// src/shared/lib/helpers/__mocks__/canvas.ts
//
// Call installCanvasMock(fn) before any pretext import to control measureText.
// The factory receives the current ctx.font string and the text to measure.
import { vi } from 'vitest';

export type MeasureFactory = (font: string, text: string) => number;

export function installCanvasMock(factory: MeasureFactory): void {
    let currentFont = '';

    const mockCtx = {
        get font() {
            return currentFont;
        },
        set font(f: string) {
            currentFont = f;
        },
        measureText: vi.fn((text: string) => ({ width: factory(currentFont, text) })),
    };

    // HTMLCanvasElement.prototype.getContext is the entry point pretext uses in DOM environments.
    // OffscreenCanvas takes priority in pretext; jsdom does not define it so DOM path is used.
    Object.defineProperty(HTMLCanvasElement.prototype, 'getContext', {
        configurable: true,
        writable: true,
        value: vi.fn(() => mockCtx),
    });
}