import { useState, useEffect, useCallback } from "react";
import { flushSync } from "react-dom";
import {
  useNavigate,
  useLocation,
  Routes,
  Route,
  Navigate,
} from "react-router-dom";
import type { Exam, ExamState, HistoryEntry, Tweaks } from "./types";
import { gradeQuestion } from "./utils/grading";
import {
  loadState,
  saveState,
  clearState,
  loadHistory,
  appendHistory,
  clearHistory,
} from "./utils/storage";
import { apiFetch, isAuthenticated } from "./utils/api";
import { slugify } from "./utils/slug";
import { AuthProvider, useAuth } from "./contexts/AuthContext";
import Landing from "./components/Landing";
import ExamRoute from "./components/ExamRoute";
import Results from "./components/Results";
import TweaksPanel from "./components/TweaksPanel";
import AuthModal from "./components/AuthModal";
import EmailVerify from "./components/EmailVerify";
import ResetPassword from "./components/ResetPassword";
import AdminDashboard from "./components/AdminDashboard";

const DEFAULT_TWEAKS: Tweaks = {
  theme: "light",
  fontSize: "medium",
  feedbackMode: "auto",
};

const withNotes = (state: ExamState): ExamState => ({
  ...state,
  notes: state.notes ?? "",
});

function AppInner() {
  const { user, loading: authLoading, logout } = useAuth();
  const navigate = useNavigate();
  const { pathname } = useLocation();
  const [exam, setExam] = useState<Exam | null>(null);
  const [examState, setExamState] = useState<ExamState | null>(null);
  const [history, setHistory] = useState<HistoryEntry[]>(() => loadHistory());
  const [tweaks, setTweaks] = useState<Tweaks>(DEFAULT_TWEAKS);
  const [tweaksOpen, setTweaksOpen] = useState(false);
  const [authModalOpen, setAuthModalOpen] = useState(false);
  const [userMenuOpen, setUserMenuOpen] = useState(false);

  useEffect(() => {
    if (!authLoading && user && isAuthenticated()) {
      apiFetch<{
        results: Array<{
          id: number;
          title: string;
          score_points: number;
          total_points: number;
          correct_count: number;
          graded_count: number;
          passing_score: number;
          elapsed_ms: number;
          completed_at: number;
          exam_id: number | null;
        }>;
      }>("/api/results")
        .then((data) => {
          const apiHistory: HistoryEntry[] = data.results.map((r) => ({
            id: String(r.id),
            title: r.title,
            completedAt: r.completed_at * 1000,
            elapsedMs: r.elapsed_ms,
            gradedCount: r.graded_count,
            correctCount: r.correct_count,
            totalPoints: r.total_points,
            scorePoints: r.score_points,
            passingScore: r.passing_score,
            exam: { title: r.title, questions: [] } as unknown as Exam,
            state: {
              currentIdx: 0,
              answers: {},
              flags: {},
              notes: "",
              startedAt: 0,
              feedbackMode: "end" as const,
            } as ExamState,
            _remoteId: r.id,
          }));
          setHistory(apiHistory);
        })
        .catch(() => {
          setHistory(loadHistory());
        });
    }
  }, [user, authLoading]);

  useEffect(() => {
    document.documentElement.dataset["theme"] = tweaks.theme;
    const sizeMap: Record<string, string> = {
      small: "14px",
      medium: "15px",
      large: "17px",
    };
    document.body.style.fontSize = sizeMap[tweaks.fontSize] ?? "15px";
  }, [tweaks]);

  useEffect(() => {
    if (pathname.startsWith("/exam/") && exam && examState)
      saveState({ exam, state: examState });
  }, [exam, examState, pathname]);

  const updateTweak = <K extends keyof Tweaks>(key: K, value: Tweaks[K]) =>
    setTweaks((t) => ({ ...t, [key]: value }));

  const setExamStateStrict: React.Dispatch<React.SetStateAction<ExamState>> = (
    nextState,
  ) => {
    setExamState((prev) => {
      if (!prev) return prev;
      return typeof nextState === "function"
        ? (nextState as (prevState: ExamState) => ExamState)(prev)
        : nextState;
    });
  };

  const activateExam = (data: Exam, state: ExamState) => {
    setExam(data);
    setExamState(withNotes(state));
  };

  const loadExam = (data: Exam) => {
    const fm =
      tweaks.feedbackMode === "auto"
        ? (data.feedbackMode ?? "end")
        : tweaks.feedbackMode;
    flushSync(() => {
      setExam(data);
      setExamState({
        currentIdx: 0,
        answers: {},
        flags: {},
        notes: "",
        revealed: {},
        startedAt: Date.now(),
        feedbackMode: fm,
      });
    });
    navigate(`/exam/${slugify(data.title)}/q1`);
  };

  const resume = () => {
    const saved = loadState();
    if (saved?.exam && saved?.state) {
      flushSync(() => {
        setExam(saved.exam);
        setExamState(withNotes(saved.state));
      });
      navigate(
        `/exam/${slugify(saved.exam.title)}/q${saved.state.currentIdx + 1}`,
      );
    }
  };

  const submit = useCallback(() => {
    if (!exam || !examState) return;
    const completedAt = Date.now();
    const elapsedMs = completedAt - examState.startedAt;
    const graded = exam.questions.map((q) =>
      gradeQuestion(q, examState.answers[q.id]),
    );
    const entry: HistoryEntry = {
      id: `${Date.now()}-${Math.random().toString(36).slice(2, 7)}`,
      title: exam.title,
      completedAt,
      elapsedMs,
      gradedCount: graded.filter((r) => r.status !== "ungraded").length,
      correctCount: graded.filter((r) => r.correct).length,
      totalPoints: exam.questions.reduce((a, q) => a + (q.points ?? 1), 0),
      scorePoints: graded.reduce((a, r) => a + r.points, 0),
      passingScore: exam.passingScore ?? 60,
      exam,
      state: { ...examState, completedAt },
    };

    if (user && isAuthenticated()) {
      void apiFetch("/api/results", {
        method: "POST",
        body: JSON.stringify({
          title: entry.title,
          scorePoints: entry.scorePoints,
          totalPoints: entry.totalPoints,
          correctCount: entry.correctCount,
          gradedCount: entry.gradedCount,
          passingScore: entry.passingScore,
          elapsedMs: entry.elapsedMs,
          notes: entry.state.notes,
          state: entry.state,
          exam: entry.exam,
        }),
      }).catch(() => {
        appendHistory(entry);
      });
    } else {
      appendHistory(entry);
    }

    setHistory((prev) => [entry, ...prev]);
    clearState();
    setExamState((s) => (s ? { ...s, completedAt } : s));
    navigate("/results");
  }, [exam, examState, user, navigate]);

  const exit = () => {
    setExam(null);
    setExamState(null);
    navigate("/");
  };

  const restart = () => {
    if (exam) loadExam(exam);
  };

  const reviewAttempt = (entry: HistoryEntry) => {
    const remoteId = (entry as HistoryEntry & { _remoteId?: number })._remoteId;
    if (remoteId && user && isAuthenticated()) {
      void apiFetch<{
        exam: Exam;
        state: ExamState;
        title: string;
        scorePoints: number;
        totalPoints: number;
        correctCount: number;
        gradedCount: number;
        passingScore: number;
        elapsedMs: number;
        completedAt: number;
      }>(`/api/results/${remoteId}`)
        .then((data) => {
          flushSync(() => {
            setExam(data.exam);
            setExamState(withNotes(data.state));
          });
          navigate(`/review/${slugify(entry.title)}`);
        })
        .catch(() => {
          flushSync(() => {
            setExam(entry.exam);
            setExamState(withNotes(entry.state));
          });
          navigate(`/review/${slugify(entry.title)}`);
        });
    } else {
      flushSync(() => {
        setExam(entry.exam);
        setExamState(withNotes(entry.state));
      });
      navigate(`/review/${slugify(entry.title)}`);
    }
  };

  const clearAllHistory = () => {
    if (confirm("Clear all past attempts?")) {
      clearHistory();
      setHistory([]);
    }
  };

  const handleAuthFlowDone = () => {
    navigate("/");
    setAuthModalOpen(true);
  };

  if (pathname === "/verify") {
    return (
      <div className="shell">
        <header className="topbar">
          <div className="brand">
            <span className="brand-mark" />
            <span className="brand-name">BrainWave</span>
          </div>
        </header>
        <EmailVerify onDone={handleAuthFlowDone} />
      </div>
    );
  }

  if (pathname === "/reset-password") {
    return (
      <div className="shell">
        <header className="topbar">
          <div className="brand">
            <span className="brand-mark" />
            <span className="brand-name">BrainWave</span>
          </div>
        </header>
        <ResetPassword onDone={handleAuthFlowDone} />
      </div>
    );
  }

  return (
    <div className="shell">
      <header className="topbar">
        <div className="brand">
          <span className="brand-mark" />
          <button
            className="brand-name"
            onClick={exit}
            aria-label="Home"
            style={{
              background: "none",
              border: "none",
              padding: 0,
              margin: 0,
              cursor: "pointer",
              font: "inherit",
              color: "inherit",
            }}
          >
            BrainWave
          </button>
          <span className="faint mono" style={{ fontSize: 11, marginLeft: 4 }}>
            / practice
          </span>
        </div>
        <div className="topbar-meta">
          {pathname.startsWith("/exam/") && exam && (
            <>
              <span className="mono" style={{ fontSize: 12 }}>
                {exam.title}
              </span>
              <button className="btn btn-ghost btn-sm" onClick={exit}>
                Exit
              </button>
            </>
          )}
          <button
            className="btn btn-ghost btn-sm"
            onClick={() => setTweaksOpen((o) => !o)}
            style={{ marginLeft: 8 }}
            aria-label="Tweaks"
          >
            ⚙
          </button>

          {!authLoading && !user && (
            <button
              className="btn btn-primary btn-sm"
              onClick={() => setAuthModalOpen(true)}
            >
              Sign In
            </button>
          )}
          {!authLoading && user && (
            <div className="user-menu-wrap">
              <button
                className="user-avatar"
                onClick={() => setUserMenuOpen((o) => !o)}
                aria-label="User menu"
              >
                {user.displayName.charAt(0).toUpperCase()}
              </button>
              {userMenuOpen && (
                <div className="user-menu">
                  <div className="user-menu-header">
                    <div className="user-menu-name">{user.displayName}</div>
                    <div className="user-menu-email">{user.email}</div>
                  </div>
                  <div className="user-menu-divider" />
                  {user.role === "admin" && (
                    <button
                      className="user-menu-item"
                      onClick={() => {
                        setUserMenuOpen(false);
                        navigate("/admin");
                      }}
                    >
                      Admin Dashboard
                    </button>
                  )}
                  <button
                    className="user-menu-item"
                    onClick={() => {
                      setUserMenuOpen(false);
                      logout();
                    }}
                  >
                    Sign Out
                  </button>
                </div>
              )}
            </div>
          )}
        </div>
      </header>

      <Routes>
        <Route
          path="/"
          element={
            <Landing
              onLoadExam={loadExam}
              history={history}
              onResume={resume}
              onClearHistory={clearAllHistory}
              onReviewAttempt={reviewAttempt}
            />
          }
        />
        <Route
          path="/exam/:slug/q:n"
          element={
            <ExamRoute
              exam={exam}
              examState={examState}
              onActivate={activateExam}
              setExamState={setExamStateStrict}
              onSubmit={submit}
              onExit={exit}
            />
          }
        />
        <Route
          path="/results"
          element={
            exam && examState ? (
              <Results
                exam={exam}
                state={examState}
                onRestart={restart}
                onExit={exit}
                reviewOnly={false}
              />
            ) : (
              <Navigate to="/" replace />
            )
          }
        />
        <Route
          path="/review/:slug"
          element={
            exam && examState ? (
              <Results
                exam={exam}
                state={examState}
                onRestart={restart}
                onExit={exit}
                reviewOnly={true}
              />
            ) : (
              <Navigate to="/" replace />
            )
          }
        />
        <Route
          path="/admin"
          element={
            user?.role === "admin" ? (
              <AdminDashboard onExit={exit} />
            ) : (
              <Navigate to="/" replace />
            )
          }
        />
        <Route path="*" element={<Navigate to="/" replace />} />
      </Routes>

      {tweaksOpen && (
        <TweaksPanel
          tweaks={tweaks}
          update={updateTweak}
          onClose={() => setTweaksOpen(false)}
        />
      )}
      {authModalOpen && (
        <AuthModal
          onClose={() => setAuthModalOpen(false)}
          onForgotPassword={() => navigate("/reset-password")}
        />
      )}
    </div>
  );
}

export default function App() {
  return (
    <AuthProvider>
      <AppInner />
    </AuthProvider>
  );
}