Implement JavaScript UI for attachments

This one is a bit of a doozy. A summary of the changes:

- Session has grown storage for attachments which have been uploaded but
  not yet sent.
- The list of attachments on a message is refcounted so that we can
  clean up the temporary files only after it's done with - i.e. after
  copying to Sent and after all of the SMTP attempts are done.
- Abandoned attachments are cleared out on process shutdown.

Future work:
- Add a limit to the maximum number of pending attachments the user can
  have in the session.
- Periodically clean out abandoned attachments?

2 files changed, 232 insertions, 10 deletions

diff --git a/themes/alps/assets/attachments.js b/themes/alps/assets/attachments.js
new file mode 100644
index 0000000..bd8c78b
--- /dev/null
+++ b/themes/alps/assets/attachments.js
@@ -0,0 +1,146 @@
+let attachments = [];
+
+const headers = document.querySelector(".create-update .headers");
+headers.classList.remove("no-js");
+
+const attachmentsNode = document.getElementById("attachment-list");
+attachmentsNode.style.display = '';
+const helpNode = attachmentsNode.querySelector(".help");
+
+const attachmentsInput = headers.querySelector("input[type='file']");
+attachmentsInput.removeAttribute("name");
+attachmentsInput.addEventListener("input", ev => {
+	const files = attachmentsInput.files;
+	for (let i = 0; i < files.length; i++) {
+		attachFile(files[i]);
+	}
+});
+
+document.body.addEventListener("drop", ev => {
+	ev.preventDefault();
+	const files = ev.dataTransfer.files;
+	for (let i = 0; i < files.length; i++) {
+		attachFile(files[i]);
+	}
+});
+
+const sendButton = document.getElementById("send-button"),
+	saveButton = document.getElementById("save-button");
+
+const XHR_UNSENT = 0,
+	XHR_OPENED = 1,
+	XHR_HEADERS_RECEIVED = 2,
+	XHR_LOADING = 3,
+	XHR_DONE = 4;
+
+const attachmentUUIDsNode = document.getElementById("attachment-uuids");
+function updateState() {
+	let complete = true;
+	for (let i = 0; i < attachments.length; i++) {
+		const a = attachments[i];
+		const progress = a.node.querySelector(".progress");
+		progress.style.width = `${Math.floor(a.progress * 100)}%`;
+		complete &= a.progress === 1.0;
+		if (a.progress === 1.0) {
+			progress.style.display = 'none';
+		}
+	}
+
+	if (complete) {
+		sendButton.removeAttribute("disabled");
+		saveButton.removeAttribute("disabled");
+	} else {
+		sendButton.setAttribute("disabled", "disabled");
+		saveButton.setAttribute("disabled", "disabled");
+	}
+
+	attachmentUUIDsNode.value = attachments.
+		filter(a => a.progress === 1.0).
+		map(a => a.uuid).
+		join(",");
+}
+
+function attachFile(file) {
+	helpNode.remove();
+
+	const xhr = new XMLHttpRequest();
+	const node = attachmentNodeFor(file);
+	const attachment = {
+		node: node,
+		progress: 0,
+		xhr: xhr,
+	};
+	attachments.push(attachment);
+	attachmentsNode.appendChild(node);
+
+	let formData = new FormData();
+	formData.append("attachments", file);
+
+	xhr.open("POST", "/compose/attachment");
+	xhr.upload.addEventListener("progress", ev => {
+		attachment.progress = ev.loaded / ev.total;
+		updateState();
+	});
+	xhr.addEventListener("load", () => {
+		// TODO: Handle errors
+		const resp = JSON.parse(xhr.responseText);
+		attachment.uuid = resp[0];
+		updateState();
+	});
+	xhr.send(formData);
+
+	updateState();
+}
+
+function attachmentNodeFor(file) {
+	const node = document.createElement("div"),
+		progress = document.createElement("span"),
+		filename = document.createElement("span"),
+		size = document.createElement("span"),
+		button = document.createElement("button");
+	node.classList.add("upload");
+
+	progress.classList.add("progress");
+	node.appendChild(progress);
+
+	filename.classList.add("filename");
+	filename.innerText = file.name;
+	node.appendChild(filename);
+
+	size.classList.add("size");
+	size.innerText = formatSI(file.size) + "B";
+	node.appendChild(size);
+
+	button.innerHTML = "&times";
+	node.appendChild(button);
+	return node;
+}
+
+// via https://github.com/ThomWright/format-si-prefix; MIT license
+// Copyright (c) 2015 Thom Wright
+const PREFIXES = {
+  '24': 'Y', '21': 'Z', '18': 'E', '15': 'P', '12': 'T', '9': 'G', '6': 'M',
+  '3': 'k', '0': '', '-3': 'm', '-6': 'µ', '-9': 'n', '-12': 'p', '-15': 'f',
+  '-18': 'a', '-21': 'z', '-24': 'y'
+};
+
+function formatSI(num) {
+  if (num === 0) {
+    return '0';
+  }
+  let sig = Math.abs(num); // significand
+  let exponent = 0;
+  while (sig >= 1000 && exponent < 24) {
+    sig /= 1000;
+    exponent += 3;
+  }
+  while (sig < 1 && exponent > -24) {
+    sig *= 1000;
+    exponent -= 3;
+  }
+  const signPrefix = num < 0 ? '-' : '';
+  if (sig > 1000) {
+    return signPrefix + sig.toFixed(0) + PREFIXES[exponent];
+  }
+  return signPrefix + parseFloat(sig.toPrecision(3)) + PREFIXES[exponent];
+}
diff --git a/themes/alps/assets/style.css b/themes/alps/assets/style.css
index 77aaf3c..389079c 100644
--- a/themes/alps/assets/style.css
+++ b/themes/alps/assets/style.css
@@ -166,19 +166,89 @@ main.create-update {
 }
 
 main.create-update { flex: 1 auto; padding: 1rem; }
-main.create-update form { flex: 1 auto; display: flex; flex-direction: column; }
-main.create-update form label { margin-top: 5px; }
+main.create-update form {
+  flex: 1 auto;
+  display: flex;
+  flex-direction: column;
+}
 
-/* TODO: CSS grid this */
-main.create-update form label span {
-  display: inline-block;
-  font-weight: bold;
-  min-width: 150px;
+main.create-update .headers {
+  display: grid;
+  grid-template-columns: auto 1fr auto;
+  grid-template-rows: auto auto auto auto;
+  grid-gap: 0.5rem;
+  align-items: center;
+}
+
+main.create-update .headers.no-js {
+  grid-template-columns: auto 1fr;
+}
+
+main.create-update .headers label {
+  grid-column-start: 1;
+}
+
+main.create-update .headers input {
+  grid-column-start: 2;
+  grid-column-end: 3;
+}
+
+main.create-update #attachment-list {
+  grid-column-start: 3;
+  grid-row-start: 1;
+  grid-row-end: 5;
+
+  width: 25rem;
+  height: 100%;
+  background: #eee;
+  overflow-y: scroll;
+  border: 1px solid #eee;
+
+  display: flex;
+  flex-direction: column;
+}
+
+main.create-update #attachment-list .help {
+  text-align: center;
+  color: #555;
+  margin-top: 1rem;
 }
 
-main.create-update form input { width: 80%; }
-main.create-update form textarea { flex: 1 auto; resize: none; margin-top: 1rem; }
-main.create-update h1 { margin: 0; }
+main.create-update #attachment-list .upload {
+  width: calc(100% - 1rem);
+  position: relative;
+  display: flex;
+  margin: 0.5rem;
+  padding: 0.25rem 0.5rem;
+  background: white;
+  align-items: center;
+}
+
+main.create-update #attachment-list *:not(:last-child) {
+  margin-right: 0.25rem;
+}
+
+main.create-update #attachment-list .upload .filename {
+  flex-grow: 1;
+}
+
+main.create-update #attachment-list .upload button {
+  padding: inherit;
+}
+
+main.create-update #attachment-list .upload .progress {
+  position: absolute;
+  height: 5px;
+  background: #50C878;
+  bottom: 0;
+  left: 0;
+}
+
+main.create-update textarea {
+  flex: 1 auto;
+  resize: none;
+  margin-top: 1rem;
+}
 
 main table { border-collapse: collapse; width: 100%; border: 1px solid #eee; }
 main table td {
@@ -683,6 +753,12 @@ button:hover,
   text-decoration: none;
 }
 
+button[disabled], button[disabled]:hover {
+  color: #555;
+  background-color: #c5c5c5;
+  cursor: default;
+}
+
 .button:active,
 button:active,
 .button-link:active {