//! # Events specification.

#![allow(missing_docs)]

use std::path::PathBuf;

use async_channel::{self as channel, Receiver, Sender, TrySendError};
use serde::Serialize;

use crate::chat::ChatId;
use crate::contact::ContactId;
use crate::ephemeral::Timer as EphemeralTimer;
use crate::message::MsgId;
use crate::webxdc::StatusUpdateSerial;

/// Event channel.
#[derive(Debug, Clone)]
pub struct Events {
    receiver: Receiver<Event>,
    sender: Sender<Event>,
}

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

impl Events {
    /// Creates a new event channel.
    pub fn new() -> Self {
        let (sender, receiver) = channel::bounded(1_000);

        Self { receiver, sender }
    }

    /// Emits an event.
    pub fn emit(&self, event: Event) {
        match self.sender.try_send(event) {
            Ok(()) => {}
            Err(TrySendError::Full(event)) => {
                // when we are full, we pop remove the oldest event and push on the new one
                let _ = self.receiver.try_recv();

                // try again
                self.emit(event);
            }
            Err(TrySendError::Closed(_)) => {
                unreachable!("unable to emit event, channel disconnected");
            }
        }
    }

    /// Retrieve the event emitter.
    pub fn get_emitter(&self) -> EventEmitter {
        EventEmitter(self.receiver.clone())
    }
}

/// A receiver of events from a [`Context`].
///
/// See [`Context::get_event_emitter`] to create an instance.  If multiple instances are
/// created events emitted by the [`Context`] will only be delivered to one of the
/// `EventEmitter`s.
///
/// The `EventEmitter` is also a [`Stream`], so a typical usage is in a `while let` loop.
///
/// [`Context`]: crate::context::Context
/// [`Context::get_event_emitter`]: crate::context::Context::get_event_emitter
/// [`Stream`]: futures::stream::Stream
#[derive(Debug, Clone)]
pub struct EventEmitter(Receiver<Event>);

impl EventEmitter {
    /// Async recv of an event. Return `None` if the `Sender` has been droped.
    pub async fn recv(&self) -> Option<Event> {
        self.0.recv().await.ok()
    }
}

impl futures::stream::Stream for EventEmitter {
    type Item = Event;

    fn poll_next(
        mut self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Option<Self::Item>> {
        std::pin::Pin::new(&mut self.0).poll_next(cx)
    }
}

/// The event emitted by a [`Context`] from an [`EventEmitter`].
///
/// Events are documented on the C/FFI API in `deltachat.h` as `DC_EVENT_*` contants.  The
/// context emits them in relation to various operations happening, a lot of these are again
/// documented in `deltachat.h`.
///
/// [`Context`]: crate::context::Context
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Event {
    /// The ID of the [`Context`] which emitted this event.
    ///
    /// This allows using multiple [`Context`]s in a single process as they are identified
    /// by this ID.
    ///
    /// [`Context`]: crate::context::Context
    pub id: u32,
    /// The event payload.
    ///
    /// These are documented in `deltachat.h` as the `DC_EVENT_*` constants.
    pub typ: EventType,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub enum EventType {
    /// The library-user may write an informational string to the log.
    ///
    /// This event should *not* be reported to the end-user using a popup or something like
    /// that.
    Info(String),

    /// Emitted when SMTP connection is established and login was successful.
    SmtpConnected(String),

    /// Emitted when IMAP connection is established and login was successful.
    ImapConnected(String),

    /// Emitted when a message was successfully sent to the SMTP server.
    SmtpMessageSent(String),

    /// Emitted when an IMAP message has been marked as deleted
    ImapMessageDeleted(String),

    /// Emitted when an IMAP message has been moved
    ImapMessageMoved(String),

    /// Emitted when an new file in the $BLOBDIR was created
    NewBlobFile(String),

    /// Emitted when an file in the $BLOBDIR was deleted
    DeletedBlobFile(String),

    /// The library-user should write a warning string to the log.
    ///
    /// This event should *not* be reported to the end-user using a popup or something like
    /// that.
    Warning(String),

    /// The library-user should report an error to the end-user.
    ///
    /// As most things are asynchronous, things may go wrong at any time and the user
    /// should not be disturbed by a dialog or so.  Instead, use a bubble or so.
    ///
    /// However, for ongoing processes (eg. configure())
    /// or for functions that are expected to fail (eg. dc_continue_key_transfer())
    /// it might be better to delay showing these events until the function has really
    /// failed (returned false). It should be sufficient to report only the *last* error
    /// in a messasge box then.
    Error(String),

    /// An action cannot be performed because the user is not in the group.
    /// Reported eg. after a call to
    /// dc_set_chat_name(), dc_set_chat_profile_image(),
    /// dc_add_contact_to_chat(), dc_remove_contact_from_chat(),
    /// dc_send_text_msg() or another sending function.
    ErrorSelfNotInGroup(String),

    /// Messages or chats changed.  One or more messages or chats changed for various
    /// reasons in the database:
    /// - Messages sent, received or removed
    /// - Chats created, deleted or archived
    /// - A draft has been set
    ///
    /// `chat_id` is set if only a single chat is affected by the changes, otherwise 0.
    /// `msg_id` is set if only a single message is affected by the changes, otherwise 0.
    MsgsChanged {
        chat_id: ChatId,
        msg_id: MsgId,
    },

    /// Reactions for the message changed.
    ReactionsChanged {
        chat_id: ChatId,
        msg_id: MsgId,
        contact_id: ContactId,
    },

    /// There is a fresh message. Typically, the user will show an notification
    /// when receiving this message.
    ///
    /// There is no extra #DC_EVENT_MSGS_CHANGED event send together with this event.
    IncomingMsg {
        chat_id: ChatId,
        msg_id: MsgId,
    },

    IncomingMsgBunch {
        msg_ids: Vec<MsgId>,
    },

    /// Messages were seen or noticed.
    /// chat id is always set.
    MsgsNoticed(ChatId),

    /// A single message is sent successfully. State changed from  DC_STATE_OUT_PENDING to
    /// DC_STATE_OUT_DELIVERED, see dc_msg_get_state().
    MsgDelivered {
        chat_id: ChatId,
        msg_id: MsgId,
    },

    /// A single message could not be sent. State changed from DC_STATE_OUT_PENDING or DC_STATE_OUT_DELIVERED to
    /// DC_STATE_OUT_FAILED, see dc_msg_get_state().
    MsgFailed {
        chat_id: ChatId,
        msg_id: MsgId,
    },

    /// A single message is read by the receiver. State changed from DC_STATE_OUT_DELIVERED to
    /// DC_STATE_OUT_MDN_RCVD, see dc_msg_get_state().
    MsgRead {
        chat_id: ChatId,
        msg_id: MsgId,
    },

    /// Chat changed.  The name or the image of a chat group was changed or members were added or removed.
    /// Or the verify state of a chat has changed.
    /// See dc_set_chat_name(), dc_set_chat_profile_image(), dc_add_contact_to_chat()
    /// and dc_remove_contact_from_chat().
    ///
    /// This event does not include ephemeral timer modification, which
    /// is a separate event.
    ChatModified(ChatId),

    /// Chat ephemeral timer changed.
    ChatEphemeralTimerModified {
        chat_id: ChatId,
        timer: EphemeralTimer,
    },

    /// Contact(s) created, renamed, blocked or deleted.
    ///
    /// @param data1 (int) If set, this is the contact_id of an added contact that should be selected.
    ContactsChanged(Option<ContactId>),

    /// Location of one or more contact has changed.
    ///
    /// @param data1 (u32) contact_id of the contact for which the location has changed.
    ///     If the locations of several contacts have been changed,
    ///     eg. after calling dc_delete_all_locations(), this parameter is set to `None`.
    LocationChanged(Option<ContactId>),

    /// Inform about the configuration progress started by configure().
    ConfigureProgress {
        /// Progress.
        ///
        /// 0=error, 1-999=progress in permille, 1000=success and done
        progress: usize,

        /// Progress comment or error, something to display to the user.
        comment: Option<String>,
    },

    /// Inform about the import/export progress started by imex().
    ///
    /// @param data1 (usize) 0=error, 1-999=progress in permille, 1000=success and done
    /// @param data2 0
    ImexProgress(usize),

    /// A file has been exported. A file has been written by imex().
    /// This event may be sent multiple times by a single call to imex().
    ///
    /// A typical purpose for a handler of this event may be to make the file public to some system
    /// services.
    ///
    /// @param data2 0
    ImexFileWritten(PathBuf),

    /// Progress information of a secure-join handshake from the view of the inviter
    /// (Alice, the person who shows the QR code).
    ///
    /// These events are typically sent after a joiner has scanned the QR code
    /// generated by dc_get_securejoin_qr().
    ///
    /// @param data1 (int) ID of the contact that wants to join.
    /// @param data2 (int) Progress as:
    ///     300=vg-/vc-request received, typically shown as "bob@addr joins".
    ///     600=vg-/vc-request-with-auth received, vg-member-added/vc-contact-confirm sent, typically shown as "bob@addr verified".
    ///     800=contact added to chat, shown as "bob@addr securely joined GROUP". Only for the verified-group-protocol.
    ///     1000=Protocol finished for this contact.
    SecurejoinInviterProgress {
        contact_id: ContactId,
        progress: usize,
    },

    /// Progress information of a secure-join handshake from the view of the joiner
    /// (Bob, the person who scans the QR code).
    /// The events are typically sent while dc_join_securejoin(), which
    /// may take some time, is executed.
    /// @param data1 (int) ID of the inviting contact.
    /// @param data2 (int) Progress as:
    ///     400=vg-/vc-request-with-auth sent, typically shown as "alice@addr verified, introducing myself."
    ///     (Bob has verified alice and waits until Alice does the same for him)
    SecurejoinJoinerProgress {
        contact_id: ContactId,
        progress: usize,
    },

    /// The connectivity to the server changed.
    /// This means that you should refresh the connectivity view
    /// and possibly the connectivtiy HTML; see dc_get_connectivity() and
    /// dc_get_connectivity_html() for details.
    ConnectivityChanged,

    SelfavatarChanged,

    WebxdcStatusUpdate {
        msg_id: MsgId,
        status_update_serial: StatusUpdateSerial,
    },

    /// Inform that a message containing a webxdc instance has been deleted
    WebxdcInstanceDeleted {
        msg_id: MsgId,
    },
}