/**
 * Client-only team color assignment for the live map.
 *
 * A fixed 20-color high-contrast palette is shuffled once per page-load and
 * assigned to teams by their stable order (the order returned by the map
 * endpoint). Colors are team-shared but NOT persisted, so a refresh may
 * reassign them. Every member of a team resolves to the same color.
 */

const PALETTE = [
  '#e6194b',
  '#3cb44b',
  '#4363d8',
  '#f58231',
  '#911eb4',
  '#46f0f0',
  '#f032e6',
  '#bcf60c',
  '#fabebe',
  '#008080',
  '#e6beff',
  '#9a6324',
  '#fffac8',
  '#800000',
  '#aaffc3',
  '#808000',
  '#ffd8b1',
  '#000075',
  '#808080',
  '#ff4d00'
] as const;

function shuffled<T>(input: readonly T[]): T[] {
  const arr = [...input];
  for (let i = arr.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [arr[i], arr[j]] = [arr[j]!, arr[i]!];
  }
  return arr;
}

/** Darken a hex color by a factor (0..1) for trail lines. */
export function darken(hex: string, factor = 0.75): string {
  const n = parseInt(hex.slice(1), 16);
  const r = Math.round(((n >> 16) & 255) * factor);
  const g = Math.round(((n >> 8) & 255) * factor);
  const b = Math.round((n & 255) * factor);
  return `#${((1 << 24) | (r << 16) | (g << 8) | b).toString(16).slice(1)}`;
}

export function useTeamColors() {
  // Shuffled once per composable instance (i.e. per page-load).
  const colors = shuffled(PALETTE);

  /** Build a teamId -> color map from an ordered list of team ids. */
  function assign(orderedTeamIds: number[]): Map<number, string> {
    const map = new Map<number, string>();
    orderedTeamIds.forEach((id, i) => {
      map.set(id, colors[i % colors.length]!);
    });
    return map;
  }

  return { assign, colors, darken };
}