//! This module implements ... TODO when I can write again.
#[macro_use] extern crate postgres;
#[macro_use] extern crate postgres_derive;
extern crate chrono;
extern crate finito;
extern crate serde;
extern crate serde_json;
extern crate uuid;
mod error;
pub use error::{Result, Error};
use chrono::prelude::{DateTime, Utc};
use finito::FSM;
use postgres::GenericConnection;
use serde::Serialize;
use serde::de::DeserializeOwned;
use serde_json::Value;
use std::fmt;
use std::marker::PhantomData;
use uuid::Uuid;
/// This struct represents rows in the database table in which
/// machines (i.e. the current state of a Finito state machine) are
/// persisted.
#[derive(Debug, ToSql, FromSql)]
struct MachineT {
/// ID of the persisted state machine.
id: Uuid,
/// Time at which the FSM was first created.
created: DateTime<Utc>,
/// Name of the type of FSM represented by this state.
fsm: String,
/// Current state of the FSM (TODO: Can the serialised FSM type be
/// used?)
state: Value,
}
/// This struct represents rows in the database table in which events
/// are persisted.
#[derive(Debug, ToSql, FromSql)]
struct EventT {
/// ID of the persisted event.
id: Uuid,
/// Timestamp at which the event was stored.
created: DateTime<Utc>,
/// Name of the type of FSM that this state belongs to.
fsm: String,
/// ID of the state machine belonging to this event.
fsm_id: Uuid,
/// Serialised content of the event.
event: Value,
}
/// This enum represents the possible statuses an action can be in.
#[derive(Debug, ToSql, FromSql)]
enum ActionStatus {
/// The action was requested but has not run yet.
Pending,
/// The action completed successfully.
Completed,
/// The action failed to run. Information about the error will
/// have been persisted in Postgres.
Failed,
}
/// This struct represents rows in the database table in which actions
/// are persisted.
#[derive(Debug, ToSql, FromSql)]
struct ActionT {
/// ID of the persisted event.
id: Uuid,
/// Timestamp at which the event was stored.
created: DateTime<Utc>,
/// Name of the type of FSM that this state belongs to.
fsm: String,
/// ID of the state machine belonging to this event.
fsm_id: Uuid,
/// Serialised content of the action.
action: Value,
/// Current status of the action.
status: ActionStatus,
/// Serialised error representation, if an error occured during
/// processing. TODO: Use some actual error type. Maybe failure
/// has serialisation support?
error: Option<String>,
}
// The following functions implement the public interface of
// `finito-postgres`.
/// This type is used as a type-safe wrapper around the ID of a state
/// machine. It carries information about the FSM type and is intended
/// to add a layer of checking to prevent IDs from being mixed up.
#[derive(Clone)]
pub struct MachineId<S: FSM> {
uuid: Uuid,
phantom: PhantomData<S>,
}
/// Custom debug implementation to format machine IDs using the name
/// of the FSM and their UUID.
impl <S: FSM> fmt::Debug for MachineId<S> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}:{}", S::FSM_NAME, self.uuid.hyphenated())
}
}
impl <S: FSM> MachineId<S> {
/// Convert a UUID into a strongly typed machine ID.
pub fn from_uuid(uuid: Uuid) -> Self {
MachineId {
uuid,
phantom: PhantomData,
}
}
/// Return the UUID contained in a machine ID.
pub fn to_uuid(&self) -> Uuid {
self.uuid
}
}
/// Insert a single state-machine into the database and return its
/// newly allocated, random UUID.
pub fn insert_machine<C, S>(conn: &C, initial: S) -> Result<MachineId<S>> where
C: GenericConnection,
S: FSM + Serialize {
let query = r#"
INSERT INTO machines (id, created, fsm, state)
VALUES ($1, NOW(), $2, $3)
"#;
let id = Uuid::new_v4();
let fsm = S::FSM_NAME.to_string();
let state = serde_json::to_value(initial).expect("TODO");
conn.execute(query, &[&id, &fsm, &state]).expect("TODO");
return Ok(MachineId::from_uuid(id));
}
/// Insert a single event into the database and return its UUID.
pub fn insert_event<C, S>(conn: &C, fsm_id: MachineId<S>, event: S::Event) -> Result<Uuid>
where
C: GenericConnection,
S: FSM,
S::Event: Serialize {
let query = r#"
INSERT INTO events (id, created, fsm, fsm_id, event)
VALUES ($1, NOW(), $2, $3, $4)
"#;
let id = Uuid::new_v4();
let fsm = S::FSM_NAME.to_string();
let event_value = serde_json::to_value(event).expect("TODO");
conn.execute(query, &[&id, &fsm, &fsm_id.to_uuid(), &event_value]).expect("TODO");
return Ok(id)
}
/// Insert a single action into the database and return its UUID.
pub fn insert_action<C, S>(conn: &C,
fsm_id: MachineId<S>,
action: S::Action) -> Result<Uuid> where
C: GenericConnection,
S: FSM,
S::Action: Serialize {
let query = r#"
INSERT INTO actions (id, created, fsm, fsm_id, action, status)
VALUES ($1, NOW(), $2, $3, $4, $5)
"#;
let id = Uuid::new_v4();
let fsm = S::FSM_NAME.to_string();
let action_value = serde_json::to_value(action).expect("TODO");
conn.execute(query, &[&id, &fsm, &fsm_id.to_uuid(), &action_value,
&ActionStatus::Pending]).expect("TODO");
return Ok(id)
}
/// Retrieve the current state of a state machine from the database.
pub fn get_machine<C, S>(conn: &C, id: MachineId<S>) -> Result<S> where
C: GenericConnection,
S: FSM + DeserializeOwned {
let query = r#"
SELECT (id, created, fsm, state) FROM machines WHERE id = $1
"#;
let rows = conn.query(query, &[&id.to_uuid()]).expect("TODO");
let mut machines = rows.into_iter().map(|row| MachineT {
id: row.get(0),
created: row.get(1),
fsm: row.get(2),
state: row.get(3),
});
if let Some(machine) = machines.next() {
Ok(serde_json::from_value(machine.state).expect("TODO"))
} else {
// TODO: return appropriate not found error
Err(Error::SomeError)
}
}
/// Advance a persisted state machine by applying an event, and
/// storing the event as well as all resulting actions.
///
/// This function holds a database-lock on the state's row while
/// advancing the machine.
///
/// **Note**: This function returns the new state of the machine
/// immediately after applying the event, however this does not
/// necessarily equate to the state of the machine after all related
/// processing is finished as running actions may result in additional
/// transitions.
pub fn advance<C, S>(conn: &C,
id: MachineId<S>,
event: S::Event) -> Result<S> where
C: GenericConnection,
S: FSM + DeserializeOwned {
unimplemented!()
}
