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use itertools::Itertools as _;
use super::{
Conversation, Id,
event::{Created, Deleted, Event},
};
use crate::{
event::{Instant, Sequence},
name::Name,
};
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct History {
pub conversation: Conversation,
}
// Lifecycle interface
impl History {
pub fn begin(name: &Name, created: Instant) -> Self {
Self {
conversation: Conversation {
id: Id::generate(),
name: name.clone(),
created,
deleted: None,
},
}
}
pub fn delete(self, deleted: Instant) -> Result<Self, DeleteError> {
if self.conversation.deleted.is_none() {
Ok(Self {
conversation: Conversation {
deleted: Some(deleted),
..self.conversation
},
})
} else {
Err(DeleteError::Deleted(self))
}
}
}
#[derive(Debug, thiserror::Error)]
pub enum DeleteError {
#[error("conversation {} already deleted", .0.conversation.id)]
Deleted(History),
}
// State interface
impl History {
pub fn id(&self) -> &Id {
&self.conversation.id
}
// Snapshot of this conversation as it was when created. (Note to the future:
// it's okay if this returns a redacted or modified version of the conversation.
// If we implement renames by redacting the original name, then this should
// return the renamed conversation, not the original, even if that's not how
// it was "as created.")
pub fn as_created(&self) -> Conversation {
self.conversation.clone()
}
pub fn as_of<S>(&self, sequence: S) -> Option<Conversation>
where
S: Into<Sequence>,
{
self.events().filter(Sequence::up_to(sequence)).collect()
}
// Snapshot of this conversation as of all events recorded in this history.
pub fn as_snapshot(&self) -> Option<Conversation> {
self.events().collect()
}
}
// Event factories
impl History {
pub fn events(&self) -> impl Iterator<Item = Event> + Clone + use<> {
[self.created()]
.into_iter()
.merge_by(self.deleted(), Sequence::merge)
}
fn created(&self) -> Event {
Created {
conversation: self.conversation.clone(),
}
.into()
}
fn deleted(&self) -> Option<Event> {
self.conversation.deleted.map(|instant| {
Deleted {
instant,
id: self.conversation.id.clone(),
}
.into()
})
}
}
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