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export class EquilateralTriangle {
/** Helper class that represent an equilateral triangle.;
Used to compute intersection of a line with a side of convoy symbol, which is an equilateral triangle. **/
constructor(x_top, y_top, x_right, y_right, x_left, y_left) {
this.x_A = x_top;
this.y_A = y_top;
this.x_B = x_right;
this.y_B = y_right;
this.x_C = x_left;
this.y_C = y_left;
this.h = this.y_B - this.y_A;
this.x_O = this.x_A;
this.y_O = this.y_A + 2 * this.h / 3;
this.line_AB_a = (this.y_B - this.y_A) / (this.x_B - this.x_A);
this.line_AB_b = this.y_B - this.x_B * this.line_AB_a;
this.line_AC_a = (this.y_C - this.y_A) / (this.x_C - this.x_A);
this.line_AC_b = this.y_C - this.x_C * this.line_AC_a;
}
__line_OM(x_M, y_M) {
const a = (y_M - this.y_O) / (x_M - this.x_O);
const b = y_M - a * x_M;
return [a, b];
}
__intersection_with_AB(x_M, y_M) {
const [a, b] = [this.line_AB_a, this.line_AB_b];
let x = null;
if (x_M === this.x_O) {
x = x_M;
} else {
const [u, v] = this.__line_OM(x_M, y_M);
if (a === u)
return [null, null];
x = (v - b) / (a - u);
}
const y = a * x + b;
if (this.x_A <= x && x <= this.x_B && this.y_A <= y && y <= this.y_B)
return [x, y];
return [null, null];
}
__intersection_with_AC(x_M, y_M) {
const [a, b] = [this.line_AC_a, this.line_AC_b];
let x = null;
if (x_M === this.x_O) {
x = x_M;
} else {
const [u, v] = this.__line_OM(x_M, y_M);
if (a === u)
return [null, null];
x = (v - b) / (a - u);
}
const y = a * x + b;
if (this.x_C <= x && x <= this.x_A && this.y_A <= y && y <= this.y_C)
return [x, y];
return [null, null];
}
__intersection_with_BC(x_M, y_M) {
const y = this.y_C;
let x = null;
if (x_M === this.x_O) {
x = x_M;
} else {
const [a, b] = this.__line_OM(x_M, y_M);
if (a === 0)
return [null, null];
x = (y - b) / a;
}
if (this.x_C <= x && x <= this.x_A)
return [x, y];
return [null, null];
}
intersection(x_M, y_M) {
if (this.x_O === x_M && this.y_O === y_M)
return [x_M, y_M];
if (this.x_O === x_M) {
if (y_M < this.y_O)
return [x_M, this.y_A];
else {
// vertical line intersects BC;
return [x_M, this.y_C];
}
} else if (this.y_O === y_M) {
let a = null;
let b = null;
if (x_M < this.x_O) {
// horizontal line intersects AC;
[a, b] = [this.line_AC_a, this.line_AC_b];
} else {
// horizontal line intersects AB;
[a, b] = [this.line_AB_a, this.line_AB_b];
}
const x = (y_M - b) / a;
return [x, y_M];
} else {
// get nearest point in intersections with AB, AC, BC;
const [p1_x, p1_y] = this.__intersection_with_AB(x_M, y_M);
const [p2_x, p2_y] = this.__intersection_with_AC(x_M, y_M);
const [p3_x, p3_y] = this.__intersection_with_BC(x_M, y_M);
const distances = [];
if (p1_x !== null) {
const d1 = Math.sqrt((p1_x - x_M) * (p1_x - x_M) + (p1_y - y_M) * (p1_y - y_M));
distances.push([d1, p1_x, p1_y]);
}
if (p2_x !== null) {
const d2 = Math.sqrt((p2_x - x_M) * (p2_x - x_M) + (p2_y - y_M) * (p2_y - y_M));
distances.push([d2, p2_x, p2_y]);
}
if (p3_x !== null) {
const d3 = Math.sqrt((p3_x - x_M) * (p3_x - x_M) + (p3_y - y_M) * (p3_y - y_M));
distances.push([d3, p3_x, p3_y]);
}
distances.sort();
const output = distances[0];
output.shift();
return output;
}
}
}
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