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use serde::{
    de::DeserializeOwned,
    Serialize,
};
use std::fmt::Debug;

use crate::{
    commands::{
        ICommand,
        ICommandHandler,
    },
    events::{
        IEvent,
        IEventHandler,
    },
};

/// In CQRS (and Domain Driven Design) an `Aggregate` is the
/// fundamental component that encapsulates the state and application
/// logic (aka business rules) for the application. An `Aggregate` is
/// always an entity along with all objects associated with it.
///
/// # Examples
/// ```rust
/// use serde::{
///     Deserialize,
///     Serialize,
/// };
/// use std::fmt::Debug;
///
/// use cqrs_es2::{
///     example_impl::{
///         AddressUpdated,
///         CustomerCommand,
///         CustomerEvent,
///         EmailUpdated,
///         NameAdded,
///     },
///     Error,
///     IAggregate,
///     ICommandHandler,IEventHandler
/// };
///
/// #[derive(
///     Debug,
///     PartialEq,
///     Default,
///     Clone,
///     Serialize,
///     Deserialize
/// )]
/// struct Customer {
///     customer_id: String,
///     name: String,
///     email: String,
///     pub addresses: Vec<String>,
/// }
///
/// impl IAggregate<CustomerCommand, CustomerEvent> for Customer {
///     fn aggregate_type() -> &'static str {
///         "customer"
///     }
/// }
///
/// impl ICommandHandler<CustomerCommand, CustomerEvent> for Customer {
///     fn handle(
///         &self,
///         command: CustomerCommand,
///     ) -> Result<Vec<CustomerEvent>, Error> {
///         match command {
///             CustomerCommand::AddCustomerName(payload) => {
///                 if self.name.as_str() != "" {
///                     return Err(Error::new(
///                         "a name has already been added for this \
///                              customer",
///                     ));
///                 }
///
///                 let payload = NameAdded {
///                     changed_name: payload.changed_name,
///                 };
///
///                 Ok(vec![CustomerEvent::NameAdded(payload)])
///             },
///             CustomerCommand::UpdateEmail(payload) => {
///                 let payload = EmailUpdated {
///                     new_email: payload.new_email,
///                 };
///
///                 Ok(vec![CustomerEvent::EmailUpdated(
///                     payload,
///                 )])
///             },
///             CustomerCommand::AddAddress(payload) => {
///                 if self
///                     .addresses
///                     .iter()
///                     .any(|i| payload.new_address.eq(i))
///                 {
///                     return Err(Error::new(
///                         "this address has already been added \
///                              for this customer",
///                     ));
///                 }
///
///                 let payload = AddressUpdated {
///                     new_address: payload.new_address,
///                 };
///
///                 Ok(vec![CustomerEvent::AddressUpdated(
///                     payload,
///                 )])
///             },
///         }
///     }}
///
/// impl IEventHandler<CustomerEvent> for Customer {
///     fn apply(
///         &mut self,
///         event: &CustomerEvent,
///     ) {
///         match event {
///             CustomerEvent::NameAdded(payload) => {
///                 self.name = payload.changed_name.clone();
///             },
///             CustomerEvent::EmailUpdated(payload) => {
///                 self.email = payload.new_email.clone();
///             },
///             CustomerEvent::AddressUpdated(payload) => {
///                 self.addresses
///                     .push(payload.new_address.clone())
///             },
///         }
///     }
/// }
/// ```
pub trait IAggregate<C: ICommand, E: IEvent>:
    Debug
    + PartialEq
    + Default
    + Clone
    + Serialize
    + DeserializeOwned
    + ICommandHandler<C, E>
    + IEventHandler<E>
    + Sync
    + Send {
    /// aggregate_type is a unique identifier for this aggregate
    fn aggregate_type() -> &'static str;
}