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100 lines
2.2 KiB
100 lines
2.2 KiB
import DataScanner from "../util/scanner";
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export enum TileType {
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WALKABLE,
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OBSTRUCTED,
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CLIFF,
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}
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export enum Corner {
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TOP_LEFT,
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TOP_RIGHT,
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BOTTOM_RIGHT,
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BOTTOM_LEFT,
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}
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export type TileAltitudes = Record<Corner, number>;
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export type Tile = {
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altitude: TileAltitudes;
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ty: TileType;
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};
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export type GAT = {
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height: number;
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tiles: Tile[];
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width: number;
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};
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export class ParseError extends Error {
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constructor(message: string) {
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super(message);
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}
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}
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const HEADER_MAGIC = 0x54415247;
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const HEADER_SIZE_BYTES = 14;
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const SUPPORTED_VERSION = "1.2";
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const TILE_SIZE_BYTES = 20;
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const SCALING_FACTOR = -1 / 5;
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const TERRAIN_TYPE_TO_TILE_TYPE: Record<number, TileType> = {
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0: TileType.WALKABLE,
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1: TileType.OBSTRUCTED,
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5: TileType.CLIFF,
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};
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export const parseGAT = (data: ArrayBuffer): GAT => {
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const scanner = new DataScanner(data);
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const magic = scanner.uint32();
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if (magic !== HEADER_MAGIC) {
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throw new ParseError("invalid magic number");
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}
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const version = `${scanner.uint8()}.${scanner.uint8()}`;
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if (version !== SUPPORTED_VERSION) {
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throw new ParseError(`unsupported file version ${version}`);
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}
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const width = scanner.uint32();
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const height = scanner.uint32();
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const expectedSize = HEADER_SIZE_BYTES + width * height * TILE_SIZE_BYTES;
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if (data.byteLength !== expectedSize) {
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throw new ParseError(`unexpected size of data`);
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}
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const tiles = [];
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for (let i = 0; i < width * height; ++i) {
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tiles[i] = parseTile(scanner);
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}
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return {
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height,
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tiles,
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width,
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};
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};
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const parseTile = (scanner: DataScanner): Tile => {
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const bottomLeft = scanner.float32();
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const bottomRight = scanner.float32();
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const topLeft = scanner.float32();
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const topRight = scanner.float32();
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const terrainType = scanner.uint32() & 0xffff;
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if (typeof TERRAIN_TYPE_TO_TILE_TYPE[terrainType] === "undefined") {
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throw new Error(`unknown terrain type 0x${terrainType.toString(16)}`);
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}
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return {
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ty: TERRAIN_TYPE_TO_TILE_TYPE[terrainType],
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altitude: {
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[Corner.TOP_LEFT]: topLeft * SCALING_FACTOR,
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[Corner.TOP_RIGHT]: topRight * SCALING_FACTOR,
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[Corner.BOTTOM_RIGHT]: bottomRight * SCALING_FACTOR,
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[Corner.BOTTOM_LEFT]: bottomLeft * SCALING_FACTOR,
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},
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};
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};
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