thi-ng/umbrella

import type { IObjectOf } from "@thi.ng/api";
import type { ReadonlyVec } from "@thi.ng/vectors";
import { __endShape } from "./internal/end-shape.js";

export const polygon = (
    ctx: CanvasRenderingContext2D,
    attribs: IObjectOf<any>,
    pts: ReadonlyVec[]
) => {
    if (pts.length < 2) return;
    __drawPoly(ctx, pts);
    ctx.closePath();
    __endShape(ctx, attribs);
};

export const packedPolygon = (
    ctx: CanvasRenderingContext2D,
    attribs: IObjectOf<any>,
    opts: IObjectOf<any>,
    pts: ArrayLike<number>
) => {
    if (pts.length < 2) return;
    __drawPackedPoly(ctx, opts, pts);
    ctx.closePath();
    __endShape(ctx, attribs);
};

/**
 * Shared internal helper for polygon & polyline fns.
 *
 * @param ctx - canvas context
 * @param pts - poly vertices
 *
 * @internal
 */
export const __drawPoly = (
    ctx: CanvasRenderingContext2D,
    pts: ReadonlyVec[]
) => {
    let p: ReadonlyVec = pts[0];
    ctx.beginPath();
    ctx.moveTo(p[0], p[1]);
    for (let i = 1, n = pts.length; i < n; i++) {
        p = pts[i];
        ctx.lineTo(p[0], p[1]);
    }
};

/**
 * Shared internal helper for packed polygon & polyline fns.
 *
 * @param ctx - canvas context
 * @param opts - original shape atttribs (here only for packing config)
 * @param pts - flat vertex buffer
 *
 * @internal
 */
export const __drawPackedPoly = (
    ctx: CanvasRenderingContext2D,
    opts: IObjectOf<any>,
    pts: ArrayLike<number>
) => {
    const { start = 0, cstride = 1, estride = 2 } = opts;
    let num =
        opts && opts.num != null
            ? opts.num
            : ((pts.length - start) / estride) | 0;
    ctx.beginPath();
    ctx.moveTo(pts[start], pts[start + cstride]);
    for (let i = start + estride; num-- > 1; i += estride) {
        ctx.lineTo(pts[i], pts[i + cstride]);
    }
};