use super::Middleware;

/// `MailDrop` can't find folders to sync because it implements `IMAPv3` and
/// sends FIND MAILBOXES /*, which does not exist in `IMAPv4`.
/// which is not understood by modern servers. It instead replaces it with
/// a LIST command.
pub struct FindMailboxesCompatibility {
    tags: Vec<String>,
}

impl FindMailboxesCompatibility {
    pub fn new() -> Self {
        FindMailboxesCompatibility { tags: vec![] }
    }
}

impl Middleware for FindMailboxesCompatibility {
    fn client_message(&mut self, input: &[u8]) -> Vec<u8> {
        let command = String::from_utf8_lossy(input);
        if command.contains("FIND MAILBOXES /*") {
            if let Some(tag) = command.split("FIND MAILBOXES /*").next() {
                // We'll need to convert the LIST to a FIND
                self.tags.push(tag.trim().to_string());
                let replacement = format!("{} LIST \"\" \"*\"\r\n", tag.trim());
                return replacement.into_bytes();
            }
        }
        input.to_vec()
    }

    fn server_message(&mut self, input: &[u8]) -> Vec<u8> {
        let command = String::from_utf8_lossy(input);
        let contains_ok_completed = self
            .tags
            .iter()
            .any(|tag| command.contains(&format!("{tag} OK Completed")));

        // We want to only modify responses that were a result of a MAILBOX call.
        if !contains_ok_completed {
            return input.to_vec();
        }

        let lines: Vec<String> = command
            .lines()
            .filter_map(|line| {
                // The IMAPv3 spec specifically says INBOX is excluded from MAILBOX
                if line.starts_with("* LIST") && line.trim_end().ends_with("\"/\" INBOX") {
                    return None;
                }

                // Transform IMAPv4 "* LIST" lines to IMAPv3 "* MAILBOX"
                if line.starts_with("* LIST") {
                    if let Some(last_slash_pos) = line.rfind("\"/\"") {
                        let mailbox_name = line[(last_slash_pos + 3)..].replace('"', "");
                        return Some(format!("* MAILBOX {}\r", mailbox_name.trim()));
                    }
                }

                if line.contains("OK") {
                    if let Some(tag) = line.split("OK").next() {
                        return Some(format!("{} OK MAILBOX Completed.\r", tag.trim()).to_string());
                    }
                }

                Some(line.to_string())
            })
            .collect();

        format!("{}\n", lines.join("\n")).into_bytes()
    }
}