feuerwerk/src/core/model/tile.ts

import type { TileAsset } from './Asset';
import { textOf } from './Properties';
import type { Project } from './Project';
import { type FrameRect, resolvePicture, type TextureRef } from './texture';

/**
 * A tile is one picture per animation step, and every picture is a *block* the editor cuts into
 * quarter tiles. `none` is the plain case: the block is the tile itself and every cell shows it as
 * it is (#131). `floor` and `wall` are the two autotile blocks of the classic RPG-Maker sheets,
 * whose quarters are picked by the neighbours – that part is `model/autotile.ts`.
 *
 * Everything below counts in *quadrants* – quarter tiles – with (0, 0) at the block's top-left
 * corner, so all three kinds are drawn the same way: four quarters per tile.
 */
export const TILE_KINDS = ['none', 'floor', 'wall'] as const;
export type TileKind = (typeof TILE_KINDS)[number];

export const TILE_KIND_KEY = 'kind';
export const TILE_FPS_KEY = 'fps';
export const TILE_PLAYBACK_KEY = 'playback';
/** Whether a cell of this tile blocks movement in the running game (#132). */
export const TILE_SOLID_KEY = 'solid';
/** How big the blocking box of a cell is against the cell, 1 = the whole cell (#140). */
export const TILE_COLLISION_SCALE_KEY = 'collisionScale';
export const TILE_COLLISION_SCALE_MIN = 0.1;
export const TILE_COLLISION_SCALE_MAX = 2;

/** Only the two that make sense for a tile that is always on screen; there is no end to hold. */
export const TILE_PLAYBACKS = ['loop', 'pingpong'] as const;
export type TilePlayback = (typeof TILE_PLAYBACKS)[number];

/** Quadrant columns of a block: one tile for `none`, two for the autotile blocks. */
export const BLOCK_COLUMNS: Record<TileKind, number> = { none: 2, floor: 4, wall: 4 };

/** Quadrant rows of a block: `none` is one tile tall, `floor` three and `wall` two. */
export const BLOCK_ROWS: Record<TileKind, number> = { none: 2, floor: 6, wall: 4 };

export function tileKind(asset: TileAsset): TileKind {
  const value = textOf(asset.props[TILE_KIND_KEY] ?? 'none');
  return (TILE_KINDS as readonly string[]).includes(value) ? (value as TileKind) : 'none';
}

export function tilePlayback(asset: TileAsset): TilePlayback {
  const value = textOf(asset.props[TILE_PLAYBACK_KEY] ?? 'loop');
  return (TILE_PLAYBACKS as readonly string[]).includes(value) ? (value as TilePlayback) : 'loop';
}

export function isTileSolid(asset: TileAsset): boolean {
  return asset.props[TILE_SOLID_KEY] === true;
}

/** The collision scale, held to the range the field offers; anything unreadable is the whole cell. */
export function tileCollisionScale(asset: TileAsset): number {
  const scale = Number(asset.props[TILE_COLLISION_SCALE_KEY] ?? 1);
  if (!Number.isFinite(scale)) return 1;
  return Math.min(TILE_COLLISION_SCALE_MAX, Math.max(TILE_COLLISION_SCALE_MIN, scale));
}

export function tileFps(asset: TileAsset): number {
  const fps = Number(asset.props[TILE_FPS_KEY]);
  return Number.isFinite(fps) && fps > 0 ? fps : 0;
}

/** A quarter tile inside the block, in quadrant units from its top-left corner. */
export interface QuadPos {
  x: number;
  y: number;
}

/** One picture of a tile: the reference it was named by, and the block it covers. */
export interface TilePicture {
  id: string;
  ref: TextureRef;
  block: FrameRect;
}

/**
 * What the tab can draw and what stands in its way. `problem` is a sentence for the reader, never
 * a reason to drop anything: a picture of the wrong size stays in the list and can be taken out
 * again or the kind switched to the one it fits.
 */
export interface TileInfo {
  kind: TileKind;
  pictures: TilePicture[];
  /** Side of one tile in image pixels, 0 while the tile has no usable picture. */
  tile: number;
  /** Side of one quarter tile – half a tile, and what the block is measured in. */
  quad: number;
  problem: string;
}

/**
 * Reads a tile against the project: resolves every picture, derives the tile size from the first
 * one and says what does not fit. The tile size is derived rather than stored – the block's width
 * is a known number of tiles, so a second number could only ever disagree with the picture.
 */
export function readTile(project: Project, asset: TileAsset): TileInfo {
  const kind = tileKind(asset);
  const columns = BLOCK_COLUMNS[kind];
  const rows = BLOCK_ROWS[kind];
  const pictures: TilePicture[] = [];
  const missing: string[] = [];
  for (const id of asset.pictures) {
    const ref = resolvePicture(project, id);
    if (!ref) {
      missing.push(id);
      continue;
    }
    pictures.push({ id, ref, block: ref.rect ?? { x: 0, y: 0, w: ref.sourceWidth, h: ref.sourceHeight } });
  }
  const first = pictures[0];
  const quad = first ? first.block.w / columns : 0;
  // A plain tile is only cut to be drawn like the others, never along a line in the picture, so
  // an odd side is fine there; an autotile block is cut along its quarters and must split evenly.
  const whole = kind === 'none' || Number.isInteger(quad);
  const fits = (rect: FrameRect) => rect.w === quad * columns && rect.h === quad * rows && whole && quad > 0;
  const problem =
    asset.pictures.length === 0
      ? 'No picture yet – add a texture or a frame that holds one block.'
      : missing.length > 0
        ? `${missing.length} picture(s) no longer exist.`
        : !first || !fits(first.block)
          ? blockProblem(kind, first?.block)
          : pictures.some((picture) => !fits(picture.block))
            ? 'The pictures have different sizes; every step of an animation must hold the same block.'
            : '';
  return { kind, pictures, tile: problem === '' ? quad * 2 : 0, quad: problem === '' ? quad : 0, problem };
}

function blockProblem(kind: TileKind, block: FrameRect | undefined): string {
  const size = block ? `, this one is ${block.w} × ${block.h} px` : '';
  if (kind === 'none') return `A plain tile is one square tile${size}.`;
  const columns = BLOCK_COLUMNS[kind];
  const rows = BLOCK_ROWS[kind];
  const shape = `${columns / 2} × ${rows / 2} tiles`;
  return `A ${kind} block is ${shape}, so its sides must divide by ${columns} and ${rows}${size}.`;
}

/** The rectangle one quarter tile is cut from, in image pixels. */
export function quadrantRect(picture: TilePicture, quad: number, position: QuadPos): FrameRect {
  return {
    x: picture.block.x + position.x * quad,
    y: picture.block.y + position.y * quad,
    w: quad,
    h: quad,
  };
}

/** That quarter as a texture reference of its own – a cut of the sheet, never nine-sliced. */
export function quadrantRef(picture: TilePicture, quad: number, position: QuadPos): TextureRef {
  return { ...picture.ref, rect: quadrantRect(picture, quad, position), slice: null };
}

/**
 * Which picture is shown `time` seconds in. One picture is a still image whatever the settings
 * say; ping-pong turns on the last one, so three pictures run 0 1 2 1 and not 0 1 2 2 1.
 */
export function pictureIndexAt(count: number, playback: TilePlayback, fps: number, time: number): number {
  if (count <= 1) return 0;
  if (!Number.isFinite(fps) || fps <= 0 || !Number.isFinite(time) || time <= 0) return 0;
  const step = Math.floor(time * fps);
  if (playback === 'loop') return step % count;
  const span = 2 * (count - 1);
  const phase = step % span;
  return phase < count ? phase : span - phase;
}