max / goingson

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1	//! Reply/forward compose-prefill construction.
2	//!
3	//! Building a reply or forward is domain logic, recipient assembly with
4	//! own-address exclusion, `Re:`/`Fwd:` subject prefixing, and body quoting.
5	//! It lives here in `core` (not the JS frontend) so the rules are uniform,
6	//! unit-tested, and driven by the authoritative account list rather than a
7	//! browser-side cache.
8
9	/// The text parts of a compose prefill. Threading/account IDs are plumbed by
10	/// the command that calls these functions.
11	#[derive(Debug, Clone, PartialEq, Eq)]
12	pub struct ComposePrefill {
13	pub to: String,
14	pub subject: String,
15	pub body: String,
16	}
17
18	/// Extract the bare address from `Name <addr@host>`, or return the trimmed input
19	/// when there is no angle-bracket form.
20	pub fn extract_email_address(addr: &str) -> &str {
21	let trimmed = addr.trim();
22	if let Some(open) = trimmed.find('<')
23	&& let Some(rel_close) = trimmed[open + 1..].find('>')
24	{
25	return trimmed[open + 1..open + 1 + rel_close].trim();
26	}
27	trimmed
28	}
29
30	/// Prefix `Re:` unless the subject already begins with it (case-insensitive),
31	/// matching the old JS `/^Re:/i` guard.
32	pub fn reply_subject(subject: &str) -> String {
33	prefix_once(subject, "Re:")
34	}
35
36	/// Prefix `Fwd:` unless the subject already begins with it (case-insensitive).
37	pub fn forward_subject(subject: &str) -> String {
38	prefix_once(subject, "Fwd:")
39	}
40
41	fn prefix_once(subject: &str, prefix: &str) -> String {
42	let already = subject.len() >= prefix.len()
43	&& subject.is_char_boundary(prefix.len())
44	&& subject[..prefix.len()].eq_ignore_ascii_case(prefix);
45	if already {
46	subject.to_string()
47	} else {
48	format!("{prefix} {subject}")
49	}
50	}
51
52	/// Build the `To` line for a reply.
53	///
54	/// - Plain reply: the original sender's address.
55	/// - Reply-all: sender + every original `To` recipient, in order, de-duplicated,
56	/// with the user's own addresses removed. `own_addresses` may be in any case.
57	pub fn reply_recipients(from: &str, to: &str, own_addresses: &[String], reply_all: bool) -> String {
58	if !reply_all {
59	let sender = extract_email_address(from);
60	return if sender.is_empty() {
61	from.trim().to_string()
62	} else {
63	sender.to_string()
64	};
65	}
66
67	let own: std::collections::HashSet<String> =
68	own_addresses.iter().map(\|a\| a.to_lowercase()).collect();
69	let mut result: Vec<String> = Vec::new();
70
71	let push_unique = \|addr: &str, result: &mut Vec<String>\| {
72	if addr.is_empty() \|\| own.contains(&addr.to_lowercase()) {
73	return;
74	}
75	if !result.iter().any(\|r\| r == addr) {
76	result.push(addr.to_string());
77	}
78	};
79
80	push_unique(extract_email_address(from), &mut result);
81	for part in to.split(',') {
82	push_unique(extract_email_address(part.trim()), &mut result);
83	}
84	result.join(", ")
85	}
86
87	/// Build the quoted body for a reply: an attribution line followed by the
88	/// original body with each line prefixed by `> `.
89	pub fn quoted_reply_body(from: &str, date: &str, body: &str) -> String {
90	let quoted: String = body
91	.split('\n')
92	.map(\|l\| format!("> {l}"))
93	.collect::<Vec<_>>()
94	.join("\n");
95	format!("\n\nOn {date}, {from} wrote:\n>\n{quoted}")
96	}
97
98	/// Build the body for a forwarded message: a header block followed by the
99	/// original body verbatim.
100	pub fn forward_body(from: &str, date: &str, subject: &str, to: &str, body: &str) -> String {
101	format!(
102	"\n\n---------- Forwarded message ----------\n\
103	From: {from}\n\
104	Date: {date}\n\
105	Subject: {subject}\n\
106	To: {to}\n\n\
107	{body}"
108	)
109	}
110
111	#[cfg(test)]
112	mod tests {
113	use super::*;
114
115	#[test]
116	fn extract_handles_angle_brackets_and_plain() {
117	assert_eq!(
118	extract_email_address("Max <max@example.com>"),
119	"max@example.com"
120	);
121	assert_eq!(
122	extract_email_address(" plain@example.com "),
123	"plain@example.com"
124	);
125	assert_eq!(
126	extract_email_address("Name < spaced@example.com >"),
127	"spaced@example.com"
128	);
129	assert_eq!(extract_email_address(""), "");
130	}
131
132	#[test]
133	fn subject_prefix_is_idempotent_and_case_insensitive() {
134	assert_eq!(reply_subject("Hello"), "Re: Hello");
135	assert_eq!(reply_subject("Re: Hello"), "Re: Hello");
136	assert_eq!(reply_subject("re: hello"), "re: hello");
137	assert_eq!(forward_subject("Hello"), "Fwd: Hello");
138	assert_eq!(forward_subject("Fwd: Hello"), "Fwd: Hello");
139	assert_eq!(forward_subject(""), "Fwd: ");
140	}
141
142	#[test]
143	fn plain_reply_targets_sender_only() {
144	let to = reply_recipients("Alice <alice@x.com>", "me@x.com, bob@x.com", &[], false);
145	assert_eq!(to, "alice@x.com");
146	}
147
148	#[test]
149	fn reply_all_includes_recipients_minus_self_deduped() {
150	let own = vec!["me@x.com".to_string()];
151	let to = reply_recipients(
152	"Alice <alice@x.com>",
153	"me@x.com, Bob <bob@x.com>, alice@x.com",
154	&own,
155	true,
156	);
157	// sender first, then To recipients; own address dropped; alice not duplicated.
158	assert_eq!(to, "alice@x.com, bob@x.com");
159	}
160
161	#[test]
162	fn reply_all_excludes_self_case_insensitively() {
163	let own = vec!["Me@X.com".to_string()];
164	let to = reply_recipients("boss@x.com", "ME@x.com, peer@x.com", &own, true);
165	assert_eq!(to, "boss@x.com, peer@x.com");
166	}
167
168	#[test]
169	fn quoted_reply_body_prefixes_each_line() {
170	let body = quoted_reply_body("Alice <a@x.com>", "Mar 1", "line1\nline2");
171	assert_eq!(
172	body,
173	"\n\nOn Mar 1, Alice <a@x.com> wrote:\n>\n> line1\n> line2"
174	);
175	}
176
177	#[test]
178	fn forward_body_has_header_block() {
179	let body = forward_body("a@x.com", "Mar 1", "Hi", "b@x.com", "original");
180	assert!(body.contains("---------- Forwarded message ----------"));
181	assert!(body.contains("From: a@x.com"));
182	assert!(body.contains("Subject: Hi"));
183	assert!(body.ends_with("original"));
184	}
185	}
186