"use client";

import { useEffect, useState } from "react";
import Link from "next/link";
import { ChevronDown, Copy, Download, ExternalLink, FileText, MessageSquareText, RefreshCcw, Trash2, X } from "lucide-react";
import { deleteNote, listNotes, type SavedNote } from "@/lib/student-activity";
import { useStudentActivityVersion } from "@/hooks/useStudentActivity";
import { buildStudyIntentUrl } from "@/lib/study-intents";

// =============================================================================
// Real saved notes — every entry here was saved by the student (from a
// StudyChat answer, a notes-generation handoff, or the tuition demo). No
// placeholder rows: the empty state points at the actions that create notes.
// Extracted from the standalone /notes route so /library can compose it as a
// tab; the /notes route is now a thin wrapper around this view.
// =============================================================================

const SOURCE_LABEL: Record<SavedNote["source"], string> = {
  "study-chat": "StudyChat",
  "learn-anything": "Learn Anything",
  "tuition-demo": "Tuition demo",
};

export function NotesView() {
  const [notes, setNotes] = useState<SavedNote[]>([]);
  const [copiedId, setCopiedId] = useState<string | null>(null);
  const [subjectFilter, setSubjectFilter] = useState("");
  const [topicFilter, setTopicFilter] = useState("");
  const [sourceFilter, setSourceFilter] = useState("");
  const [openNote, setOpenNote] = useState<SavedNote | null>(null);
  const activityVersion = useStudentActivityVersion();

  useEffect(() => {
    // localStorage read on mount + whenever notes change (this tab or another).
    let cancelled = false;
    void Promise.resolve().then(() => {
      if (!cancelled) setNotes(listNotes());
    });
    return () => {
      cancelled = true;
    };
  }, [activityVersion]);

  function handleCopy(note: SavedNote) {
    void navigator.clipboard?.writeText(`${note.title}\n\n${note.content}`).then(() => {
      setCopiedId(note.id);
      setTimeout(() => setCopiedId(null), 1500);
    });
  }

  function handleDelete(id: string) {
    deleteNote(id);
    setNotes(listNotes());
    if (openNote?.id === id) setOpenNote(null);
  }

  function handleExport(note: SavedNote) {
    const blob = new Blob([`${note.title}\n\n${note.content}`], { type: "text/plain;charset=utf-8" });
    const url = URL.createObjectURL(blob);
    const anchor = document.createElement("a");
    anchor.href = url;
    anchor.download = `${note.title.replace(/[^a-z0-9]+/gi, "-").replace(/^-|-$/g, "") || "docdoe-note"}.txt`;
    anchor.click();
    URL.revokeObjectURL(url);
  }

  const subjects = Array.from(new Set(notes.map((note) => note.subject).filter((value): value is string => Boolean(value)))).sort();
  const topics = Array.from(new Set(notes.map((note) => note.topic).filter((value): value is string => Boolean(value)))).sort();
  const filteredNotes = notes.filter(
    (note) =>
      (!subjectFilter || note.subject === subjectFilter) &&
      (!topicFilter || note.topic === topicFilter) &&
      (!sourceFilter || note.source === sourceFilter),
  );

  return (
    <div className="text-white">
      <header className="mb-8">
        <h2 className="text-2xl font-semibold text-white sm:text-3xl">Your saved notes</h2>
        <p className="mt-2 max-w-2xl text-sm leading-6 text-white/52">
          Answers you saved from StudyChat and notes generated from your lessons. Stored on this device.
        </p>
      </header>

      {openNote ? (
        <article className="mb-6 rounded-2xl border border-white/[0.12] bg-[#0B0B0B] p-5 sm:p-6">
          <div className="flex items-start justify-between gap-4">
            <div>
              <p className="text-[10px] font-bold uppercase tracking-[0.14em] text-white/40">Open note</p>
              <h3 className="mt-2 text-xl font-semibold text-white">{openNote.title}</h3>
              <p className="mt-1 text-xs text-white/45">
                {[openNote.subject, openNote.topic, SOURCE_LABEL[openNote.source]].filter(Boolean).join(" · ")}
              </p>
            </div>
            <button type="button" onClick={() => setOpenNote(null)} aria-label="Close open note" className="rounded-lg p-2 text-white/45 hover:text-white">
              <X className="size-4" />
            </button>
          </div>
          <p className="mt-5 whitespace-pre-line text-sm leading-7 text-white/75">{openNote.content}</p>
        </article>
      ) : null}

      {notes.length > 0 ? (
        <div className="mb-6 grid gap-3 rounded-2xl border border-white/[0.08] bg-[#0B0B0B] p-4 sm:grid-cols-3">
          <label className="text-[11px] font-semibold text-white/55">
            Subject
            <select
              aria-label="Filter notes by subject"
              value={subjectFilter}
              onChange={(event) => setSubjectFilter(event.target.value)}
              className="mt-1.5 min-h-10 w-full rounded-lg border border-white/[0.1] bg-black px-3 text-sm text-white"
            >
              <option value="">All subjects</option>
              {subjects.map((subject) => <option key={subject} value={subject}>{subject}</option>)}
            </select>
          </label>
          <label className="text-[11px] font-semibold text-white/55">
            Topic
            <select
              aria-label="Filter notes by topic"
              value={topicFilter}
              onChange={(event) => setTopicFilter(event.target.value)}
              className="mt-1.5 min-h-10 w-full rounded-lg border border-white/[0.1] bg-black px-3 text-sm text-white"
            >
              <option value="">All topics</option>
              {topics.map((topic) => <option key={topic} value={topic}>{topic}</option>)}
            </select>
          </label>
          <label className="text-[11px] font-semibold text-white/55">
            Source
            <select
              aria-label="Filter notes by source"
              value={sourceFilter}
              onChange={(event) => setSourceFilter(event.target.value)}
              className="mt-1.5 min-h-10 w-full rounded-lg border border-white/[0.1] bg-black px-3 text-sm text-white"
            >
              <option value="">All sources</option>
              {Object.entries(SOURCE_LABEL).map(([value, label]) => <option key={value} value={value}>{label}</option>)}
            </select>
          </label>
        </div>
      ) : null}

      {notes.length === 0 ? (
        <div className="rounded-2xl border border-dashed border-white/[0.12] bg-black/30 p-10 text-center">
          <FileText className="mx-auto mb-4 size-8 text-white/40" />
          <p className="text-base font-semibold text-white">No notes saved yet</p>
          <p className="mx-auto mt-2 max-w-sm text-sm leading-6 text-white/52">
            Ask a doubt in Study Chat and press <span className="text-white/80">&quot;Save as note&quot;</span> on the
            answer, or use the notes generator from any lesson.
          </p>
          <Link
            href={buildStudyIntentUrl({ intent: "generate_notes", prompt: "Make exam notes on a topic I choose" })}
            className="mt-6 inline-flex rounded-xl bg-white px-6 py-2.5 text-sm font-semibold text-black"
          >
            Make your first note
          </Link>
        </div>
      ) : (
        <div className="dd-stagger space-y-3">
          {filteredNotes.map((note) => (
            <details key={note.id} className="group rounded-2xl border border-white/[0.08] bg-[#0B0B0B]">
              <summary className="flex cursor-pointer list-none items-center gap-3 px-5 py-4 [&::-webkit-details-marker]:hidden">
                <FileText className="size-4 shrink-0 text-white/45" />
                <span className="min-w-0 flex-1 truncate text-sm font-semibold text-white">{note.title}</span>
                <span className="hidden shrink-0 text-[11px] text-white/40 sm:inline">
                  {SOURCE_LABEL[note.source]}
                  {note.provenance === "starter" ? " · starter/sample" : ""}
                  {` · ${new Date(note.at).toLocaleDateString()}`}
                </span>
                <ChevronDown className="size-4 shrink-0 text-white/40 transition-transform group-open:rotate-180" />
              </summary>
              <div className="border-t border-white/[0.06] px-5 py-4">
                <p className="whitespace-pre-line text-sm leading-7 text-white/70">{note.content}</p>
                <div className="mt-4 flex flex-wrap items-center gap-2">
                  <button
                    type="button"
                    onClick={() => setOpenNote(note)}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg bg-white px-3 text-xs font-semibold text-black"
                  >
                    <ExternalLink className="size-3.5" /> Open
                  </button>
                  <button
                    type="button"
                    onClick={() => handleCopy(note)}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    <Copy className="size-3.5" />
                    {copiedId === note.id ? "Copied ✓" : "Copy"}
                  </button>
                  <button
                    type="button"
                    onClick={() => handleExport(note)}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    <Download className="size-3.5" /> Export .txt
                  </button>
                  <Link
                    href={buildStudyIntentUrl({
                      intent: "generate_notes",
                      prompt: `Regenerate clearer exam-ready notes for:\n${note.title}\n${note.content.slice(0, 400)}`,
                      run: true,
                    })}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    <RefreshCcw className="size-3.5" />
                    Regenerate
                  </Link>
                  <Link
                    href={buildStudyIntentUrl({
                      intent: "teach_topic",
                      prompt: `Use this saved note as context and help me study it:\n${note.title}\n${note.content.slice(0, 400)}`,
                      run: false,
                    })}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    <MessageSquareText className="size-3.5" /> Send to StudyChat
                  </Link>
                  <Link
                    href={buildStudyIntentUrl({
                      intent: "generate_quiz",
                      prompt: `Make a 5-question practice quiz from this note:\n${note.title}\n${note.content.slice(0, 400)}`,
                      run: true,
                    })}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    Turn into quiz
                  </Link>
                  <Link
                    href={buildStudyIntentUrl({
                      intent: "generate_flashcards",
                      prompt: `Turn this note into flashcards:\n${note.title}\n${note.content.slice(0, 400)}`,
                      run: true,
                    })}
                    className="inline-flex min-h-9 items-center gap-1.5 rounded-lg border border-white/[0.1] bg-white/[0.03] px-3 text-xs font-semibold text-white/70 transition hover:text-white"
                  >
                    Turn into flashcards
                  </Link>
                  <button
                    type="button"
                    onClick={() => handleDelete(note.id)}
                    className="ml-auto inline-flex min-h-9 items-center gap-1.5 rounded-lg px-3 text-xs font-semibold text-white/40 transition hover:text-white/70"
                  >
                    <Trash2 className="size-3.5" />
                    Delete
                  </button>
                </div>
              </div>
            </details>
          ))}
          {filteredNotes.length === 0 ? (
            <div className="rounded-2xl border border-dashed border-white/[0.12] p-8 text-center text-sm text-white/52">
              No saved notes match these filters.
            </div>
          ) : null}
        </div>
      )}
    </div>
  );
}