<script lang="ts" module>
	import { Layout, type PageFragment } from '$gql/graphql';
	import { getContext, setContext } from 'svelte';

	export interface Chunk {
		main: PageFragment;
		secondary?: PageFragment;
		index: number;
	}

	class ReaderContext {
		visible = $state(false);
		sidebar = $state(false);
		pages: PageFragment[] = $state([]);
		page = $state(0);

		open = (page: number) => {
			this.page = page;
			this.visible = true;
		};
	}

	export function initReaderContext() {
		return setContext<ReaderContext>('reader', new ReaderContext());
	}

	export function getReaderContext() {
		return getContext<ReaderContext>('reader');
	}

	export function partition(pages: PageFragment[], layout: Layout): [Chunk[], number[]] {
		const single = layout === Layout.Single;
		const offset = layout === Layout.DoubleOffset;

		const chunks: Chunk[] = [];
		const lookup: number[] = Array<number>(pages.length);

		for (let chunkIndex = 0, pageIndex = 0; pageIndex < pages.length; chunkIndex++) {
			const wide = () => pages[pageIndex].image.aspectRatio > 1;

			const nextPage = () => {
				lookup[pageIndex] = chunkIndex;
				return pages[pageIndex++];
			};

			const offsetFirst = pageIndex === 0 && offset;
			const full = single || wide() || offsetFirst;

			const chunk: Chunk = { index: pageIndex, main: nextPage() };

			if (!full && pageIndex < pages.length) {
				if (!wide()) {
					chunk.secondary = nextPage();
				}
			}

			chunks.push(chunk);
		}
		return [chunks, lookup];
	}
</script>

<script lang="ts">
	import { trapFocus } from '$lib/Actions';
	import { fadeDefault, slideXDefault } from '$lib/Transitions';
	import type { Snippet } from 'svelte';
	import { fade, slide } from 'svelte/transition';
	import CloseReaderButton from './components/CloseReaderButton.svelte';
	import PageIndicator from './components/PageIndicator.svelte';
	import ReaderMenuButton from './components/ReaderMenuButton.svelte';

	let { sidebar, children }: { sidebar?: Snippet; children?: Snippet } = $props();

	const reader = getReaderContext();
</script>

{#if reader.visible}
	<div
		role="dialog"
		class="fixed bottom-0 left-0 right-0 top-0 z-10 flex h-full w-full bg-black"
		transition:fade={fadeDefault}
		use:trapFocus
	>
		{#if sidebar && reader.sidebar}
			<aside class="w-[36rem] shrink-0 bg-slate-800" transition:slide={slideXDefault}>
				<div class="flex h-full min-w-[36rem] flex-col gap-4 overflow-auto p-4">
					{@render sidebar?.()}
				</div>
			</aside>
		{/if}
		<main class="relative flex grow">
			<div class="absolute flex w-full p-1 text-lg [&>*:last-child]:ml-auto">
				{#if sidebar}
					<ReaderMenuButton />
				{/if}
				<CloseReaderButton />
			</div>
			<div class="absolute bottom-0 right-0 z-10 flex p-1 text-lg">
				<PageIndicator />
			</div>

			<div class="flex grow">
				{@render children?.()}
			</div>
		</main>
	</div>
{/if}