import { useEffect, useMemo, useState } from "react";
import { ChevronRight, ChevronDown } from "lucide-react";
import { useGameAPI } from "@/shared/api/GameAPIContext";
import type { LeaderboardSnapshot, UnsubscribeFn } from "@/shared/api/types";

// Smart precision algorithm for percentage display
function calculatePrecision(percentages: number[]): number {
  if (percentages.length === 0) return 0;

  // Find the minimum non-zero difference between consecutive percentages
  const sorted = [...percentages].sort((a, b) => b - a);
  let minDiff = Infinity;

  for (let i = 0; i < sorted.length - 1; i++) {
    const diff = sorted[i] - sorted[i + 1];
    if (diff > 0) {
      minDiff = Math.min(minDiff, diff);
    }
  }

  // If all percentages are the same, use 0 decimal places
  if (minDiff === Infinity) return 0;

  // Determine precision based on the minimum difference
  if (minDiff >= 0.1) return 0; // 0.1% or more difference -> 0 decimals
  if (minDiff >= 0.01) return 1; // 0.01% or more difference -> 1 decimal
  return 2; // 0.001% or more difference -> 2 decimals (max precision)
}

export function Leaderboard({
  topN = 8,
  initialSnapshot,
  highlightedNation,
  onNationHover,
}: {
  topN?: number;
  initialSnapshot?: LeaderboardSnapshot | null;
  highlightedNation: number | null;
  onNationHover: (nationId: number | null) => void;
}) {
  const gameAPI = useGameAPI();
  const [collapsed, setCollapsed] = useState(false);
  const [snapshot, setSnapshot] = useState<LeaderboardSnapshot | null>(initialSnapshot || null);
  const [status, setStatus] = useState<"loading" | "waiting" | "ready" | "error">(initialSnapshot ? "ready" : "waiting");

  useEffect(() => {
    let unsubscribe: UnsubscribeFn = () => {};

    // Subscribe to leaderboard snapshots
    try {
      unsubscribe = gameAPI.onLeaderboardSnapshot((snapshotData) => {
        setSnapshot(snapshotData);
        setStatus("ready");
      });
    } catch (error) {
      console.warn("Failed to subscribe to leaderboard snapshots:", error);
      setStatus("error");
    }

    return () => {
      unsubscribe();
    };
  }, [gameAPI]);

  const rows = useMemo(() => {
    if (!snapshot) return [];

    const topEntries = snapshot.entries.slice(0, topN);

    // Check if local player is in top N
    const playerEntry = snapshot.entries.find(e => e.id === snapshot.client_player_id);
    const playerInTopN = playerEntry && topEntries.some(e => e.id === playerEntry.id);

    // If player exists but not in top N, add them at the end
    if (playerEntry && !playerInTopN) {
      const playerPosition = snapshot.entries.findIndex(e => e.id === playerEntry.id);
      return [...topEntries, { ...playerEntry, position: playerPosition + 1 }];
    }

    return topEntries;
  }, [snapshot, topN]);

  const precision = useMemo(() => {
    if (!snapshot || rows.length === 0) return 0;
    const percentages = rows.map((r) => r.territory_percent);
    return calculatePrecision(percentages);
  }, [snapshot, rows]);

  return (
    <div className="leaderboard no-drag block-game-input" onMouseLeave={() => onNationHover(null)}>
      <div className={`leaderboard__header ${collapsed ? 'leaderboard__header--collapsed' : ''}`} onClick={() => setCollapsed((c) => !c)}>
        <span>Leaderboard</span>
        {collapsed ? <ChevronRight size={16} /> : <ChevronDown size={16} />}
      </div>
      {!collapsed && (
        <div className="leaderboard__body">
          {status === "ready" && snapshot ? (
            <table className="leaderboard__table">
              <tbody>
                {rows.map((r) => {
                  const position = "position" in r ? r.position : snapshot.entries.findIndex(e => e.id === r.id) + 1;
                  const isPlayer = r.id === snapshot.client_player_id;
                  const isEliminated = r.territory_percent === 0;
                  const isHighlighted = highlightedNation === r.id;
                  return (
                    <tr
                      key={r.id}
                      className={`leaderboard__row ${isPlayer ? 'leaderboard__row--player' : ''} ${isEliminated ? 'leaderboard__row--eliminated' : ''} ${isHighlighted ? 'leaderboard__row--highlighted' : ''}`}
                      onClick={() => !isEliminated && console.log("select", r.id)}
                      onMouseEnter={() => !isEliminated && onNationHover(r.id)}
                      onMouseLeave={() => !isEliminated && onNationHover(null)}
                    >
                      <td className="leaderboard__position">{isEliminated ? '' : position}</td>
                      <td className="leaderboard__name">
                        <div className="leaderboard__name-content">
                          <div
                            className="leaderboard__color-circle"
                            style={{
                              backgroundColor: `#${r.color}`,
                            }}
                          />
                          <span>{r.name}</span>
                        </div>
                      </td>
                      <td className="leaderboard__percent">{isEliminated ? '—' : `${(r.territory_percent * 100).toFixed(precision)}%`}</td>
                      <td className="leaderboard__troops">{isEliminated ? '—' : r.troops.toLocaleString()}</td>
                    </tr>
                  );
                })}
              </tbody>
            </table>
          ) : (
            <div className="leaderboard__placeholder">
              {status === "loading" && "Loading leaderboard…"}
              {status === "waiting" && "Waiting for updates…"}
              {status === "error" && "Error loading leaderboard"}
            </div>
          )}
        </div>
      )}
    </div>
  );
}