/**
 * Stream persistence layer — overlay layout and visual/voice settings I/O.
 *
 * Extracted from stream-routes.ts to keep that file focused on route handling.
 * All functions here deal with reading/writing JSON files under the
 * `data/stream/` directory.
 *
 * @module api/stream-persistence
 */
import type { StreamingDestination } from "./streaming-types";
export interface StreamVoiceSettings {
    enabled: boolean;
    provider?: string;
    autoSpeak?: boolean;
}
export interface StreamVisualSettings {
    theme?: string;
    avatarIndex?: number;
    voice?: StreamVoiceSettings;
}
/** Sanitize destination ID for use as a filename segment. */
export declare function safeDestId(id: string): string;
/** Extract `?destination=<id>` from the raw request URL. */
export declare function parseDestinationQuery(url?: string): string | undefined;
/**
 * Read overlay layout for a destination.
 * Falls back: destination-specific -> global -> plugin default -> null.
 */
export declare function readOverlayLayout(destinationId?: string | null, destination?: StreamingDestination): unknown;
/** Write overlay layout (to destination-specific or global file). */
export declare function writeOverlayLayout(layout: unknown, destinationId?: string | null): void;
/**
 * Seed the plugin's default overlay layout on first stream start.
 * Only writes if no destination-specific layout file exists yet.
 */
export declare function seedOverlayDefaults(destination: StreamingDestination): void;
/**
 * Validate and sanitize a raw settings object into a safe StreamVisualSettings.
 * Only allows known keys with expected types — rejects everything else.
 * Returns null with an error message if validation fails.
 */
export declare function validateStreamSettings(raw: unknown): {
    settings: StreamVisualSettings;
    error?: undefined;
} | {
    settings?: undefined;
    error: string;
};
export declare function readStreamSettings(): StreamVisualSettings;
export declare function writeStreamSettings(settings: StreamVisualSettings): void;
/**
 * Build the visual config for browser-capture by merging:
 *   1. Server-side stream-settings.json (authoritative)
 *   2. Environment variables (STREAM_THEME, STREAM_AVATAR_INDEX) as fallback
 *
 * Reads the active destination's overlay layout when available.
 */
export declare function getHeadlessCaptureConfig(destinationId?: string | null): {
    overlayLayout?: string;
    theme?: string;
    avatarIndex?: number;
    destinationId?: string;
};
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