/**
* Composable HTML transforms applied after rendering. Use via
* middleware so the pipeline runs just before `driver.send`:
*
* ```ts
* email.use(htmlPipeline(withPreheader(), inlineCss(), cidRewrite()))
* ```
*
* Each transform is a pure function over the rendered HTML string.
*
* @module
*/
import type { EmailMessage, Middleware } from "../types.mjs";
export type HtmlTransform = (html: string, msg: EmailMessage) => string | Promise<string>;
/** Pipe `EmailMessage.html` through each transform in order. */
export declare function htmlPipeline(...transforms: HtmlTransform[]): Middleware;
/** Inject a hidden preheader snippet (Litmus-approved) before the
*  visible content. Uses `msg.preheader` when present, or falls back
*  to the supplied function. */
export interface PreheaderOptions {
	/** Explicit text to use. Overrides `msg.preheader`. */
	text?: string | ((msg: EmailMessage) => string | undefined);
}
export declare function withPreheader(options?: PreheaderOptions): HtmlTransform;
/** Dark-mode CSS hook — injects Outlook.com / Apple Mail dark-mode
*  meta tags + a `[data-ogsc]` scope. Consumers supply the rules. */
export interface DarkModeOptions {
	/** CSS block applied via `[data-ogsc]` (Outlook.com) and
	*  `@media (prefers-color-scheme: dark)`. */
	darkCss?: string;
}
export declare function darkModeHook(options?: DarkModeOptions): HtmlTransform;
/** CID auto-rewrite — scan for `<img src="…">` tags whose src matches
*  a CID on one of the message attachments and rewrite to `cid:<id>`. */
export declare function cidRewrite(): HtmlTransform;
/** CSS inliner — lazy-loads `juice` if you have it installed. Passes
*  through HTML unchanged when juice isn't available. */
export declare function inlineCss(): HtmlTransform;