Add spyglass context and file watcher

src/app/contexts/Spyglass.tsx

@@ -0,0 +1,64 @@
+import type { DocAndNode } from '@spyglassmc/core'
+import type { ComponentChildren } from 'preact'
+import { createContext } from 'preact'
+import type { Inputs } from 'preact/hooks'
+import { useContext, useEffect, useState } from 'preact/hooks'
+import { useAsync } from '../hooks/useAsync.js'
+import { Spyglass } from '../services/Spyglass.js'
+import { useVersion } from './Version.jsx'
+
+interface SpyglassContext {
+	spyglass?: Spyglass,
+	spyglassLoading: boolean,
+}
+
+const SpyglassContext = createContext<SpyglassContext | undefined>(undefined)
+
+export function useSpyglass(): SpyglassContext {
+	return useContext(SpyglassContext) ?? { spyglassLoading: true }
+}
+
+export function watchSpyglassUri(
+	uri: string | undefined,
+	handler: (docAndNode: DocAndNode) => void,
+	inputs: Inputs = [],
+) {
+	const { spyglass, spyglassLoading } = useSpyglass()
+
+	useEffect(() => {
+		if (!uri || !spyglass || spyglassLoading) {
+			return
+		}
+		spyglass.watchFile(uri, handler)
+		return () => spyglass.unwatchFile(uri, handler)
+	}, [spyglass, uri, handler, ...inputs])
+}
+
+export function useDocAndNode(origina: DocAndNode, inputs?: Inputs): DocAndNode
+export function useDocAndNode(origina: DocAndNode | undefined, inputs?: Inputs): DocAndNode | undefined
+export function useDocAndNode(original: DocAndNode | undefined, inputs: Inputs = []) {
+	const [wrapped, setWrapped] = useState(original)
+
+	watchSpyglassUri(original?.doc.uri, updated => {
+		setWrapped(updated)
+	}, [original?.doc.uri, setWrapped, ...inputs])
+
+	return wrapped
+}
+
+export function SpyglassProvider({ children }: { children: ComponentChildren }) {
+	const { version } = useVersion()
+
+	const { value: spyglass, loading: spyglassLoading } = useAsync(() => {
+		return Spyglass.initialize(version)
+	}, [version])
+
+	const value: SpyglassContext = {
+		spyglass,
+		spyglassLoading,
+	}
+
+	return <SpyglassContext.Provider value={value}>
+		{children}
+	</SpyglassContext.Provider>
+}