let r = String.raw
let whitespace = r`\s\u00AD\u2060\u200A\u200B\u200C\u200D\u20e2`
let url = r`[-\w/%&=#+~@$*'!?,.;:]*`
let url_final = r`[-\w/%&=#+~@$*']`
let big_regex = RegExp([
	r`\b(?<link>https?://${url}${url_final}([(]${url}[)](${url}${url_final})?)?)`,
	r`(?<=^|\s)[#＃](?<hashtag>(?!\uFE0F)[^${whitespace}]*[^\p{P}${whitespace}])`, // note: must filter out #123
	r`(?<=^|\s|[(])@(?<mention>[-a-zA-Z0-9]+([.][-a-zA-Z0-9]+)+)\b`,
	r`\[(?<tag_open>[a-z]+)(?:=(?<attr>[^\x5D]*))?\]`,
	r`\[/(?<tag_close>[a-z]+)\]`,
].join("|"), 'gu')
	
const STYLE_SURROUND = {
	__proto__: null,
	italic: Object.freeze(["/","/"]),
	bold: Object.freeze(["**","**"]),
	underline: Object.freeze(["__","__"]),
	strikethrough: Object.freeze(["~~","~~"]),
	code: Object.freeze(["`","`"]),
}
const TAG_FEATURES = {
	__proto__: null,
	i: Object.freeze({$type:MARKUP_TYPE, style:'italic', strip:STYLE_SURROUND['italic']}),
	b: Object.freeze({$type:MARKUP_TYPE, style:'bold', strip:STYLE_SURROUND['bold']}),
	u: Object.freeze({$type:MARKUP_TYPE, style:'underline', strip:STYLE_SURROUND['underline']}),
	s: Object.freeze({$type:MARKUP_TYPE, style:'strikethrough', strip:STYLE_SURROUND['strikethrough']}),
	code: Object.freeze({$type:MARKUP_TYPE, style:'code', strip:STYLE_SURROUND['code']}),
}

class ParseExample extends Parser {
	constructor(text) {
		super(text)
		let open_tags = new Map() // type → feature
		
		for (let match of this.run()) {
			let start = match.index
			let end = start + match[0].length
			let g = match.groups
			
			if (g.mention!=null) {
				let feature = {$type:"app.bsky.richtext.facet#mention", did:g.mention}
				this.overlay(start)
				this.event_open(feature)
				this.overlay(end, feature)
				this.event_text(match[0])
				this.event_close(feature)
			} else if (g.link!=null) {
				let feature = {$type:"app.bsky.richtext.facet#link", uri:g.link}
				this.overlay(start)
				this.event_open(feature)
				this.overlay(end, feature)
				this.event_text(g.link)
				this.event_close(feature)
			} else if (g.hashtag!=null && !/^\d+$/.test(g.hashtag)) {
				let feature = {$type:"app.bsky.richtext.facet#tag", tag:g.hashtag}
				this.overlay(start)
				this.event_open(feature)
				this.overlay(end, feature)
				this.event_text(match[0])
				this.event_close(feature)
			} else if (g.close!=null && open_brackets.length) {
				let feature = open_brackets.pop()
				if (feature) {
					this.overlay(start)
					if (feature instanceof Array) {
						for (let f of feature)
							this.event_close(f) // nn
						this.overlay(end, {$type:"#multi"})
					} else {
						this.event_close(feature, match[0])
						this.overlay(end, feature)
					}
				} else {
					this.event_text(match[0])
				}
			} else if (g.tag_open!=null) {
				let feature = TAG_FEATURES[g.tag_open]
				if (feature) {
					feature = {...feature}
					this.overlay(start)
					this.overlay(end, feature)
					this.event_open(feature, match[0])
					open_tags.set(g.tag_open, feature)
				} else {
					this.event_text(match[0])
				}
			} else if (g.tag_close!=null) {
				let feature = open_tags.get(g.tag_close)
				if (feature) {
					this.overlay(start)
					this.overlay(end, feature)
					this.event_close(feature, match[0])
				} else {
					this.event_text(match[0])
				}
			} else {
				this.overlay(end)
				this.event_text(match[0])
			}
		}
	}
}
ParseExample.prototype.regex = big_regex