/**
 * Palette of distinguishable colors for character markers (readable on typical map tiles).
 * Same character id always maps to the same color via id % palette.length.
 */
const CHARACTER_PALETTE_FILL: string[] = [
  '#0d9488', // teal
  '#dc2626', // red
  '#2563eb', // blue
  '#16a34a', // green
  '#ea580c', // orange
  '#7c3aed', // violet
  '#db2777', // pink
  '#ca8a04', // yellow/amber
  '#0891b2', // cyan
  '#65a30d', // lime
  '#4f46e5', // indigo
  '#b45309', // brown/amber-dark
]

/** Darken a hex color by a factor (0–1). Used for stroke. */
function darkenHex(hex: string, factor: number): string {
  const n = hex.slice(1)
  const r = Math.max(0, parseInt(n.slice(0, 2), 16) * (1 - factor))
  const g = Math.max(0, parseInt(n.slice(2, 4), 16) * (1 - factor))
  const b = Math.max(0, parseInt(n.slice(4, 6), 16) * (1 - factor))
  return '#' + [r, g, b].map((x) => Math.round(x).toString(16).padStart(2, '0')).join('')
}

export interface CharacterColors {
  fill: string
  stroke: string
}

/**
 * Returns stable fill and stroke colors for a character by id.
 * Optionally use a distinct style for "owned by me" (e.g. brighter stroke).
 */
export function getColorForCharacterId(
  id: number,
  options?: { ownedByMe?: boolean }
): CharacterColors {
  const fill = CHARACTER_PALETTE_FILL[Math.abs(id) % CHARACTER_PALETTE_FILL.length]
  const stroke = darkenHex(fill, 0.25)
  if (options?.ownedByMe) {
    return { fill, stroke: '#1e293b' }
  }
  return { fill, stroke }
}