {
                ...state,
                currentStoryId: action.id,
            };
        }
        default:
            return state;
    }
}

// ─── Context ─────────────────────────────────────────────────────────────────

interface IStateContext {
    stories: Story[];
    currentStory: Story | null;
    dispatch: (action: Action) => void;
}

const StateContext = createContext<IStateContext>({} as IStateContext);

export const useAppState = () => useContext(StateContext);

// ─── Provider ────────────────────────────────────────────────────────────────

export const StateContextProvider = ({ children }: { children?: any }) => {
    const [state, dispatch] = useReducer(reducer, DEFAULT_STATE);

    const value = useMemo<IStateContext>(() => ({
        stories: state.stories,
        currentStory: state.stories.find(s => s.id === state.currentStoryId) ?? null,
        dispatch,
    }), [state]);

    return (
        <StateContext.Provider value={value}>
            {children}
        </StateContext.Provider>
    );
};