mtgc/src/views/DeckView.tsx

import { open, save } from "@tauri-apps/plugin-dialog";
import { useEffect, useMemo, useRef, useState, useCallback } from "react";
import {
  api,
  CardRef,
  COLORS,
  Deck,
  DeckEntry,
  DeckImportResult,
  legalStatusFor,
  libraryKey,
  Partner,
  PreviewContext,
} from "../api";
import {
  CardSearchBox,
  CardThumb,
  CardTile,
  ColorDistributionBar,
  ColorPips,
  ConfirmDialog,
  GroupBySelect,
  GroupMode,
  IconButton,
  Icons,
  InfoDialog,
  ManaCurve,
  PromptDialog,
  QtyStepper,
  SampleHandModal,
  StatTile,
  TileColumnsControl,
  ViewToggle,
  groupCards,
  useClickPreview,
  useHoverPreview,
  usePersistedState,
  useTileColumns,
  useViewMode,
} from "../components";
import { SuggestionsModal } from "../SuggestionsModal";
import { useBackButton } from "../backButton";

/** Whether a CSS media query currently matches, kept live across resizes. */
function useMediaQuery(query: string) {
  const [matches, setMatches] = useState(() => window.matchMedia(query).matches);
  useEffect(() => {
    const mql = window.matchMedia(query);
    const onChange = () => setMatches(mql.matches);
    onChange();
    mql.addEventListener("change", onChange);
    return () => mql.removeEventListener("change", onChange);
  }, [query]);
  return matches;
}

/** Tooltip/label + icon for the per-card mainboard/maybeboard toggle. */
function boardToggleProps(e: DeckEntry) {
  return e.is_maybeboard
    ? { icon: Icons.arrowLeftCircle, label: "Move to deck" }
    : { icon: Icons.helpCircle, label: "Move to maybeboard" };
}

type DeckDialog =
  | { kind: "delete"; deck: Deck }
  | { kind: "rename"; deck: Deck }
  | { kind: "duplicate"; deck: Deck }
  | { kind: "import-name"; suggestedName: string; path: string }
  | { kind: "import-result"; result: DeckImportResult }
  | null;

function friendlyDeckError(err: unknown): string {
  const msg = String(err);
  return msg.includes("UNIQUE constraint failed") ? "A deck with that name already exists." : msg;
}

interface DeckStats {
  totalCards: number;
  uniqueCards: number;
  landCount: number;
  avgManaValue: number;
  curve: {
    label: string;
    count: number;
    colorCounts: [number, number, number, number, number];
    colorlessCount: number;
  }[];
  colorCounts: [number, number, number, number, number];
  colorlessCount: number;
  manaProduction: [number, number, number, number, number];
  colorlessProduction: number;
  manaConsumption: [number, number, number, number, number];
  colorlessConsumption: number;
}

/**
 * Deck composition stats, excluding the commander (shown separately in its
 * own hero display) and the maybeboard (cards under consideration, not
 * actually part of the deck) — matches the usual "99 + commander" framing
 * even for non-Commander decks, where it's just "everything but those".
 */
function computeDeckStats(contents: DeckEntry[]): DeckStats {
  const cards = contents.filter((e) => !e.is_commander && !e.is_maybeboard);
  const totalCards = cards.reduce((sum, e) => sum + e.quantity, 0);
  const lands = cards.filter((e) => e.type_line.includes("Land"));
  const nonlands = cards.filter((e) => !e.type_line.includes("Land"));
  const landCount = lands.reduce((sum, e) => sum + e.quantity, 0);
  const nonlandCount = nonlands.reduce((sum, e) => sum + e.quantity, 0);
  const avgManaValue = nonlandCount
    ? nonlands.reduce((sum, e) => sum + e.mana_value * e.quantity, 0) / nonlandCount
    : 0;

  const bucketLabels = ["0", "1", "2", "3", "4", "5", "6+"];
  const curveBuckets = new Map(
    bucketLabels.map((l) => [
      l,
      { count: 0, colorCounts: [0, 0, 0, 0, 0] as [number, number, number, number, number], colorlessCount: 0 },
    ]),
  );
  for (const e of nonlands) {
    const label = e.mana_value >= 6 ? "6+" : String(Math.floor(e.mana_value));
    const bucket = curveBuckets.get(label)!;
    bucket.count += e.quantity;
    if (e.color_identity === 0) {
      bucket.colorlessCount += e.quantity;
    } else {
      COLORS.forEach((c, i) => {
        if (e.color_identity & c.bit) bucket.colorCounts[i] += e.quantity;
      });
    }
  }
  const curve = bucketLabels.map((label) => ({ label, ...curveBuckets.get(label)! }));

  const colorCounts: [number, number, number, number, number] = [0, 0, 0, 0, 0];
  let colorlessCount = 0;
  for (const e of cards) {
    if (e.color_identity === 0) {
      colorlessCount += e.quantity;
    } else {
      COLORS.forEach((c, i) => {
        if (e.color_identity & c.bit) colorCounts[i] += e.quantity;
      });
    }
  }

  const manaProduction: [number, number, number, number, number] = [0, 0, 0, 0, 0];
  let colorlessProduction = 0;
  for (const e of cards) {
    if (e.produces_colorless) colorlessProduction += e.quantity;
    COLORS.forEach((c, i) => {
      if (e.produced_mana & c.bit) manaProduction[i] += e.quantity;
    });
  }

  // Consumption: colored cost requirements of the spells actually cast —
  // lands are excluded since they have no colored casting cost.
  const manaConsumption: [number, number, number, number, number] = [0, 0, 0, 0, 0];
  let colorlessConsumption = 0;
  for (const e of nonlands) {
    if (e.colors === 0) {
      colorlessConsumption += e.quantity;
    } else {
      COLORS.forEach((c, i) => {
        if (e.colors & c.bit) manaConsumption[i] += e.quantity;
      });
    }
  }

  return {
    totalCards,
    uniqueCards: cards.length,
    landCount,
    avgManaValue,
    curve,
    colorCounts,
    colorlessCount,
    manaProduction,
    colorlessProduction,
    manaConsumption,
    colorlessConsumption,
  };
}

/** A prominent, art-forward display for a deck's commander (Commander/Brawl). */
function CommanderHero({
  card,
  onClear,
  preview,
}: {
  card: DeckEntry;
  onClear: () => void;
  preview?: PreviewContext;
}) {
  const { handlers } = useHoverPreview();
  const { open } = useClickPreview();
  return (
    <div className="panel commander-hero">
      {card.image_uri ? (
        <img
          className="commander-hero-img"
          src={card.image_uri}
          alt={card.name}
          onClick={() => open(card, preview)}
          {...handlers(card)}
        />
      ) : (
        <div className="commander-hero-noimg">{card.name}</div>
      )}
      <div className="commander-hero-info">
        <span className="commander-hero-label">Commander</span>
        <span className="commander-hero-name">{card.name}</span>
        <span className="commander-hero-type">{card.type_line}</span>
        <ColorPips mask={card.color_identity} />
      </div>
      <IconButton icon={Icons.close} label={`Clear ${card.name} as commander`} onClick={onClear} />
    </div>
  );
}

/** Whether two cards can be commanders together. Mirrors `pairs_with` in
 * crates/mtgc-core/src/partner.rs — keep the two in step. */
function pairsWith(a: DeckEntry, b: DeckEntry): boolean {
  const p = a.partner;
  const q = b.partner;
  if (!p || !q) return false;
  switch (p.kind) {
    case "partner":
      return q.kind === "partner" && a.oracle_id !== b.oracle_id;
    case "variant":
      return q.kind === "variant" && q.name === p.name && a.oracle_id !== b.oracle_id;
    case "with":
      return q.kind === "with" && p.name === b.name && q.name === a.name;
    case "chooses_background":
      return q.kind === "background";
    case "background":
      return q.kind === "chooses_background";
    case "doctors_companion":
      return q.kind === "doctor";
    case "doctor":
      return q.kind === "doctors_companion";
  }
}

/** What the second-commander search box asks for, given the first's ability. */
function partnerPlaceholder(partner: Partner): string {
  switch (partner.kind) {
    case "chooses_background":
      return "Search to add a Background…";
    case "background":
      return "Search to add a commander that chooses a Background…";
    case "doctors_companion":
      return "Search to add a Doctor…";
    case "doctor":
      return "Search to add a Doctor's companion…";
    case "with":
      return `Search to add ${partner.name}…`;
    case "variant":
      return `Search to add a partner (${partner.name})…`;
    case "partner":
      return "Search to add a partner…";
  }
}

// How long a card decremented to 0 copies lingers (dimmed, still adjustable)
// before actually dropping out of the deck — same grace-period pattern as
// the Library tab, so a mistaken removal can be undone with +.
const REMOVAL_GRACE_MS = 5000;

const STARTING_HAND_SIZE = 7;

const FORMATS = [
  "",
  "Commander",
  "Brawl",
  "Standard",
  "Pioneer",
  "Modern",
  "Legacy",
  "Vintage",
  "Pauper",
  "Other",
];
const COMMANDER_FORMATS = ["Commander", "Brawl"];

interface DeckLegality {
  status: "legal" | "illegal" | "unchecked";
  reasons: string[];
}

const COMMANDER_DECK_SIZE = 100;
const CONSTRUCTED_MIN_DECK_SIZE = 60;
const CONSTRUCTED_MAX_COPIES = 4;

/**
 * Format-legality check for the deck as a whole: structural deck-building
 * rules (size, singleton/copy limits, commander color identity) plus
 * Scryfall's per-format banned/restricted lists (via each card's
 * `legalities` bitmask). Blank format and "Other" run no checks at all —
 * "unchecked" is a neutral state, distinct from "illegal".
 */
function computeDeckLegality(deck: Deck | null | undefined, contents: DeckEntry[]): DeckLegality {
  if (!deck || deck.format === "" || deck.format === "Other") {
    return { status: "unchecked", reasons: [] };
  }

  const reasons: string[] = [];
  const cards = contents.filter((e) => !e.is_maybeboard);
  const isBasicLand = (e: DeckEntry) => e.type_line.includes("Basic Land");

  // NOTE: a handful of real cards (Relentless Rats, Persistent Petitioners,
  // Shadowborn Apostle, Dragon's Approach, Seven Dwarves, etc.) override the
  // singleton/copy-limit rule via oracle text ("a deck can have any number
  // of cards named..."). Detecting this needs oracle_text on CardRef, which
  // isn't wired through yet — known limitation, not blocking this feature.

  if (COMMANDER_FORMATS.includes(deck.format)) {
    // Brawl (Scryfall's `brawl` legality key = paper/Historic Brawl) is
    // structurally identical to Commander — 100 cards incl. commander,
    // singleton, commander color-identity restriction — differing only in
    // which legal/banned card pool applies. Both formats share this
    // rule-set and differ only in which legalities bit (deck.format itself,
    // "Commander" or "Brawl") is consulted for the banned/restricted check
    // below.
    const totalCards = cards.reduce((sum, e) => sum + e.quantity, 0);
    if (totalCards !== COMMANDER_DECK_SIZE) {
      reasons.push(
        `Deck has ${totalCards} cards; ${deck.format} decks need exactly ${COMMANDER_DECK_SIZE} (including the commander).`,
      );
    }

    // Two commanders are allowed when their partner abilities pair them up.
    const commanders = cards.filter((e) => e.is_commander);
    if (commanders.length === 0) {
      reasons.push(`No commander is set.`);
    } else if (commanders.length > 2) {
      reasons.push(`More than two cards are marked as commanders.`);
    } else if (commanders.length === 2 && !pairsWith(commanders[0], commanders[1])) {
      reasons.push(`${commanders[0].name} and ${commanders[1].name} can't be commanders together.`);
    }

    for (const e of cards) {
      if (e.is_commander) continue;
      if (!isBasicLand(e) && e.quantity > 1) {
        reasons.push(
          `${e.name} has ${e.quantity} copies; ${deck.format} decks allow only 1 (except basic lands).`,
        );
      }
    }

    if (commanders.length > 0) {
      const identity = commanders.reduce((mask, e) => mask | e.color_identity, 0);
      const whose = commanders.length > 1 ? "commanders'" : "commander's";
      for (const e of cards) {
        if (e.is_commander) continue;
        const outsideIdentity = e.color_identity & ~identity;
        if (outsideIdentity !== 0) {
          reasons.push(`${e.name}'s color identity is outside the ${whose} color identity.`);
        }
      }
    }

    for (const e of cards) {
      const status = legalStatusFor(e.legalities, deck.format);
      if (status === "banned") {
        reasons.push(`${e.name} is banned in ${deck.format}.`);
      } else if (status === "restricted" && e.quantity > 1) {
        reasons.push(
          `${e.name} is restricted in ${deck.format} (max 1 copy), deck has ${e.quantity}.`,
        );
      }
    }
  } else {
    // 60-card constructed formats: Standard, Pioneer, Modern, Legacy,
    // Vintage, Pauper. No commander concept — is_commander is ignored here.
    const totalCards = cards.reduce((sum, e) => sum + e.quantity, 0);
    if (totalCards < CONSTRUCTED_MIN_DECK_SIZE) {
      reasons.push(
        `Deck has ${totalCards} cards; ${deck.format} decks need at least ${CONSTRUCTED_MIN_DECK_SIZE}.`,
      );
    }

    for (const e of cards) {
      if (!isBasicLand(e) && e.quantity > CONSTRUCTED_MAX_COPIES) {
        reasons.push(
          `${e.name} has ${e.quantity} copies; ${deck.format} allows at most ${CONSTRUCTED_MAX_COPIES} (except basic lands).`,
        );
      }
    }

    for (const e of cards) {
      const status = legalStatusFor(e.legalities, deck.format);
      if (status === "banned") {
        reasons.push(`${e.name} is banned in ${deck.format}.`);
      } else if (status === "restricted" && e.quantity > 1) {
        // In practice this only ever fires for Vintage among the 8 tracked
        // formats, since Vintage is the only format with a restricted list —
        // but the check is generic/future-proof rather than Vintage-special-cased.
        reasons.push(
          `${e.name} is restricted in ${deck.format} (max 1 copy), deck has ${e.quantity}.`,
        );
      }
    }
  }

  return { status: reasons.length ? "illegal" : "legal", reasons };
}

/**
 * Deck editor. A deck's mainboard cards are split into two groups — "In your
 * library" (owned) and "Not owned" — each with its own search box and each
 * groupable by card attribute; "Combine sections" merges these two into one
 * list. The maybeboard is always shown as its own separate section. Deck-level
 * format + commander metadata sit at the top.
 *
 * `refreshSignal` is bumped by `App` when something outside this view's own
 * control changes deck contents — e.g. undoing a Library bulk add-to-deck
 * from the command palette while this view is already mounted — so the
 * card list, mana curve, and legality tile recompute immediately instead of
 * only on the next mount.
 */
export function DeckView({ refreshSignal }: { refreshSignal?: number }) {
  const [decks, setDecks] = useState<Deck[]>([]);
  const [selected, setSelected] = usePersistedState<number | null>(libraryKey("deck-selected"), null);
  const [newName, setNewName] = useState("");
  const [contents, setContents] = useState<DeckEntry[]>([]);
  const [view, setView] = useViewMode("deck-view");
  const tiles = useTileColumns();
  const [groupBy, setGroupBy] = usePersistedState<GroupMode>("deck-group", "none");
  const [combineSections, setCombineSections] = usePersistedState("deck-combine-sections", false);
  const [filterQuery, setFilterQuery] = useState("");
  const [dialog, setDialog] = useState<DeckDialog>(null);
  const [dialogError, setDialogError] = useState<string | null>(null);
  // On narrow screens the deck list and the deck-building interface are
  // separate "screens" (only one visible at a time) rather than stacked —
  // this only matters below the .deck-layout stacking breakpoint; CSS keeps
  // both panes visible side by side above it regardless of this flag.
  const [mobileShowList, setMobileShowList] = useState(true);
  // Android back from the deck-building screen returns to the deck list, like
  // its ← button. Only while they're separate screens (the ≤720px
  // `.deck-layout` breakpoint): side by side, flipping the flag changes
  // nothing visible, so back would seem to do nothing.
  const listIsSeparateScreen = useMediaQuery("(max-width: 720px)");
  useBackButton(() => setMobileShowList(true), listIsSeparateScreen && !mobileShowList);

  const [libQuery, setLibQuery] = useState("");
  const [libResults, setLibResults] = useState<CardRef[]>([]);
  const [anyQuery, setAnyQuery] = useState("");
  const [anyResults, setAnyResults] = useState<CardRef[]>([]);
  const [cmdQuery, setCmdQuery] = useState("");
  const [cmdResults, setCmdResults] = useState<CardRef[]>([]);
  const [partnerQuery, setPartnerQuery] = useState("");
  const [partnerResults, setPartnerResults] = useState<CardRef[]>([]);
  const [maybeQuery, setMaybeQuery] = useState("");
  const [maybeResults, setMaybeResults] = useState<CardRef[]>([]);

  const [pendingRemoval, setPendingRemoval] = useState<Set<string>>(new Set());
  const removalTimers = useRef<Map<string, ReturnType<typeof setTimeout>>>(new Map());
  const [selectedCards, setSelectedCards] = useState<Set<string>>(new Set());
  const [bulkBusy, setBulkBusy] = useState(false);
  const selectAllRef = useRef<HTMLInputElement>(null);

  const [handOpen, setHandOpen] = useState(false);
  const [hand, setHand] = useState<DeckEntry[]>([]);
  const [libraryStack, setLibraryStack] = useState<DeckEntry[]>([]);
  const [suggestOpen, setSuggestOpen] = useState(false);

  const deck = decks.find((d) => d.id === selected) ?? null;

  const loadDecks = useCallback(async () => {
    const d = await api.listDecks();
    setDecks(d);
    // Keep the persisted selection if it still exists, else fall back to the first.
    if (d.length && (selected === null || !d.some((x) => x.id === selected))) {
      setSelected(d[0].id);
    }
  }, [selected, setSelected]);

  useEffect(() => {
    loadDecks();
  }, [loadDecks]);

  const loadContents = useCallback(async () => {
    if (selected === null) {
      setContents([]);
      return;
    }
    setContents(await api.deckContents(selected));
  }, [selected]);

  useEffect(() => {
    loadContents();
    setSelectedCards(new Set());
    setHandOpen(false);
    setHand([]);
    setLibraryStack([]);
    setFilterQuery("");
  }, [loadContents]);

  // Refetch on an external refresh signal without resetting the UI state
  // above (unlike a deck switch, this shouldn't clear the user's filter,
  // selection, or open sample hand). Skips the first render so it doesn't
  // duplicate the mount-time fetch above.
  const skipFirstRefresh = useRef(true);
  useEffect(() => {
    if (skipFirstRefresh.current) {
      skipFirstRefresh.current = false;
      return;
    }
    loadContents();
  }, [refreshSignal]);

  // Cancel any in-flight removal timers on unmount so they don't fire against
  // an unmounted component.
  useEffect(() => () => removalTimers.current.forEach(clearTimeout), []);

  // Keep selection in sync with what's actually visible — drop ids that fall
  // out of the deck (deck switched, or a card's qty hit 0 and its grace
  // period expired).
  useEffect(() => {
    setSelectedCards((s) => {
      const visible = new Set(contents.map((e) => e.oracle_id));
      const next = new Set([...s].filter((id) => visible.has(id)));
      return next.size === s.size ? s : next;
    });
  }, [contents]);

  useEffect(() => {
    if (selectAllRef.current) {
      selectAllRef.current.indeterminate = selectedCards.size > 0 && selectedCards.size < contents.length;
    }
  }, [selectedCards, contents]);

  useEffect(() => {
    const q = libQuery.trim();
    if (!q) return setLibResults([]);
    const t = setTimeout(() => api.searchLibrary({ text: q }).then(setLibResults), 100);
    return () => clearTimeout(t);
  }, [libQuery]);

  useEffect(() => {
    const q = anyQuery.trim();
    if (!q) return setAnyResults([]);
    const t = setTimeout(() => api.searchCards(q, 12).then(setAnyResults), 80);
    return () => clearTimeout(t);
  }, [anyQuery]);

  useEffect(() => {
    const q = maybeQuery.trim();
    if (!q) return setMaybeResults([]);
    const t = setTimeout(() => api.searchCards(q, 12).then(setMaybeResults), 80);
    return () => clearTimeout(t);
  }, [maybeQuery]);

  useEffect(() => {
    const q = cmdQuery.trim();
    if (!q) return setCmdResults([]);
    const t = setTimeout(() => api.searchCards(q, 12).then(setCmdResults), 80);
    return () => clearTimeout(t);
  }, [cmdQuery]);

  // The primary commander, whose partner ability the second search box serves.
  const partnerOf =
    deck?.commander_oracle_id ?? contents.find((e) => e.is_commander && !e.is_maybeboard)?.oracle_id ?? null;
  useEffect(() => {
    const q = partnerQuery.trim();
    if (!q || !partnerOf) return setPartnerResults([]);
    const t = setTimeout(() => api.searchPartners(partnerOf, q, 12).then(setPartnerResults), 80);
    return () => clearTimeout(t);
  }, [partnerQuery, partnerOf]);

  async function createDeck() {
    if (!newName.trim()) return;
    const d = await api.createDeck(newName.trim(), null);
    setNewName("");
    await loadDecks();
    setSelected(d.id);
    setMobileShowList(false);
  }

  async function exportDeck(d: Deck) {
    const path = await save({
      title: "Export deck",
      defaultPath: `${d.name}.txt`,
      filters: [{ name: "Decklist", extensions: ["txt"] }],
    });
    if (typeof path === "string") await api.exportDeck(d.id, path);
  }

  async function pickImportFile() {
    const path = await open({
      title: "Import deck",
      filters: [{ name: "Decklist", extensions: ["txt"] }],
    });
    if (typeof path !== "string") return;
    const base = path.split(/[/\\]/).pop() ?? "Imported deck";
    const suggestedName = base.replace(/\.txt$/i, "");
    setDialog({ kind: "import-name", suggestedName, path });
  }

  async function confirmImportName(name: string) {
    if (dialog?.kind !== "import-name") return;
    try {
      const result = await api.importDeck(dialog.path, name);
      setDialog({ kind: "import-result", result });
      setDialogError(null);
      await loadDecks();
      setSelected(result.deck.id);
      setMobileShowList(false);
    } catch (err) {
      setDialogError(friendlyDeckError(err));
    }
  }

  async function addToDeck(card: CardRef) {
    if (selected === null) return;
    const existing = contents.find((e) => e.oracle_id === card.oracle_id);
    const qty = existing ? existing.quantity + 1 : 1;
    await api.setDeckCard(selected, card.oracle_id, qty, false, false);
    setLibQuery("");
    setLibResults([]);
    setAnyQuery("");
    setAnyResults([]);
    await loadContents();
  }

  async function addToMaybeboard(card: CardRef) {
    if (selected === null) return;
    const existing = contents.find((e) => e.oracle_id === card.oracle_id);
    const qty = existing ? existing.quantity + 1 : 1;
    await api.setDeckCard(selected, card.oracle_id, qty, false, true);
    setMaybeQuery("");
    setMaybeResults([]);
    await loadContents();
  }

  /** Move a card between the mainboard and the maybeboard. Clears commander
   * status (dropping it from the deck's commanders) when maybeboarding. */
  async function setMaybeboard(entry: DeckEntry, isMaybeboard: boolean) {
    if (selected === null) return;
    const isCommander = isMaybeboard ? false : entry.is_commander;
    await api.setDeckCard(selected, entry.oracle_id, entry.quantity, isCommander, isMaybeboard);
    if (isMaybeboard && entry.is_commander) {
      await api.setDeckCommanders(
        selected,
        commanders.filter((e) => e.oracle_id !== entry.oracle_id).map((e) => e.oracle_id),
      );
      await loadDecks();
    }
    await loadContents();
  }

  /** Every mainboard copy (commander/maybeboard excluded), one entry per
   * physical copy so a card at quantity N is N times as likely to be drawn,
   * shuffled in place (Fisher-Yates). */
  function shuffledLibrary(): DeckEntry[] {
    const pool: DeckEntry[] = [];
    for (const e of contents) {
      if (e.is_commander || e.is_maybeboard) continue;
      for (let i = 0; i < e.quantity; i++) pool.push(e);
    }
    for (let i = pool.length - 1; i > 0; i--) {
      const j = Math.floor(Math.random() * (i + 1));
      [pool[i], pool[j]] = [pool[j], pool[i]];
    }
    return pool;
  }

  function drawNewHand() {
    const shuffled = shuffledLibrary();
    setHand(shuffled.slice(0, STARTING_HAND_SIZE));
    setLibraryStack(shuffled.slice(STARTING_HAND_SIZE));
    setHandOpen(true);
  }

  function drawOneMore() {
    if (libraryStack.length === 0) return;
    setHand((h) => [...h, libraryStack[0]]);
    setLibraryStack((stack) => stack.slice(1));
  }

  async function setQty(oracleId: string, qty: number) {
    if (selected === null) return;
    const clamped = Math.max(0, qty);
    const existing = contents.find((e) => e.oracle_id === oracleId);
    await api.setDeckCard(
      selected,
      oracleId,
      clamped,
      existing?.is_commander ?? false,
      existing?.is_maybeboard ?? false,
    );
    setContents((cs) => cs.map((e) => (e.oracle_id === oracleId ? { ...e, quantity: clamped } : e)));

    // Re-adding during the grace period below cancels the pending removal.
    const timer = removalTimers.current.get(oracleId);
    if (timer) {
      clearTimeout(timer);
      removalTimers.current.delete(oracleId);
      setPendingRemoval((p) => {
        const next = new Set(p);
        next.delete(oracleId);
        return next;
      });
    }

    if (clamped <= 0) {
      // deck_contents wouldn't include this card on a fresh fetch anymore —
      // rather than dropping the row immediately, dim it and give the user a
      // window to undo a mistaken decrement (via +) before it disappears.
      setPendingRemoval((p) => new Set(p).add(oracleId));
      removalTimers.current.set(
        oracleId,
        setTimeout(() => {
          setContents((cs) => cs.filter((e) => e.oracle_id !== oracleId));
          setPendingRemoval((p) => {
            const next = new Set(p);
            next.delete(oracleId);
            return next;
          });
          removalTimers.current.delete(oracleId);
        }, REMOVAL_GRACE_MS),
      );
    }
  }

  function toggleCard(oracleId: string) {
    setSelectedCards((s) => {
      const next = new Set(s);
      if (next.has(oracleId)) next.delete(oracleId);
      else next.add(oracleId);
      return next;
    });
  }

  function toggleSelectAllCards() {
    setSelectedCards((s) =>
      s.size === contents.length ? new Set() : new Set(contents.map((e) => e.oracle_id)),
    );
  }

  async function bulkRemoveFromDeck() {
    setBulkBusy(true);
    try {
      await Promise.all([...selectedCards].map((id) => setQty(id, 0)));
    } finally {
      setBulkBusy(false);
    }
  }

  async function confirmDelete() {
    if (dialog?.kind !== "delete") return;
    await api.deleteDeck(dialog.deck.id);
    if (selected === dialog.deck.id) {
      setSelected(null);
      setMobileShowList(true);
    }
    setDialog(null);
    await loadDecks();
  }

  async function confirmRename(name: string) {
    if (dialog?.kind !== "rename") return;
    try {
      await api.renameDeck(dialog.deck.id, name);
      setDialog(null);
      setDialogError(null);
      await loadDecks();
    } catch (err) {
      setDialogError(friendlyDeckError(err));
    }
  }

  async function confirmDuplicate(newName: string) {
    if (dialog?.kind !== "duplicate") return;
    try {
      const d = await api.duplicateDeck(dialog.deck.id, newName);
      setDialog(null);
      setDialogError(null);
      await loadDecks();
      setSelected(d.id);
    } catch (err) {
      setDialogError(friendlyDeckError(err));
    }
  }

  async function changeFormat(format: string) {
    if (selected === null) return;
    await api.setDeckFormat(selected, format);
    await loadDecks();
  }

  async function setCommander(card: CardRef) {
    if (selected === null) return;
    // Ensure the card is in the deck (mainboard, not maybeboard) and flagged
    // commander — covers both "not in the deck yet" and "was maybeboarded".
    const existing = contents.find((e) => e.oracle_id === card.oracle_id);
    await api.setDeckCard(selected, card.oracle_id, existing?.quantity ?? 1, true, false);
    // Keep the partner only if it can still pair with the new commander; if
    // not, it stays in the deck as an ordinary card.
    const picked = (await api.deckContents(selected)).find((e) => e.oracle_id === card.oracle_id);
    const keepPartner =
      partnerEntry && partnerEntry.oracle_id !== card.oracle_id && picked && pairsWith(picked, partnerEntry);
    await api.setDeckCommanders(
      selected,
      keepPartner ? [card.oracle_id, partnerEntry.oracle_id] : [card.oracle_id],
    );
    setCmdQuery("");
    setCmdResults([]);
    await loadContents();
    await loadDecks();
  }

  async function addPartner(card: CardRef) {
    if (selected === null || !commanderEntry) return;
    const existing = contents.find((e) => e.oracle_id === card.oracle_id);
    await api.setDeckCard(selected, card.oracle_id, existing?.quantity ?? 1, true, false);
    await api.setDeckCommanders(selected, [commanderEntry.oracle_id, card.oracle_id]);
    setPartnerQuery("");
    setPartnerResults([]);
    await loadContents();
    await loadDecks();
  }

  /** Stop treating a card as a commander; it stays in the deck. Clearing the
   * primary commander promotes its partner. */
  async function clearCommander(entry: DeckEntry) {
    if (selected === null) return;
    await api.setDeckCommanders(
      selected,
      commanders.filter((e) => e.oracle_id !== entry.oracle_id).map((e) => e.oracle_id),
    );
    await loadContents();
    await loadDecks();
  }

  // Quick-search over cards already in the deck/maybeboard — a display
  // filter only, distinct from the CardSearchBox boxes below (which search
  // the library/reference db to find NEW cards to add).
  function matchesFilter(e: DeckEntry): boolean {
    const q = filterQuery.trim().toLowerCase();
    if (!q) return true;
    return e.name.toLowerCase().includes(q) || e.type_line.toLowerCase().includes(q);
  }

  const owned = contents.filter((e) => !e.is_maybeboard && e.quantity_owned > 0 && matchesFilter(e));
  const unowned = contents.filter((e) => !e.is_maybeboard && e.quantity_owned === 0 && matchesFilter(e));
  const maybeboard = contents.filter((e) => e.is_maybeboard && matchesFilter(e));
  // The primary commander first, then its partner, if any.
  const isPrimary = (e: DeckEntry) => Number(e.oracle_id === deck?.commander_oracle_id);
  const commanders = contents
    .filter((e) => e.is_commander && !e.is_maybeboard)
    .sort((a, b) => isPrimary(b) - isPrimary(a));
  const commanderEntry: DeckEntry | undefined = commanders[0];
  const partnerEntry: DeckEntry | undefined = commanders[1];
  const deckStats = useMemo(() => computeDeckStats(contents), [contents]);
  const deckLegality = useMemo(() => computeDeckLegality(deck, contents), [deck, contents]);

  // Lets the click preview track copies and choose each slot's printing.
  const preview: PreviewContext | undefined =
    selected === null ? undefined : { deckId: selected, onChanged: loadContents };

  function deckTiles(entries: DeckEntry[]) {
    return (
      <div {...tiles.gridProps}>
        {entries.map((e) => (
          <CardTile
            key={e.oracle_id}
            card={e}
            preview={preview}
            selected={selectedCards.has(e.oracle_id)}
            cornerLeft={
              <span className="tile-select">
                <input
                  type="checkbox"
                  checked={selectedCards.has(e.oracle_id)}
                  onChange={() => toggleCard(e.oracle_id)}
                />
              </span>
            }
            corner={
              <QtyStepper
                overlay
                value={e.quantity}
                onDecrement={() => setQty(e.oracle_id, e.quantity - 1)}
                onIncrement={() => setQty(e.oracle_id, e.quantity + 1)}
                warn={e.quantity_owned > 0 && e.quantity > e.quantity_owned}
                pending={pendingRemoval.has(e.oracle_id)}
              />
            }
            cornerBottomLeft={
              <IconButton overlay {...boardToggleProps(e)} onClick={() => setMaybeboard(e, !e.is_maybeboard)} />
            }
            footer={e.is_commander ? <span className="tile-badge">★ commander</span> : undefined}
          />
        ))}
      </div>
    );
  }

  function deckTable(entries: DeckEntry[]) {
    return (
      <table>
        <thead>
          <tr>
            <th></th>
            <th></th>
            <th>Colors</th>
            <th>Name</th>
            <th>Type</th>
            <th>In deck</th>
            <th>Owned</th>
            <th></th>
          </tr>
        </thead>
        <tbody>
          {entries.map((e) => (
            <tr key={e.oracle_id}>
              <td className="cell-check">
                <input
                  type="checkbox"
                  checked={selectedCards.has(e.oracle_id)}
                  onChange={() => toggleCard(e.oracle_id)}
                />
              </td>
              <td className="cell-thumb">
                <CardThumb card={e} preview={preview} />
              </td>
              <td>
                <ColorPips mask={e.color_identity} />
              </td>
              <td className="card-name">
                {e.is_commander && <span title="Commander">★ </span>}
                {e.name}
              </td>
              <td className="card-type">{e.type_line}</td>
              <td data-label="In deck">
                <QtyStepper
                  value={e.quantity}
                  onDecrement={() => setQty(e.oracle_id, e.quantity - 1)}
                  onIncrement={() => setQty(e.oracle_id, e.quantity + 1)}
                  warn={e.quantity_owned > 0 && e.quantity > e.quantity_owned}
                  pending={pendingRemoval.has(e.oracle_id)}
                />
              </td>
              <td data-label="Owned">{e.quantity_owned}</td>
              <td>
                <IconButton {...boardToggleProps(e)} onClick={() => setMaybeboard(e, !e.is_maybeboard)} />
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    );
  }

  function cardsGroup(entries: DeckEntry[]) {
    if (entries.length === 0) return <p className="hint">None yet.</p>;
    return groupCards(entries, groupBy).map((g) => (
      <div key={g.label || "all"} style={{ marginBottom: g.label ? 14 : 0 }}>
        {g.label && (
          <h4 className="group-header">
            {g.label} <span className="badge">{g.cards.length}</span>
          </h4>
        )}
        {view === "tiles" ? deckTiles(g.cards) : deckTable(g.cards)}
      </div>
    ));
  }

  return (
    <div className={`deck-layout ${mobileShowList ? "show-list" : "show-detail"}`}>
      <div className="deck-sidebar">
        <div className="row" style={{ justifyContent: "space-between" }}>
          <h2>Decks</h2>
          <IconButton icon={Icons.upload} label="Import deck…" onClick={pickImportFile} />
        </div>
        <div className="row" style={{ marginBottom: 10 }}>
          <input
            value={newName}
            placeholder="New deck name"
            onChange={(e) => setNewName(e.target.value)}
            onKeyDown={(e) => e.key === "Enter" && createDeck()}
          />
          <button className="primary" onClick={createDeck}>
            +
          </button>
        </div>
        <ul className="result-list deck-list">
          {decks.map((d) => (
            <li
              key={d.id}
              style={d.id === selected ? { background: "var(--accent-subtle)" } : undefined}
              onClick={() => {
                setSelected(d.id);
                setMobileShowList(false);
              }}
            >
              <div className="deck-list-row">
                <span className="card-name">{d.name}</span>
              </div>
              <div className="deck-list-row deck-list-actions-row">
                {d.format ? <span className="deck-chip">{d.format}</span> : <span />}
                <span className="row-actions">
                  <IconButton
                    icon={Icons.pencil}
                    label="Rename deck"
                    onClick={(e) => {
                      e.stopPropagation();
                      setDialogError(null);
                      setDialog({ kind: "rename", deck: d });
                    }}
                  />
                  <IconButton
                    icon={Icons.copy}
                    label="Duplicate deck"
                    onClick={(e) => {
                      e.stopPropagation();
                      setDialogError(null);
                      setDialog({ kind: "duplicate", deck: d });
                    }}
                  />
                  <IconButton
                    icon={Icons.trash}
                    label="Delete deck"
                    danger
                    onClick={(e) => {
                      e.stopPropagation();
                      setDialog({ kind: "delete", deck: d });
                    }}
                  />
                </span>
              </div>
            </li>
          ))}
          {decks.length === 0 && (
            <li style={{ cursor: "default" }} className="hint">
              No decks yet.
            </li>
          )}
        </ul>
      </div>

      <div className="deck-detail-pane">
        {selected === null || !deck ? (
          <p className="hint">Select or create a deck.</p>
        ) : (
          <>
            <div className="row" style={{ justifyContent: "space-between" }}>
              <div className="row" style={{ gap: 8 }}>
                <span className="deck-back-btn">
                  <IconButton
                    icon={Icons.arrowLeftCircle}
                    label="Back to decks"
                    onClick={() => setMobileShowList(true)}
                  />
                </span>
                <h2>{deck.name}</h2>
              </div>
              <div className="row" style={{ gap: 8 }}>
                <button
                  onClick={() => setSuggestOpen(true)}
                  disabled={contents.filter((e) => !e.is_maybeboard).length === 0}
                >
                  {Icons.cards}
                  Suggest cards
                </button>
                <button onClick={() => exportDeck(deck)}>
                  {Icons.download}
                  Export deck
                </button>
                <button
                  onClick={drawNewHand}
                  disabled={!contents.some((e) => !e.is_commander && !e.is_maybeboard)}
                >
                  {Icons.cards}
                  Sample hand
                </button>
              </div>
            </div>

            <div className="deck-top-grid">
              {COMMANDER_FORMATS.includes(deck.format) && commanderEntry && (
                <div className="deck-top-commander">
                  {commanders.map((c) => (
                    <CommanderHero key={c.oracle_id} card={c} onClear={() => clearCommander(c)} preview={preview} />
                  ))}
                </div>
              )}

              {/* Deck metadata: format + (for Commander/Brawl) the commander card. */}
              <div className="deck-top-meta">
                <div className="panel deck-meta">
                  <label className="row" style={{ gap: 6 }}>
                    <span className="muted">Format</span>
                    <select value={deck.format} onChange={(e) => changeFormat(e.target.value)}>
                      {FORMATS.map((f) => (
                        <option key={f} value={f}>
                          {f || "—"}
                        </option>
                      ))}
                    </select>
                  </label>

                  {COMMANDER_FORMATS.includes(deck.format) && (
                    <div className="commander-box">
                      {!commanderEntry && <span className="muted">No commander set yet.</span>}
                      <CardSearchBox
                        placeholder={
                          commanderEntry
                            ? "Search to change the commander…"
                            : "Search to set the commander…"
                        }
                        value={cmdQuery}
                        onChange={setCmdQuery}
                        results={cmdResults}
                        onPick={setCommander}
                      />
                      {commanderEntry?.partner && !partnerEntry && (
                        <CardSearchBox
                          placeholder={partnerPlaceholder(commanderEntry.partner)}
                          value={partnerQuery}
                          onChange={setPartnerQuery}
                          results={partnerResults}
                          onPick={addPartner}
                        />
                      )}
                    </div>
                  )}
                </div>
              </div>

              {contents.length > 0 && (
                <div className="deck-top-stats">
                  <div className="panel deck-stats">
                    <div className="deck-stats-head section-label">Deck analysis</div>
                    <div className="deck-stats-body">
                      <div className="deck-stats-numbers">
                        <div className="stat-tiles-row">
                          <StatTile value={deckStats.totalCards} label="cards" />
                          <StatTile value={deckStats.uniqueCards} label="unique" />
                          <StatTile value={deckStats.landCount} label="lands" />
                          <StatTile value={deckStats.avgManaValue.toFixed(2)} label="avg MV" />
                        </div>
                        <div className="deck-stats-curve-label">Color identity</div>
                        <ColorDistributionBar
                          colorCounts={deckStats.colorCounts}
                          colorlessCount={deckStats.colorlessCount}
                        />
                        <div className="deck-stats-curve-label">Mana production</div>
                        <ColorDistributionBar
                          colorCounts={deckStats.manaProduction}
                          colorlessCount={deckStats.colorlessProduction}
                        />
                        <div className="deck-stats-curve-label">Mana consumption</div>
                        <ColorDistributionBar
                          colorCounts={deckStats.manaConsumption}
                          colorlessCount={deckStats.colorlessConsumption}
                        />
                      </div>
                      <div className="deck-stats-curve">
                        <div className="deck-stats-curve-label">Mana curve (nonland)</div>
                        <ManaCurve buckets={deckStats.curve} />
                      </div>
                    </div>
                  </div>
                </div>
              )}

              {deck.format !== "Other" && (
                <div className="deck-top-legality">
                  <div className={`legality-tile ${deckLegality.status}`}>
                    <div className="legality-tile-head">
                      <span className="legality-tile-icon">
                        {deckLegality.status === "legal" ? "✓" : deckLegality.status === "illegal" ? "✗" : "—"}
                      </span>
                      <div className="legality-tile-info">
                        <span className="legality-tile-status">
                          {deckLegality.status === "legal"
                            ? "Legal"
                            : deckLegality.status === "illegal"
                              ? "Illegal"
                              : "Not checked"}
                        </span>
                        <span className="legality-tile-detail">
                          {deckLegality.status === "legal"
                            ? `Meets all ${deck.format} deck-building rules.`
                            : deckLegality.status === "illegal"
                              ? `${deckLegality.reasons.length} issue${deckLegality.reasons.length === 1 ? "" : "s"} found:`
                              : deck.format
                                ? `Legality isn't checked for "${deck.format}".`
                                : "Set a format to check legality."}
                        </span>
                      </div>
                    </div>
                    {deckLegality.status === "illegal" && (
                      <ul className="legality-tile-reasons">
                        {deckLegality.reasons.map((r, i) => (
                          <li key={i}>{r}</li>
                        ))}
                      </ul>
                    )}
                  </div>
                </div>
              )}
            </div>

            <hr className="deck-section-divider" />

            <div className="row" style={{ gap: 16 }}>
              <label className="row" style={{ gap: 6, cursor: "pointer" }} title="Select all cards">
                <input
                  ref={selectAllRef}
                  type="checkbox"
                  checked={contents.length > 0 && selectedCards.size === contents.length}
                  onChange={toggleSelectAllCards}
                  disabled={contents.length === 0}
                />
                <span className="muted" style={{ fontSize: 12 }}>
                  Select all
                </span>
              </label>
              <label className="row" style={{ gap: 6, cursor: "pointer" }} title="Combine owned/unowned into one section">
                <input
                  type="checkbox"
                  checked={combineSections}
                  onChange={(e) => setCombineSections(e.target.checked)}
                />
                <span className="muted" style={{ fontSize: 12 }}>
                  Combine sections
                </span>
              </label>
              <input
                value={filterQuery}
                onChange={(e) => setFilterQuery(e.target.value)}
                placeholder="Filter cards in deck…"
                style={{ width: 200 }}
              />
              <span className="spacer" />
              <GroupBySelect value={groupBy} onChange={setGroupBy} />
              <ViewToggle mode={view} onChange={setView} />
              {view === "tiles" && <TileColumnsControl tiles={tiles} />}
            </div>

            {selectedCards.size > 0 && (
              <div className="bulk-bar">
                <span className="bulk-bar-count">{selectedCards.size} selected</span>
                <div className="bulk-bar-actions">
                  <button className="danger" onClick={bulkRemoveFromDeck} disabled={bulkBusy}>
                    Remove from deck
                  </button>
                </div>
                <span className="spacer" />
                <button onClick={() => setSelectedCards(new Set())} disabled={bulkBusy}>
                  Clear
                </button>
              </div>
            )}

            {combineSections ? (
              <section style={{ marginTop: 10 }}>
                <h3>
                  All cards <span className="badge">{owned.length + unowned.length}</span>
                </h3>
                <CardSearchBox
                  placeholder="Search all cards to add to your deck…"
                  value={anyQuery}
                  onChange={setAnyQuery}
                  results={anyResults}
                  onPick={addToDeck}
                />
                {cardsGroup([...owned, ...unowned])}
              </section>
            ) : (
              <>
                <section style={{ marginTop: 10 }}>
                  <h3>
                    In your library <span className="badge">{owned.length}</span>
                  </h3>
                  <CardSearchBox
                    placeholder="Search your library to add owned cards…"
                    value={libQuery}
                    onChange={setLibQuery}
                    results={libResults}
                    onPick={addToDeck}
                  />
                  {cardsGroup(owned)}
                </section>

                <section style={{ marginTop: 26 }}>
                  <h3>
                    Not owned <span className="badge">{unowned.length}</span>
                  </h3>
                  <CardSearchBox
                    placeholder="Search all cards to add ones you don't own…"
                    value={anyQuery}
                    onChange={setAnyQuery}
                    results={anyResults}
                    onPick={addToDeck}
                  />
                  {cardsGroup(unowned)}
                </section>
              </>
            )}

            <section style={{ marginTop: 26 }}>
              <h3>
                Maybeboard <span className="badge">{maybeboard.length}</span>
              </h3>
              <p className="hint" style={{ marginTop: -4 }}>
                Cards under consideration — not counted in deck analysis.
              </p>
              <CardSearchBox
                placeholder="Search all cards to add one to the maybeboard…"
                value={maybeQuery}
                onChange={setMaybeQuery}
                results={maybeResults}
                onPick={addToMaybeboard}
              />
              {cardsGroup(maybeboard)}
            </section>
          </>
        )}
      </div>

      {dialog?.kind === "delete" && (
        <ConfirmDialog
          title="Delete deck"
          message={`Delete "${dialog.deck.name}"? This can't be undone.`}
          confirmLabel="Delete"
          danger
          onConfirm={confirmDelete}
          onCancel={() => setDialog(null)}
        />
      )}
      {dialog?.kind === "rename" && (
        <PromptDialog
          title="Rename deck"
          label="Deck name"
          defaultValue={dialog.deck.name}
          confirmLabel="Rename"
          error={dialogError}
          onConfirm={confirmRename}
          onCancel={() => setDialog(null)}
        />
      )}
      {dialog?.kind === "duplicate" && (
        <PromptDialog
          title="Duplicate deck"
          label="Name for the copy"
          defaultValue={`${dialog.deck.name} (copy)`}
          confirmLabel="Duplicate"
          error={dialogError}
          onConfirm={confirmDuplicate}
          onCancel={() => setDialog(null)}
        />
      )}
      {dialog?.kind === "import-name" && (
        <PromptDialog
          title="Import deck"
          label="Deck name"
          defaultValue={dialog.suggestedName}
          confirmLabel="Import"
          error={dialogError}
          onConfirm={confirmImportName}
          onCancel={() => setDialog(null)}
        />
      )}
      {dialog?.kind === "import-result" && (
        <InfoDialog
          title="Deck imported"
          message={
            dialog.result.unresolved.length > 0
              ? `Imported "${dialog.result.deck.name}". ${dialog.result.unresolved.length} card name${dialog.result.unresolved.length === 1 ? "" : "s"} couldn't be matched:`
              : `Imported "${dialog.result.deck.name}" — every card matched.`
          }
          items={dialog.result.unresolved}
          onClose={() => setDialog(null)}
        />
      )}
      {handOpen && (
        <SampleHandModal
          hand={hand}
          libraryCount={libraryStack.length}
          onDrawOne={drawOneMore}
          onNewHand={drawNewHand}
          onClose={() => setHandOpen(false)}
        />
      )}
      {suggestOpen && deck && (
        <SuggestionsModal
          deckId={deck.id}
          onClose={() => setSuggestOpen(false)}
          onCardAdded={loadContents}
        />
      )}
    </div>
  );
}