-- Which port a machine uses for what a module needs reachable.
--
-- novox/hq ADR 0038. A module cannot choose this: it is written once and assigned anywhere, so any
-- number it picks is a guess about a machine it has never seen. Two modules guessing the same one
-- is not a mistake either of them made -- it is a database module meeting the mesh's own store and
-- being told, by a container runtime three layers down, that the port is already allocated.
--
-- **Made once and kept**, exactly as a credential is. A port that moved on every declaration would
-- restart both ends each time, and would hand a consumer a number that was true when it was read.

create table port_assignment (
    node    uuid not null references node(id) on delete cascade,
    module  text not null references module(name) on delete cascade,

    -- The port the software itself uses -- what a module writes down, and the only part it knows.
    wanted  integer not null,
    -- What the machine publishes it on. The same as `wanted` when the protocol fixes it.
    machine integer not null,

    -- Whether the protocol fixed it. Kept rather than derived: *this is 25 because it must be*
    -- and *this is 25 because it was free* are different facts, and only the first refuses a
    -- second holder.
    fixed   boolean not null default false,

    assigned_at timestamptz not null default now(),

    primary key (node, module, wanted),

    -- **One machine port, one holder.** The constraint is the point: a second module cannot be
    -- given a port the first has, and finding that out here is finding it out at assignment
    -- rather than at apply.
    unique (node, machine)
);