"use client";

import { create } from "zustand";
import { Test, Answer, Question } from "@/types/exam";
import { API_URL, getToken } from "@/lib/auth";
import { ExamResult } from "@/types/exam";

// Result type (based on your API response)

type ExamStatus = "not-started" | "in-progress" | "finished";

interface ExamState {
  test: Test | null;
  answers: Answer[];
  result: ExamResult | null;
  status: ExamStatus;
  setStatus: (status: ExamStatus) => void;

  startExam: (testType: string, testId: string) => Promise<Test | null>;
  setAnswer: (questionIndex: number, answer: Answer) => void;
  submitExam: (testType: string) => Promise<ExamResult | null>;
  cancelExam: () => void;
  clearResult: () => void;
}

export const useExamStore = create<ExamState>((set, get) => ({
  test: null,
  answers: [],
  result: null,
  status: "not-started",
  setStatus: (status) => set({ status }),

  // start exam
  startExam: async (testType: string, testId: string) => {
    try {
      const token = await getToken();
      const res = await fetch(`${API_URL}/tests/${testType}/${testId}`, {
        method: "GET",
        headers: {
          Authorization: `Bearer ${token}`,
        },
      });

      if (!res.ok) throw new Error(`Failed to fetch test: ${res.status}`);
      const data: Test = await res.json();

      set({
        test: data,
        answers: Array(data.questions.length).fill(null),
        result: null, // clear old result
      });

      return data;
    } catch (err) {
      console.error("startExam error:", err);
      return null;
    }
  },

  // set an answer
  setAnswer: (questionIndex: number, answer: Answer) => {
    set((state) => {
      const updated = [...state.answers];
      updated[questionIndex] = answer;
      return { answers: updated };
    });
  },

  // submit exam
  submitExam: async (testType: string) => {
    const { test, answers } = get();
    if (!test) return null;

    const token = await getToken();

    try {
      const { test_id, attempt_id } = test.metadata;
      const res = await fetch(
        `${API_URL}/tests/${testType}/${test_id}/${attempt_id}`,
        {
          method: "POST",
          headers: {
            "Content-Type": "application/json",
            Authorization: `Bearer ${token}`,
          },
          body: JSON.stringify({ answers }),
        }
      );

      if (!res.ok) throw new Error("Failed to submit exam");
      const result: ExamResult = await res.json();

      // save result, clear test+answers
      set({ test: null, answers: [], result });

      return result;
    } catch (err) {
      console.error("Failed to submit exam. Reason:", err);
      return null;
    }
  },

  // cancel exam
  cancelExam: () => {
    set({ test: null, answers: [], result: null });
  },

  // clear result manually (e.g., when leaving results page)
  clearResult: () => {
    set({ result: null });
  },
}));