HALF WORK!:

1 files changed, 140 insertions, 0 deletions

diff --git a/deno/mail-relay/mail-parsing.ts b/deno/mail-relay/mail-parsing.ts
new file mode 100644
index 0000000..8edaf77
--- /dev/null
+++ b/deno/mail-relay/mail-parsing.ts
@@ -0,0 +1,140 @@
+import emailAddresses from "email-addresses";
+
+function parseHeaderSection(section: string) {
+  const headers = [] as [key: string, value: string][];
+
+  let field: string | null = null;
+  let lineNumber = 1;
+
+  const handleField = () => {
+    if (field == null) return;
+    const sepPos = field.indexOf(":");
+    if (sepPos === -1) {
+      throw new Error(`Expect ':' in the header field line: ${field}`);
+    }
+    headers.push([field.slice(0, sepPos).trim(), field.slice(sepPos + 1)]);
+    field = null;
+  };
+
+  for (const line of section.trimEnd().split(/\r?\n|\r/)) {
+    if (line.match(/^\s/)) {
+      if (field == null) {
+        throw new Error("Header section starts with a space.");
+      }
+      field += line;
+    } else {
+      handleField();
+      field = line;
+    }
+    lineNumber += 1;
+  }
+
+  handleField();
+
+  return headers;
+}
+
+function findFirst(fields: readonly [string, string][], key: string) {
+  for (const [k, v] of fields) {
+    if (key.toLowerCase() === k.toLowerCase()) return v;
+  }
+  return undefined;
+}
+
+function findMessageId(fields: readonly [string, string][]) {
+  const messageIdField = findFirst(fields, "message-id");
+  if (messageIdField == null) return undefined;
+
+  const match = messageIdField.match(/\<(.*?)\>/);
+  if (match != null) {
+    return match[1];
+  } else {
+    console.warn(`Invalid syntax in header 'message-id': ${messageIdField}`);
+    return undefined;
+  }
+}
+
+function findDate(fields: readonly [string, string][]) {
+  const dateField = findFirst(fields, "date");
+  if (dateField == null) return undefined;
+
+  const date = new Date(dateField);
+  if (isNaN(date.getTime())) {
+    console.warn(`Invalid date string in header 'date': ${dateField}`);
+    return undefined;
+  }
+  return date;
+}
+
+function findFrom(fields: readonly [string, string][]) {
+  const fromField = findFirst(fields, "from");
+  if (fromField == null) return undefined;
+
+  const addr = emailAddresses.parseOneAddress(fromField);
+  return addr?.type === "mailbox" ? addr.address : undefined;
+}
+
+function findRecipients(fields: readonly [string, string][]) {
+  const headers = ["to", "cc", "bcc", "x-original-to"];
+  const recipients = new Set<string>();
+  for (const [key, value] of fields) {
+    if (headers.includes(key.toLowerCase())) {
+      emailAddresses
+        .parseAddressList(value)
+        ?.flatMap((a) => (a.type === "mailbox" ? a : a.addresses))
+        ?.forEach(({ address }) => recipients.add(address));
+    }
+  }
+  return recipients;
+}
+
+function parseSections(raw: string) {
+  const twoEolMatch = raw.match(/(\r?\n)(\r?\n)/);
+  if (twoEolMatch == null) {
+    throw new Error(
+      "No header/body section separator (2 successive EOLs) found.",
+    );
+  }
+
+  const [eol, sep] = [twoEolMatch[1], twoEolMatch[2]];
+
+  if (eol !== sep) {
+    console.warn("Different EOLs (\\r\\n, \\n) found.");
+  }
+
+  return {
+    header: raw.slice(0, twoEolMatch.index!),
+    body: raw.slice(twoEolMatch.index! + eol.length + sep.length),
+    eol,
+    sep,
+  };
+}
+
+export type ParsedMail = Readonly<{
+  header: string;
+  body: string;
+  sep: string;
+  eol: string;
+  headers: readonly [string, string][];
+  messageId: string | undefined;
+  date: Date | undefined;
+  from: string | undefined;
+  recipients: readonly string[];
+}>;
+
+export function simpleParseMail(raw: string): ParsedMail {
+  const sections = Object.freeze(parseSections(raw));
+  const headers = Object.freeze(parseHeaderSection(sections.header));
+  const messageId = findMessageId(headers);
+  const date = findDate(headers);
+  const from = findFrom(headers);
+  const recipients = Object.freeze([...findRecipients(headers)]);
+  return Object.freeze({
+    ...sections,
+    headers,
+    messageId,
+    date,
+    from,
+    recipients,
+  });
+}