use {
    super::*,
    crate::{
        message::Parser as MessageParser,
        prelude::{ClientCertificateStore, Certificate, ParseMailboxError},
    },
    rustls_pemfile::{read_one, Item},
    std::{
        ffi::OsString,
        fs::{self, File},
        io::{self, BufReader, BufWriter, Write},
        iter,
        os::{fd::AsRawFd, unix::{fs::DirBuilderExt, prelude::OpenOptionsExt}},
        path::{Path, PathBuf},
    },
};
mod error;
pub use error::Error;

pub trait MultiDomain: MailStore {
    type Error;
    fn domains(&self) -> Result<Vec<String>, <Self as filesystem::MultiDomain>::Error>;
    fn add_domain(&mut self, domain: &str) -> Result<(), <Self as filesystem::MultiDomain>::Error>;
    fn remove_domain(
        &mut self,
        domain: &str,
    ) -> Result<(), <Self as filesystem::MultiDomain>::Error>;
}

/// The Filestore storage backend uses the filesystem to map folders to domains,
/// mail users and folders of messages. It can also be used as a `ClientCertificateStore`.
/// The layout of files inside a filesystem mailstore is as below.
/// ```Sh
/// test/mailstore/
/// └── misfin.example.org
///     ├── dick
///     │   ├── Inbox
///     │   │   ├── 619310.gmi
///     │   │   └── 868379.gmi
///     │   ├── blurb
///     │   └── certificate.pem
///     └── jane
///         ├── Inbox
///         │   ├── 252366.gmi
///         │   └── 654064.gmi
///         ├── blurb
///         └── certificate.pem
/// ```
/// In this made up example the Misfin server in question serves the domain
/// "misfin.example.org", which has the users "dick" and "jane", whose mailbox
/// addresses would be "dick@misfin.example.org" and "jane@misfin.example.org".
/// Within each account folder any subfolders are to be considered as mail folders,
/// with the default folder for delivering new mail being "Inbox". The "blurb"
/// file (optional) contains the display name of the user, and their client
/// certificate is stored in pem-encoded ascii armor format in "certificate.pem",
/// if the `Filesystem` is also to be used as a `ClientCertificateStore`.
///
/// The permissions on each individual account folder are set to 0o2700 at the
/// time of creation, such that the folder is read/write for the user and group
/// and any entries created within will have the same group membership. If the
/// username of the account corresponds to a group name on the system, and the
/// user which the server runs as is a member of this group, then said group will
/// own the directory. In this way the server will be able to write incoming
/// mail into the folder and the user will be able to read and manage their
/// folders and messages, without being able to see any other user's mail and
/// without the server requiring elevated privileges.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
pub struct Filesystem {
    pub path: PathBuf,
}

impl From<String> for Filesystem {
    fn from(value: String) -> Self {
        Self { path: value.into() }
    }
}

impl From<&str> for Filesystem {
    fn from(value: &str) -> Self {
        Self { path: value.into() }
    }
}

impl From<&Path> for Filesystem {
    fn from(value: &Path) -> Self {
        Self { path: value.into() }
    }
}

impl From<PathBuf> for Filesystem {
    fn from(value: PathBuf) -> Self {
        Self { path: value }
    }
}

impl From<OsString> for Filesystem {
    fn from(value: OsString) -> Self {
        Self { path: value.into() }
    }
}

impl MailStore for Filesystem {
    type Error = Error;

    fn users(&self) -> Vec<Mailuser> {
        let mut users = vec![];
        let Ok(domains) = fs::read_dir(&self.path) else {
            return users;
        };
        for d in domains {
            let Ok(dom) = d else {
                continue;
            };
            let name = dom.file_name().to_string_lossy().to_string();
            let Ok(host) = name.parse::<Host>() else {
                continue;
            };
            let dom_path = dom.path();
            let Ok(dom_users) = fs::read_dir(&dom_path) else {
                continue;
            };
            for u in dom_users {
                let Ok(user) = u else {
                    continue;
                };
                if let Ok(ft) = user.file_type() {
                    if ft.is_dir() {
                        let username = user.file_name().to_string_lossy().to_string();
                        users.push(Mailuser {
                            username,
                            host: host.clone(),
                        });
                    }
                }
            }
        }
        users
    }

    fn serves_domain(&self, domain: &str) -> bool {
        let mut path = self.path.clone();
        path.push(domain);
        path.exists()
    }

    fn has_mailuser(&self, mailuser: &str) -> bool {
        if let Some((user, host)) = mailuser.rsplit_once('@') {
            let mut path = self.path.clone();
            if host.contains('.') && !host.contains(char::is_whitespace) {
                path.push(host);
                path.push(user);
                return path.exists();
            }
        }
        false
    }

    fn get_folder(&self, user: &str, folder: &str) -> Option<Folder> {
        let Some((user, host)) = user.rsplit_once('@') else {
            return None;
        };
        let mut path = self.path.clone();
        path.push(host);
        path.push(user);
        path.push(folder);
        let Ok(dir) = fs::read_dir(path) else {
            return None;
        };
        let mut folder = Folder {
            name: folder.to_string(),
            messages: HashMap::new(),
        };
        dir.filter_map(Result::ok).for_each(|e| {
            if let Ok(contents) = fs::read_to_string(e.path()) {
                if let Some(Some(p)) = e.path().file_stem().map(|s| s.to_str()) {
                    let parser = MessageParser::new(p);
                    if let Ok(message) = parser.parse(&contents) {
                        folder.messages.insert(message.id.clone(), message);
                    }
                }
            }
        });
        Some(folder)
    }

    fn create_folder(&self, user: &str, folder: &str) -> Result<(), Error> {
        if self.has_mailuser(user) {
            let user: Mailbox = user.parse()?;
            let user: Mailuser = user.into();
            let mut path = self.path.clone();
            path.push(&user.host.to_string());
            path.push(&user.username);
            path.push(folder);
            fs::create_dir_all(&path)?;
        }
        Ok(())
    }

    fn get_message(&self, user: &str, folder: &str, id: &str) -> Option<Message> {
        self.get_folder(user, folder)
            .and_then(|f| f.messages.get(id).cloned())
    }

    fn add_message(
        &mut self,
        user: &str,
        folder: &str,
        message: Message,
    ) -> Result<(), Self::Error> {
        let mb: Mailbox = user.parse()?;
        let mut path = self.path.clone();
        path.push(&mb.host.to_string());
        path.push(&mb.username);
        path.push(folder);
        path.push(&message.id);
        path.set_extension("gmi");
        let mut fd = File::create(path)?;
        write!(fd, "{message}")?;
        Ok(())
    }

    fn delete_message(&mut self, user: &str, folder: &str, id: &str) -> Result<(), Self::Error> {
        let mb: Mailbox = user.parse()?;
        let mut path = self.path.clone();
        path.push(&mb.host.to_string());
        path.push(&mb.username);
        path.push(folder);
        path.push(id);
        path.set_extension("gmi");
        if path.exists() {
            fs::remove_file(&path)?;
        }
        Ok(())
    }

    fn move_message(
        &mut self,
        user: &str,
        id: &str,
        folder1: &str,
        folder2: &str,
    ) -> Result<(), Self::Error> {
        let mb: Mailbox = user.parse()?;
        let mut infile = self.path.clone();
        infile.push(&mb.host.to_string());
        infile.push(&mb.username);
        let mut outfile = infile.clone();
        infile.push(folder1);
        infile.push(id);
        infile.set_extension("gmi");
        outfile.push(folder2);
        outfile.push(id);
        outfile.set_extension("gmi");
        fs::copy(&infile, &outfile)?;
        fs::remove_file(infile)?;
        Ok(())
    }

    fn add_user(&mut self, user: &str) -> Result<(), Self::Error> {
        let mb: Mailbox = user.parse()?;
        let mut path = self.path.clone();
        path.push(&mb.host.to_string());
        path.push(&mb.username);
        fs::create_dir_all(&path)?;
        if let Some(ref blurb) = mb.blurb {
            path.push("blurb");
            let fd = File::options()
                .create(true)
                .write(true)
                .truncate(true)
                .mode(0o2770)
                .open(&path)?;
            if let Some(pw) = pw::Passwd::getpw()?
            {
                let groups = pw.groups()?;
                if let Some(gr) = groups.iter().find(|g| g.name == mb.username) {
                    unsafe {
                        if libc::fchown(fd.as_raw_fd(), pw.uid, gr.gid) != 0 {
                            return Err(io::Error::last_os_error().into());
                        }
                    }
                }
            }
            let mut writer = BufWriter::new(fd);
            writer.write_all(blurb.as_bytes())?;
        }
        let _last = path.pop();
        path.push("Inbox");
        fs::create_dir_all(&path)?;
        Ok(())
    }

    fn remove_user(&mut self, user: &str) -> bool {
        let Ok(mb) = user.parse::<Mailbox>() else {
            return false;
        };
        let mut path = self.path.clone();
        path.push(&mb.host.to_string());
        path.push(&mb.username);
        if path.exists() {
            if fs::remove_dir_all(path).is_ok() {
                return true;
            }
        }
        false
    }
}

impl MultiDomain for Filesystem {
    type Error = io::Error;

    fn domains(&self) -> Result<Vec<String>, io::Error> {
        Ok(self
            .path
            .read_dir()?
            .filter(|x| {
                if let Ok(x) = x {
                    if let Ok(t) = x.file_type() {
                        return t.is_dir();
                    }
                }
                false
            })
            .map(|x| x.unwrap().file_name().to_string_lossy().to_string())
            .collect::<Vec<String>>())
    }

    fn add_domain(&mut self, domain: &str) -> Result<(), io::Error> {
        let mut path = self.path.clone();
        path.push(domain);
        if !path.exists() {
            fs::DirBuilder::new()
                .recursive(true)
                .mode(0o700)
                .create(path)?;
        }
        Ok(())
    }

    fn remove_domain(&mut self, domain: &str) -> Result<(), io::Error> {
        let mut path = self.path.clone();
        path.push(domain);
        if path.exists() {
            fs::remove_dir_all(path)?;
        }
        Ok(())
    }
}

impl ClientCertificateStore for Filesystem {
    fn get_certificate(&self, user: &Mailuser) -> Option<Certificate> {
        let mut path = self.path.clone();
        path.push(&user.host.to_string());
        path.push(&user.username);
        path.push("certificate.pem");
        if path.exists() {
            let Ok(fd) = File::open(&path) else {
                return None;
            };
            let mut reader = BufReader::new(fd);
            let mut certificate = Certificate {
                der: vec![],
                key: vec![],
            };
            for item in iter::from_fn(|| read_one(&mut reader).transpose()) {
                match item {
                    Ok(Item::X509Certificate(cert)) => {
                        if certificate.der.is_empty() {
                            certificate.der = cert;
                        } else {
                            return None;
                        }
                    }
                    Ok(Item::RSAKey(key)) => {
                        if certificate.key.is_empty() {
                            certificate.key = key;
                        } else {
                            return None;
                        }
                    }
                    Ok(Item::PKCS8Key(key)) => {
                        if certificate.key.is_empty() {
                            certificate.key = key;
                        } else {
                            return None;
                        }
                    }
                    Ok(Item::ECKey(key)) => {
                        if certificate.key.is_empty() {
                            certificate.key = key;
                        } else {
                            return None;
                        }
                    }
                    _ => {}
                }
            }
            if certificate.der.is_empty() || certificate.key.is_empty() {
                None
            } else {
                Some(certificate)
            }
        } else {
            None
        }
    }

    fn insert_certificate(
        &mut self,
        user: &Mailuser,
        certificate: Certificate,
    ) -> Option<Certificate> {
        todo!()
    }

    fn contains_certificate(&self, user: &Mailuser) -> bool {
        self.get_certificate(user).is_some()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn store() -> Filesystem {
        "test/mailstore".into()
    }

    #[test]
    fn users() {
        let users = store().users();
        assert!(users
            .iter()
            .any(|u| u.host.to_string() == "mail.gmi.org" && u.username == "jane"));
        assert!(users
            .iter()
            .any(|u| u.host.to_string() == "mail.gmi.org" && u.username == "dick"));
        assert!(users
            .iter()
            .any(|u| u.host.to_string() == "misfin.example.org" && u.username == "jane"));
        assert!(users
            .iter()
            .any(|u| u.host.to_string() == "misfin.example.org" && u.username == "dick"));
        assert!(users.len() >= 4 && users.len() < 6);
    }

    #[test]
    fn serves_domain() {
        let store = store();
        assert!(store.serves_domain("mail.gmi.org"));
        assert!(store.serves_domain("misfin.example.org"));
        assert!(!store.serves_domain("iron.maiden.org"));
    }

    #[test]
    fn has_user() {
        let store = store();
        assert!(store.has_mailuser("jane@mail.gmi.org"));
        assert!(store.has_mailuser("dick@mail.gmi.org"));
        assert!(store.has_mailuser("jane@misfin.example.org"));
        assert!(store.has_mailuser("dick@misfin.example.org"));
        assert!(!store.has_mailuser("fred@mail.gmi.org"));
    }

    #[test]
    fn get_folder() {
        let store = store();
        let folder = store.get_folder("jane@mail.gmi.org", "Inbox").unwrap();
        let msg = folder.messages.get("867017");
        assert!(msg.is_some());
        let msg = folder.messages.get("488571");
        assert!(msg.is_some());
    }

    #[test]
    fn get_message() {
        let msg = store()
            .get_message("jane@mail.gmi.org", "Inbox", "867017")
            .unwrap();
        assert_eq!(msg.from.username, "april");
        assert_eq!(msg.from.host.subdomain.unwrap(), "we.wear");
    }

    #[test]
    fn add_move_delete_message() {
        let msg = Message {
            id: String::from("1687407844"),
            from: Mailbox::from_str("suzie@thebanshees.legs").unwrap(),
            senders: vec![],
            recipients: vec![],
            timestamp: None,
            title: Some(String::from("Get a look at 'is 'orse")),
            body: String::from("Gorgeous, innit?"),
        };
        store()
            .add_message("dick@mail.gmi.org", "Inbox", msg)
            .unwrap();
        assert!(PathBuf::from("test/mailstore/mail.gmi.org/dick/Inbox/1687407844.gmi").exists());
        store()
            .move_message("dick@mail.gmi.org", "1687407844", "Inbox", "Lists")
            .unwrap();
        assert!(!PathBuf::from("test/mailstore/mail.gmi.org/dick/Inbox/1687407844.gmi").exists());
        assert!(PathBuf::from("test/mailstore/mail.gmi.org/dick/Lists/1687407844.gmi").exists());
        store()
            .delete_message("dick@mail.gmi.org", "Lists", "1687407844")
            .unwrap();
        assert!(!PathBuf::from("test/mailstore/mail.gmi.org/dick/Lists/1687407844.gmi").exists());
    }

    #[test]
    fn add_remove_user() {
        store()
            .add_user("rob@misfin.example.org Rob Zombie")
            .unwrap();
        assert!(store().has_mailuser("rob@misfin.example.org"));
        assert!(store().remove_user("rob@misfin.example.org"));
        assert!(!store().has_mailuser("rob@misfin.example.org"));
    }
}