thi-ng/umbrella

import { isNumber } from "@thi.ng/checks";
import { illegalArgs } from "@thi.ng/errors";
import type { CropSpec, Dim, Processor } from "../api.js";
import {
    computeMargins,
    computeSize,
    computeSizeWithAspect,
    gravityPosition,
    positionOrGravity,
} from "../units.js";

export const cropProc: Processor = async (spec, input, ctx) => {
    const { aspect, border, gravity, pos, size, ref, unit } = <CropSpec>spec;
    if (border == null && size == null)
        illegalArgs("require `border` or `size` option");
    if (border != null) {
        const sides = computeMargins(border, ctx.size, ref, unit);
        const [left, right, top, bottom] = sides;
        return [
            input.extract({
                left,
                top,
                width: ctx.size[0] - left - right,
                height: ctx.size[1] - top - bottom,
            }),
            true,
        ];
    }
    let $size: Dim;
    if (aspect != undefined) {
        if (!isNumber(size))
            illegalArgs("size must be numeric if aspect is used");
        $size = computeSizeWithAspect(size, ctx.size, aspect, unit);
    } else {
        $size = computeSize(size!, ctx.size, ref, unit);
    }
    let left = 0,
        top = 0;
    if (pos) {
        ({ left = 0, top = 0 } =
            positionOrGravity($size, ctx.size, <CropSpec>spec) || {});
    } else {
        [left, top] = gravityPosition(gravity || "c", $size, ctx.size);
    }
    return [
        input.extract({
            left,
            top,
            width: $size[0],
            height: $size[1],
        }),
        true,
    ];
};