-- What modules exist, and which nodes run them.
--
-- novox/hq ADR 0006 gives inventory nodes, modules, assignments and versions. Nodes were built
-- first because everything needs to name one; these are the rest, and they are what lets the
-- control plane decide what a node runs rather than relay what a person wrote.

create table module (
    name       text        primary key,

    -- The manifest exactly as given: what it provides, requires, claims, needs of the machine,
    -- and the resources it puts on a node.
    --
    -- Held whole rather than shredded into columns. Every field of it is read together when a
    -- node is resolved, nothing here queries one part of it, and a manifest that gains a field
    -- should not need a migration before it can be stored -- the module system is the thing most
    -- likely to grow (ADR 0009).
    manifest   jsonb       not null,

    version    text,
    registered timestamptz not null default now()
);

create table assignment (
    node     uuid        not null references node(id) on delete cascade,
    module   text        not null references module(name) on delete restrict,
    assigned timestamptz not null default now(),

    primary key (node, module)
);

-- Removing a node takes its assignments; removing a module does NOT, and that asymmetry is
-- deliberate. A node that is gone cannot be running anything. A module that is still assigned
-- somewhere is being run by a machine right now, and deleting the record would leave that machine
-- holding something the mesh can no longer describe -- so it is refused until it is unassigned.

create index assignment_module on assignment (module);