//! Crate `ruma_events` contains serializable types for the events in the [Matrix](https://matrix.org)
//! specification that can be shared by client and server code.
//!
//! All data exchanged over Matrix is expressed as an event.
//! Different event types represent different actions, such as joining a room or sending a message.
//! Events are stored and transmitted as simple JSON structures.
//! While anyone can create a new event type for their own purposes, the Matrix specification
//! defines a number of event types which are considered core to the protocol, and Matrix clients
//! and servers must understand their semantics.
//! ruma-events contains Rust types for each of the event types defined by the specification and
//! facilities for extending the event system for custom event types.
//!
//! # Event types
//!
//! ruma-events includes a Rust enum called `EventType`, which provides a simple enumeration of
//! all the event types defined by the Matrix specification. Matrix event types are serialized to
//! JSON strings in [reverse domain name
//! notation](https://en.wikipedia.org/wiki/Reverse_domain_name_notation), although the core event
//! types all use the special "m" TLD, e.g. *m.room.message*.
//! `EventType` also includes a variant called `Custom`, which is a catch-all that stores a string
//! containing the name of any event type that isn't part of the specification.
//! `EventType` is used throughout ruma-events to identify and differentiate between events of
//! different types.
//!
//! # Event kinds
//!
//! Matrix defines three "kinds" of events:
//!
//! 1.  **Events**, which are arbitrary JSON structures that have two required keys:
//!     *   `type`, which specifies the event's type
//!     *   `content`, which is a JSON object containing the "payload" of the event
//! 2.  **Room events**, which are a superset of events and represent actions that occurred within
//!     the context of a Matrix room.
//!     They have at least the following additional keys:
//!     *   `event_id`, which is a unique identifier for the event
//!     *   `room_id`, which is a unique identifier for the room in which the event occurred
//!     *   `sender`, which is the unique identifier of the Matrix user who created the event
//!     *   Optionally, `unsigned`, which is a JSON object containing arbitrary additional metadata
//!     that is not digitally signed by Matrix homeservers.
//! 3.  **State events**, which are a superset of room events and represent persistent state
//!     specific to a room, such as the room's member list or topic.
//!     Within a single room, state events of the same type and with the same "state key" will
//!     effectively "replace" the previous one, updating the room's state.
//!     They have at least the following additional keys:
//!     *   `state_key`, a string which serves as a sort of "sub-type."
//!         The state key allows a room to persist multiple state events of the same type.
//!         You can think of a room's state events as being a `BTreeMap` where the keys are the tuple
//!         `(event_type, state_key)`.
//!     *   Optionally, `prev_content`, a JSON object containing the `content` object from the
//!     previous event of the given `(event_type, state_key)` tuple in the given room.
//!
//! ruma-events represents these three event kinds as traits, allowing any Rust type to serve as a
//! Matrix event so long as it upholds the contract expected of its kind.
//!
//! # Core event types
//!
//! ruma-events includes Rust types for every one of the event types in the Matrix specification.
//! To better organize the crate, these types live in separate modules with a hierarchy that
//! matches the reverse domain name notation of the event type.
//! For example, the *m.room.message* event lives at `ruma_events::room::message::MessageEvent`.
//! Each type's module also contains a Rust type for that event type's `content` field, and any
//! other supporting types required by the event's other fields.
//!
//! # Custom event types
//!
//! Although any Rust type that implements `Event`, `RoomEvent`, or `StateEvent` can serve as a
//! Matrix event type, ruma-events also includes a few convenience types for representing events
//! that are not covered by the spec and not otherwise known by the application.
//! `CustomEvent`, `CustomRoomEvent`, and `CustomStateEvent` are simple implementations of their
//! respective event traits whose `content` field is simply a `serde_json::Value` value, which
//! represents arbitrary JSON.
//!
//! # Serialization and deserialization
//!
//! All concrete event types in ruma-events can be serialized via the `Serialize` trait from
//! [serde](https://serde.rs/) and can be deserialized from as `EventJson<EventType>`. In order to
//! handle incoming data that may not conform to `ruma-events`' strict definitions of event
//! structures, deserialization will return `EventJson::Err` on error. This error covers both
//! structurally invalid JSON data as well as structurally valid JSON that doesn't fulfill
//! additional constraints the matrix specification defines for some event types. The error exposes
//! the deserialized `serde_json::Value` so that developers can still work with the received
//! event data. This makes it possible to deserialize a collection of events without the entire
//! collection failing to deserialize due to a single invalid event. The "content" type for each
//! event also implements `Serialize` and either `TryFromRaw` (enabling usage as
//! `EventJson<ContentType>` for dedicated content types) or `Deserialize` (when the content is a
//! type alias), allowing content to be converted to and from JSON indepedently of the surrounding
//! event structure, if needed.
//!
//! # Collections
//!
//! With the trait-based approach to events, it's easy to write generic collection types like
//! `Vec<Box<R: RoomEvent>>`.
//! However, there are APIs in the Matrix specification that involve heterogeneous collections of
//! events, i.e. a list of events of different event types.
//! Because Rust does not have a facility for arrays, vectors, or slices containing multiple
//! concrete types, ruma-events provides special collection types for this purpose.
//! The collection types are enums which effectively "wrap" each possible event type of a
//! particular event "kind."
//!
//! Because of the hierarchical nature of event kinds in Matrix, these collection types are divied
//! into two modules, `ruma_events::collections::all` and `ruma_events::collections::only`.
//! The "all" versions include every event type that implements the relevant event trait as well as
//! more specific event traits.
//! The "only" versions include only the event types that implement "at most" the relevant event
//! trait.
//!
//! For example, the `ruma_events::collections::all::Event` enum includes *m.room.message*, because
//! that event type is both an event and a room event.
//! However, the `ruma_events::collections::only::Event` enum does *not* include *m.room.message*,
//! because *m.room.message* implements a *more specific* event trait than `Event`.

#![recursion_limit = "1024"]
#![warn(missing_debug_implementations, missing_docs, rust_2018_idioms)]
// Since we support Rust 1.36.0, we can't apply this suggestion yet
#![allow(clippy::use_self)]

use std::{fmt::Debug, time::SystemTime};

use js_int::Int;
use ruma_identifiers::{EventId, RoomId, UserId};
use serde::{Deserialize, Serialize};

use self::room::redaction::RedactionEvent;

pub use self::custom::{CustomEvent, CustomRoomEvent, CustomStateEvent};

#[deprecated = "Use ruma_serde::empty::Empty directly instead."]
pub use ruma_serde::empty::Empty;

#[macro_use]
mod macros;

mod algorithm;
mod error;
mod event_type;
mod from_raw;
mod json;
#[doc(hidden)] // only public for external tests
pub mod util;

// Hack to allow both ruma-events itself and external crates (or tests) to use procedural macros
// that expect `ruma_events` to exist in the prelude.
extern crate self as ruma_events;

pub mod call;
pub mod custom;
/// Enums for heterogeneous collections of events.
pub mod collections {
    pub mod all;
    pub mod only;

    mod raw {
        pub mod all;
        pub mod only;
    }
}
pub mod direct;
pub mod dummy;
pub mod forwarded_room_key;
pub mod fully_read;
pub mod ignored_user_list;
pub mod key;
pub mod presence;
pub mod push_rules;
pub mod receipt;
pub mod room;
pub mod room_key;
pub mod room_key_request;
pub mod sticker;
pub mod stripped;
pub mod tag;
pub mod to_device;
pub mod typing;

pub use self::{
    algorithm::Algorithm,
    error::{FromStrError, InvalidEvent, InvalidInput},
    event_type::EventType,
    from_raw::{FromRaw, TryFromRaw},
    json::EventJson,
};

/// A basic event.
pub trait Event: Debug + Serialize + Sized + TryFromRaw {
    /// The type of this event's `content` field.
    type Content: Debug + Serialize;

    /// The event's content.
    fn content(&self) -> &Self::Content;

    /// The type of the event.
    fn event_type(&self) -> EventType;
}

/// An event within the context of a room.
pub trait RoomEvent: Event {
    /// The unique identifier for the event.
    fn event_id(&self) -> &EventId;

    /// Time on originating homeserver when this event was sent.
    fn origin_server_ts(&self) -> SystemTime;

    /// The unique identifier for the room associated with this event.
    ///
    /// This can be `None` if the event came from a context where there is
    /// no ambiguity which room it belongs to, like a `/sync` response for example.
    fn room_id(&self) -> Option<&RoomId>;

    /// The unique identifier for the user who sent this event.
    fn sender(&self) -> &UserId;

    /// Additional key-value pairs not signed by the homeserver.
    fn unsigned(&self) -> &UnsignedData;
}

/// An event that describes persistent state about a room.
pub trait StateEvent: RoomEvent {
    /// The previous content for this state key, if any.
    fn prev_content(&self) -> Option<&Self::Content>;

    /// A key that determines which piece of room state the event represents.
    fn state_key(&self) -> &str;
}

/// Extra information about an event that is not incorporated into the event's
/// hash.
#[derive(Clone, Debug, Default, Deserialize, Serialize)]
pub struct UnsignedData {
    /// The time in milliseconds that has elapsed since the event was sent. This
    /// field is generated by the local homeserver, and may be incorrect if the
    /// local time on at least one of the two servers is out of sync, which can
    /// cause the age to either be negative or greater than it actually is.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub age: Option<Int>,

    /// The event that redacted this event, if any.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub redacted_because: Option<EventJson<RedactionEvent>>,

    /// The client-supplied transaction ID, if the client being given the event
    /// is the same one which sent it.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub transaction_id: Option<String>,
}

impl UnsignedData {
    /// Whether this unsigned data is empty (all fields are `None`).
    ///
    /// This method is used to determine whether to skip serializing the
    /// `unsigned` field in room events. Do not use it to determine whether
    /// an incoming `unsigned` field was present - it could still have been
    /// present but contained none of the known fields.
    pub fn is_empty(&self) -> bool {
        self.age.is_none() && self.redacted_because.is_none() && self.transaction_id.is_none()
    }
}