import { create } from "zustand";

import {
  generateSession,
  gradeAnswer,
} from "@/lib/engine/parenthesis-sign";
import type { ParenthesisTermCount } from "@/lib/engine/parenthesis-sign";
import type {
  GradeResult,
  ParenthesisSignProblem,
  UserAnswer,
} from "@/lib/engine/types";

export interface GameSession {
  problems: ParenthesisSignProblem[];
  currentIndex: number;
  results: (GradeResult | null)[];
  termCount: ParenthesisTermCount;
}

export type ProblemCount = 5 | 10;
export type MaxTermCount = ParenthesisTermCount;

interface GameState {
  session: GameSession | null;
  selectedProblemCount: ProblemCount;
  selectedMaxTermCount: MaxTermCount;
  setProblemCount: (count: ProblemCount) => void;
  setMaxTermCount: (count: MaxTermCount) => void;
  initSession: (count?: ProblemCount, maxTermCount?: MaxTermCount) => void;
  submitAnswer: (answer: UserAnswer) => void;
  nextProblem: () => void;
  resetSession: () => void;
}

const DEFAULT_SESSION_COUNT: ProblemCount = 10;
const DEFAULT_MAX_TERM_COUNT: MaxTermCount = 2;

function createSession(
  count: ProblemCount = DEFAULT_SESSION_COUNT,
  maxTermCount: MaxTermCount = DEFAULT_MAX_TERM_COUNT,
): GameSession {
  const problems = generateSession(count, maxTermCount);

  return {
    problems,
    currentIndex: 0,
    results: problems.map(() => null),
    termCount: maxTermCount,
  };
}

export const useGameStore = create<GameState>((set, get) => ({
  session: null,
  selectedProblemCount: DEFAULT_SESSION_COUNT,
  selectedMaxTermCount: DEFAULT_MAX_TERM_COUNT,
  setProblemCount: (count) => {
    set({ selectedProblemCount: count });
  },
  setMaxTermCount: (count) => {
    set({ selectedMaxTermCount: count });
  },
  initSession: (count, maxTermCount) => {
    const selectedProblemCount = count ?? get().selectedProblemCount;
    const selectedMaxTermCount = maxTermCount ?? get().selectedMaxTermCount;

    set({ session: createSession(selectedProblemCount, selectedMaxTermCount) });
  },
  submitAnswer: (answer) => {
    const { session } = get();

    if (!session || session.currentIndex >= session.problems.length) return;
    if (session.results[session.currentIndex] !== null) return;

    const problem = session.problems[session.currentIndex];
    const result = gradeAnswer(problem, answer);
    const results = [...session.results];
    results[session.currentIndex] = result;

    set({
      session: {
        ...session,
        results,
      },
    });
  },
  nextProblem: () => {
    const { session } = get();

    if (!session || session.currentIndex >= session.problems.length) return;
    if (session.results[session.currentIndex] === null) return;

    set({
      session: {
        ...session,
        currentIndex: session.currentIndex + 1,
      },
    });
  },
  resetSession: () => {
    set({
      session: createSession(
        get().selectedProblemCount,
        get().selectedMaxTermCount,
      ),
    });
  },
}));