"use client";

import Link from "next/link";
import { motion } from "framer-motion";
import { useState } from "react";

import { ApiError, generateDeck } from "@/lib/client-api";
import { activityTypes, materialiseActivities } from "@/lib/deck-ops";
import { createFolder as makeFolder, listFolders } from "@/lib/folders";
import { haptic } from "@/lib/haptics";
import { useI18n } from "@/lib/i18n";
import { springGentle } from "@/lib/motion";
import { UNORGANIZED_ID, type Deck, type Folder } from "@/lib/schemas";
import { shareDeck } from "@/lib/share";
import { appendActivities, deleteDeck, deleteNotesText, downloadDeck, renameDeck, upsertDeck } from "@/lib/storage";
import { showToast } from "@/lib/toast";
import { useBackClose } from "@/lib/use-back-close";
import { useIsPhone } from "@/lib/use-phone";
import { cn, formatDate, truncate } from "@/lib/utils";
import { ChatIcon, ChevronDownIcon, DownloadIcon, EllipsisIcon, FolderIcon, PlayIcon, RefreshIcon, ShareIcon, TeacherIcon, XCircleIcon } from "@/components/icons";
import { Button, ProgressBar } from "@/components/ui";

type Busy = null | "more" | "regenerate";

const ADD_OPTIONS = [3, 5, 8];

/**
 * One deck in the dashboard grid: title, muted metadata, tags, summary and a
 * prominent Study CTA with quiet secondary actions.
 */
export function DeckCard({
  deck,
  folders: foldersProp,
  onMove,
  index = 0,
}: {
  deck: Deck;
  folders?: Folder[];
  onMove?: (folderId: string | undefined) => void;
  /** Position in the list — used for the capped first-load stagger. */
  index?: number;
}) {
  const { t, plural } = useI18n();
  const isPhone = useIsPhone();
  const folders = foldersProp ?? listFolders();
  const [busy, setBusy] = useState<Busy>(null);
  const [menuOpen, setMenuOpen] = useState(false);
  const [renaming, setRenaming] = useState(false);
  const [title, setTitle] = useState(deck.title);
  const [error, setError] = useState<string | null>(null);
  const [notice, setNotice] = useState<string | null>(null);
  const [addCount, setAddCount] = useState(5);
  const [newFolder, setNewFolder] = useState<string | null>(null);
  const [expanded, setExpanded] = useState(false);

  /* System Back closes the actions panel first. */
  useBackClose(isPhone && menuOpen, () => setMenuOpen(false));

  const hasSource = deck.sourceText.trim().length > 20;

  const saveTitle = () => {
    const trimmed = title.trim();
    if (trimmed && trimmed !== deck.title) renameDeck(deck.id, trimmed);
    else setTitle(deck.title);
    setRenaming(false);
    setMenuOpen(false);
  };

  const addMore = async () => {
    if (!hasSource) {
      setError(t("deck.noSourceExtend"));
      return;
    }
    setBusy("more");
    setError(null);
    try {
      const { deck: generated } = await generateDeck({
        text: deck.sourceText,
        difficulty: deck.difficulty,
        language: deck.language,
        count: addCount,
        mode: "more",
        existing: { title: deck.title, types: activityTypes(deck.activities), count: deck.activities.length },
      });
      appendActivities(deck.id, materialiseActivities(generated.activities, deck.difficulty));
      setNotice(plural(generated.activities.length, "deck.added"));
      setMenuOpen(false);
      window.setTimeout(() => setNotice(null), 3000);
    } catch (addError) {
      setError(addError instanceof ApiError ? addError.message : t("deck.couldNotAdd"));
    } finally {
      setBusy(null);
    }
  };

  const regenerate = async () => {
    if (!hasSource) {
      setError(t("deck.noSourceRegenerate"));
      return;
    }
    setBusy("regenerate");
    setError(null);
    try {
      const { deck: generated } = await generateDeck({
        text: deck.sourceText,
        difficulty: deck.difficulty,
        language: deck.language,
        count: Math.max(8, deck.activities.length),
      });
      upsertDeck({
        ...deck,
        title: generated.title || deck.title,
        subject: generated.subject ?? deck.subject,
        summary: generated.summary ?? deck.summary,
        language: generated.language ?? deck.language,
        activities: materialiseActivities(generated.activities, deck.difficulty),
        attempts: 0,
        bestScore: undefined,
        updatedAt: Date.now(),
      });
      setNotice(t("deck.regenerated"));
      setMenuOpen(false);
      window.setTimeout(() => setNotice(null), 3000);
    } catch (regenerateError) {
      setError(regenerateError instanceof ApiError ? regenerateError.message : t("deck.couldNotRegenerate"));
    } finally {
      setBusy(null);
    }
  };

  const menuRow =
    "flex w-full items-center gap-2.5 rounded-xl px-3 py-2 text-left text-[13px] font-medium text-[var(--text)] transition hover:bg-[var(--hover)]";

  /* Phones: cards fade up in a short capped stagger, glide when the grid
     reflows (folder moves, filtering) and shrink away on delete. */
  const cardVariants = {
    hidden: { opacity: 0, y: 12 },
    show: { opacity: 1, y: 0, transition: { ...springGentle, delay: Math.min(index, 8) * 0.04 } },
    exit: { opacity: 0, scale: 0.97, transition: { duration: 0.16 } },
  };

  return (
    <motion.li
      layout={isPhone}
      variants={isPhone ? cardVariants : undefined}
      initial={isPhone ? "hidden" : false}
      animate={isPhone ? "show" : undefined}
      exit={isPhone ? "exit" : undefined}
      className="card card-hover group relative flex flex-col p-4 sm:p-5"
    >
      {/* Phones: the whole card is tappable too; interactive children sit above it. */}
      <Link
        href={`/deck/${deck.id}`}
        aria-hidden="true"
        tabIndex={-1}
        className="absolute inset-0 hidden rounded-[1.5rem] max-sm:block lg:block"
      />

      {/* header ------------------------------------------------------- */}
      <div className="flex items-start justify-between gap-3">
        <div className="min-w-0 flex-1">
          {renaming ? (
            <div className="relative z-10 flex items-center gap-2">
              <label className="sr-only" htmlFor={`rename-${deck.id}`}>
                {t("deck.titleLabel")}
              </label>
              <input
                id={`rename-${deck.id}`}
                value={title}
                autoFocus
                onChange={(event) => setTitle(event.target.value)}
                onKeyDown={(event) => {
                  event.stopPropagation();
                  if (event.key === "Enter") saveTitle();
                  if (event.key === "Escape") {
                    setTitle(deck.title);
                    setRenaming(false);
                  }
                }}
                className="min-w-0 flex-1 rounded-lg border border-[var(--hairline)] bg-[var(--surface-strong)] px-2.5 py-1.5 text-[15px] font-semibold text-[var(--text)] outline-none focus:border-accent-400"
              />
              <Button size="sm" onClick={saveTitle}>
                {t("common.save")}
              </Button>
            </div>
          ) : (
            <h2
              className="line-clamp-2 text-[15px] font-semibold leading-snug tracking-[-0.01em] text-[var(--text)]"
              title={deck.title}
            >
              {truncate(deck.title, 90)}
            </h2>
          )}
          {/* Phones: one compact meta line. */}
          <p className="mt-1 text-[12.5px] text-[var(--text-subtle)] sm:hidden">
            {plural(deck.activities.length, "deck.activities")}
            <span aria-hidden> · </span>
            <span className={difficultyClass(deck.difficulty)}>
              {deck.difficulty === "easy"
                ? t("upload.easy")
                : deck.difficulty === "hard"
                  ? t("upload.hard")
                  : t("upload.medium")}
            </span>
            {deck.bestScore !== undefined ? (
              <>
                <span aria-hidden> · </span>
                <span className="text-emerald-700 dark:text-emerald-300">
                  {t("deck.bestLabel")} {deck.bestScore}%
                </span>
              </>
            ) : null}
          </p>
          <p className="mt-1 hidden text-[12.5px] text-[var(--text-subtle)] sm:block lg:mt-3">
            {/* Phones keep the original date · activities · runs line. */}
            <span className="lg:hidden">
              {formatDate(deck.updatedAt)}
              <span aria-hidden> · </span>
            </span>
            {plural(deck.activities.length, "deck.activities")}
            <span className="lg:hidden">
              {deck.attempts > 0 ? (
                <>
                  <span aria-hidden> · </span>
                  {plural(deck.attempts, "deck.runs")}
                </>
              ) : null}
            </span>
            {/* Desktop always shows the same two fields. */}
            <span className="hidden lg:inline-flex items-center">
              {deck.attempts > 0 ? (
                <>
                  <span aria-hidden> · </span>
                  {plural(deck.attempts, "deck.runs")}
                </>
              ) : (
                <span className="tint-sky ml-1 rounded-full px-2 py-0.5 text-[10.5px] font-semibold">
                  {t("deck.new")}
                </span>
              )}
            </span>
          </p>
        </div>

        <button
          type="button"
          aria-label={t("deck.actions")}
          aria-expanded={menuOpen}
          onClick={() => {
            haptic("tap");
            setMenuOpen((value) => !value);
          }}
          className={cn(
            "relative z-10 grid size-8 shrink-0 place-items-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)] lg:-mt-1.5",
            menuOpen && "bg-[var(--hover)] text-[var(--text)]",
          )}
        >
          <span aria-hidden className="lg:hidden">⋯</span>
          <EllipsisIcon className="hidden size-4 lg:block" />
        </button>
      </div>

      {/* tags --------------------------------------------------------- */}
      <div className="mt-3 hidden flex-wrap items-center gap-1.5 sm:flex">
        {deck.subject ? <Tag>{deck.subject}</Tag> : null}
        <Tag>
          <span className={difficultyClass(deck.difficulty)}>
            {deck.difficulty === "easy"
              ? t("upload.easy")
              : deck.difficulty === "hard"
                ? t("upload.hard")
                : t("upload.medium")}
          </span>
        </Tag>
        {deck.folderId ? (
          <Tag>
            <FolderIcon className="size-3.5 opacity-70" />
            {folders.find((entry) => entry.id === deck.folderId)?.name ?? t("common.unorganized")}
          </Tag>
        ) : null}
        {deck.bestScore !== undefined ? (
          <>
            <Tag className="lg:hidden">
              {t("deck.bestLabel")}{" "}
              <span className="text-emerald-700 dark:text-emerald-300">{deck.bestScore}%</span>
            </Tag>
            <span className="hidden text-[12px] font-medium tabular-nums text-[var(--text-muted)] lg:ml-1 lg:inline">
              {t("deck.bestLabel")} {deck.bestScore}%
            </span>
          </>
        ) : null}
      </div>

      {/* summary ------------------------------------------------------ */}
      {deck.summary ? (
        <>
          <button
            type="button"
            aria-expanded={expanded}
            onClick={() => setExpanded((value) => !value)}
            className="relative z-10 mt-2 flex w-full items-start gap-1 text-left text-[13px] leading-relaxed text-[var(--text-muted)] sm:hidden"
          >
            <span className={cn("min-w-0 flex-1", !expanded && "line-clamp-1")}>{deck.summary}</span>
            <ChevronDownIcon
              className={cn("mt-0.5 size-4 shrink-0 text-[var(--text-subtle)] transition-transform", expanded && "rotate-180")}
            />
          </button>
          <p className="mt-3 hidden line-clamp-2 text-[13.5px] leading-relaxed text-[var(--text-muted)] sm:block">
            {truncate(deck.summary, 160)}
          </p>
        </>
      ) : null}

      {/* status ------------------------------------------------------- */}
      {busy ? (
        <div className="mt-4 space-y-2">
          <ProgressBar
            value={1}
            max={2}
            label={busy === "more" ? t("deck.addingActivities") : t("deck.regeneratingDeck")}
          />
          <p className="text-[12.5px] font-medium text-[var(--text-muted)]">
            {busy === "more" ? t("deck.addingNew") : t("deck.regeneratingWhole")}
          </p>
        </div>
      ) : null}

      {notice ? (
        <p className="mt-3 rounded-xl bg-emerald-500/10 px-3 py-2 text-[12.5px] font-medium text-emerald-700 dark:text-emerald-300">
          {notice}
        </p>
      ) : null}
      {error ? (
        <p className="mt-3 rounded-xl bg-rose-500/10 px-3 py-2 text-[12.5px] font-medium text-rose-700 dark:text-rose-300">
          {error}
        </p>
      ) : null}

      {/* single action ------------------------------------------------ */}
      <div className="mt-4 flex justify-end lg:mt-4">
        <Link
          href={`/deck/${deck.id}`}
          className="btn-primary touch-target relative z-10 h-9 gap-1.5 px-3.5 text-[13px] sm:hidden"
        >
          <PlayIcon className="size-4" />
          {t("deck.study")}
        </Link>
        <Link
          href={`/deck/${deck.id}`}
          className="btn-primary hidden h-10 w-full px-4 text-sm sm:flex lg:hidden"
        >
          <PlayIcon className="size-4" />
          {t("deck.study")}
        </Link>
        <div className="relative z-10 hidden lg:flex lg:justify-end">
          <Link href={`/deck/${deck.id}`} className="btn-primary h-9 px-4 text-[13px]">
            <PlayIcon className="size-4" />
            {t("deck.study")}
          </Link>
        </div>
      </div>

      {/* actions panel ------------------------------------------------ */}
      {menuOpen ? (
        <div
          data-testid="deck-actions"
          className="animate-rise relative z-10 mt-3 space-y-1 border-t border-[var(--hairline)] pt-3"
        >
          <button type="button" className={menuRow} onClick={() => setRenaming(true)} disabled={Boolean(busy)}>
            <span aria-hidden className="w-4 text-center text-[var(--text-subtle)]">
              ✎
            </span>
            {t("common.rename")}
          </button>
          <button type="button" className={menuRow} onClick={() => downloadDeck(deck)} disabled={Boolean(busy)}>
            <DownloadIcon className="size-4 text-[var(--text-subtle)]" />
            {t("deck.export")}
          </button>
          <button
            type="button"
            className={menuRow}
            onClick={() => {
              setMenuOpen(false);
              void shareDeck(deck);
            }}
            disabled={Boolean(busy)}
          >
            <ShareIcon className="size-4 text-[var(--text-subtle)]" />
            {t("deck.share")}
          </button>
          <Link
            href={`/chat?deck=${deck.id}`}
            className={menuRow}
          >
            <ChatIcon className="size-4 text-[var(--text-subtle)]" />
            {t("chat.askAboutDeck")}
          </Link>
          <Link
            href={`/teach?deck=${deck.id}`}
            className={menuRow}
          >
            <TeacherIcon className="size-4 text-[var(--text-subtle)]" />
            {t("teach.nav")}
          </Link>
          <button
            type="button"
            className={menuRow}
            onClick={() => void regenerate()}
            disabled={Boolean(busy) || !hasSource}
          >
            <RefreshIcon className="size-4 text-[var(--text-subtle)]" />
            {t("deck.regenerate")}
          </button>

          {hasSource ? (
            <button
              type="button"
              className={menuRow}
              onClick={() => {
                setMenuOpen(false);
                deleteNotesText(deck.id);
                showToast({ message: t("chat.notesDeleted") });
              }}
            >
              <XCircleIcon className="size-4 text-[var(--text-subtle)]" />
              {t("chat.deleteNotes")}
            </button>
          ) : null}

          {/* Deleting is reversible: no confirm, just an Undo toast. */}
          <button
            type="button"
            className={cn(menuRow, "text-rose-600 dark:text-rose-300")}
            onClick={() => {
              setMenuOpen(false);
              deleteDeck(deck.id);
              showToast({
                message: t("toast.deckDeleted"),
                actionLabel: t("toast.undo"),
                onAction: () => upsertDeck(deck),
              });
            }}
          >
            <span aria-hidden className="w-4 text-center">
              ⌫
            </span>
            {t("deck.delete")}
          </button>

          {/* folder ---------------------------------------------------- */}
          <div className="mt-2 rounded-xl bg-[var(--surface-sunken)] p-2.5">
            <p className="px-1 pb-2 text-[11px] font-semibold uppercase tracking-wide text-[var(--text-subtle)]">
              {t("common.folder")}
            </p>
            <div className="flex flex-wrap items-center gap-1.5">
              {[{ id: UNORGANIZED_ID, name: t("common.unorganized") }, ...folders].map((folder) => {
                const current = (deck.folderId ?? UNORGANIZED_ID) === folder.id;
                return (
                  <button
                    key={folder.id}
                    type="button"
                    aria-pressed={current}
                    onClick={() => {
                      onMove?.(folder.id === UNORGANIZED_ID ? undefined : folder.id);
                      setMenuOpen(false);
                    }}
                    className={cn(
                      "rounded-full px-2.5 py-1 text-[12px] font-medium transition",
                      current
                        ? "grad-ice text-[#06111f]"
                        : "text-[var(--text-muted)] hover:bg-[var(--hover)] hover:text-[var(--text)]",
                    )}
                  >
                    {folder.name}
                  </button>
                );
              })}
              {newFolder === null ? (
                <button
                  type="button"
                  onClick={() => setNewFolder("")}
                  className="rounded-full px-2.5 py-1 text-[12px] font-medium text-[var(--text-subtle)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
                >
                  {t("deck.newFolder")}
                </button>
              ) : (
                <span className="inline-flex items-center gap-1 rounded-full border border-[var(--hairline)] bg-[var(--surface-strong)] py-0.5 pl-2.5 pr-1">
                  <input
                    autoFocus
                    value={newFolder}
                    onChange={(event) => setNewFolder(event.target.value)}
                    onKeyDown={(event) => {
                      event.stopPropagation();
                      if (event.key === "Escape") setNewFolder(null);
                      if (event.key === "Enter" && newFolder.trim()) {
                        const created = makeFolder(newFolder);
                        if ("folder" in created) {
                          onMove?.(created.folder.id);
                          setNewFolder(null);
                          setMenuOpen(false);
                        } else {
                          setError(created.error);
                        }
                      }
                    }}
                    aria-label={t("common.newFolderName")}
                    placeholder={t("common.folderName")}
                    maxLength={60}
                    className="w-24 bg-transparent text-[12px] text-[var(--text)] outline-none placeholder:text-[var(--text-subtle)]"
                  />
                  <button
                    type="button"
                    className="btn-primary h-6 px-2.5 text-[11px]"
                    onClick={() => {
                      const created = makeFolder(newFolder);
                      if ("folder" in created) {
                        onMove?.(created.folder.id);
                        setNewFolder(null);
                        setMenuOpen(false);
                      } else {
                        setError(created.error);
                      }
                    }}
                  >
                    {t("common.add")}
                  </button>
                </span>
              )}
            </div>
          </div>

          {/* add more -------------------------------------------------- */}
          <div className="mt-1 rounded-xl bg-[var(--surface-sunken)] p-2.5">
            <p className="px-1 pb-2 text-[11px] font-semibold uppercase tracking-wide text-[var(--text-subtle)]">
              {t("deck.addMore")}
            </p>
            <div className="flex flex-wrap items-center gap-1.5">
              {ADD_OPTIONS.map((option) => (
                <button
                  key={option}
                  type="button"
                  onClick={() => setAddCount(option)}
                  aria-pressed={addCount === option}
                  className={cn(
                    "min-w-9 rounded-full px-2.5 py-1 text-[12px] font-medium transition",
                    addCount === option
                      ? "grad-ice text-[#06111f]"
                      : "text-[var(--text-muted)] hover:bg-[var(--hover)] hover:text-[var(--text)]",
                  )}
                >
                  +{option}
                </button>
              ))}
              <Button size="sm" onClick={() => void addMore()} disabled={Boolean(busy) || !hasSource} loading={busy === "more"}>
                {t("deck.generate")}
              </Button>
            </div>
            {!hasSource ? (
              <p className="px-1 pt-2 text-[11px] text-amber-700 dark:text-amber-300">
                {t("deck.noSource")}
              </p>
            ) : null}
          </div>
        </div>
      ) : null}

    </motion.li>
  );
}

function difficultyClass(difficulty: Deck["difficulty"]): string {
  if (difficulty === "easy") return "diff-easy";
  if (difficulty === "hard") return "diff-hard";
  return "diff-medium";
}

/** Neutral pill; colour is only ever used on the text inside it. */
function Tag({ children, className }: { children: React.ReactNode; className?: string }) {
  return (
    <span
      className={cn(
        "inline-flex items-center gap-1.5 rounded-full bg-[var(--surface-sunken)] px-2.5 py-1 text-[12px] font-medium leading-none text-[var(--text-muted)]",
        className,
      )}
    >
      {children}
    </span>
  );
}