import type {
    FontLoadRequestConfig,
    UnifiedFont,
} from '../../model';
import { getFontUrl } from '../getFontUrl/getFontUrl';

/**
 * Build the font-lifecycle load request for a single font at a given weight.
 *
 * Returns a 0-or-1 element array rather than `FontLoadRequestConfig | undefined`
 * so call sites can `flatMap` over a font list — resolve the URL and drop fonts
 * that have none in a single pass, with no separate filter step. An empty array
 * means the font has no loadable asset for this weight (or its fallbacks) and is
 * silently skipped.
 *
 * `isVariable` is forwarded from the font's features so the lifecycle manager can
 * dedupe variable fonts per ID (they load once regardless of weight) while still
 * loading static fonts per weight.
 *
 * @param font - Unified font to load
 * @param weight - Numeric weight (100-900)
 * @returns Single-element config array, or `[]` when no URL resolves
 * @throws Error when weight is outside the valid 100-900 range (propagated from `getFontUrl`)
 */
export function createFontLoadRequestContfig(font: UnifiedFont, weight: number): FontLoadRequestConfig[] {
    const url = getFontUrl(font, weight);

    if (!url) {
        return [];
    }

    return [{ id: font.id, name: font.name, weight, url, isVariable: font.features?.isVariable }];
}