path: root/src/rfc822.rs

use chrono::DateTime;
use maildir::MailEntryError;
use mailparse::{
    addrparse_header, body::Body, dateparse, DispositionType, MailParseError, ParsedMail,
};

use crate::de_jmhoffmann_jwebmail_mailstorage::MIMEHeader_content_dispo as CD;
use crate::de_jmhoffmann_jwebmail_mailstorage::*;

fn parse_mail_addrs(
    inp: &mailparse::MailHeader,
) -> std::result::Result<Vec<MailAddr>, MailParseError> {
    let mut mal = addrparse_header(inp)?;

    Ok(mal
        .drain(..)
        .flat_map(|mail_addr| match mail_addr {
            mailparse::MailAddr::Group(mut g) => g
                .addrs
                .drain(..)
                .map(|s| MailAddr {
                    name: Some(s.display_name.unwrap_or_default()),
                    address: s.addr,
                })
                .collect(),
            mailparse::MailAddr::Single(s) => {
                let addr = MailAddr {
                    name: Some(s.display_name.unwrap_or_default()),
                    address: s.addr,
                };
                vec![addr]
            }
        })
        .collect())
}

// ----------------

fn get_received(me: &mut maildir::MailEntry) -> i64 {
    me.received().unwrap_or_else(|_| {
        let mut id = me.id();
        id = &id[..id.find('.').unwrap()];
        id.parse().unwrap_or_default()
    })
}

pub fn me_to_lmh(
    mut me: maildir::MailEntry,
) -> std::result::Result<ListMailHeader, MailEntryError> {
    let lmh = ListMailHeader {
        byte_size: me.path().metadata()?.len() as i64,
        unread: !me.is_seen(),
        rec_date: DateTime::from_timestamp(get_received(&mut me), 0)
            .unwrap()
            .to_rfc3339(),
        mid: me.id().to_owned(),
        header: parse_mail_header(&me.parsed()?)?,
    };

    Ok(lmh)
}

pub fn parse_mail_content(v: &ParsedMail) -> MIMEHeader {
    let mut val = v.ctype.mimetype.clone();
    if let Some(i) = val.find(';') {
        val.truncate(i);
    }
    let j = val.find('/').unwrap();
    let subtype = val.split_off(j + 1);
    val.pop();
    let maintype = val;

    let mut file_name = None;

    let cd = match v.get_content_disposition().disposition {
        DispositionType::Inline => CD::inline,
        DispositionType::Attachment => {
            if let Some(fname) = v.get_content_disposition().params.remove("filename") {
                file_name = Some(fname);
            }
            CD::attachment
        }
        _ => CD::none,
    };

    for h in &v.headers {
        let mut key = h.get_key();
        let val = h.get_value();

        key.make_ascii_lowercase();

        if key == "filename" {
            file_name = Some(val);
        }
    }

    MIMEHeader {
        mime_type: MIMEHeader_mime_type {
            main_type: maintype,
            sub_type: subtype,
        },
        content_dispo: cd,
        file_name,
    }
}

fn parse_mail_header(pm: &ParsedMail) -> std::result::Result<MailHeader, MailParseError> {
    let v = &pm.headers;

    let mut val = pm.ctype.mimetype.clone();
    if let Some(i) = val.find(';') {
        val.truncate(i);
    }
    let j = val.find('/').unwrap();
    let sub_type = val.split_off(j + 1);
    val.pop();
    let main_type = val;

    let mut file_name = None;
    let mut content_dispo = CD::none;
    let mut cc = vec![];
    let mut bcc = vec![];
    let mut comments = vec![];
    let mut keywords = vec![];
    let mut reply_to = vec![];
    let mut written_from = vec![];
    let mut send_to = vec![];
    let mut subject = String::new();
    let mut sender = None;
    let mut send_date = String::new();

    let mut key = String::new();

    for y in v {
        key.push_str(&y.get_key_ref());
        let mut val = y.get_value();

        key.make_ascii_lowercase();

        match key.as_str() {
            "date" => {
                send_date = DateTime::from_timestamp(dateparse(&val)?, 0)
                    .unwrap()
                    .to_rfc3339()
            }
            "from" => {
                if !written_from.is_empty() {
                    const FROM_MULTIPLE_TIMES_ERROR: &str = "from already set";
                    return Err(MailParseError::Generic(FROM_MULTIPLE_TIMES_ERROR));
                }
                written_from = parse_mail_addrs(y)?
            }
            "sender" => sender = parse_mail_addrs(y)?.drain(0..1).next(),
            "reply-to" => reply_to = parse_mail_addrs(y)?,
            "to" => send_to = parse_mail_addrs(y)?,
            "cc" => cc = parse_mail_addrs(y)?,
            "bcc" => bcc = parse_mail_addrs(y)?,
            "subject" => {
                subject = val;
            }
            "comments" => {
                comments.push(val);
            }
            "keywords" => {
                keywords.push(val);
            }
            "mime-version" => {
                strip_comments(&mut val);
                if val.trim() != "1.0" {
                    const UNKNOWN_MIME_VERSION_ERROR: &str = "unknown mime version";
                    return Err(MailParseError::Generic(UNKNOWN_MIME_VERSION_ERROR));
                }
            }
            "content-disposition" => {
                let cd = val.to_ascii_lowercase();
                match cd.as_ref() {
                    "inline" => content_dispo = CD::inline,
                    "attachment" => content_dispo = CD::attachment,
                    _ => {}
                };
            }
            "filename" => {
                file_name = Some(val);
            }
            _ => {}
        };

        key.clear();
    }
    Ok(MailHeader {
        written_from,
        sender,
        send_to,
        cc,
        bcc,
        reply_to,
        subject,
        send_date,
        keywords,
        comments,
        mime: MIMEHeader {
            mime_type: MIMEHeader_mime_type {
                main_type,
                sub_type,
            },
            content_dispo,
            file_name,
        },
    })
}

fn parse_mail_body(pm: &ParsedMail) -> std::result::Result<MailBody, MailParseError> {
    let body = if pm.ctype.mimetype.starts_with("message/") {
        MailBody {
            mail: Some(Box::new(parsed_mail_to_mail(mailparse::parse_mail(
                pm.get_body()?.as_ref(),
            )?)?)),
            discrete: None,
            multipart: None,
        }
    } else if pm.subparts.is_empty() && pm.ctype.mimetype.starts_with("text/") {
        MailBody {
            discrete: Some(pm.get_body()?),
            multipart: None,
            mail: None,
        }
    } else if pm.subparts.is_empty() {
        MailBody {
            discrete: Some(match pm.get_body_encoded() {
                Body::Base64(eb) => {
                    let db = eb.get_raw();
                    if db.len() < 512 * 1024 {
                        String::from_utf8_lossy(db).into_owned()
                    } else {
                        String::new()
                    }
                }
                Body::SevenBit(eb) => eb.get_as_string()?,
                Body::QuotedPrintable(eb) => eb.get_decoded_as_string()?,
                _ => todo!(),
            }),
            multipart: None,
            mail: None,
        }
    } else {
        let mp = Multipart {
            parts: pm
                .subparts
                .iter()
                .map(|part| -> std::result::Result<MIMEPart, MailParseError> {
                    Ok(MIMEPart {
                        mime_header: parse_mail_content(part),
                        body: parse_mail_body(part)?,
                    })
                })
                .filter_map(|p| p.ok())
                .collect(),
            preamble: None,
            epilogue: None,
        };
        MailBody {
            multipart: Some(mp),
            discrete: None,
            mail: None,
        }
    };
    Ok(body)
}

enum FindMatchParen {
    Open,
    Close,
}

impl FindMatchParen {
    fn value(&self) -> char {
        match self {
            FindMatchParen::Open => '(',
            FindMatchParen::Close => ')',
        }
    }

    fn len(&self) -> usize {
        1
    }

    fn of_char(c: char) -> Option<Self> {
        match c {
            '(' => Some(FindMatchParen::Open),
            ')' => Some(FindMatchParen::Close),
            _ => None,
        }
    }
}

fn find_in_header(s: &str, f: FindMatchParen) -> Option<usize> {
    let mut in_q = false;
    let mut q_pair = false;
    let mut open_p = 0;

    for (i, c) in s.char_indices() {
        if q_pair {
            q_pair = false;
            continue;
        }
        match c {
            '\\' => {
                q_pair = true;
            }
            '"' => {
                in_q = !in_q;
            }
            _ if !in_q => {
                if open_p == 0 {
                    if c == f.value() {
                        return Some(i);
                    }
                    if c == FindMatchParen::Open.value() {
                        open_p += 1;
                    }
                } else {
                    match FindMatchParen::of_char(c) {
                        Some(FindMatchParen::Open) => open_p += 1,
                        Some(FindMatchParen::Close) => open_p -= 1,
                        None => {}
                    }
                }
            }
            _ => {}
        };
    }
    None
}

fn find_pair(offset: usize, s: &str) -> Option<std::ops::Range<usize>> {
    if let Some(open) = find_in_header(s, FindMatchParen::Open) {
        if let Some(mut close) = find_in_header(
            &s[open + FindMatchParen::Open.len()..],
            FindMatchParen::Close,
        ) {
            close += open + FindMatchParen::Open.len();
            Some(offset + open..offset + close + FindMatchParen::Close.len())
        } else {
            find_pair(
                offset + open + FindMatchParen::Open.len(),
                &s[open + FindMatchParen::Open.len()..],
            )
        }
    } else {
        None
    }
}

fn strip_comments(s: &mut String) {
    let mut off = 0;

    while let Some(r) = find_pair(off, &s[off..]) {
        s.drain(r.clone());
        off = r.start;
    }
}

pub fn parsed_mail_to_mail(pm: ParsedMail) -> std::result::Result<Mail, MailParseError> {
    Ok(Mail {
        head: parse_mail_header(&pm)?,
        body: parse_mail_body(&pm)?,
    })
}