plenum-bot/src/email.rs

use crate::config_spec::{CfgField, CfgGroup};
use lettre::message::{header, SinglePart};
use lettre::transport::smtp::authentication::Credentials;
use lettre::{Message, SmtpTransport, Transport};
use std::error::Error;
use uuid::Uuid;

pub const CONFIG: CfgGroup<'static> = CfgGroup {
    name: "email",
    description: "Sending emails.",
    fields: &[
        CfgField::Default {
            key: "server",
            default: "mail.berlin.ccc.de",
            description: "SMTP server used for sending emails.",
        },
        CfgField::Default {
            key: "user",
            default: "plenum-bot@berlin.ccc.de",
            description: "User name used for authenticating with the mail server.",
        },
        CfgField::Password {
            key: "password",
            description: "Password for authenticating with the mail server.",
        },
        CfgField::Default {
            key: "sender",
            default: "Plenumsbot <plenum-bot@berlin.ccc.de>",
            description: "Email address to use for \"From:\".",
        },
        CfgField::Default {
            key: "to",
            default: "CCCB Intern <intern@berlin.ccc.de>",
            description: "Recipient of the emails sent.",
        },
        CfgField::Optional {
            key: "last-message-id",
            description:
                "Message-Id of last initial announcement to send In-Reply-To (if applicable).",
        },
    ],
};

#[derive(Clone)]
pub struct Email {
    server: String,
    credentials: Credentials,
    message_id_suffix: String,
    is_dry_run: bool,
}

pub struct SimpleEmail {
    base: Email,
    from: String,
    to: String,
    in_reply_to: Option<String>,
}

impl SimpleEmail {
    pub fn new(base: Email, from: &str, to: &str, in_reply_to: Option<String>) -> Self {
        Self { base: base.clone(), from: from.to_string(), to: to.to_string(), in_reply_to }
    }
    pub fn send_email(&self, subject: String, body: String) -> Result<String, Box<dyn Error>> {
        self.base.send_email(
            self.from.clone(),
            self.to.clone(),
            subject,
            body,
            self.in_reply_to.clone(),
        )
    }
}

impl Email {
    pub fn new(server: &str, user: &str, pass: &str, is_dry_run: bool) -> Self {
        let message_id_suffix = user.split('@').next_back().unwrap_or(&server).to_string();
        let credentials = Credentials::new(user.to_string(), pass.to_string());
        Self { server: server.to_string(), credentials, message_id_suffix, is_dry_run }
    }

    pub fn send_email(
        &self, from: String, to: String, subject: String, body: String, in_reply_to: Option<String>,
    ) -> Result<String, Box<dyn Error>> {
        let message_id = Uuid::new_v4().to_string() + &self.message_id_suffix;
        let email = Message::builder()
            .from(from.parse().unwrap())
            .to(to.parse().unwrap())
            .message_id(Some(message_id.clone()));
        let email =
            if in_reply_to.is_some() { email.in_reply_to(in_reply_to.unwrap()) } else { email }
                .subject(subject)
                .singlepart(
                    SinglePart::builder().header(header::ContentType::TEXT_PLAIN).body(body),
                )
                .unwrap();

        if !self.is_dry_run {
            let mailer = SmtpTransport::starttls_relay(&self.server)?
                .credentials(self.credentials.clone())
                .build();
            mailer.send(&email)?;
            Ok(message_id)
        } else {
            println!(
                "[DRY RUN - NOT sending email]\n(raw message:)\n{}",
                std::str::from_utf8(&email.formatted()).unwrap_or("((UTF-8 error))")
            );
            Ok("dummy-message-id@localhost".to_string())
        }
    }
}