refactor: make array types in public API readonly

Mark all array properties in the public API as readonly since the
library is not supposed to mutate any of the props. Update internal
function signatures to accept readonly arrays accordingly.

Author: igordanchenko

src/config.ts

@@ -30,7 +30,7 @@ function traverse(nodes: Node[], target: string, apply: (node: Node) => Node[] |
 
 export function withPlugins(
   root: Node[],
-  plugins: Plugin[] = [],
+  plugins: readonly Plugin[] = [],
   augmentations: Augmentation[] = [],
 ): { config: Node[]; augmentation: Augmentation } {
   let config = root;

src/plugins/video/index.ts

@@ -38,7 +38,7 @@ declare module "../../types.js" {
     /** disables the capability of remote playback */
     disableRemotePlayback?: boolean;
     /** an array of video files */
-    sources: {
+    sources: readonly {
       /** video source URL */
       src: string;
       /** video source type (e.g., `video/mp4`) */

src/types.ts

@@ -28,13 +28,13 @@ export interface LightboxProps {
   /** starting slide index */
   index: number;
   /** slides to display in the lightbox */
-  slides: Slide[];
+  slides: readonly Slide[];
   /** custom render functions */
   render: Render;
   /** custom UI labels / translations */
   labels: Labels;
   /** enabled plugins */
-  plugins: Plugin[];
+  plugins: readonly Plugin[];
   /** toolbar settings */
   toolbar: ToolbarSettings;
   /** carousel settings */
@@ -87,7 +87,7 @@ export interface SlideImage extends GenericSlide {
   /** `object-fit` setting */
   imageFit?: ImageFit;
   /** alternative images to be passed to the 'srcSet' */
-  srcSet?: ImageSource[];
+  srcSet?: readonly ImageSource[];
 }
 
 /** Image source */
@@ -281,14 +281,14 @@ export type LightboxStateSwipeAction = {
 /** Lightbox state update action */
 export type LightboxStateUpdateAction = {
   type: "update";
-  slides: Slide[];
+  slides: readonly Slide[];
   index: number;
 };
 
 /** Lightbox state */
 export interface LightboxState {
   /** lightbox slides */
-  slides: Slide[];
+  slides: readonly Slide[];
   /** current slide index */
   currentIndex: number;
   /** current slide index in the (-∞, +∞) range */
@@ -414,7 +414,7 @@ export type Label = keyof Labels;
 /** Toolbar settings */
 export interface ToolbarSettings {
   /** buttons to render in the toolbar */
-  buttons: (ToolbarButtonKey | React.ReactNode)[];
+  buttons: readonly (ToolbarButtonKey | React.ReactNode)[];
 }
 
 export type ToolbarButtonKey = keyof ToolbarButtonKeys;
@@ -469,7 +469,7 @@ export type DeepPartial<T extends object, K extends keyof T = keyof T, E extends
 };
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
-export type DeepPartialValue<T, E extends string = never> = T extends any[]
+export type DeepPartialValue<T, E extends string = never> = T extends readonly any[]
   ? T
   : // eslint-disable-next-line @typescript-eslint/no-explicit-any
     T extends (...props: any[]) => any

src/utils.ts

@@ -43,7 +43,7 @@ export function label(labels: Labels | undefined, defaultLabel: Label) {
   return translateLabel(labels, defaultLabel);
 }
 
-export function translateSlideCounter(labels: Labels | undefined, slides: Slide[], index: number) {
+export function translateSlideCounter(labels: Labels | undefined, slides: readonly Slide[], index: number) {
   return translateLabel(labels, "{index} of {total}")
     .replace(/\{index}/g, `${getSlideIndex(index, slides.length) + 1}`)
     .replace(/\{total}/g, `${slides.length}`);
@@ -120,15 +120,15 @@ export function getSlideIndex(index: number, slidesCount: number) {
   return slidesCount > 0 ? ((index % slidesCount) + slidesCount) % slidesCount : 0;
 }
 
-export function hasSlides(slides: Slide[]): slides is [Slide, ...Slide[]] {
+export function hasSlides(slides: readonly Slide[]): slides is [Slide, ...Slide[]] {
   return slides.length > 0;
 }
 
 export function getSlide(slides: [Slide, ...Slide[]], index: number) {
   return slides[getSlideIndex(index, slides.length)];
 }
 
-export function getSlideIfPresent(slides: Slide[], index: number) {
+export function getSlideIfPresent(slides: readonly Slide[], index: number) {
   return hasSlides(slides) ? getSlide(slides, index) : undefined;
 }
 
@@ -162,7 +162,7 @@ export function stopNavigationEventsPropagation() {
   return { onPointerDown: stopPropagation, onKeyDown: stopPropagation, onWheel: stopPropagation };
 }
 
-export function calculatePreload(carousel: CarouselSettings, slides: Slide[], minimum = 0) {
+export function calculatePreload(carousel: CarouselSettings, slides: readonly Slide[], minimum = 0) {
   return Math.min(
     carousel.preload,
     Math.max(carousel.finite ? slides.length - 1 : Math.floor(slides.length / 2), minimum),