/**
 * Canonical tile patterns for linear features.
 * Each pattern has a base edge mask and can be rotated in 60° increments.
 * Coastlines only use 2-edge patterns and have an additional waterSide property.
 */

import type { EdgeMask } from './types.js';
import { HexEdge } from './types.js';
import { edgeMask, rotateMask } from './edge-connectivity.js';

export interface TilePattern {
  id: string;
  name: string;
  baseMask: EdgeMask;
  /** Max distinct rotations (accounting for symmetry) */
  rotations: number;
  /** Number of connected edges */
  edgeCount: number;
}

/** General patterns for road/river (all edge counts) */
export const GENERAL_PATTERNS: TilePattern[] = [
  {
    id: 'dead-end',
    name: 'Dead End',
    baseMask: edgeMask(HexEdge.E),
    rotations: 6,
    edgeCount: 1,
  },
  {
    id: 'straight',
    name: 'Straight',
    baseMask: edgeMask(HexEdge.E, HexEdge.W),
    rotations: 3,
    edgeCount: 2,
  },
  {
    id: 'gentle-curve',
    name: 'Wide Curve',
    baseMask: edgeMask(HexEdge.E, HexEdge.SW),
    rotations: 6,
    edgeCount: 2,
  },
  {
    id: 'sharp-bend',
    name: 'Sharp Bend',
    baseMask: edgeMask(HexEdge.E, HexEdge.SE),
    rotations: 6,
    edgeCount: 2,
  },
  {
    id: 'y-junction',
    name: 'Y Split',
    baseMask: edgeMask(HexEdge.NE, HexEdge.SE, HexEdge.W),
    rotations: 6,
    edgeCount: 3,
  },
  {
    id: 'y-junction-wide',
    name: 'Y Wide',
    baseMask: edgeMask(HexEdge.NE, HexEdge.SW, HexEdge.SE),
    rotations: 6,
    edgeCount: 3,
  },
  {
    id: 'crossroads',
    name: 'Cross',
    baseMask: edgeMask(HexEdge.NE, HexEdge.E, HexEdge.SW, HexEdge.W),
    rotations: 3,
    edgeCount: 4,
  },
];

/** Coastline patterns — only 2-edge (a coast is always a line from A to B) */
export const COASTLINE_PATTERNS: TilePattern[] = [
  {
    id: 'straight',
    name: 'Straight',
    baseMask: edgeMask(HexEdge.E, HexEdge.W),
    rotations: 3,
    edgeCount: 2,
  },
  {
    id: 'gentle-curve',
    name: 'Wide Curve',
    baseMask: edgeMask(HexEdge.E, HexEdge.SW),
    rotations: 6,
    edgeCount: 2,
  },
  {
    id: 'sharp-bend',
    name: 'Sharp Bend',
    baseMask: edgeMask(HexEdge.E, HexEdge.SE),
    rotations: 6,
    edgeCount: 2,
  },
];

/**
 * Get the appropriate patterns for a terrain type.
 */
export function getPatternsForTerrain(terrainId: string): TilePattern[] {
  if (terrainId === 'coastline') return COASTLINE_PATTERNS;
  return GENERAL_PATTERNS;
}

/**
 * Rotate a mask by N steps (each step = 60° clockwise).
 */
export function rotatePattern(mask: EdgeMask, steps: number): EdgeMask {
  return rotateMask(mask, steps);
}