melib 0.8.12

/*
 * meli - email module
 *
 * Copyright 2017 Manos Pitsidianakis
 *
 * This file is part of meli.
 *
 * meli is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * meli is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with meli. If not, see <http://www.gnu.org/licenses/>.
 */

//! Email parsing and composing.
//!
//! # Parsing bytes into an `Envelope`
//!
//! An [`Envelope`] represents the information you can get from an email's
//! headers and body structure. Addresses in `To`, `From` fields etc are parsed
//! into [`Address`] types.
//!
//! ```
//! use melib::{email::attachment_types::Text, Attachment, Envelope};
//!
//! let raw_mail = r#"From: "some name" <some@example.com>
//! To: "me" <myself@example.com>
//! Cc:
//! Subject: =?utf-8?Q?gratuitously_encoded_subject?=
//! Message-ID: <h2g7f.z0gy2pgaen5m@example.com>
//! MIME-Version: 1.0
//! Content-Type: multipart/mixed; charset="utf-8";
//!  boundary="bzz_bzz__bzz__"
//!
//! This is a MIME formatted message with attachments. Use a MIME-compliant client to view it properly.
//! --bzz_bzz__bzz__
//!
//! hello world.
//! --bzz_bzz__bzz__
//! Content-Type: image/gif; name="test_image.gif"; charset="utf-8"
//! Content-Disposition: attachment
//! Content-Transfer-Encoding: base64
//!
//! R0lGODdhKAAXAOfZAAABzAADzQAEzgQFtBEAxAAGxBcAxwALvRcFwAAPwBcLugATuQEUuxoNuxYQ
//! sxwOvAYVvBsStSAVtx8YsRUcuhwhth4iuCQsyDAwuDc1vTc3uDg4uT85rkc9ukJBvENCvURGukdF
//! wUVKt0hLuUxPvVZSvFlYu1hbt2BZuFxdul5joGhqlnNuf3FvlnBvwXJyt3Jxw3N0oXx1gH12gV99
//! z317f3N7spFxwHp5wH99gYB+goF/g25+26tziIOBhWqD3oiBjICAuudkjIN+zHeC2n6Bzc1vh4eF
//! iYaBw8F0kImHi4KFxYyHmIWIvI2Lj4uIvYaJyY+IuJGMi5iJl4qKxZSMmIuLxpONnpGPk42NvI2M
//! 1LKGl46OvZePm5ORlZiQnJqSnpaUmLyJnJuTn5iVmZyUoJGVyZ2VoZSVw5iXoZmWrO18rJiUyp6W
//! opuYnKaVnZ+Xo5yZncaMoaCYpJiaqo+Z2Z2annuf5qGZpa2WoJybpZmayZ2Z0KCZypydrZ6dp6Cd
//! oZ6a0aGay5ucy5+eqKGeouWMgp+b0qKbzKCfqdqPnp2ezaGgqqOgpKafqrScpp+gz6ajqKujr62j
//! qayksKmmq62lsaiosqqorOyWnaqqtKeqzLGptaurta2rr7Kqtq+ssLOrt6+uuLGusuqhfbWtubCv
//! ubKvs7GwurOwtPSazbevu+ali7SxtbiwvOykjLOyvLWytuCmqOankrSzvbazuLmyvrW0vre0uba1
//! wLi1ury0wLm2u721wbe3wbq3vMC2vLi4wr+3w7m5w8C4xLi6yry6vsG5xbu7xcC6zMK6xry8xry+
//! u8O7x729x8C9wb++yMG+wsO+vMK/w8a+y8e/zMnBzcXH18nL2///////////////////////////
//! ////////////////////////////////////////////////////////////////////////////
//! /////////////////////////////////////////////////////ywAAAAAKAAXAAAI/gBP4Cjh
//! IYMLEh0w4EgBgsMLEyFGFBEB5cOFABgzatS4AVssZAOsLOHCxooVMzCyoNmzaBOkJlS0VEDyZMjG
//! mxk3XOMF60CDBgsoPABK9KcDCRImPCiQYAECAgQCRMU4VSrGCjFarBgUSJCgQ10FBTrkNRCfPnz4
//! dA3UNa1btnDZqgU7Ntqzu3ej2X2mFy9eaHuhNRtMGJrhwYYN930G2K7eaNIY34U2mfJkwpgzI9Yr
//! GBqwR2KSvAlMOXHnw5pTNzPdLNoWIWtU9XjGjDEYS8LAlFm1SrVvzIKj5TH0KpORSZOryPgCZgqL
//! Ob+jG0YVRBErUrOiiGJ8KxgtYsh27xWL/tswnTtEbsiRVYdJNMHk4yOGhswGjR88UKjQ9Ey+/8TL
//! XKKGGn7Akph/8XX2WDTTcAYfguVt9hhrEPqmzIOJ3VUheb48WJiHG6amC4i+WVJKKCimqGIoYxyj
//! WWK8kKjaJ9bA18sxvXjYhourmbbMMrjI+OIn1QymDCVXANGFK4S1gQw0PxozzC+33FLLKUJq9gk1
//! gyWDhyNwrMLkYGUEM4wvuLRiCiieXIJJJVlmJskcZ9TZRht1lnFGGmTMkMoonVQSSSOFAGJHHI0w
//! ouiijDaaCCGQRgrpH3q4QYYXWDihxBE+7KCDDjnUIEVAADs=
//! --bzz_bzz__bzz__--"#;
//!
//! let envelope = Envelope::from_bytes(raw_mail.as_bytes(), None).expect("Could not parse mail");
//! assert_eq!(envelope.subject().as_ref(), "gratuitously encoded subject");
//! assert_eq!(envelope.message_id(), "h2g7f.z0gy2pgaen5m@example.com");
//!
//! let body = envelope.body_bytes(raw_mail.as_bytes());
//! assert_eq!(body.content_type().to_string().as_str(), "multipart/mixed");
//!
//! let body_text = body.text(Text::Plain);
//! assert_eq!(body_text.as_str(), "hello world.");
//!
//! let subattachments: Vec<Attachment> = body.attachments();
//! assert_eq!(subattachments.len(), 3);
//! assert_eq!(
//!     subattachments[2].content_type().name().unwrap(),
//!     "test_image.gif"
//! );
//! ```

pub mod address;
pub mod attachment_types;
pub mod attachments;
pub mod compose;
pub mod headers;
pub mod list_management;
pub mod mailto;
pub mod parser;
pub mod pgp;

use std::{borrow::Cow, ops::Deref};

pub use address::{Address, MessageID, References, StrBuild, StrBuilder};
pub use attachments::{Attachment, AttachmentBuilder};
pub use compose::{attachment_from_file, Draft};
pub use headers::*;
use indexmap::IndexSet;
use smallvec::SmallVec;

use crate::{
    error::{Error, Result},
    parser::BytesExt,
    thread::ThreadNodeHash,
    TagHash, UnixTimestamp,
};

bitflags! {
    #[derive(Default, Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
    pub struct Flag: u8 {
        const PASSED  =  0b0000_0001;
        const REPLIED =  0b0000_0010;
        const SEEN    =  0b0000_0100;
        const TRASHED =  0b0000_1000;
        const DRAFT   =  0b0001_0000;
        const FLAGGED =  0b0010_0000;
    }
}

impl PartialEq<&str> for Flag {
    fn eq(&self, other: &&str) -> bool {
        (other.eq_ignore_ascii_case("passed") && self.contains(Self::PASSED))
            || (other.eq_ignore_ascii_case("replied") && self.contains(Self::REPLIED))
            || (other.eq_ignore_ascii_case("seen") && self.contains(Self::SEEN))
            || (other.eq_ignore_ascii_case("read") && self.contains(Self::SEEN))
            || (other.eq_ignore_ascii_case("junk") && self.contains(Self::TRASHED))
            || (other.eq_ignore_ascii_case("trash") && self.contains(Self::TRASHED))
            || (other.eq_ignore_ascii_case("trashed") && self.contains(Self::TRASHED))
            || (other.eq_ignore_ascii_case("draft") && self.contains(Self::DRAFT))
            || (other.eq_ignore_ascii_case("flagged") && self.contains(Self::FLAGGED))
    }
}

macro_rules! flag_impl {
    (fn $name:ident, $val:expr) => {
        pub const fn $name(&self) -> bool {
            self.contains($val)
        }
    };
}

impl Flag {
    flag_impl!(fn is_passed, Self::PASSED);
    flag_impl!(fn is_replied, Self::REPLIED);
    flag_impl!(fn is_seen, Self::SEEN);
    flag_impl!(fn is_trashed, Self::TRASHED);
    flag_impl!(fn is_draft, Self::DRAFT);
    flag_impl!(fn is_flagged, Self::FLAGGED);
}

/// Container type for both envelope and bytes data.
///
/// `Mail` holds both the envelope info of an email in its `envelope` field and
/// the raw bytes that describe the email in `bytes`. Its body as an
/// [`Attachment`] can be parsed on demand
/// with the [`Mail::body`] method.
#[derive(Clone, Default)]
pub struct Mail {
    pub envelope: Envelope,
    pub bytes: Vec<u8>,
}

impl std::fmt::Debug for Mail {
    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
        fmt.debug_struct(crate::identify!(Mail))
            .field("bytes", &self.bytes.len())
            .field("envelope", &self.envelope)
            .finish()
    }
}

impl Deref for Mail {
    type Target = Envelope;

    fn deref(&self) -> &Self::Target {
        &self.envelope
    }
}

impl Mail {
    pub fn new(bytes: Vec<u8>, flags: Option<Flag>) -> Result<Self> {
        Ok(Self {
            envelope: Envelope::from_bytes(&bytes, flags)?,
            bytes,
        })
    }

    pub fn envelope(&self) -> &Envelope {
        &self.envelope
    }

    pub fn bytes(&self) -> &[u8] {
        &self.bytes
    }

    pub fn body(&self) -> Attachment {
        self.envelope.body_bytes(&self.bytes)
    }

    pub fn as_mbox(&self) -> Vec<u8> {
        use crate::mbox::*;
        let mut out = std::io::BufWriter::new(Vec::with_capacity(self.bytes.len() + 120));
        let format = MboxFormat::MboxCl2;
        format
            .append(
                &mut out,
                self.bytes(),
                None,                          // Envelope From
                Some(self.envelope.timestamp), // Delivered date
                Default::default(),            // Flags and tags
                MboxMetadata::None,
                true,
                false,
            )
            .expect("Could not write mbox");
        out.into_inner().unwrap()
    }
}

crate::declare_u64_hash!(EnvelopeHash);

/// `Envelope` represents all the header and structure data of an email we need
/// to know.
///
///  Attachments (the email's body) is parsed on demand with `body` method.
///
///To access the email attachments, you need to parse them from the raw email
/// bytes into an `Attachment` object.
#[derive(Clone, Deserialize, Serialize)]
pub struct Envelope {
    pub date: String,
    pub subject: Option<String>,
    pub from: SmallVec<[Address; 1]>,
    pub to: SmallVec<[Address; 1]>,
    pub cc: SmallVec<[Address; 1]>,
    pub bcc: Vec<Address>,
    pub in_reply_to: Option<References>,
    pub references: Option<References>,
    pub message_id: MessageID,
    pub other_headers: HeaderMap,
    // ----- Other -----
    pub hash: EnvelopeHash,
    pub timestamp: UnixTimestamp,
    pub thread: ThreadNodeHash,
    pub flags: Flag,
    pub has_attachments: bool,
    pub tags: IndexSet<TagHash>,
}

impl std::fmt::Debug for Envelope {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        f.debug_struct(crate::identify!(Envelope))
            .field("Subject", &self.subject())
            .field("Date", &self.date)
            .field("From", &self.from)
            .field("To", &self.to)
            .field("Message-ID", &self.message_id)
            .field("In-Reply-To", &self.in_reply_to)
            .field("References", &self.references)
            .field("Flags", &self.flags)
            .field("Hash", &self.hash)
            .finish()
    }
}

impl Default for Envelope {
    fn default() -> Self {
        Self::new(EnvelopeHash::default())
    }
}

impl Envelope {
    pub fn new(hash: EnvelopeHash) -> Self {
        Self {
            hash,
            date: String::new(),
            timestamp: 0,
            from: SmallVec::new(),
            to: SmallVec::new(),
            cc: SmallVec::new(),
            bcc: Vec::new(),
            subject: None,
            message_id: MessageID::default(),
            in_reply_to: None,
            references: None,
            other_headers: Default::default(),
            thread: ThreadNodeHash::null(),
            has_attachments: false,
            flags: Flag::default(),
            tags: IndexSet::new(),
        }
    }

    pub fn set_hash(&mut self, new_hash: EnvelopeHash) -> &mut Self {
        self.hash = new_hash;
        self
    }

    pub fn from_bytes(bytes: &[u8], flags: Option<Flag>) -> Result<Self> {
        let mut e = Self::new(EnvelopeHash::from_bytes(bytes.trim()));
        let res = e.populate_headers(bytes).ok();
        if res.is_some() {
            if let Some(f) = flags {
                e.flags = f;
            }
            return Ok(e);
        }
        Err(Error::new("Couldn't parse mail."))
    }

    pub fn hash(&self) -> EnvelopeHash {
        self.hash
    }

    pub fn populate_headers(&mut self, mut bytes: &[u8]) -> Result<()> {
        if bytes.starts_with(b"From ") {
            /* Attempt to recover if message includes the mbox From label as first line */
            if let Some(offset) = bytes.find(b"\n") {
                bytes = &bytes[offset + 1..];
            }
        }
        let (headers, body) = match parser::mail(bytes) {
            Ok(v) => v,
            Err(e) => {
                log::debug!("error in parsing mail\n{:?}\n", e);
                let error_msg = String::from("Mail cannot be shown because of errors.");
                return Err(Error::new(error_msg));
            }
        };
        for (name, value) in headers {
            match name {
                HeaderName::TO => {
                    let parse_result = parser::address::rfc2822address_list(value);
                    if let Ok((_, value)) = parse_result {
                        self.set_to(value);
                    };
                }
                HeaderName::CC => {
                    let parse_result = parser::address::rfc2822address_list(value);
                    if let Ok((_, value)) = parse_result {
                        self.set_cc(value);
                    };
                }
                HeaderName::BCC => {
                    let parse_result = parser::address::rfc2822address_list(value);
                    if let Ok((_, value)) = parse_result {
                        self.set_bcc(value.to_vec());
                    };
                }
                HeaderName::FROM => {
                    let parse_result = parser::address::rfc2822address_list(value);
                    if let Ok((_, value)) = parse_result {
                        self.set_from(value);
                    }
                }
                HeaderName::SUBJECT => {
                    let parse_result = parser::encodings::phrase(value.trim(), false);
                    if let Ok((_, value)) = parse_result {
                        self.set_subject(value);
                    };
                }
                HeaderName::MESSAGE_ID => {
                    self.set_message_id(value);
                }
                HeaderName::REFERENCES => {
                    self.set_references(value);
                }
                HeaderName::IN_REPLY_TO => {
                    self.set_in_reply_to(value);
                }
                HeaderName::DATE => {
                    let parse_result = parser::encodings::phrase(value, false);
                    if let Ok((_, value)) = parse_result {
                        self.set_date(value.as_slice());
                    } else {
                        self.set_date(value);
                    }
                }
                HeaderName::CONTENT_TYPE => match parser::attachments::content_type(value) {
                    Ok((_, (ct, cst, ref params)))
                        if ct.eq_ignore_ascii_case(b"multipart")
                            && cst.eq_ignore_ascii_case(b"mixed") =>
                    {
                        let mut builder = AttachmentBuilder::default();
                        builder.set_content_type_from_bytes(value);
                        let mut boundary = None;
                        for (n, v) in params {
                            if n.eq_ignore_ascii_case(b"boundary") {
                                boundary = Some(v);
                                break;
                            }
                        }
                        if let Some(boundary) = boundary {
                            self.has_attachments =
                                Attachment::check_if_has_attachments_quick(body, boundary);
                        } else {
                            log::debug!(
                                "{:?} has no boundary field set in multipart/mixed content-type \
                                 field.",
                                &self
                            );
                        }
                    }
                    _ => {}
                },
                _ => {}
            }
            self.other_headers.insert(
                name,
                parser::encodings::phrase(value, false)
                    .map(|(_, value)| {
                        String::from_utf8(value)
                            .unwrap_or_else(|err| String::from_utf8_lossy(&err.into_bytes()).into())
                    })
                    .unwrap_or_else(|_| String::from_utf8_lossy(value).into()),
            );
        }
        /*
         * https://tools.ietf.org/html/rfc5322#section-3.6.4
         *
         * if self.message_id.is_none()  ...
         */
        if let Some(ref x) = self.in_reply_to {
            match self.references {
                Some(ref mut s) => {
                    s.extend(x.refs());
                }
                None => {
                    self.references = Some(x.clone());
                }
            }
        }
        if let Ok(d) = parser::dates::rfc5322_date(self.date.as_bytes()) {
            self.set_datetime(d);
        }
        if self.message_id.raw().is_empty() {
            let hash = self.hash;
            self.set_message_id(format!("<{:x}>", hash.0).as_bytes());
        }
        if let Some(ref mut r) = self.references {
            r.remove(&self.message_id);
        }

        Ok(())
    }

    pub fn date(&self) -> UnixTimestamp {
        self.timestamp
    }

    pub fn datetime(&self) -> UnixTimestamp {
        self.timestamp
    }

    pub fn date_as_str(&self) -> &str {
        &self.date
    }

    pub fn from(&self) -> &[Address] {
        self.from.as_slice()
    }

    pub fn field_bcc_to_string(&self) -> String {
        if self.bcc.is_empty() {
            self.other_headers
                .get("Bcc")
                .unwrap_or_default()
                .to_string()
        } else {
            Address::display_slice(self.bcc(), None)
        }
    }

    pub fn field_cc_to_string(&self) -> String {
        if self.cc.is_empty() {
            self.other_headers.get("Cc").unwrap_or_default().to_string()
        } else {
            Address::display_slice(self.cc(), None)
        }
    }

    pub fn field_from_to_string(&self) -> String {
        if self.from.is_empty() {
            self.other_headers
                .get("From")
                .unwrap_or_default()
                .to_string()
        } else {
            Address::display_slice(self.from(), None)
        }
    }

    pub fn to(&self) -> &[Address] {
        self.to.as_slice()
    }

    pub fn cc(&self) -> &[Address] {
        self.cc.as_slice()
    }

    pub fn bcc(&self) -> &[Address] {
        self.bcc.as_slice()
    }

    pub fn field_to_to_string(&self) -> String {
        if self.to.is_empty() {
            self.other_headers.get("To").unwrap_or_default().to_string()
        } else {
            Address::display_slice(self.to(), None)
        }
    }

    pub fn field_references_to_string(&self) -> String {
        let refs = self.references();
        if refs.is_empty() {
            self.other_headers
                .get("References")
                .unwrap_or_default()
                .to_string()
        } else {
            MessageID::display_slice(refs, Some("\n "))
        }
    }

    pub fn body_bytes(&self, bytes: &[u8]) -> Attachment {
        let builder = AttachmentBuilder::new(bytes);
        builder.build()
    }

    pub fn headers<'a>(&self, bytes: &'a [u8]) -> Result<Vec<(HeaderName, &'a str)>> {
        let ret = parser::headers::headers(bytes)?.1;
        let len = ret.len();
        ret.into_iter()
            .try_fold(Vec::with_capacity(len), |mut acc, (a, b)| {
                Ok({
                    acc.push((a, std::str::from_utf8(b)?));
                    acc
                })
            })
    }

    pub fn subject(&self) -> Cow<str> {
        match self.subject {
            Some(ref s) => Cow::from(s),
            _ => Cow::from(String::new()),
        }
    }

    pub fn in_reply_to(&'_ self) -> Option<Cow<'_, References>> {
        self.in_reply_to.as_ref().map(Cow::Borrowed).or_else(|| {
            self.references
                .as_ref()
                .and_then(|r| r.refs().last())
                .and_then(|msgid| Some(Cow::Owned(References::new(vec![msgid.clone()])?)))
        })
    }

    pub fn message_id(&self) -> &MessageID {
        &self.message_id
    }

    pub fn set_date(&mut self, new_val: &[u8]) -> &mut Self {
        let new_val = new_val.trim();
        self.date = String::from_utf8_lossy(new_val).into_owned();
        self
    }

    pub fn set_bcc(&mut self, new_val: Vec<Address>) -> &mut Self {
        self.bcc = new_val;
        self
    }

    pub fn set_cc(&mut self, new_val: SmallVec<[Address; 1]>) -> &mut Self {
        self.cc = new_val;
        self
    }

    pub fn set_from(&mut self, new_val: SmallVec<[Address; 1]>) -> &mut Self {
        self.from = new_val;
        self
    }

    pub fn set_to(&mut self, new_val: SmallVec<[Address; 1]>) -> &mut Self {
        self.to = new_val;
        self
    }

    pub fn set_in_reply_to(&mut self, new_val: &[u8]) -> &mut Self {
        if !new_val.is_empty() {
            self.in_reply_to = None;
            {
                let parse_result = parser::address::msg_id_list(new_val);
                if let Ok((_, value)) = parse_result {
                    for v in value {
                        self.push_in_reply_to(v);
                    }
                }
            }
            self.other_headers_mut().insert(
                HeaderName::IN_REPLY_TO,
                String::from_utf8_lossy(new_val).to_string(),
            );
        }
        self
    }

    pub fn push_in_reply_to(&mut self, new_ref: MessageID) {
        match self.in_reply_to {
            Some(ref mut s) => {
                s.extend(std::iter::once(new_ref));
            }
            None => {
                self.in_reply_to = References::new(vec![new_ref]);
            }
        }
    }

    pub fn set_subject(&mut self, new_val: Vec<u8>) -> &mut Self {
        let mut new_val = String::from_utf8(new_val)
            .unwrap_or_else(|err| String::from_utf8_lossy(&err.into_bytes()).into());
        while new_val
            .chars()
            .last()
            .map(char::is_control)
            .unwrap_or(false)
        {
            new_val.pop();
        }

        self.subject = Some(new_val);
        self
    }

    pub fn set_message_id(&mut self, new_val: &[u8]) -> &mut Self {
        let new_val = new_val.trim();
        match parser::address::msg_id(new_val) {
            Ok((_, val)) => {
                self.message_id = val;
            }
            Err(_) => {
                self.message_id = MessageID::new(new_val, new_val);
            }
        }
        self
    }

    pub fn push_references(&mut self, new_refs: &References) {
        match self.references {
            Some(ref mut s) => {
                s.extend(new_refs.refs());
            }
            None => {
                self.references = Some(new_refs.clone());
            }
        }
    }

    pub fn set_references(&mut self, new_val: &[u8]) -> &mut Self {
        let new_val = new_val.trim();
        if !new_val.is_empty() {
            self.references = None;
            {
                let parse_result = parser::address::msg_id_list(new_val);
                if let Ok((_, value)) = parse_result {
                    self.references = References::new(value);
                }
            }
            self.other_headers_mut().insert(
                HeaderName::REFERENCES,
                String::from_utf8_lossy(new_val).to_string(),
            );
        }
        self
    }

    pub fn references(&self) -> &[MessageID] {
        match self.references {
            Some(ref s) => s.refs(),
            None => &[],
        }
    }

    pub fn other_headers(&self) -> &HeaderMap {
        &self.other_headers
    }

    pub fn other_headers_mut(&mut self) -> &mut HeaderMap {
        &mut self.other_headers
    }

    pub fn thread(&self) -> ThreadNodeHash {
        self.thread
    }

    pub fn set_thread(&mut self, new_val: ThreadNodeHash) -> &mut Self {
        self.thread = new_val;
        self
    }

    pub fn set_datetime(&mut self, new_val: UnixTimestamp) -> &mut Self {
        self.timestamp = new_val;
        self
    }

    pub fn set_flag(&mut self, f: Flag, value: bool) -> &mut Self {
        self.flags.set(f, value);
        self
    }

    pub fn set_flags(&mut self, f: Flag) -> &mut Self {
        self.flags = f;
        self
    }

    pub fn flags(&self) -> Flag {
        self.flags
    }

    pub fn set_seen(&mut self) -> &mut Self {
        self.set_flag(Flag::SEEN, true);
        self
    }

    pub fn set_unseen(&mut self) -> &mut Self {
        self.set_flag(Flag::SEEN, false);
        self
    }

    pub fn is_seen(&self) -> bool {
        self.flags.contains(Flag::SEEN)
    }

    pub fn set_has_attachments(&mut self, new_val: bool) -> &mut Self {
        self.has_attachments = new_val;
        self
    }

    pub fn has_attachments(&self) -> bool {
        self.has_attachments
    }

    pub fn tags(&self) -> &IndexSet<TagHash> {
        &self.tags
    }

    pub fn tags_mut(&mut self) -> &mut IndexSet<TagHash> {
        &mut self.tags
    }

    /// Returns `true` if `is_recipient` address is included in To:, Cc: or Bcc:
    /// headers.
    pub fn recipient_any(&self, is_recipient: &Address) -> bool {
        self.to()
            .iter()
            .chain(self.cc().iter())
            .chain(self.bcc().iter())
            .any(|a| a == is_recipient)
    }

    /// Returns `true` if `is_sender` address is included in From:, Author:
    /// headers.
    pub fn sender_any(&self, is_sender: &Address) -> bool {
        if self.from().iter().any(|a| a == is_sender) {
            return true;
        }
        if let Some(author_raw) = self.other_headers.get(HeaderName::AUTHOR) {
            if let Ok((_, value)) = parser::address::rfc2822address_list(author_raw.as_bytes()) {
                if value.iter().any(|a| a == is_sender) {
                    return true;
                }
            }
        }
        false
    }
}

impl Eq for Envelope {}

impl Ord for Envelope {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.datetime().cmp(&other.datetime())
    }
}

impl PartialOrd for Envelope {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl PartialEq for Envelope {
    fn eq(&self, other: &Self) -> bool {
        self.hash == other.hash
    }
}