Add button and js for buying inbound

public/index.html

@@ -78,6 +78,28 @@ <h2>PayJoin here to open these channels</h2>
 					<a href="" id="bip21"></a>
 					<p>Please use <a href="https://en.bitcoin.it/wiki/PayJoin_adoption" target="_blank">a wallet that supports</a> BIP 78 <a href="https://bitcoinmagazine.com/culture/blockchain-analysis-about-get-harder-p2ep-enters-testing-phase" target="blank">P2EP</a> PayJoins!</p>
 				</output>
+				<br>
+				<br>
+			</fieldset>
+			<fieldset id="getinbound-wrapper">
+				<legend>Buy Inbound Lighning Channel</legend>
+				<div id="getinbound-button-wrapper">
+					<button type="button" onclick="get_inbound_quote()">Send Refund Address and Get Quote</button>
+				</div>
+				<div id="getinbound-response" class="invisible"> 
+					<small>
+							A <span id="getinbound-capacity"></span> satoshi inbound lightning channel currently costs <span id="getinbound-price"></span> sats. (<span id="getinbound-duration"></span> month).
+						<br>
+							To open, send <span id="getinbound-price-2"></span> sats to:
+					</small>
+					<br>
+					<code><span id="getinbound-address"></span></code>
+					<br>
+					<br>
+					<small>Your lightning channel should open within a few hours.</small>
+					<small>If the channel fails to open you will be refunded using an address we received from your LND onchain wallet.</small>
+				</div>
+			</fieldset>
 			</form>
 
 		</main>
@@ -90,6 +112,24 @@ <h2>PayJoin here to open these channels</h2>
 				channels.appendChild(div.lastChild);
 			}
 
+			async function get_inbound_quote(){
+				try {
+					quote = await (await fetch('/getinbound', {
+						method: 'GET',
+					})).json()
+					document.getElementById("getinbound-button-wrapper").classList.add("invisible");
+					document.getElementById("getinbound-response").classList.remove("invisible");
+					document.getElementById("getinbound-price").innerHTML = quote.price;
+					document.getElementById("getinbound-price-2").innerHTML = quote.price;
+					document.getElementById("getinbound-capacity").innerHTML = quote.size;
+					document.getElementById("getinbound-duration").innerHTML = quote.duration;
+					document.getElementById("getinbound-address").innerHTML = quote.address;
+			} catch (error) {
+					console.error(error)
+					alert("Something went wrong. Please try again.")
+				}
+			}
+
 			function remove_channel() {
 				let channels = document.getElementById("channels");
 				let channelInputs = channels.getElementsByTagName("input");