"use client";

import { useEffect, useMemo, useState } from "react";
import Link from "next/link";
import {
  BookOpen,
  Brain,
  CheckCircle2,
  FileText,
  LineChart,
  MessageSquareText,
  Play,
  Target,
} from "lucide-react";
import { hydratePhase3Activity, readPhase3Activity, type Phase3Activity } from "@/lib/phase3-learning";
import {
  buildStudentProgressSummary,
  listActivities,
  type ActivityEvent,
} from "@/lib/student-activity";
import { getLocalStudentContext, loadStudentContext, type StudentContext } from "@/lib/student-context";
import { useStudentActivityVersion } from "@/hooks/useStudentActivity";

// =============================================================================
// Truthful progress: every number traces to something the student actually did
// (the student-activity ledger) or real weak-topic evidence (phase3 aggregate,
// fed by quiz mistakes). No sample metrics. Extracted from the /progress route
// so /library can compose it as a tab.
// =============================================================================

const KIND_META: Record<ActivityEvent["kind"], { label: string; icon: typeof Play }> = {
  question_asked: { label: "Asked in StudyChat", icon: MessageSquareText },
  lesson_started: { label: "Lesson started", icon: Play },
  lesson_completed: { label: "Lesson completed", icon: CheckCircle2 },
  note_saved: { label: "Note saved", icon: FileText },
  quiz_attempted: { label: "Quiz attempted", icon: Brain },
  demo_class_completed: { label: "Demo class completed", icon: CheckCircle2 },
};

export function ProgressView() {
  const [events, setEvents] = useState<ActivityEvent[]>([]);
  const [phase3, setPhase3] = useState<Phase3Activity>({});
  const [ctx, setCtx] = useState<StudentContext>(() => getLocalStudentContext());
  // Live token: re-read the ledger whenever activity changes (this tab or another).
  const activityVersion = useStudentActivityVersion();

  useEffect(() => {
    let cancelled = false;
    void Promise.resolve().then(() => {
      if (cancelled) return;
      setEvents(listActivities(30));
      setPhase3(readPhase3Activity());
    });
    return () => {
      cancelled = true;
    };
  }, [activityVersion]);

  useEffect(() => {
    let cancelled = false;
    void loadStudentContext().then((merged) => {
      if (!cancelled) setCtx(merged);
    });
    // Pull the saved weak-topic aggregate from the backend on fresh devices.
    void hydratePhase3Activity().then((remote) => {
      if (!cancelled && remote) setPhase3(readPhase3Activity());
    });
    return () => {
      cancelled = true;
    };
  }, []);

  const summary = useMemo(() => buildStudentProgressSummary(events, phase3), [events, phase3]);

  return (
    <div className="text-white">
      <header className="mb-8">
        <h2 className="text-2xl font-semibold text-white sm:text-3xl">Study progress</h2>
        <p className="mt-2 max-w-3xl text-sm leading-6 text-white/52">
          Built only from what you actually did — questions, lessons, notes, and quiz results on this device.
        </p>
        {ctx.onboardingComplete ? (
          <div className="mt-3 space-y-1 text-[12px] text-white/55">
            <p className="inline-flex items-center gap-1.5">
              <CheckCircle2 className="size-3.5 text-white/70" />
              Onboarding completed{ctx.classLevel ? ` · ${ctx.classLevel}` : ""}{ctx.board ? ` · ${ctx.board}` : ""}
            </p>
            <p>{ctx.synced ? "Account profile synced." : "Local profile active · account sync unavailable."}</p>
          </div>
        ) : (
          <p className="mt-3 text-[12px] text-white/55">
            <Link href="/onboarding" className="underline hover:text-white">
              Complete onboarding
            </Link>{" "}
            to set your study focus.
          </p>
        )}
      </header>

      {!summary.hasActivity ? (
        <div className="rounded-2xl border border-dashed border-white/[0.12] bg-black/30 p-10 text-center">
          <LineChart className="mx-auto mb-4 size-8 text-white/40" />
          <p className="text-base font-semibold text-white">
            Start a lesson, ask a question, or take a quiz to build your progress.
          </p>
          <div className="mt-6 flex flex-wrap justify-center gap-2">
            <Link href="/learn-anything" className="inline-flex rounded-xl bg-white px-5 py-2.5 text-sm font-semibold text-black">
              Start a lesson
            </Link>
            <Link href="/study-chat" className="inline-flex rounded-xl border border-white/[0.14] px-5 py-2.5 text-sm font-semibold text-white/75 hover:text-white">
              Ask a question
            </Link>
            <Link href="/library?tab=quizzes" className="inline-flex rounded-xl border border-white/[0.14] px-5 py-2.5 text-sm font-semibold text-white/75 hover:text-white">
              Take a quiz
            </Link>
          </div>
        </div>
      ) : (
        <>
          <div className="dd-stagger grid gap-5 sm:grid-cols-2 lg:grid-cols-4">
            {summary.metrics.map((metric) => (
              <div key={metric.label} className="rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-5">
                <p className="text-[10px] font-bold uppercase tracking-[0.14em] text-white/34">{metric.label}</p>
                <p className="mt-3 text-2xl font-semibold tabular-nums text-white">{metric.value}</p>
              </div>
            ))}
          </div>

          {summary.sampleActivityCount > 0 ? (
            <p className="mt-4 rounded-xl border border-white/[0.08] bg-white/[0.03] px-4 py-3 text-xs text-white/55">
              Demo activity is labelled below and does not represent full tuition progress.
            </p>
          ) : null}

          <div className="mt-6 grid gap-5 lg:grid-cols-[minmax(0,1fr)_320px]">
            <div className="space-y-5">
              {/* ── Recent activity (real ledger) ── */}
              <section className="rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-5">
                <h3 className="mb-4 text-lg font-semibold text-white">Recent activity</h3>
                <div className="space-y-2.5">
                  {summary.recentActivities.slice(0, 10).map((event) => {
                    const meta = KIND_META[event.kind];
                    const Icon = meta.icon;
                    return (
                      <div key={event.id} className="flex items-center gap-3 rounded-xl border border-white/[0.06] bg-black/25 px-4 py-3">
                        <Icon className="size-4 shrink-0 text-white/50" />
                        <div className="min-w-0 flex-1">
                          <p className="truncate text-sm font-medium text-white/85">{event.title}</p>
                          <p className="text-[11px] text-white/40">
                            {meta.label}
                            {event.detail ? ` · ${event.detail}` : ""}
                            {event.sample ? " · demo/sample" : ""} · {new Date(event.at).toLocaleString()}
                          </p>
                        </div>
                      </div>
                    );
                  })}
                  {summary.recentActivities.length === 0 ? (
                    <p className="text-sm text-white/50">No activity recorded yet.</p>
                  ) : null}
                </div>
              </section>

              {/* ── Weak areas (evidence only) ── */}
              <section className="rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-5">
                <div className="mb-3 flex items-center gap-2">
                  <Target className="size-5 text-white/56" />
                  <h3 className="text-lg font-semibold text-white">Weak topics</h3>
                </div>
                {summary.weakTopics.length > 0 ? (
                  <div className="grid gap-3 sm:grid-cols-2">
                    {summary.weakTopics.map((topic) => (
                      <div key={topic} className="rounded-xl border border-white/[0.07] bg-black/25 p-4">
                        <p className="text-sm font-semibold text-white">{topic}</p>
                        <p className="mt-1 text-xs leading-5 text-white/44">From a missed quiz question or saved feedback.</p>
                      </div>
                    ))}
                  </div>
                ) : (
                  <p className="text-sm text-white/50">
                    No weak topics yet — they appear here when you miss a quiz question.
                  </p>
                )}
              </section>
            </div>

            <aside className="space-y-5">
              {/* ── Revision queue ── */}
              <section className="rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-5">
                <h3 className="mb-3 text-lg font-semibold text-white">Revision queue</h3>
                {summary.revisionQueue.length > 0 ? (
                  <div className="space-y-2">
                    {summary.revisionQueue.map((topic) => (
                      <p key={topic} className="rounded-lg bg-white/[0.03] px-3 py-2 text-sm text-white/70">
                        {topic}
                      </p>
                    ))}
                  </div>
                ) : (
                  <p className="text-sm text-white/50">Nothing saved for revision yet.</p>
                )}
              </section>

              {/* ── Next actions ── */}
              <section className="rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-5">
                <div className="mb-4 flex items-center gap-2">
                  <BookOpen className="size-5 text-white/56" />
                  <h3 className="text-lg font-semibold text-white">Next actions</h3>
                </div>
                <div className="space-y-2">
                  {[
                    { label: "Take a quiz", href: "/library?tab=quizzes" },
                    { label: "Review your notes", href: "/library?tab=notes" },
                    { label: "Ask in Study Chat", href: "/study-chat" },
                  ].map((action) => (
                    <Link
                      key={action.href}
                      href={action.href}
                      className="dd-lift dd-press flex min-h-11 items-center justify-between rounded-xl border border-white/[0.08] bg-white/[0.03] px-3 text-sm font-semibold text-white/64 hover:text-white"
                    >
                      {action.label}
                      <span aria-hidden="true">→</span>
                    </Link>
                  ))}
                </div>
              </section>
            </aside>
          </div>
        </>
      )}
    </div>
  );
}