import type { Corner } from "./corner.js";
import { cross, toUnitVector } from "flo-vector2d";
import { getInterfaceCcw } from './get-interface-ccw.js';


/** 
 * @internal
 * Angle in degrees to radians.
 */
const DEGREES = {
    //'0'    : 0.0000,
    0.25 : 0.0050,
    1    : 0.0167,
    4    : 0.0698,
    16   : 0.2756,
};


/** @internal */
// const DEGREE_LIMIT = DEGREES[1];
const DEGREE_LIMIT = DEGREES[4]; 
//const DEGREE_LIMIT = DEGREES[16]; 


/**
 * @internal
 * Returns a new corner with properties.
 * 
 * @param psI The incoming bezier that ends in the corner
 * @param psO The outgoing bezier that starts at the corner
 */
function getCorner(
        psI: number[][],
        psO: number[][]): Corner {

    // `getInterfaceCcw` must return a number !== 0 if `psI` and `psO` are not
    // the same up to a curve extension with `t ∈ [-∞,+∞]`
    const { ccw, tangentI, tangentO, dotTangents } = getInterfaceCcw(psI, psO);
    const isSharp = ccw < 0;
    const isDull  = ccw > 0;

    // These use square root and are thus not exact
    const unitTangents = [
        toUnitVector(tangentI.map(v => v[1])),
        toUnitVector(tangentO.map(v => v[1])),
    ];

    // The cross calculated below should be exact due to beziers having been
    // normalized!
    const crossTangents = cross(unitTangents[0], unitTangents[1]);

    let isQuiteSharp: boolean; 
    let isQuiteDull: boolean; 
    if (dotTangents > 0) {
        // Curves go in same direction
        isQuiteSharp = crossTangents < -DEGREE_LIMIT;
        isQuiteDull = crossTangents > +DEGREE_LIMIT;
    } else {
        isQuiteSharp = isSharp;
        isQuiteDull  = isDull;
    }

    return {
        tangents: unitTangents, 
        isSharp,
        isDull, 
        isQuiteSharp,
        isQuiteDull
    };
}


export { getCorner }