Merge pull request 'Refactor homeserver lookup code' (#12) from refactor-homeserver-lookup into princess

Reviewed-on: #12

src/js/login.js

@@ -77,40 +77,16 @@ class Form extends ElemJS {
 		if (!username.isValid()) return this.cancel("Username is not valid.")
 
 		// Resolve homeserver address
-		let currentAddress = homeserver.value
-		let ok = false
-		while (!ok) {
-			if (!currentAddress.match(/^https?:\/\//)) {
-				console.warn(`${currentAddress} doesn't specify the protocol, assuming https`)
-				currentAddress = "https://" + currentAddress
-		}
-			currentAddress = currentAddress.replace(/\/*$/, "")
-			this.status(`Looking up homeserver... trying ${currentAddress}`)
-			try {
-				// check if we found the actual matrix server
-				try {
-					const versions = await fetch(`${currentAddress}/_matrix/client/versions`).then(res => res.json())
-					if (Array.isArray(versions.versions)) {
-						ok = true
-						break
-					}
-				} catch (e) {}
-				// find the next matrix server in the chain
-				const root = await fetch(`${currentAddress}/.well-known/matrix/client`).then(res => res.json())
-				let nextAddress = root["m.homeserver"].base_url
-				nextAddress = nextAddress.replace(/\/*$/, "")
-				if (currentAddress === nextAddress) {
-					ok = true
-				}
-				currentAddress = nextAddress
-			} catch (e) {
-				return this.cancel(`Failed to look up server ${currentAddress}`)
-			}
+		let domain
+		try {
+			domain = await this.findHomeserver(homeserver.value)
+		} catch(e) {
+			return this.cancel(e.message)
 		}
 
 		// Request access token
 		this.status("Logging in...")
-		const root = await fetch(`${currentAddress}/_matrix/client/r0/login`, {
+		const root = await fetch(`${domain}/_matrix/client/r0/login`, {
 			method: "POST",
 			body: JSON.stringify({
 				type: "m.login.password",
@@ -130,12 +106,52 @@ class Form extends ElemJS {
 		}
 
 		localStorage.setItem("mx_user_id", root.user_id)
-		localStorage.setItem("domain", currentAddress)
+		localStorage.setItem("domain", domain)
 		localStorage.setItem("access_token", root.access_token)
 
 		location.assign("../")
 	}
 
+	async findHomeserver(address, maxDepth = 5) {
+
+		//Protects from servers sending us on a redirect loop
+		maxDepth--
+		if (maxDepth <= 0) throw new Error(`Failed to look up homeserver, maximum search depth reached`)
+	
+		//Normalise the address
+		if (!address.match(/^https?:\/\//)) {
+			console.warn(`${address} doesn't specify the protocol, assuming https`)
+			address = "https://" + address
+		}
+		address = address.replace(/\/*$/, "")
+		
+		this.status(`Looking up homeserver... trying ${address}`)
+	
+		// Check if we found the actual matrix server
+		try {
+			const versionsReq = await fetch(`${address}/_matrix/client/versions`)
+			if (versionsReq.ok) {
+				const versions = await versionsReq.json()
+				if (Array.isArray(versions.versions)) return address
+			}
+		} catch(e) {}
+	
+		// Find the next matrix server in the chain
+		const root = await fetch(`${address}/.well-known/matrix/client`).then(res => res.json()).catch(e => {
+ 			console.error(e)
+			throw new Error(`Failed to look up server ${address}`)
+		})
+
+		let nextAddress = root["m.homeserver"].base_url
+		nextAddress = nextAddress.replace(/\/*$/, "")
+
+		if (address === nextAddress) {
+			throw new Error(`Failed to look up server ${address}, /.well-known/matrix/client found a redirect loop`);
+		}
+
+		return this.findHomeserver(nextAddress, maxDepth)
+	}
+
 	status(message) {
 		feedback.setLoading(true)
 		feedback.message(message)