-- A config value comes from four sources, the last set winning (novox/hq issue 630): the module's
-- default, mesh config, node config, and the module's own value on the node. Mesh config and node config
-- hold values only for the predefined keys, a fixed list kept in the catalogue (`predefined.json`). An
-- assignment is one module on one node: there is no module layer for the whole mesh any more.

-- The list of predefined keys, as the catalogue's predefined.json last said it. Replaced whole when a
-- build of the catalogue carries the file; `repository` and `commit` say which.
create table predefined_key (
    key        text        primary key,
    type       text        not null check (type in ('number', 'string', 'boolean')),
    why        text        not null,
    repository text,
    commit     text,
    listed_at  timestamptz not null default now()
);

-- Mesh config (node null) and node config: one value per predefined key, and per node. Not a foreign key
-- to predefined_key: a key the list drops keeps its value, said as reaching nothing, rather than losing it.
create table config (
    key    text        not null,
    node   uuid        references node(id) on delete cascade,
    value  jsonb       not null,
    set_at timestamptz not null default now(),
    set_by text,
    why    text        not null
);
create unique index config_for_the_mesh on config (key) where node is null;
create unique index config_for_a_node   on config (key, node) where node is not null;

-- Every value that was replaced or cleared, with who set it and why, and who replaced it and why.
create table config_history (
    key          text        not null,
    node         uuid        references node(id) on delete cascade,
    value        jsonb       not null,
    set_at       timestamptz,
    set_by       text,
    why          text,
    replaced_at  timestamptz not null default now(),
    -- set · clear
    replaced_by  text        not null,
    replaced_why text
);
create index config_history_by_key on config_history (key, node, replaced_at desc);

-- The module layer for the whole mesh goes: each one is laid under the layer of every node the module is
-- assigned to — the mesh's values first, the node's over them, maps merged key by key as composition
-- merged them — so every machine composes what it did. Every layer replaced, and the mesh-wide layer
-- itself, is kept in settings_history (ADR 0217) with the reason `moved-to-nodes`. A mesh-wide layer of
-- a module assigned nowhere is kept in the history only: no machine read it.
create function pg_temp.config_630_merge(under jsonb, over jsonb) returns jsonb language plpgsql immutable as $$
declare
    merged jsonb;
    k      text;
begin
    if jsonb_typeof(under) is distinct from 'object' or jsonb_typeof(over) is distinct from 'object' then
        return over;
    end if;
    merged := under;
    for k in select jsonb_object_keys(over) loop
        if merged ? k then
            merged := jsonb_set(merged, array[k], pg_temp.config_630_merge(merged -> k, over -> k));
        else
            merged := merged || jsonb_build_object(k, over -> k);
        end if;
    end loop;
    return merged;
end
$$;

insert into settings_history (node, module, values, set_at, replaced_by, set_by)
select t.node, t.module, t.values, t.set_at, 'moved-to-nodes', t.set_by
  from settings t
  join settings s on s.module = t.module and s.node is null
 where t.node is not null
   and exists (select 1 from assignment a where a.node = t.node and a.module = t.module);

insert into settings_history (node, module, values, set_at, replaced_by, set_by)
select null, module, values, set_at, 'moved-to-nodes', set_by from settings where node is null;

insert into settings (node, module, values, set_at, set_by)
select a.node, s.module, s.values, now(),
       coalesce(s.set_by || '; ', '') || 'moved from the whole mesh''s layer to this node''s (novox/hq issue 630)'
  from settings s
  join assignment a on a.module = s.module
 where s.node is null
on conflict (node, module) where node is not null
do update set values = pg_temp.config_630_merge(excluded.values, settings.values),
              set_at = now(),
              set_by = coalesce(settings.set_by || '; ', '') ||
                       'the whole mesh''s layer laid under it (novox/hq issue 630)';

delete from settings where node is null;