// ─── ClientLibraryContext.jsx ───────────────────────────────────────────────
// Standalone Unit / Lesson browsing (junction revamp). Units run independently
// of Courses — this context drives the /units grid, /units/:uuid detail page,
// and /units/:uuid/read reader.

import { createContext, useCallback, useContext, useState } from "react";
import api from "@/utils/api.util";
import { toast } from "sonner";

const ClientLibraryContext = createContext(null);

export function useLibrary() {
  const ctx = useContext(ClientLibraryContext);
  if (!ctx) throw new Error("useLibrary must be used within a ClientLibraryProvider");
  return ctx;
}

export function ClientLibraryProvider({ children }) {
  // ── List state
  const [units, setUnits] = useState([]);
  const [unitsLoading, setUnitsLoading] = useState(false);
  const [lessons, setLessons] = useState([]);
  const [lessonsLoading, setLessonsLoading] = useState(false);

  // ── Detail state — GET /client/units/:uuid/lessons returns unit + lessons + quiz in one call
  const [unitDetail, setUnitDetail] = useState(null);
  const [unitDetailLoading, setUnitDetailLoading] = useState(false);
  const [unitBlocked, setUnitBlocked] = useState(false);
  const [unitBlockedInfo, setUnitBlockedInfo] = useState(null); // { message, course }

  // ── Lesson state (standalone reader)
  const [lesson, setLesson] = useState(null);
  const [lessonLoading, setLessonLoading] = useState(false);

  // ── Quiz state
  const [quiz, setQuiz] = useState(null);
  const [quizLoading, setQuizLoading] = useState(false);

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

  const getUnits = useCallback(async () => {
    setUnitsLoading(true);
    try {
      const { data } = await api.get("/client/units");
      setUnits(data.data ?? []);
    } catch (err) {
      toast(err?.response?.data?.message ?? "Could not load units.");
    } finally {
      setUnitsLoading(false);
    }
  }, []);

  const getLessons = useCallback(async () => {
    setLessonsLoading(true);
    try {
      const { data } = await api.get("/client/lessons");
      setLessons(data.data ?? []);
    } catch (err) {
      toast(err?.response?.data?.message ?? "Could not load lessons.");
    } finally {
      setLessonsLoading(false);
    }
  }, []);

  const getUnitDetail = useCallback(async (uuid) => {
    setUnitDetailLoading(true);
    setUnitBlocked(false);
    setUnitBlockedInfo(null);
    try {
      const { data } = await api.get(`/client/units/${uuid}/lessons`);
      setUnitDetail(data.data ?? null);
    } catch (err) {
      if (err?.response?.status === 403) {
        setUnitBlocked(true);
        setUnitBlockedInfo(err.response.data ?? null);
      } else {
        toast(err?.response?.data?.message ?? "Could not load unit.");
      }
    } finally {
      setUnitDetailLoading(false);
    }
  }, []);

  const getLesson = useCallback(async (uuid) => {
    setLessonLoading(true);
    try {
      const { data } = await api.get(`/client/lessons/${uuid}`);
      setLesson(data.data ?? null);
    } catch (err) {
      if (err?.response?.status === 403) {
        setUnitBlocked(true);
        setUnitBlockedInfo(err.response.data ?? null);
      } else {
        toast(err?.response?.data?.message ?? "Could not load lesson.");
      }
    } finally {
      setLessonLoading(false);
    }
  }, []);

  const getUnitQuiz = useCallback(async (uuid) => {
    setQuizLoading(true);
    try {
      const { data } = await api.get(`/client/units/${uuid}/quiz`);
      setQuiz(data.data ?? null);
    } catch (err) {
      toast(err?.response?.data?.message ?? "Could not load quiz.");
    } finally {
      setQuizLoading(false);
    }
  }, []);

  const submitUnitQuiz = useCallback(async (uuid, quizId, answers) => {
    try {
      const { data } = await api.post(`/client/units/${uuid}/quiz/${quizId}/submit`, { answers });
      return data.data ?? null;
    } catch (err) {
      toast(err?.response?.data?.message ?? "Could not submit quiz.");
      return null;
    }
  }, []);

  const saveUnitQuizDraft = useCallback(async (uuid, quizId, answers) => {
    try {
      await api.patch(`/client/units/${uuid}/quiz/${quizId}/draft`, { answers });
    } catch { /* silent — draft saves are best-effort */ }
  }, []);

  // Writes lesson progress, then locally patches unitDetail so the reader/detail
  // page updates without a full refetch (matched by numeric lesson_id — the
  // response is keyed by id, not uuid).
  const upsertLessonProgress = useCallback(async (lessonUuid, status, unitUuid) => {
    try {
      const { data } = await api.post(`/client/lessons/${lessonUuid}/progress`, {
        status,
        ...(unitUuid ? { unit_uuid: unitUuid } : {}),
      });
      const result = data.data ?? null;

      // Trust the server's evaluated status for both lesson and unit — no local
      // re-derivation (previously `lessons.every(status === 'completed')` here,
      // which drifted from the consolidated evaluator once per-lesson completion
      // requirements could be configured; the server already ran that same
      // evaluator via recomputeCascade and returned the authoritative result).
      setUnitDetail((prev) => {
        if (!prev || !result?.lesson) return prev;
        const nextLessons = prev.lessons.map((l) =>
          l.lesson_id === result.lesson.lesson_id
            ? { ...l, status: result.lesson.status, completed_at: status === "completed" ? new Date().toISOString() : l.completed_at }
            : l
        );
        const is_completed = result.unit ? result.unit.status === "completed" : prev.is_completed;
        return { ...prev, lessons: nextLessons, is_completed };
      });

      return result;
    } catch (err) {
      toast(err?.response?.data?.message ?? "Could not update progress.");
      return null;
    }
  }, []);

  // ─── Resets ─────────────────────────────────────────────────────────────

  const resetUnitDetail = useCallback(() => {
    setUnitDetail(null);
    setUnitBlocked(false);
    setUnitBlockedInfo(null);
  }, []);
  const resetLesson = useCallback(() => setLesson(null), []);
  const resetQuiz = useCallback(() => setQuiz(null), []);

  // ─── Value ──────────────────────────────────────────────────────────────

  const value = {
    units, unitsLoading,
    lessons, lessonsLoading,
    unitDetail, unitDetailLoading, unitBlocked, unitBlockedInfo,
    lesson, lessonLoading,
    quiz, quizLoading,

    getUnits,
    getLessons,
    getUnitDetail,
    getLesson,
    getUnitQuiz,
    submitUnitQuiz,
    saveUnitQuizDraft,
    upsertLessonProgress,

    resetUnitDetail,
    resetLesson,
    resetQuiz,
  };

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

export default ClientLibraryContext;