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import emailAddresses from "email-addresses";
class MailSimpleParseError extends Error {}
function lazy<T>(calculator: () => T): () => T {
const tag = new Object();
let cache: typeof tag | T = tag;
return () => {
if (cache === tag) cache = calculator();
return cache as T;
};
}
class MailSimpleParsedHeaders {
#headerSection;
#headers = lazy(() => {
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 MailSimpleParseError(`No ':' in the header line: ${field}`);
}
headers.push([field.slice(0, sepPos).trim(), field.slice(sepPos + 1)]);
field = null;
};
for (const line of this.#headerSection.trimEnd().split(/\r?\n|\r/)) {
if (line.match(/^\s/)) {
if (field == null) {
throw new MailSimpleParseError("Header section starts with a space.");
}
field += line;
} else {
handleField();
field = line;
}
lineNumber += 1;
}
handleField();
return headers;
});
#messageId = lazy(() => {
const messageIdField = this.#getFirst("message-id");
if (messageIdField == null) return undefined;
const match = messageIdField.match(/\<(.*?)\>/);
if (match != null) {
return match[1];
} else {
console.warn("Invalid message-id header of mail: " + messageIdField);
return undefined;
}
});
#date = lazy(() => {
const dateField = this.#getFirst("date");
if (dateField == null) return undefined;
const date = new Date(dateField);
if (isNaN(date.getTime())) {
console.warn(`Invalid date string (${dateField}) found in header.`);
return undefined;
}
return date;
});
#from = lazy(() => {
const fromField = this.#getFirst("from");
if (fromField == null) return undefined;
const addr = emailAddresses.parseOneAddress(fromField);
return addr?.type === "mailbox" ? addr.address : undefined;
});
#recipients = lazy(() => {
const headers = ["to", "cc", "bcc", "x-original-to"];
const recipients = new Set<string>();
for (const [key, value] of this.#headers()) {
if (headers.includes(key.toLowerCase())) {
emailAddresses
.parseAddressList(value)
?.flatMap((a) => (a.type === "mailbox" ? a : a.addresses))
?.forEach(({ address }) => recipients.add(address));
}
}
return recipients;
});
constructor(headerSection: string) {
this.#headerSection = headerSection;
}
#getFirst(fieldKey: string): string | undefined {
for (const [key, value] of this.#headers()) {
if (key.toLowerCase() === fieldKey.toLowerCase()) return value;
}
return undefined;
}
get messageId() {
return this.#messageId();
}
get date() {
return this.#date();
}
get from() {
return this.#from();
}
get recipients() {
return this.#recipients();
}
toList(): [string, string][] {
return [...this.#headers()];
}
}
class MailSimpleParsed {
#raw;
#sections = lazy(() => {
const twoEolMatch = this.#raw.match(/(\r?\n)(\r?\n)/);
if (twoEolMatch == null) {
throw new MailSimpleParseError(
"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: this.#raw.slice(0, twoEolMatch.index!),
body: this.#raw.slice(twoEolMatch.index! + eol.length + sep.length),
eol,
sep,
};
});
#headers = lazy(() => {
return new MailSimpleParsedHeaders(this.header);
});
constructor(raw: string) {
this.#raw = raw;
}
get header() {
return this.#sections().header;
}
get body() {
return this.#sections().body;
}
get sep() {
return this.#sections().sep;
}
get eol() {
return this.#sections().eol;
}
get headers() {
return this.#headers();
}
get date() {
return this.headers.date;
}
get messageId() {
return this.headers.messageId;
}
get from() {
return this.headers.from;
}
get recipients() {
return this.headers.recipients;
}
}
export function simpleParseMail(raw: string): MailSimpleParsed {
return new MailSimpleParsed(raw);
}
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