import { useEffect, useState } from "react";
import { api, CardSuggestion } from "./api";
import { CardThumb, ColorPips, DialogFrame } from "./components";

// Matches the backend's hardcoded per-page limit (src-tauri/src/commands.rs).
// A batch shorter than this means there's nothing left to fetch.
const PAGE_SIZE = 50;

// Fixed display order, matching the four synergy families the backend scores.
const CATEGORY_ORDER = ["Tribal", "Mechanic", "Archetype", "Mana base"];

function categorySlug(category: string): string {
  return category.toLowerCase().replace(/[^a-z]+/g, "-");
}

/**
 * On-demand modal listing scored card suggestions for a deck, each with an
 * explainable synergy breakdown and "Add to deck"/"Add to maybeboard"
 * actions. Fetches a page on open; toggleable chips filter which reason
 * categories must be present (client-side, over everything loaded so far);
 * "Suggest more" fetches and appends the next page. Adding a card removes
 * its row in place so several can be added in one sitting. An "Unusual
 * picks" toggle re-fetches from the backend restricted to (and reordered
 * toward) cards that aren't widely played, surfacing underappreciated
 * synergy hits instead of the usual staples — that reordering only makes
 * sense server-side, before pagination slices the result, so toggling it
 * resets and re-fetches rather than filtering what's already loaded.
 */
export function SuggestionsModal({
  deckId,
  onClose,
  onCardAdded,
}: {
  deckId: number;
  onClose: () => void;
  onCardAdded: () => void;
}) {
  const [suggestions, setSuggestions] = useState<CardSuggestion[] | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [busy, setBusy] = useState<Set<string>>(new Set());
  const [hasMore, setHasMore] = useState(true);
  const [loadingMore, setLoadingMore] = useState(false);
  const [activeCategories, setActiveCategories] = useState<Set<string>>(new Set());
  // Second level: the specific tribe/keyword/archetype. Knowing a suggestion is
  // an "Archetype" hit is rarely enough — a deck usually has several and you
  // want one of them.
  const [activeSubjects, setActiveSubjects] = useState<Set<string>>(new Set());
  const [unusual, setUnusual] = useState(false);

  useEffect(() => {
    let cancelled = false;
    setSuggestions(null);
    setError(null);
    api
      .suggestCards(deckId, 0, unusual)
      .then((s) => {
        if (cancelled) return;
        setSuggestions(s);
        setHasMore(s.length === PAGE_SIZE);
      })
      .catch((e) => {
        if (!cancelled) setError(String(e));
      });
    return () => {
      cancelled = true;
    };
  }, [deckId, unusual]);

  async function loadMore() {
    if (!suggestions) return;
    setLoadingMore(true);
    try {
      const more = await api.suggestCards(deckId, suggestions.length, unusual);
      setSuggestions((cur) => {
        const seen = new Set((cur ?? []).map((s) => s.card.oracle_id));
        return [...(cur ?? []), ...more.filter((s) => !seen.has(s.card.oracle_id))];
      });
      setHasMore(more.length === PAGE_SIZE);
    } finally {
      setLoadingMore(false);
    }
  }

  async function add(s: CardSuggestion, maybeboard: boolean) {
    const oid = s.card.oracle_id;
    setBusy((b) => new Set(b).add(oid));
    try {
      await api.setDeckCard(deckId, oid, 1, false, maybeboard);
      onCardAdded();
      setSuggestions((cur) => (cur ? cur.filter((x) => x.card.oracle_id !== oid) : cur));
    } finally {
      setBusy((b) => {
        const next = new Set(b);
        next.delete(oid);
        return next;
      });
    }
  }

  function toggleCategory(cat: string) {
    setActiveCategories((cur) => {
      const next = new Set(cur);
      if (next.has(cat)) next.delete(cat);
      else next.add(cat);
      return next;
    });
    // Subjects belong to categories, so narrowing the categories can strand a
    // selected subject that's no longer offered — clear rather than leave an
    // invisible filter applied.
    setActiveSubjects(new Set());
  }

  function toggleSubject(subject: string) {
    setActiveSubjects((cur) => {
      const next = new Set(cur);
      if (next.has(subject)) next.delete(subject);
      else next.add(subject);
      return next;
    });
  }

  const availableCategories = suggestions
    ? CATEGORY_ORDER.filter((cat) => suggestions.some((s) => s.reasons.some((r) => r.category === cat)))
    : [];
  /** Reasons still in play once the category chips are applied. */
  const inCategory = (r: { category: string }) =>
    activeCategories.size === 0 || activeCategories.has(r.category);

  // Offered subjects follow the category selection, so the second row is always
  // a drill-down into the first rather than an unrelated list. Ordered by how
  // many suggestions each explains, so the most useful narrowing comes first.
  const subjectCounts = new Map<string, { count: number; category: string }>();
  for (const s of suggestions ?? []) {
    for (const r of s.reasons) {
      if (!inCategory(r) || !r.subject) continue;
      const prev = subjectCounts.get(r.subject);
      subjectCounts.set(r.subject, {
        count: (prev?.count ?? 0) + 1,
        category: prev?.category ?? r.category,
      });
    }
  }
  const availableSubjects = [...subjectCounts.entries()]
    .sort((a, b) => b[1].count - a[1].count || a[0].localeCompare(b[0]))
    .map(([subject, meta]) => ({ subject, ...meta }));

  const visible = suggestions?.filter((s) =>
    s.reasons.some(
      (r) =>
        inCategory(r) && (activeSubjects.size === 0 || activeSubjects.has(r.subject)),
    ),
  );

  return (
    <DialogFrame title="Suggested cards" onCancel={onClose} wide>
      <div className="row" style={{ gap: 8, marginBottom: 12 }}>
        <button
          type="button"
          className={`filter-chip ${unusual ? "active" : ""}`}
          onClick={() => setUnusual((u) => !u)}
          title="Only show cards that fit your deck's strategy but aren't widely played — cool, underappreciated picks."
        >
          ✦ Unusual picks
        </button>
      </div>
      {error ? (
        <p className="hint">{error}</p>
      ) : suggestions === null ? (
        <p className="hint">Analyzing your deck…</p>
      ) : suggestions.length === 0 ? (
        <p className="hint">
          {unusual
            ? "No unusual picks found — try turning off \"Unusual picks\" to see the widely-played suggestions too."
            : "No suggestions yet — add a few cards (and a commander, if it's a Commander deck) so there's a strategy to build on."}
        </p>
      ) : (
        <>
          {availableCategories.length > 1 && (
            <div className="suggestion-filters">
              <span className="muted" style={{ fontSize: 12 }}>
                Filter by why:
              </span>
              {availableCategories.map((cat) => (
                <button
                  key={cat}
                  type="button"
                  className={`filter-chip filter-chip-${categorySlug(cat)} ${
                    activeCategories.has(cat) ? "active" : ""
                  }`}
                  onClick={() => toggleCategory(cat)}
                >
                  {cat}
                </button>
              ))}
              {activeCategories.size > 0 && (
                <button
                  type="button"
                  className="filter-chip-clear"
                  onClick={() => {
                    setActiveCategories(new Set());
                    setActiveSubjects(new Set());
                  }}
                >
                  Clear
                </button>
              )}
            </div>
          )}

          {availableSubjects.length > 1 && (
            <div className="suggestion-filters">
              <span className="muted" style={{ fontSize: 12 }}>
                Narrow to:
              </span>
              {availableSubjects.map(({ subject, count, category }) => (
                <button
                  key={subject}
                  type="button"
                  className={`filter-chip filter-chip-${categorySlug(category)} ${
                    activeSubjects.has(subject) ? "active" : ""
                  }`}
                  onClick={() => toggleSubject(subject)}
                  title={`${category} · ${count} suggestion${count === 1 ? "" : "s"}`}
                >
                  {subject} <span className="filter-chip-count">{count}</span>
                </button>
              ))}
              {activeSubjects.size > 0 && (
                <button
                  type="button"
                  className="filter-chip-clear"
                  onClick={() => setActiveSubjects(new Set())}
                >
                  Clear
                </button>
              )}
            </div>
          )}

          {visible && visible.length === 0 ? (
            <p className="hint">No suggestions match the selected filters.</p>
          ) : (
            <ul className="result-list suggestion-list">
              {visible?.map((s) => (
                <li key={s.card.oracle_id}>
                  <div className="suggestion-row">
                    <CardThumb card={s.card} />
                    <div className="suggestion-main">
                      <div className="suggestion-head">
                        <ColorPips mask={s.card.color_identity} />
                        <span className="card-name">{s.card.name}</span>
                        {s.quantity_owned > 0 ? (
                          <span className="badge">Owned ×{s.quantity_owned}</span>
                        ) : (
                          <span className="muted" style={{ fontSize: 12 }}>
                            Not owned
                          </span>
                        )}
                        {s.edhrec_rank !== null && s.edhrec_rank < 2000 && (
                          <span className="muted" style={{ fontSize: 12 }}>
                            ★ Popular
                          </span>
                        )}
                        <span className="spacer" />
                        <span className="suggestion-score">{s.score.toFixed(0)}</span>
                      </div>
                      <div className="suggestion-reasons">
                        {s.reasons.map((r, i) => (
                          <span key={i} className={`reason-chip reason-chip-${categorySlug(r.category)}`}>
                            <span className="reason-chip-category">{r.category}</span>
                            {r.detail}
                          </span>
                        ))}
                      </div>
                    </div>
                    <div className="suggestion-actions">
                      <button onClick={() => add(s, false)} disabled={busy.has(s.card.oracle_id)}>
                        Add to deck
                      </button>
                      <button onClick={() => add(s, true)} disabled={busy.has(s.card.oracle_id)}>
                        Add to maybeboard
                      </button>
                    </div>
                  </div>
                </li>
              ))}
            </ul>
          )}

          {hasMore && (
            <div className="row" style={{ justifyContent: "center", marginTop: 12 }}>
              <button onClick={loadMore} disabled={loadingMore}>
                {loadingMore ? "Loading…" : "Suggest more"}
              </button>
            </div>
          )}
        </>
      )}
      <div className="dialog-actions">
        <button className="primary" onClick={onClose} autoFocus>
          Close
        </button>
      </div>
    </DialogFrame>
  );
}