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//! Types for the *m.key.verification.cancel* event.

use std::{
    borrow::Cow,
    fmt::{Display, Formatter, Result as FmtResult},
};

use ruma_events_macros::ruma_event;
use serde::{Deserialize, Serialize};

ruma_event! {
    /// Cancels a key verification process/request.
    ///
    /// Typically sent as a to-device event.
    CancelEvent {
        kind: Event,
        event_type: "m.key.verification.cancel",
        content: {
            /// The opaque identifier for the verification process/request.
            pub transaction_id: String,

            /// A human readable description of the `code`.
            ///
            /// The client should only rely on this string if it does not understand the `code`.
            pub reason: String,

            /// The error code for why the process/request was cancelled by the user.
            pub code: CancelCode,
        },
    }
}

/// An error code for why the process/request was cancelled by the user.
///
/// Custom error codes should use the Java package naming convention.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
// Cow<str> because deserialization sometimes needs to copy to unescape things
#[serde(from = "Cow<'_, str>", into = "String")]
pub enum CancelCode {
    /// The user cancelled the verification.
    User,

    /// The verification process timed out. Verification processes can define their own timeout
    /// parameters.
    Timeout,

    /// The device does not know about the given transaction ID.
    UnknownTransaction,

    /// The device does not know how to handle the requested method.
    ///
    /// This should be sent for *m.key.verification.start* messages and messages defined by
    /// individual verification processes.
    UnknownMethod,

    /// The device received an unexpected message.
    ///
    /// Typically raised when one of the parties is handling the verification out of order.
    UnexpectedMessage,

    /// The key was not verified.
    KeyMismatch,

    /// The expected user did not match the user verified.
    UserMismatch,

    /// The message received was invalid.
    InvalidMessage,

    /// An *m.key.verification.request* was accepted by a different device.
    ///
    /// The device receiving this error can ignore the verification request.
    Accepted,

    /// Any code that is not part of the specification.
    Custom(String),

    /// Additional variants may be added in the future and will not be considered breaking changes
    /// to ruma-events.
    #[doc(hidden)]
    __Nonexhaustive,
}

impl Display for CancelCode {
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        let cancel_code_str = match *self {
            CancelCode::User => "m.user",
            CancelCode::Timeout => "m.timeout",
            CancelCode::UnknownTransaction => "m.unknown_transaction",
            CancelCode::UnknownMethod => "m.unknown_method",
            CancelCode::UnexpectedMessage => "m.unexpected_message",
            CancelCode::KeyMismatch => "m.key_mismatch",
            CancelCode::UserMismatch => "m.user_mismatch",
            CancelCode::InvalidMessage => "m.invalid_message",
            CancelCode::Accepted => "m.accepted",
            CancelCode::Custom(ref cancel_code) => cancel_code,
            CancelCode::__Nonexhaustive => {
                panic!("__Nonexhaustive enum variant is not intended for use.")
            }
        };

        write!(f, "{}", cancel_code_str)
    }
}

impl From<Cow<'_, str>> for CancelCode {
    fn from(s: Cow<'_, str>) -> CancelCode {
        match &s as &str {
            "m.user" => CancelCode::User,
            "m.timeout" => CancelCode::Timeout,
            "m.unknown_transaction" => CancelCode::UnknownTransaction,
            "m.unknown_method" => CancelCode::UnknownMethod,
            "m.unexpected_message" => CancelCode::UnexpectedMessage,
            "m.key_mismatch" => CancelCode::KeyMismatch,
            "m.user_mismatch" => CancelCode::UserMismatch,
            "m.invalid_message" => CancelCode::InvalidMessage,
            "m.accepted" => CancelCode::Accepted,
            _ => CancelCode::Custom(s.into_owned()),
        }
    }
}

impl From<&str> for CancelCode {
    fn from(s: &str) -> CancelCode {
        CancelCode::from(Cow::Borrowed(s))
    }
}

impl From<CancelCode> for String {
    fn from(cancel_code: CancelCode) -> String {
        cancel_code.to_string()
    }
}

#[cfg(test)]
mod tests {
    use serde_json::{from_str, to_string};

    use super::CancelCode;

    #[test]
    fn cancel_codes_serialize_to_display_form() {
        assert_eq!(to_string(&CancelCode::User).unwrap(), r#""m.user""#);
    }

    #[test]
    fn custom_cancel_codes_serialize_to_display_form() {
        assert_eq!(
            to_string(&CancelCode::Custom("io.ruma.test".to_string())).unwrap(),
            r#""io.ruma.test""#
        );
    }

    #[test]
    fn cancel_codes_deserialize_from_display_form() {
        assert_eq!(
            from_str::<CancelCode>(r#""m.user""#).unwrap(),
            CancelCode::User
        );
    }

    #[test]
    fn custom_cancel_codes_deserialize_from_display_form() {
        assert_eq!(
            from_str::<CancelCode>(r#""io.ruma.test""#).unwrap(),
            CancelCode::Custom("io.ruma.test".to_string())
        )
    }
}