// Pure mapping from the public PDFRenderer options to the underlying
// Playwright `page.pdf()` options. Kept side-effect free and browser-free so it
// can be unit-tested without launching Chromium.

import type { PageMargin, PaperSize } from "./print-css";

export interface PDFRenderOptions {
  /** Paper size. Defaults to "Letter". */
  paperSize?: PaperSize;
  /**
   * Page margin. A single CSS length applies to all sides; an object sets
   * sides individually (missing sides default to "0"). Defaults to "0.5in".
   */
  margin?: PageMargin;
  /**
   * Whether to print CSS backgrounds (colors/images). Defaults to `true` —
   * invoices and reports rely on background fills for headers/zebra rows.
   */
  printBackground?: boolean;
}

/** Per-side margin object as Playwright's `page.pdf()` expects it. */
export interface PlaywrightMargin {
  top: string;
  right: string;
  bottom: string;
  left: string;
}

/** Subset of Playwright's PDFOptions this module produces. */
export interface PlaywrightPdfOptions {
  format: "Letter" | "A4";
  margin: PlaywrightMargin;
  printBackground: boolean;
  /**
   * When true, a template's own `@page` size/margin wins over `format`/`margin`.
   * Always enabled so the shared print-CSS base remains authoritative while the
   * options provide a sane fallback for HTML that omits an `@page` rule.
   */
  preferCSSPageSize: true;
}

const DEFAULT_MARGIN = "0.5in";

export function resolveMargin(
  margin: PageMargin | undefined,
): PlaywrightMargin {
  if (margin === undefined) {
    return {
      top: DEFAULT_MARGIN,
      right: DEFAULT_MARGIN,
      bottom: DEFAULT_MARGIN,
      left: DEFAULT_MARGIN,
    };
  }
  if (typeof margin === "string") {
    return { top: margin, right: margin, bottom: margin, left: margin };
  }
  return {
    top: margin.top ?? "0",
    right: margin.right ?? "0",
    bottom: margin.bottom ?? "0",
    left: margin.left ?? "0",
  };
}

/**
 * Translate public render options into Playwright `page.pdf()` options. Pure:
 * no browser, no I/O.
 */
export function toPdfOptions(
  options: PDFRenderOptions = {},
): PlaywrightPdfOptions {
  return {
    format: options.paperSize === "A4" ? "A4" : "Letter",
    margin: resolveMargin(options.margin),
    printBackground: options.printBackground ?? true,
    preferCSSPageSize: true,
  };
}