Add JSONP mode and captcha

JSONP mode is on by default. It will fetch main wiki pages in the
browser, without the server needing to make any requests. To turn it
off, add [feature_json] enabled = false to config.ini.

Captcha is off by default. It is a custom solution and is still
experimental at this stage. If you turn it on, please monitor the logs
to see how it goes! config.ini options are as follows:

[captcha]
enabled = true|false
log = true|false
ip_header = <header name set by your reverse proxy, like x-forwarded-for>

static/captcha.js

@@ -0,0 +1,24 @@
+const u = new URL(location)
+const from = u.searchParams.get("from") || location.href
+let answered = false
+
+const area = document.getElementById("captcha-area")
+const areaBox = area.getBoundingClientRect()
+const width = Math.floor(areaBox.width)
+const height = Math.floor(window.innerHeight - areaBox.bottom - areaBox.left)
+const img = document.createElement("img")
+img.src = `/captcha/img/${width}/${height}`
+img.addEventListener("click", event => {
+	if (answered) return
+	answered = true
+	location = `/captcha/verify/${width}/${height}/${event.offsetX}/${event.offsetY}?` + new URLSearchParams({from})
+})
+area.appendChild(img)
+
+document.addEventListener("keydown", event => {
+	if (event.repeat) {
+		if (answered) return
+		answered = true
+		location = `/captcha/verify/0/0/${event.key}/0?` + new URLSearchParams({from})
+	}
+})

static/jsonp.js

@@ -0,0 +1,57 @@
+const loading = document.getElementById("loading")
+loading.textContent = "Loading, please wait..."
+const progress = document.getElementById("progress")
+
+let wikiPage = null
+function wikiPageCallback(data) {
+	wikiPage = data
+	cont()
+}
+
+let siteinfo = null
+function siteinfoCallback(data) {
+	siteinfo = data
+	cont()
+}
+
+async function cont() {
+	if (!(wikiPage && siteinfo)) return
+
+	const xhr = new XMLHttpRequest();
+
+	const uploadFraction = 0.7
+
+	// Upload progress
+	xhr.upload.addEventListener("progress", event => {
+		if (event.lengthComputable) {
+			progress.value = (event.loaded / event.total) * uploadFraction
+			console.log(
+				`Uploaded ${((event.loaded / event.total) * 100).toFixed(2)}%`,
+			)
+		}
+	})
+
+	// Download progress
+	xhr.addEventListener("progress", event => {
+		if (event.lengthComputable) {
+			progress.value = (event.loaded / event.total) * (1 - uploadFraction) + uploadFraction
+			console.log(
+				`Downloaded ${((event.loaded / event.total) * 100).toFixed(2)}%`,
+			)
+		}
+	})
+
+	xhr.addEventListener("load", () => {
+		console.log(xhr)
+		document.body = xhr.responseXML.body
+	})
+
+	xhr.open("POST", "/api/render/wiki")
+	xhr.responseType = "document"
+	xhr.send(JSON.stringify({
+		data: wikiPage,
+		siteinfo,
+		wikiname,
+		path
+	}));
+}

static/robots.txt

@@ -2,3 +2,4 @@ User-Agent: *
 Disallow: /*/wiki/*
 Disallow: /proxy
 Disallow: /set-user-settings
+Disallow: /captcha