// the css side of pierre theming lives in src/pierre.css

import {
	getSharedHighlighter,
	type FileDiffOptions,
	type FileOptions,
	type VirtualFileMetrics
} from "@pierre/diffs";
import { browser } from "$app/environment";
import diffShadowCSS from "$lib/components/repo/pierreDiff.css?raw";
import { SYNTAX_THEME_NAME } from "$lib/syntax";
import type { WorkerPoolManager } from "@pierre/diffs/worker";

// pierre's two diff layouts, threaded from the ?diff= url param down to the
// FileDiff instances
export type DiffStyle = NonNullable<FileDiffOptions<undefined, undefined>["diffStyle"]>;

// pierre stops highlighting after 1000 characters, lockfiles often run longer
const PIERRE_TOKENIZE_MAX_LINE_LENGTH = 5000;

const PIERRE_BASE_OPTIONS = {
	theme: SYNTAX_THEME_NAME,
	themeType: "system",
	tokenizeMaxLineLength: PIERRE_TOKENIZE_MAX_LINE_LENGTH
} as const;

// pierre's core stylesheet reaches a container two ways: the `diffs-container`
// custom element adopts it in its constructor, but bails when the element already
// has a shadow root — which an ssr'd `<template shadowrootmode>` gives it — and the
// ssr preloads embed it as a `<style data-core-css>` child instead. so clearing
// every child of an ssr'd shadow root leaves each later client render unstyled:
// pierre rebuilds the <pre> but never re-emits core css for a managed container.
// one sheet covers unified, split and wrap, so the ssr'd one stays correct.
export const clearPierreRender = (host: HTMLElement): void => {
	for (const node of [...(host.shadowRoot?.children ?? [])])
		if (node instanceof HTMLPreElement) node.remove();
};

// Pierre's CodeView accepts only a strict subset of Diff options.
export const pierreCodeViewOptions = (style: DiffStyle, wrap: boolean = false) => ({
	...PIERRE_BASE_OPTIONS,
	diffStyle: style,
	diffIndicators: "bars" as const,
	lineDiffType: "word-alt" as const,
	hunkSeparators: "line-info" as const,
	overflow: wrap ? ("wrap" as const) : ("scroll" as const),
	unsafeCSS: diffShadowCSS
});

export const pierreFileOptions = (wrap: boolean): FileOptions<undefined, undefined> => ({
	...PIERRE_BASE_OPTIONS,
	disableFileHeader: true,
	overflow: wrap ? "wrap" : "scroll"
});

export const prerenderFile = async (
	name: string,
	contents: string | null
): Promise<string | undefined> => {
	if (browser || contents === null) return undefined;
	const { preloadFile } = await import("@pierre/diffs/ssr");
	const { prerenderedHTML } = await preloadFile({
		file: { name, contents },
		options: pierreFileOptions(false)
	});
	return prerenderedHTML;
};

// lazy dynamic imports: pierre's worker bundle trips vite's dev dependency optimizer
let workerPool: WorkerPoolManager | undefined;
let workerPoolFailed = false;
let workerPoolPromise: Promise<WorkerPoolManager | undefined> | undefined;

const createWorkerPool = async (): Promise<WorkerPoolManager | undefined> => {
	try {
		const [{ getOrCreateWorkerPoolSingleton }, { default: PierreWorker }] = await Promise.all([
			import("@pierre/diffs/worker"),
			import("@pierre/diffs/worker/worker.js?worker")
		]);
		workerPool = getOrCreateWorkerPoolSingleton({
			poolOptions: {
				workerFactory: () => new PierreWorker(),
				poolSize: Math.max(2, Math.min(4, (navigator.hardwareConcurrency ?? 4) - 1)),
				totalASTLRUCacheSize: 24
			},
			highlighterOptions: {
				theme: SYNTAX_THEME_NAME,
				useTokenTransformer: false,
				lineDiffType: "word-alt",
				maxLineDiffLength: 1000,
				tokenizeMaxLineLength: PIERRE_TOKENIZE_MAX_LINE_LENGTH,
				preferredHighlighter: "shiki-js",
				langs: []
			}
		});
	} catch {
		workerPoolFailed = true;
	}
	return workerPool;
};

export const getPierreWorkerPool = (): Promise<WorkerPoolManager | undefined> => {
	if (!browser) return Promise.resolve(workerPool);

	if (workerPoolFailed) {
		workerPoolFailed = false;
		workerPoolPromise = undefined;
	}
	return (workerPoolPromise ??= createWorkerPool());
};

// without this warmup pierre's first render of a missing language is blank
if (browser) void getSharedHighlighter({ themes: [SYNTAX_THEME_NAME], langs: [] });

export const PIERRE_VALIDATE_ITEM_HEIGHTS =
	import.meta.env.DEV && browser && new URLSearchParams(location.search).has("diffmetrics");

export const PIERRE_LINE_HEIGHT = 21;
export const PIERRE_HUNK_LINE_COUNT = 50;

export const PIERRE_ITEM_METRICS: Partial<VirtualFileMetrics> = {
	lineHeight: PIERRE_LINE_HEIGHT,
	hunkLineCount: PIERRE_HUNK_LINE_COUNT,
	hunkSeparatorHeight: PIERRE_LINE_HEIGHT,
	spacing: 0
};