import Path from "path"
import FS from "fs/promises"
import { JSDOM } from "jsdom"
import Mustache from "mustache"

//     |   o |
// . . |-  . | ,-.
// | | |   | | `-.
// `-` `-' ' ' `-'

export function PromiseBatch() {
	let promises = []

	this.add = (promise) =>
		promises.push(promise)

	this.complete = () =>
		Promise.all(promises)
}

export const annotate = annotation =>
	data => {
		console.log(annotation),
		data
	}

export const write = async (path, content) => {
	let dir = Path.dirname(path)
	
	try {
		await FS.access(dir)
	} catch(e) {
		await FS.mkdir(dir, { recursive: true })
	}

	return await FS.writeFile(path, content)
}

export const createNetworkingError = response => {
	return new Error(`Request failed for ${response.url}, ${response.status}: ${response.statusText}`)
}

export const getLinkExtname = link =>
	Path.extname(new URL(link).pathname)

export const getImageBasePath = (source, postId) =>
	`${source.name}-${postId}`

export const writeStylesheet = (path, view) =>
	view.batch.add(
		FS.readFile(path)
			.then(content => write(Path.join(view.path, 'style.css'), content))
	)

export const getPostIdFromPathname = post => {
	let { pathname } = new URL(post.link)
	return pathname.slice(pathname.lastIndexOf('/') + 1)
}

export const doesExist = async (path) => {
	let exists

	try {
		await FS.access(path)
		exists = true
	} catch(err) {
		exists = false
	}

	return exists
}

export const ensureDir = async (path) => {
	let exists = doesExist(path)

	if(!exists) {
		await FS.mkdir(path, { recursive: true })
	}

	return exists
}

export const isUnset = (value) => {
	return typeof value === "undefined" || value === null
}

let waitingList = new Map()
export const sleep = delay => new Promise(resolve => setTimeout(() => resolve(), delay) )

export const delayedFetch = async (url, options, courtesyWait = 5 * 1000) => {
	let [ domain ] = /[\w-]+.[\w-]+$/.exec(new URL(url).hostname)
	let waitFor = waitingList.get(domain) ?? 0

	waitingList.set(domain, waitFor + courtesyWait)
	if(waitFor !== 0) {
		console.log(`Waiting ${waitFor}ms to download ${url}`)
		await sleep(waitFor)
	}

	return await fetch(url, options)
}

export const retryDelayedFetch = async (url, options, courtesyWait, retryAttempts) => {
	let attemptsTried = 0
	let response = undefined

	while(isUnset(response) && attemptsTried <= (retryAttempts ?? 3)) {
		if(attemptsTried > 0)
			console.error(`Failed to fetch ${url}, retrying...`)

		response = await delayedFetch(url, options, courtesyWait)
		attemptsTried++
	}

	return response
}



//
// ;-. ,-. ,-.
// |   `-. `-.
// '   `-' `-'

export const fetchChannel = async (source) => {
	let { hostname } = source
	let error
	let response
	let rss
	let channel

	try {
		response = await delayedFetch(
			new URL(source.pathname, 'https://' + hostname),
			{},
			source.courtesyWait
		)
	} catch(err) {
		error = err
	}

	source.errored = error !== undefined || !response.ok
	if(source.errored) {
		source.error = error ?? createNetworkingError(response)
		return
	}
	
	console.log(`Found ${source.name} at ${hostname}`)
	
	try {
		channel = createChannel(await response.text())
	} catch(err) {
		error = err
	}

	source.errored = error !== undefined
	if(source.errored) {
		source.error = error
		return
	}

	return channel
}

export const createChannel = rss => {
	let { document } = new JSDOM(rss, { contentType: 'text/xml' }).window

	return document.querySelector('channel')
}

export const readPubDate = (pubDate) =>
	pubDate ? new Date(pubDate.textContent).valueOf() : 0

export const createPosts = async (channel, source, fromDate, reducerCallback) => {
	let items = channel.querySelectorAll('item')

	let promises = []

	for(let item of items) {
		let post = createPost(item, source)

		if(post.date <= fromDate)
			continue

		source.items.push(item)

		let postResolvable = reducerCallback(post)
		
		if(postResolvable instanceof Promise) {
			postResolvable
				.then(post => {
					if(post) {
						source.posts.push(post)
					}
				})
		} else {
			if(postResolvable) {
				source.posts.push(postResolvable)
			}
		}

		promises.push(postResolvable)
	}

	await Promise.all(promises)
	return source
}

export const createPost = (item, source) => {
	let description = item.querySelector('description')
	description = new JSDOM(description === null ? '' : description.textContent).window.document
	
	let date = readPubDate(item.querySelector('pubDate'))
	let link = item.querySelector('link')?.textContent
	let guid = item.querySelector('guid')?.textContent
	let title = item.querySelector('title')?.textContent

	let post = {
		source,
		item,
		description,
		date,
		link,
		guid,
		title,
		occurances: []
	}
	
	return post
}

export const extractImages = (post) => {
	let images = post.description.querySelectorAll('img')

	if(images) {
		let imageUrls = []

		for(let image of images) {
			let { src } = image

			if(isUnset(src)) {
				let finalSrc = image.srcset.split(', ').pop()

				src = finalSrc.slice(0, finalSrc.indexOf(' ') )
			}
			
			// Sending through URL prevents potential XSS
			imageUrls.push(new URL(src).href)
		}

		return imageUrls
	}
}

export const processCategories = (post) => {
	let categoryMatches = post.item.querySelectorAll('category')
	post.categories = []

	for(let category of categoryMatches) {
		post.categories.push(category.textContent)
	}

	return post
}



//             .
//             |
// ,-. ,-: ,-. |-. ,-.
// |   | | |   | | |-'
// `-' `-` `-' ' ' `-'

export const createCache = async (cache = {}) => {
	if(isUnset(cache.enabled)) {
		cache.enabled = false
		return cache
	}

	if(isUnset(cache.batch))
		cache.batch = new PromiseBatch()

	await ensureDir(cache.path)

	return cache
}

export const getCachePath = (source, cache) =>
	Path.join(cache.path, source.cacheFilename)

export const cacheSource = (source, cache) =>
	write(getCachePath(source, cache), renderCache(source, cache))

export const cacheSources = (sources, cache) =>
	Promise.all(sources.map(source => cacheSource(source, cache)))

export const openCache = async (source, cache) => {
	let path = getCachePath(source, cache)
	let exists = await doesExist(path)

	let rss

	if(exists)
		rss = await FS.readFile(path, { encoding: 'utf8' })

	if(exists && rss) {
		// if(source.user == 'nanoraptor') {
		//   source.asdf = 'b'
		//   source.cache.asdf = 'b'
		// }
		let channel = createChannel(rss)

		source.cache = {
			channel,
			date: readPubDate(channel.querySelector('pubDate')),
			link: new URL(channel.querySelector('link').textContent),
		}
	} else {
		source.cache = {
			date: new Date(0)
		}

		if(source.hostname)
			source.cache.link = buildCacheLink(source)
	}

	source.latestPostDate = source.cache.date

	return source
}

export const buildCacheLink = source =>
	new URL('https://' + source.hostname)

// .replaceAll(/\n\s*/g, '')
export const renderCache = (source, cache) => `\
<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">

<channel>

<title>${source.displayName}</title>
<description>${source.description}</description>
<link>${buildCacheLink(source)}</link>
<atom:link href="${new URL(source.cacheFilename, cache.directoryUrl)}" rel="self" type="application/rss+xml" />
<pubDate>${new Date(source.latestPostDate).toUTCString()}</pubDate>
<generator>rssssing</generator>
${source.items.map(item => item.outerHTML.replaceAll(/\n\s*/g, '')).join('\n')}

</channel>

</rss>`



//         | |     |   o
// ,-. ,-. | | ,-: |-  . ,-. ;-.
// |   | | | | | | |   | | | | |
// `-' `-' ' ' `-` `-' ' `-' ' '

export const createFeed = (name, sources, main = false) => {
	return {
		name,
		displayName: name,
		main,
		posts: sources.reduce((posts, source) => posts.concat(source.posts), [])
	}
}

export const downloadImage = async (url, basename, source, view) => {
	let response = await retryDelayedFetch(url, {}, source.courtesyWait, source.retryAttempts)
		.catch(err => console.error(`Failed download of ${url}:`, err, err.errors) )

	if(response == undefined) {
		console.error('Could not download image: ' + url)
		return url
	}

	if(response.ok) {
		let mimetype = response.headers.get('Content-Type').split(';')[0]
		let extension = imageExtensions[mimetype]
		
		if(typeof extension !== 'string') {
			console.error(`Unknown mimetype for ${url}: ${mimetype}. Cannot download`)
			return url
		}

		let pathname = Path.join(view.imageStoreDirectory, basename + extension)
		let path = Path.join(view.path, pathname)

		const download = () => write(path, response.body)
			.then(annotate( `Downloaded ${pathname}`))

		view.batch.add(FS.access(path).catch(download))
		return pathname
	} else {
		console.error( createNetworkingError(response) )
		return url
	}
}

export const downloadImages = (images, source, postId, view) => {
	let basePath = getImageBasePath(source, postId)
	let pathnames = []

	for(let i = 0; i < images.length; i++) {
		let basename = images.length > 1 ? basePath + '-' + i : basePath
		let pathname = view.imageStore.get(basename)

		if(pathname === undefined) {
			pathname = downloadImage(images[i], basename, source, view)
		}

		pathnames.push(pathname)
	}
	
	return Promise.all(pathnames)
}

export const imageExtensions = {
	'image/apng': '.apng',
	'image/avif': '.avif',
	'image/bmp': '.bmp',
	'image/gif': '.gif',
	'image/gifv': '.gifv',
	'image/vnd.microsoft.icon': '.icon',
	'image/jpeg': '.jpg',
	'image/png': '.png',
	'image/svg+xml': '.xml',
	'image/tiff': '.tif',
	'image/webp': '.webp',
	'image/webm': '.gifv'
}

export const pullImages = async (post, view, discardPostIfNoImages = false, getPostId = getPostIdFromPathname) => {
	let images = extractImages(post)

	if(!discardPostIfNoImages || images.length > 0) {
		post.images = await downloadImages(
			images,
			post.source,
			getPostId(post),
			view
		)
		return post
	}
}



//     o 
// . , . ,-. , , ,
// |/  | |-' |/|/
// '   ' `-' ' '

export const createView = async (view = {}) => {
	if(isUnset(view.batch))
		view.batch = new PromiseBatch()

	if(isUnset(view.header))
		view.header = ''

	await ensureDir(view.path)

	if(view.imageStoreDirectory)
		await openImageStore(view)

	if(isUnset(view.templatesPath)) {
		view.templatesPath = Path.join(import.meta.dirname, 'templates')
	}

	if(isUnset(view.stylesheetPath)) {
		view.stylesheetPath = Path.join(import.meta.dirname, 'assets/style.css')
	}

	view.batch.add(openTemplates(view))

	return view
}

export const openImageStore = async view => {
	let imageStorePath = Path.join(view.path, view.imageStoreDirectory)
	view.imageStore = new Map()

	if(!await ensureDir(imageStorePath)) {
		return view
	}
	
	let dirents = await FS.readdir(imageStorePath, { withFileTypes: true })

	for(let dirent of dirents) {
		if(!dirent.isFile())
			continue
		
		let basename = dirent.name.slice(0, dirent.name.lastIndexOf('.'))
		view.imageStore.set(basename, Path.join(view.imageStoreDirectory, dirent.name))
	}

	return view
}

export const openTemplates = async (view) => {
	view.templates = {}
	let exists = await doesExist(view.templatesPath)
	let dirents
	
	if(exists)
		dirents = await FS.readdir(view.templatesPath, { withFileTypes: true })

	if(!exists || dirents.length === 0)
		throw new Error('Assets directory must contain a "nav" and "main" file.')

	for(let dirent of dirents) {
		if(!dirent.isFile())
			continue

		let extensionStart = dirent.name.lastIndexOf('.')
		let basename = dirent.name.slice(0, extensionStart)
		let extension = dirent.name.slice(extensionStart + 1)

		if(basename == 'main' && isUnset(view.formatExtension))
			view.formatExtension = extension
		
		view.batch.add(
			FS.readFile(Path.join(view.templatesPath, dirent.name), { encoding: 'utf-8' })
				// Must remove trailing newlines so partials will work cleanly
				.then(template => view.templates[basename] = template )
		)
	}

	return view
}

export const writeView = (sources, feeds, view) => {
	for(let source of sources)
		labelList(source, view)

	for(let feed of feeds)
		labelList(feed, view)

	view.header = renderNav(sources, feeds, view)
	let pages = []
	
	for(let source of sources) {
		pages = pages.concat(createPages(source, view))
	}

	for(let feed of feeds) {
		pages = pages.concat(createPages(feed, view))
	}

	for(let page of pages) {
		console.log('Writing page', page)
		writePage(page, view)
	}

	writeStylesheet(view.stylesheetPath, view)
}

export const labelList = (list, view) => {
	list.indexFilename = nameFinalPage(list, view)
	list.empty = list.posts.length == 0
}

export const createPages = (list, view) => {
	let posts = []
	let pages = []
	let lastPageLink = 'about:blank'

	list.posts.sort((a, b) => b.date - a.date)

	for(let i = list.posts.length - 1; i >= 0; i--) {
		posts.push(list.posts[i])

		if(i % view.pageSize == 0) {
			let filename = i < view.pageSize ? list.indexFilename :	namePage(list, pages.length, view)

			let page = {
				filename,
				title: list.displayName,
				index: pages.length,
				posts: posts.reverse(),
				lastPageLink
			}

			for(let i = 0; i < page.posts.length; i++) {
				page.posts[i].occurances.push({
					index: i,
					list,
					page
				})
			}

			pages.push(page)
			posts = []
			lastPageLink = filename
		}
	}

	console.log(list)

	return pages
}

export const namePage = (list, number, view) =>
	list.name + '-' + number + '.' + view.formatExtension

export const nameFinalPage = (list, view) =>
	(list.main ? 'index' : list.name) + '.' + view.formatExtension

export const writePage = (page, view) => {
	let content = renderPage(page, view)
	let promise = write(Path.join(view.path, page.filename), content)

	view.batch.add(promise.then(annotate(`Created ${page.filename}`)))
}

export const renderPage = (page, view) => 
	Mustache.render(view.templates.main, {
		...page,
		sections: page.posts.map(createSection),
		header: view.header,
		footer: view.footer
	}, view.templates)

export const createMustacheDelimitedArray = (array) => {
	if(isUnset(array) || array.length === 0)
		return false

	return {
		final: array[array.length -1],
		entries: array.slice(0, -1)
	}
}

export const createSection = (post, index) => {
	let date = new Date(post.date)

	return {
		post,
		index,
		date: {
			month: date.getMonth() + 1,
			day: date.getDate(),
			year: date.getFullYear()
		},
		categories: createMustacheDelimitedArray(post.categories),
		occurances: createMustacheDelimitedArray(post.occurances)
	}
}

export const renderNav = (sources, feeds, view) => {
	let sourceTypes = []

	for(let source of sources) {
		let section = sourceTypes[source.type]

		if(section) {
			section.push(source)
		} else {
			sourceTypes[source.type] = [
				source
			]
		}
	}

	return Mustache.render(view.templates.nav, {
		sourceTypes: Object.values(sourceTypes).map(createMustacheDelimitedArray),
		feeds: createMustacheDelimitedArray(feeds),
	}, view.templates)
}

//
// ,-. ,-. . . ;-. ,-. ,-.
// `-. | | | | |   |   |-'
// `-' `-' `-` '   `-' `-'

export const populateSource = async (channel, source, postReducerCallback, cache) => {
	let fromDate = 0
	source.items = []
	source.posts = []

	if(cache.enabled) {
		fromDate = source.latestPostDate

		if(source.cache.channel)
			source = await createPosts(source.cache.channel, source, 0, postReducerCallback)
	}

	let remoteReducerCallback = post => {
		if(post.date > source.latestPostDate)
			source.latestPostDate = post.date

		return postReducerCallback(post)
	}

	if(channel ?? false)
		source = await createPosts(channel, source, fromDate, remoteReducerCallback)

	return source
}

export const createSource = async (source, getChannel, postReducerCallback, cache) => {
	source.cacheFilename = source.name + '.xml'
	
	if(cache.enabled)
		source = await openCache(source, cache)
	source = await populateSource(await getChannel(source), source, postReducerCallback, cache)

	if(cache.enabled)
		cache.batch.add(cacheSource(source, cache))
	return source
}

export const createSourceOptions = (options, view) => {
	if(isUnset(options.courtesyWait))
		options.courtesyWait = 1000

	if(isUnset(options.retryAttempts))
		options.retryAttempts = 3

	return options
}