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chip.gleam
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chip.gleam
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////Chip is a gleam process registry that plays along gleam erlang/OTP `Subject` type.
////
////It lets us group subjects of the same type so that we can later reference them all
////as a group, or sub-group if we decide to name them. Will also automatically delist
////dead processes.
import gleam/list
import gleam/dict.{type Dict}
import gleam/set.{type Set}
import gleam/result.{try}
import gleam/function.{identity}
import gleam/erlang/process.{
type Pid, type ProcessDown, type ProcessMonitor, type Selector, type Subject,
}
import gleam/otp/actor
pub opaque type Message(name, message) {
All(client: Subject(List(Subject(message))))
Named(client: Subject(List(#(name, Subject(message)))))
Lookup(client: Subject(List(Subject(message))), name: name)
Register(subject: Subject(message))
RegisterAs(subject: Subject(message), name: name)
Deregister(name: name)
Demonitor(subject: Subject(message))
RebuildSelector
Stop(client: Subject(process.ExitReason))
}
type State(name, message) {
State(
self: Subject(Message(name, message)),
index: Dict(Pid, ProcessMonitor),
group: Set(Subject(message)),
named: Dict(name, Set(Subject(message))),
selector: Selector(Message(name, message)),
)
}
/// Starts the registry.
///
/// ## Example
///
/// ```gleam
/// > chip.start()
/// Ok(registry)
/// ```
pub fn start() -> Result(Subject(Message(name, message)), actor.StartError) {
actor.start_spec(actor.Spec(
init: handle_init,
init_timeout: 10,
loop: handle_message,
))
}
/// Returns all registered `Subject`s.
///
/// ### Example
///
/// ```gleam
/// > chip.all(registry)
/// [subject_a, subject_b, subject_c]
/// ```
pub fn all(registry: Subject(Message(name, message))) -> List(Subject(message)) {
process.call(registry, All(_), 100)
}
/// Returns all named `Subject's` indexed by its key.
///
/// ### Example
///
/// ```gleam
/// > chip.named(registry)
/// [#(GroupA, subject_a), #(GroupA, subject_b), #(GroupC, subject_c)]
pub fn named(
registry: Subject(Message(name, message)),
) -> List(#(name, Subject(message))) {
process.call(registry, Named(_), 100)
}
/// Looks up named subgroup of `Subject`s.
///
/// ### Example
///
/// ```gleam
/// > chip.lookup(registry, "MySubjects")
/// [subject_a, subject_c]
/// ```
pub fn lookup(
registry: Subject(Message(name, message)),
name: name,
) -> List(Subject(message)) {
process.call(registry, Lookup(_, name), 100)
}
/// Manually registers a `Subject`.
///
/// ## Example
///
/// ```gleam
/// > chip.register(registry, fn() { start_my_subject() })
/// Ok(registered_subject)
/// ```
pub fn register(
registry: Subject(Message(name, message)),
start: fn() -> Result(Subject(message), actor.StartError),
) -> Result(Subject(message), actor.StartError) {
use subject <- try(start())
process.send(registry, Register(subject))
Ok(subject)
}
/// Manually registers a `Subject` under a named group.
///
/// ## Example
///
/// ```gleam
/// > chip.register(registry, "MySubjects", fn() { start_my_subject() })
/// Ok(registered_subject)
/// ```
pub fn register_as(
registry: Subject(Message(name, message)),
name: name,
start: fn() -> Result(Subject(message), actor.StartError),
) -> Result(Subject(message), actor.StartError) {
use subject <- try(start())
process.send(registry, RegisterAs(subject, name))
Ok(subject)
}
/// Manually deregister a named group of `Subject`s.
///
/// ## Example
///
/// ```gleam
/// > chip.deregister(registry, "MySubjects")
/// Nil
/// ```
pub fn deregister(registry: Subject(Message(name, message)), name: name) -> Nil {
process.send(registry, Deregister(name))
}
/// Stops the registry, all grouped `Subject`s will be gone.
///
/// ## Example
///
/// ```gleam
/// > chip.stop(registry)
/// Normal
/// ```
pub fn stop(registry: Subject(Message(name, message))) -> process.ExitReason {
process.call(registry, Stop(_), 10)
}
fn handle_init() -> actor.InitResult(
State(name, message),
Message(name, message),
) {
let subject = process.new_subject()
let selector =
process.new_selector()
|> process.selecting(subject, identity)
let state =
State(
self: subject,
index: dict.new(),
group: set.new(),
named: dict.new(),
selector: selector,
)
actor.Ready(state, selector)
}
fn handle_message(message: Message(name, message), state: State(name, message)) {
case message {
All(client) -> {
let subjects = set.to_list(state.group)
process.send(client, subjects)
actor.continue(state)
}
Named(client) -> {
let indexed =
dict.fold(state.named, [], fn(acc, key, subjects) {
let indexed =
subjects
|> set.to_list()
|> list.map(fn(subject) { #(key, subject) })
list.append(indexed, acc)
})
process.send(client, indexed)
actor.continue(state)
}
Lookup(client, name) -> {
let subjects =
get_group(state.named, name)
|> set.to_list()
process.send(client, subjects)
actor.continue(state)
}
Register(subject) -> {
let state = insert(state, subject)
actor.continue(state)
|> actor.with_selector(state.selector)
}
RegisterAs(subject, name) -> {
let state = insert_as(state, subject, name)
actor.continue(state)
|> actor.with_selector(state.selector)
}
Deregister(name) -> {
let state = delete_named(state, name)
process.send(state.self, RebuildSelector)
actor.continue(state)
}
Demonitor(subject) -> {
let state = demonitor_subject(state, subject)
process.send(state.self, RebuildSelector)
actor.continue(state)
}
RebuildSelector -> {
let state = rebuild_process_down_selectors(state)
actor.continue(state)
|> actor.with_selector(state.selector)
}
Stop(client) -> {
process.send(client, process.Normal)
actor.Stop(process.Normal)
}
}
}
fn insert(
state: State(name, message),
subject: Subject(message),
) -> State(name, message) {
let pid = process.subject_owner(subject)
case dict.get(state.index, pid) {
Ok(monitor) -> {
let group = set.insert(state.group, subject)
let selector = receive_process_down(state.selector, monitor, subject)
State(..state, group: group, selector: selector)
}
Error(Nil) -> {
let monitor = process.monitor_process(pid)
let index = dict.insert(state.index, pid, monitor)
let group = set.insert(state.group, subject)
let selector = receive_process_down(state.selector, monitor, subject)
State(..state, index: index, group: group, selector: selector)
}
}
}
fn insert_as(
state: State(name, message),
subject: Subject(message),
name: name,
) -> State(name, message) {
let subjects =
state.named
|> get_group(name)
|> set.insert(subject)
let named = dict.insert(state.named, name, subjects)
State(..state, named: named)
|> insert(subject)
}
fn delete_named(state: State(name, message), name: name) -> State(name, message) {
let other_named = dict.delete(state.named, name)
let other_subjects =
dict.fold(other_named, set.new(), fn(all_subjects, _name, subjects) {
set.union(all_subjects, subjects)
})
let subjects = get_group(state.named, name)
let subjects_to_keep =
set.intersection(subjects, other_subjects)
|> set.to_list()
let subjects_to_delete =
set.drop(subjects, subjects_to_keep)
|> set.to_list()
let pids_to_delete =
subjects_to_delete
|> list.map(fn(subject) { process.subject_owner(subject) })
let monitors =
state.index
|> dict.take(pids_to_delete)
|> dict.values()
list.each(monitors, process.demonitor_process)
let index = dict.drop(state.index, pids_to_delete)
let group = set.drop(state.group, subjects_to_delete)
let named = dict.delete(state.named, name)
State(..state, index: index, group: group, named: named)
}
fn demonitor_subject(
state: State(name, message),
subject: Subject(message),
) -> State(name, message) {
let pid = process.subject_owner(subject)
case dict.get(state.index, pid) {
Ok(monitor) -> {
process.demonitor_process(monitor)
let index = dict.delete(state.index, pid)
let group = set.delete(state.group, subject)
let delete = fn(_name, subjects) { set.delete(subjects, subject) }
let named = dict.map_values(state.named, delete)
State(..state, index: index, group: group, named: named)
}
Error(Nil) -> state
}
}
fn get_group(
named: Dict(name, Set(Subject(message))),
name: name,
) -> Set(Subject(message)) {
case dict.get(named, name) {
Ok(subjects) -> subjects
Error(Nil) -> set.new()
}
}
fn rebuild_process_down_selectors(
state: State(name, message),
) -> State(name, message) {
let self = process.new_subject()
let subjects = set.to_list(state.group)
let selector =
process.new_selector()
|> process.selecting(self, identity)
|> list.fold(
subjects,
_,
fn(selector, subject) {
let pid = process.subject_owner(subject)
case dict.get(state.index, pid) {
Ok(monitor) -> receive_process_down(selector, monitor, subject)
Error(Nil) -> selector
}
},
)
State(..state, self: self, selector: selector)
}
fn receive_process_down(
selector: Selector(Message(name, message)),
monitor: ProcessMonitor,
subject: Subject(message),
) -> Selector(Message(name, message)) {
let handle = fn(_process: ProcessDown) { Demonitor(subject) }
process.selecting_process_down(selector, monitor, handle)
}