//! Matrix identifiers for places where a room ID or room alias ID are used interchangeably.

use std::{borrow::Cow, convert::TryFrom, hint::unreachable_unchecked, num::NonZeroU8};

#[cfg(feature = "diesel")]
use diesel::sql_types::Text;

use crate::{error::Error, parse_id};

/// A Matrix room ID or a Matrix room alias ID.
///
/// `RoomIdOrAliasId` is useful for APIs that accept either kind of room identifier. It is converted
/// from a string slice, and can be converted back into a string as needed. When converted from a
/// string slice, the variant is determined by the leading sigil character.
///
/// ```
/// # use std::convert::TryFrom;
/// # use ruma_identifiers::RoomIdOrAliasId;
/// assert_eq!(
///     RoomIdOrAliasId::try_from("#ruma:example.com").unwrap().as_ref(),
///     "#ruma:example.com"
/// );
///
/// assert_eq!(
///     RoomIdOrAliasId::try_from("!n8f893n9:example.com").unwrap().as_ref(),
///     "!n8f893n9:example.com"
/// );
/// ```
#[derive(Clone, Debug)]
#[cfg_attr(feature = "diesel", derive(FromSqlRow, QueryId, AsExpression, SqlType))]
#[cfg_attr(feature = "diesel", sql_type = "Text")]
pub struct RoomIdOrAliasId {
    full_id: String,
    colon_idx: NonZeroU8,
}

impl RoomIdOrAliasId {
    /// Returns the host of the room (alias) ID, containing the server name (including the port) of
    /// the originating homeserver.
    pub fn hostname(&self) -> &str {
        &self.full_id[self.colon_idx.get() as usize + 1..]
    }

    /// Returns the local part (everything after the `!` or `#` and before the first colon).
    pub fn localpart(&self) -> &str {
        &self.full_id[1..self.colon_idx.get() as usize]
    }

    /// Whether this is a room id (starts with `'!'`)
    pub fn is_room_id(&self) -> bool {
        self.variant() == Variant::RoomId
    }

    /// Whether this is a room alias id (starts with `'#'`)
    pub fn is_room_alias_id(&self) -> bool {
        self.variant() == Variant::RoomAliasId
    }

    fn variant(&self) -> Variant {
        match self.full_id.bytes().next() {
            Some(b'!') => Variant::RoomId,
            Some(b'#') => Variant::RoomAliasId,
            _ => unsafe { unreachable_unchecked() },
        }
    }
}

#[derive(PartialEq)]
enum Variant {
    RoomId,
    RoomAliasId,
}

impl TryFrom<Cow<'_, str>> for RoomIdOrAliasId {
    type Error = Error;

    /// Attempts to create a new Matrix room ID or a room alias ID from a string representation.
    ///
    /// The string must either include the leading ! sigil, the localpart, a literal colon, and a
    /// valid homeserver host or include the leading # sigil, the alias, a literal colon, and a
    /// valid homeserver host.
    fn try_from(room_id_or_alias_id: Cow<'_, str>) -> Result<Self, Error> {
        let colon_idx = parse_id(&room_id_or_alias_id, &['#', '!'])?;
        Ok(Self {
            full_id: room_id_or_alias_id.into_owned(),
            colon_idx,
        })
    }
}

common_impls!(RoomIdOrAliasId, "a Matrix room ID or room alias ID");

#[cfg(test)]
mod tests {
    use std::convert::TryFrom;

    use serde_json::{from_str, to_string};

    use super::RoomIdOrAliasId;
    use crate::error::Error;

    #[test]
    fn valid_room_id_or_alias_id_with_a_room_alias_id() {
        assert_eq!(
            RoomIdOrAliasId::try_from("#ruma:example.com")
                .expect("Failed to create RoomAliasId.")
                .as_ref(),
            "#ruma:example.com"
        );
    }

    #[test]
    fn valid_room_id_or_alias_id_with_a_room_id() {
        assert_eq!(
            RoomIdOrAliasId::try_from("!29fhd83h92h0:example.com")
                .expect("Failed to create RoomId.")
                .as_ref(),
            "!29fhd83h92h0:example.com"
        );
    }

    #[test]
    fn missing_sigil_for_room_id_or_alias_id() {
        assert_eq!(
            RoomIdOrAliasId::try_from("ruma:example.com").unwrap_err(),
            Error::MissingSigil
        );
    }

    #[test]
    fn serialize_valid_room_id_or_alias_id_with_a_room_alias_id() {
        assert_eq!(
            to_string(
                &RoomIdOrAliasId::try_from("#ruma:example.com")
                    .expect("Failed to create RoomAliasId.")
            )
            .expect("Failed to convert RoomAliasId to JSON."),
            r##""#ruma:example.com""##
        );
    }

    #[test]
    fn serialize_valid_room_id_or_alias_id_with_a_room_id() {
        assert_eq!(
            to_string(
                &RoomIdOrAliasId::try_from("!29fhd83h92h0:example.com")
                    .expect("Failed to create RoomId.")
            )
            .expect("Failed to convert RoomId to JSON."),
            r#""!29fhd83h92h0:example.com""#
        );
    }

    #[test]
    fn deserialize_valid_room_id_or_alias_id_with_a_room_alias_id() {
        assert_eq!(
            from_str::<RoomIdOrAliasId>(r##""#ruma:example.com""##)
                .expect("Failed to convert JSON to RoomAliasId"),
            RoomIdOrAliasId::try_from("#ruma:example.com").expect("Failed to create RoomAliasId.")
        );
    }

    #[test]
    fn deserialize_valid_room_id_or_alias_id_with_a_room_id() {
        assert_eq!(
            from_str::<RoomIdOrAliasId>(r##""!29fhd83h92h0:example.com""##)
                .expect("Failed to convert JSON to RoomId"),
            RoomIdOrAliasId::try_from("!29fhd83h92h0:example.com")
                .expect("Failed to create RoomAliasId.")
        );
    }
}