/**
 * Shared typography math for dashboard preview ↔ FFmpeg output parity.
 * Preview container uses a fixed reference width; scale from target encode resolution.
 */

import type { WatermarkFontKey } from "./fonts";
import { CURATED_FONTS } from "./fonts";

/** Matches LayoutStudio max preview width (tailwind max-w-xl ≈ 576px; use 576 for scaling). */
export const PREVIEW_REFERENCE_WIDTH = 576;

export function titleFontSizeForWidth(width: number): number {
  return Math.max(22, Math.round(width * 0.032));
}

export function artistFontSizeForWidth(width: number): number {
  return Math.max(16, Math.round(width * 0.02));
}

export function watermarkFontSizeForWidth(width: number): number {
  return Math.max(16, Math.round(width * 0.018));
}

/** Scale encode-resolution px to preview container px. */
export function scaleFontToPreview(fontPx: number, encodeWidth: number): number {
  const ref = encodeWidth > 0 ? encodeWidth : 1280;
  return Math.max(8, Math.round((fontPx * PREVIEW_REFERENCE_WIDTH) / ref));
}

export function previewFontFamilyCss(fontKey: WatermarkFontKey | undefined): string {
  if (!fontKey || fontKey === "system") {
    return "Arial, Helvetica, sans-serif";
  }
  if (fontKey === "custom") {
    return "'S2VIDCustomWm', Arial, sans-serif";
  }
  const meta = CURATED_FONTS.find((f) => f.key === fontKey);
  return meta ? `'S2VIDPreview-${meta.key}', Arial, sans-serif` : "Arial, sans-serif";
}

export function curatedFontApiUrl(key: string): string {
  return `/api/fonts/${key}`;
}

/** Watermark overlay width as fraction of frame (matches encode.ts). */
export const WATERMARK_WIDTH_FRACTION = 0.32;