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fixpoint lib solver store store.ex
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lib/solver/store/store.ex

defmodule CPSolver.ConstraintStore do
@moduledoc """
Constraint store is a key-value store, where `key` is a variable id,
and `value` is a implementation-dependent structure that allows to
update and keep track of variables' domains.
"""
#################
alias CPSolver.{Common, Variable}
alias CPSolver.Propagator.ConstraintGraph
require Logger
@type get_operation :: Common.domain_get_operation() | nil
@type update_operation :: Common.domain_update_operation()
@mandatory_notifications [:fixed, :fail]
def default_store() do
CPSolver.Store.ETS
end
### Callbacks
## Tell basic constraints (a.k.a, domains) to a constraint store
@callback create(variables :: Enum.t(), opts :: Keyword.t()) ::
{:ok, any()} | {:error, any()}
## Get variable details
@callback get(store :: any(), variable :: Variable.t(), get_operation(), [any()]) ::
{:ok, any()} | {:error, any()}
@callback update(store :: any(), variable :: Variable.t(), update_operation(), [any()]) ::
any()
@callback update_domain(store :: any(), variable :: Variable.t(), update_operation(), [any()]) ::
any()
@callback dispose(store :: any(), variables :: [Variable.t()]) :: :ok | :not_found
@callback domain(store :: any(), variable :: Variable.t()) :: {:ok, any()} | {:error, any()}
@callback on_fail(store :: any(), variable :: Variable.t()) :: any()
@callback on_no_change(store :: any(), variable :: Variable.t()) :: any()
@callback on_change(
store :: any(),
variable :: Variable.t(),
change :: Common.domain_change()
) :: any()
@callback get_variables(store :: any()) :: [any()]
@callback subscribe(
store :: any(),
subscriptions :: [%{pid: pid(), variable: any(), events: [any()]}]
) :: :ok | :not_found
### API
defmacro __using__(_) do
quote do
@behaviour CPSolver.ConstraintStore
@domain_events CPSolver.Common.domain_events()
require Logger
def update(store, variable, operation, args) do
update_domain(store, variable, operation, args)
|> tap(fn
:fail ->
on_fail(store, variable)
:no_change ->
on_no_change(store, variable)
change when change in @domain_events ->
on_change(store, variable, change)
end)
end
defoverridable update: 4
end
end
def default_store_opts() do
[space: self(), store_impl: default_store()]
end
def create_store(variables, opts \\ [])
def create_store(variables, opts) do
opts = Keyword.merge(default_store_opts(), opts)
space = Keyword.get(opts, :space)
store_impl = Keyword.get(opts, :store_impl)
constraint_graph = Keyword.get(opts, :constraint_graph)
{:ok, store_handle} = store_impl.create(variables, opts)
store = %{
space: space,
handle: store_handle,
store_impl: store_impl,
constraint_graph: constraint_graph
}
{:ok,
Enum.map(variables, fn var ->
var
|> Map.put(:id, var.id)
|> Map.put(:name, var.name)
|> Map.put(:store, store)
end), store}
end
def domain(%{handle: handle, store_impl: store_impl} = _store, variable) do
store_impl.domain(handle, variable)
end
def get(%{handle: handle, store_impl: store_impl} = _store, variable, operation, args \\ []) do
store_impl.get(handle, variable, operation, args)
end
def subscribe(%{handle: handle, store_impl: store_impl} = _store, variables) do
store_impl.subscribe(handle, variables)
end
def update(
%{handle: handle, store_impl: store_impl} = _store,
variable,
operation,
args \\ []
) do
store_impl.update(handle, variable, operation, args)
end
def get_variables(%{handle: handle, store_impl: store_impl} = _store) do
store_impl.get_variables(handle)
end
def dispose(%{handle: handle, store_impl: store_impl} = _store, variables) do
store_impl.dispose(handle, variables)
end
def normalize_subscription(%{variable: variable, events: events} = subscription) do
%{subscription | variable: variable_id(variable), events: normalize_events(events)}
end
def notify(_variable, _event, opts \\ [])
def notify(_variable, :no_change, _opts) do
:ignore
end
@doc """
Notify on variable event.
If space = nil (the store is detached from space), then notifications are passed directly to propagators.
Otherwise they go to the space process.
"""
def notify(%{id: var_id, subscriptions: subscriptions, store: store} = variable, event, opts) do
(store.constraint_graph &&
(
## Don't notify the propagator that fired this event.
source_propagator = Keyword.get(opts, :source)
propagator_refs =
ConstraintGraph.get_propagators(store.constraint_graph, var_id, event)
|> List.delete(source_propagator)
notify_space(variable, event, propagator_refs)
)) ||
(
propagator_pids =
Enum.flat_map(subscriptions, fn s -> (notify_subscriber?(s, event) && [s.pid]) || [] end)
Enum.each(propagator_pids, fn pid -> notify_process(pid, var_id, event) end)
)
end
defp notify_subscriber?(%{events: events} = _subscription, event) do
event in (@mandatory_notifications ++ events)
end
defp notify_space(%{id: var_id, store: store} = _variable, :fail, _propagator_pids) do
notify_process(store.space, var_id, :fail)
end
defp notify_space(
%{id: var_id, store: store} = _variable,
domain_change,
propagator_pids
)
when is_list(propagator_pids) do
length(propagator_pids) > 0 &&
notify_process(store.space, var_id, {domain_change, propagator_pids})
end
defp notify_process(pid, var_id, event) do
send(pid, {event, var_id})
end
def variable_id(%Variable{id: id}) do
id
end
def variable_id(id) do
id
end
defp normalize_events(events) do
## :fixed and :fail are mandatory
[:fixed, :fail | events]
|> Enum.uniq()
end
end