"use client";

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

import { ApiError, generateDeck } from "@/lib/client-api";
import { activityTypes, materialiseActivities } from "@/lib/deck-ops";
import { createFolder as makeFolder, folderName, listFolders } from "@/lib/folders";
import { UNORGANIZED_ID, type Deck } from "@/lib/schemas";
import { appendActivities, deleteDeck, downloadDeck, renameDeck, upsertDeck } from "@/lib/storage";
import { cn, formatDate, truncate } from "@/lib/utils";
import { DownloadIcon, FolderIcon, PlayIcon, RefreshIcon } 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, onMove }: { deck: Deck; onMove?: (folderId: string | undefined) => void }) {
  const folders = listFolders();
  const [busy, setBusy] = useState<Busy>(null);
  const [menuOpen, setMenuOpen] = useState(false);
  const [renaming, setRenaming] = useState(false);
  const [title, setTitle] = useState(deck.title);
  const [confirmDelete, setConfirmDelete] = useState(false);
  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 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("This deck has no stored source notes, so it can't be extended.");
      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(`Added ${generated.activities.length} activities`);
      setMenuOpen(false);
      window.setTimeout(() => setNotice(null), 3000);
    } catch (addError) {
      setError(addError instanceof ApiError ? addError.message : "Could not add more activities.");
    } finally {
      setBusy(null);
    }
  };

  const regenerate = async () => {
    if (!hasSource) {
      setError("This deck has no stored source notes, so it can't be regenerated.");
      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("Deck regenerated");
      setMenuOpen(false);
      window.setTimeout(() => setNotice(null), 3000);
    } catch (regenerateError) {
      setError(regenerateError instanceof ApiError ? regenerateError.message : "Could not regenerate the deck.");
    } 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)]";

  return (
    <li className="card card-hover group relative flex flex-col p-5">
      {/* header ------------------------------------------------------- */}
      <div className="flex items-start justify-between gap-3">
        <div className="min-w-0 flex-1">
          {renaming ? (
            <div className="flex items-center gap-2">
              <label className="sr-only" htmlFor={`rename-${deck.id}`}>
                Deck title
              </label>
              <input
                id={`rename-${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}>
                Save
              </Button>
            </div>
          ) : (
            <h3
              className="line-clamp-2 text-[15px] font-semibold leading-snug tracking-[-0.01em] text-[var(--text)]"
              title={deck.title}
            >
              {truncate(deck.title, 90)}
            </h3>
          )}
          <p className="mt-1 text-[12.5px] text-[var(--text-subtle)]">
            {formatDate(deck.updatedAt)}
            <span aria-hidden> · </span>
            {deck.activities.length} activities
            {deck.attempts > 0 ? (
              <>
                <span aria-hidden> · </span>
                {deck.attempts} {deck.attempts === 1 ? "run" : "runs"}
              </>
            ) : null}
          </p>
        </div>

        <button
          type="button"
          aria-label="Deck actions"
          aria-expanded={menuOpen}
          onClick={() => setMenuOpen((value) => !value)}
          className={cn(
            "grid size-8 shrink-0 place-items-center rounded-full text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]",
            menuOpen && "bg-[var(--hover)] text-[var(--text)]",
          )}
        >
          ⋯
        </button>
      </div>

      {/* tags --------------------------------------------------------- */}
      <div className="mt-3 flex flex-wrap items-center gap-1.5">
        {deck.subject ? <Tag>{deck.subject}</Tag> : null}
        <Tag>
          <span className={difficultyClass(deck.difficulty)}>{deck.difficulty}</span>
        </Tag>
        {deck.folderId ? (
          <Tag>
            <FolderIcon className="size-3.5 opacity-70" />
            {folderName(deck.folderId)}
          </Tag>
        ) : null}
        {deck.bestScore !== undefined ? (
          <Tag>
            Best <span className="text-emerald-700 dark:text-emerald-300">{deck.bestScore}%</span>
          </Tag>
        ) : null}
      </div>

      {/* summary ------------------------------------------------------ */}
      {deck.summary ? (
        <p className="mt-3 line-clamp-2 text-[13.5px] leading-relaxed text-[var(--text-muted)]">
          {truncate(deck.summary, 160)}
        </p>
      ) : null}

      {/* status ------------------------------------------------------- */}
      {busy ? (
        <div className="mt-4 space-y-2">
          <ProgressBar value={1} max={2} label={busy === "more" ? "Adding activities" : "Regenerating deck"} />
          <p className="text-[12.5px] font-medium text-[var(--text-muted)]">
            {busy === "more" ? "Adding new activities…" : "Regenerating the whole deck…"}
          </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-5">
        <Link href={`/deck/${deck.id}`} className="btn-primary h-10 w-full px-4 text-sm">
          <PlayIcon className="size-4" />
          Study
        </Link>
      </div>

      {/* actions panel ------------------------------------------------ */}
      {menuOpen ? (
        <div
          data-testid="deck-actions"
          className="animate-rise 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>
            Rename
          </button>
          <button type="button" className={menuRow} onClick={() => downloadDeck(deck)} disabled={Boolean(busy)}>
            <DownloadIcon className="size-4 text-[var(--text-subtle)]" />
            Export JSON
          </button>
          <button
            type="button"
            className={menuRow}
            onClick={() => void regenerate()}
            disabled={Boolean(busy) || !hasSource}
          >
            <RefreshIcon className="size-4 text-[var(--text-subtle)]" />
            Regenerate deck
          </button>

          {confirmDelete ? (
            <div className="flex items-center gap-2 px-3 py-2">
              <Button size="sm" variant="danger" onClick={() => deleteDeck(deck.id)}>
                Really delete
              </Button>
              <Button size="sm" variant="ghost" onClick={() => setConfirmDelete(false)}>
                Cancel
              </Button>
            </div>
          ) : (
            <button type="button" className={cn(menuRow, "text-rose-600 dark:text-rose-300")} onClick={() => setConfirmDelete(true)}>
              <span aria-hidden className="w-4 text-center">
                ⌫
              </span>
              Delete deck
            </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)]">
              Folder
            </p>
            <div className="flex flex-wrap items-center gap-1.5">
              {[{ id: UNORGANIZED_ID, name: "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
                        ? "bg-[var(--text)] text-white dark:bg-white dark:text-[#0d0d0d]"
                        : "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)]"
                >
                  + New folder
                </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="New folder name"
                    placeholder="Folder name"
                    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);
                      }
                    }}
                  >
                    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)]">
              Add more activities
            </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
                      ? "bg-[var(--text)] text-white dark:bg-white dark:text-[#0d0d0d]"
                      : "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"}>
                Generate
              </Button>
            </div>
            {!hasSource ? (
              <p className="px-1 pt-2 text-[11px] text-amber-700 dark:text-amber-300">
                No stored source text for this deck (imported decks don&apos;t carry it).
              </p>
            ) : null}
          </div>
        </div>
      ) : null}

    </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 }: { children: React.ReactNode }) {
  return (
    <span className="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)]">
      {children}
    </span>
  );
}