-- =============================================================================
-- knoe.ekosystem_objects — Modular object kind registry, naming, and
--                          cross-ekosystem sharing / grant model
--
-- Depends on: ekosystem.sql (knoe.tenants, knoe.ekosystem_decode)
--
-- Object naming convention:
--   {prefix}_{uuid}             — standalone objects (project, user, embedding)
--   {prefix}_{uuid}_{name}      — compound objects (table, index, view)
--
-- All prefixes are {letter}_ so ekosystem_tenant() works uniformly:
--   substring(object_name FROM 3 FOR 16) always extracts the UUID.
--
-- Cross-ekosystem sharing:
--   UUIDs embed the originating tenant_id in bits — ownership is always
--   decodable without a registry join, so imported objects cannot collide
--   even when mixed across ekosystems. knoe.cross_grants records the
--   explicit sharing approvals that LDAP/Samba AD will eventually enforce.
-- =============================================================================

-- ---------------------------------------------------------------------------
-- knoe.object_kinds — Modular kind registry
-- Add new kinds here; ekosystem_object() picks them up automatically.
-- ---------------------------------------------------------------------------
CREATE TABLE IF NOT EXISTS knoe.object_kinds (
    kind        text    PRIMARY KEY,
    prefix      char(1) NOT NULL UNIQUE CHECK (prefix ~ '^[a-z]$'),
    description text    NOT NULL
);

INSERT INTO knoe.object_kinds (kind, prefix, description) VALUES
    ('project',   'p', 'Project namespace — schema or resource root'),
    ('user',      'u', 'Service account / PostgreSQL role'),
    ('embedding', 'e', 'Vector embedding store'),
    ('table',     't', 'Data table'),
    ('index',     'x', 'Index or search structure'),
    ('view',      'v', 'Logical view or materialised view'),
    ('sequence',  's', 'Auto-increment sequence'),
    ('function',  'f', 'Stored function or procedure')
ON CONFLICT DO NOTHING;

GRANT SELECT ON TABLE knoe.object_kinds TO knoe;

-- ---------------------------------------------------------------------------
-- knoe.ekosystem_object(uuid, kind) → '{prefix}_{uuid}'
--
-- Returns the canonical identifier for any typed object.
-- Unknown kind raises — register it in knoe.object_kinds first.
--
-- Compound names (tables, indexes):
--   knoe.ekosystem_object(uuid, 'table') || '_accounts'
--   → 't_3k9mxqt2f8vn0r7b_accounts'
--
-- The 2-char prefix is the same width for every kind, so
-- ekosystem_tenant() always finds the UUID at position 3.
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.ekosystem_object(p_uuid text, p_kind text)
RETURNS text
LANGUAGE plpgsql STABLE
AS $$
DECLARE
    v_prefix char(1);
BEGIN
    SELECT prefix INTO v_prefix FROM knoe.object_kinds WHERE kind = p_kind;
    IF NOT FOUND THEN
        RAISE EXCEPTION
            'Unknown object kind: %. Register it in knoe.object_kinds first.', p_kind;
    END IF;
    RETURN v_prefix || '_' || p_uuid;
END;
$$;

-- ---------------------------------------------------------------------------
-- knoe.ekosystem_kind(object_name) → kind
--
-- Reverse lookup: given any prefixed object name, return its kind.
-- Returns NULL if the prefix is unregistered (not an error — enables routing
-- filters that skip non-ekosystem objects).
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.ekosystem_kind(p_object_name text)
RETURNS text
LANGUAGE sql STABLE
AS $$
    SELECT kind
    FROM   knoe.object_kinds
    WHERE  prefix = substring(p_object_name FROM 1 FOR 1);
$$;

-- ---------------------------------------------------------------------------
-- knoe.cross_grants — Cross-ekosystem sharing policy
--
-- Records that grantor_tenant has shared an object with grantee_tenant.
-- This table is the policy source of truth; actual PG GRANT statements
-- and future LDAP/Samba AD group memberships are derived from it.
--
-- Ownership is always decodable from the UUID itself via ekosystem_decode(),
-- so this table only needs to record the *exceptions* (sharing across
-- tenant boundaries). Within a single ekosystem, use standard PG GRANT.
--
-- privileges: PostgreSQL privilege names, e.g. '{SELECT}', '{SELECT,INSERT}'
-- expires_at: NULL = permanent until explicitly revoked
-- ---------------------------------------------------------------------------
CREATE TABLE IF NOT EXISTS knoe.cross_grants (
    id              text        PRIMARY KEY
                                DEFAULT knoe.ekosystem_id(0, 0),
    object_uuid     text        NOT NULL,
    object_kind     text        NOT NULL REFERENCES knoe.object_kinds(kind),
    grantor_tenant  smallint    NOT NULL REFERENCES knoe.tenants(tenant_id),
    grantee_tenant  smallint    NOT NULL REFERENCES knoe.tenants(tenant_id),
    privileges      text[]      NOT NULL CHECK (array_length(privileges, 1) > 0),
    granted_at      timestamptz NOT NULL DEFAULT now(),
    expires_at      timestamptz,
    CONSTRAINT cross_grants_no_self
        CHECK (grantor_tenant != grantee_tenant),
    CONSTRAINT cross_grants_unique
        UNIQUE (object_uuid, object_kind, grantee_tenant)
);

CREATE INDEX IF NOT EXISTS cross_grants_grantee_idx
    ON knoe.cross_grants (grantee_tenant, object_kind);

CREATE INDEX IF NOT EXISTS cross_grants_object_idx
    ON knoe.cross_grants (object_uuid);

GRANT SELECT, INSERT, DELETE ON TABLE knoe.cross_grants TO knoe;

-- ---------------------------------------------------------------------------
-- knoe.grant_object(object_uuid, kind, grantee_tenant, privileges, expires_at)
--
-- Record that the owning tenant shares an object with another ekosystem.
-- Validates that the caller's tenant actually owns the object (via UUID bits).
-- On conflict: refreshes privileges and expiry (upsert semantics).
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.grant_object(
    p_object_uuid    text,
    p_kind           text,
    p_grantee_tenant smallint,
    p_privileges     text[]             DEFAULT '{SELECT}',
    p_expires_at     timestamptz        DEFAULT NULL
) RETURNS knoe.cross_grants
LANGUAGE plpgsql
AS $$
DECLARE
    v_grantor  smallint;
    v_row      knoe.cross_grants;
BEGIN
    -- Derive owner from UUID bits — no registry join needed
    SELECT tenant_id INTO v_grantor FROM knoe.ekosystem_decode(p_object_uuid);

    IF NOT EXISTS (SELECT 1 FROM knoe.tenants WHERE tenant_id = p_grantee_tenant) THEN
        RAISE EXCEPTION 'Grantee tenant % is not a registered ekosystem', p_grantee_tenant;
    END IF;

    IF v_grantor = p_grantee_tenant THEN
        RAISE EXCEPTION
            'Grant target is the object owner (tenant %). Use standard PG GRANT within an ekosystem.',
            v_grantor;
    END IF;

    INSERT INTO knoe.cross_grants
        (object_uuid, object_kind, grantor_tenant, grantee_tenant, privileges, expires_at)
    VALUES
        (p_object_uuid, p_kind, v_grantor, p_grantee_tenant, p_privileges, p_expires_at)
    ON CONFLICT (object_uuid, object_kind, grantee_tenant) DO UPDATE
        SET privileges = EXCLUDED.privileges,
            expires_at = EXCLUDED.expires_at,
            granted_at = now()
    RETURNING * INTO v_row;

    RETURN v_row;
END;
$$;

-- ---------------------------------------------------------------------------
-- knoe.revoke_object(object_uuid, kind, grantee_tenant)
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.revoke_object(
    p_object_uuid    text,
    p_kind           text,
    p_grantee_tenant smallint
) RETURNS boolean
LANGUAGE plpgsql
AS $$
BEGIN
    DELETE FROM knoe.cross_grants
    WHERE  object_uuid    = p_object_uuid
      AND  object_kind    = p_kind
      AND  grantee_tenant = p_grantee_tenant;
    RETURN FOUND;
END;
$$;

-- ---------------------------------------------------------------------------
-- knoe.can_access(object_uuid, kind, tenant_id) → boolean
--
-- True when:
--   (a) the tenant owns the object (tenant_id embedded in UUID), OR
--   (b) a non-expired cross-grant exists, OR
--   (c) tenant 0 (knoe-db root) — root has universal read access
--
-- STABLE: safe in WHERE clauses and on replicas.
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.can_access(
    p_object_uuid text,
    p_kind        text,
    p_tenant_id   smallint
) RETURNS boolean
LANGUAGE sql STABLE
AS $$
    SELECT
        p_tenant_id = 0                          -- root authority
        OR
        (SELECT tenant_id
         FROM   knoe.ekosystem_decode(p_object_uuid)) = p_tenant_id   -- owner
        OR
        EXISTS (
            SELECT 1 FROM knoe.cross_grants
            WHERE  object_uuid    = p_object_uuid
              AND  object_kind    = p_kind
              AND  grantee_tenant = p_tenant_id
              AND  (expires_at IS NULL OR expires_at > now())
        );
$$;

-- ---------------------------------------------------------------------------
-- knoe.my_grants(tenant_id) → active cross-grants visible to this ekosystem
-- Includes both grants received and grants issued by this tenant.
-- ---------------------------------------------------------------------------
CREATE OR REPLACE FUNCTION knoe.my_grants(p_tenant_id smallint)
RETURNS TABLE(
    direction     text,       -- 'received' | 'issued'
    object_uuid   text,
    object_kind   text,
    object_name   text,       -- prefixed identifier
    other_tenant  smallint,
    privileges    text[],
    granted_at    timestamptz,
    expires_at    timestamptz
)
LANGUAGE sql STABLE
AS $$
    SELECT 'received'::text,
           g.object_uuid,
           g.object_kind,
           knoe.ekosystem_object(g.object_uuid, g.object_kind),
           g.grantor_tenant,
           g.privileges,
           g.granted_at,
           g.expires_at
    FROM   knoe.cross_grants g
    WHERE  g.grantee_tenant = p_tenant_id
      AND  (g.expires_at IS NULL OR g.expires_at > now())

    UNION ALL

    SELECT 'issued'::text,
           g.object_uuid,
           g.object_kind,
           knoe.ekosystem_object(g.object_uuid, g.object_kind),
           g.grantee_tenant,
           g.privileges,
           g.granted_at,
           g.expires_at
    FROM   knoe.cross_grants g
    WHERE  g.grantor_tenant = p_tenant_id
      AND  (g.expires_at IS NULL OR g.expires_at > now());
$$;

-- ---------------------------------------------------------------------------
-- Grants (mirrors existing knoe schema pattern)
-- ---------------------------------------------------------------------------
GRANT EXECUTE ON FUNCTION knoe.ekosystem_object(text, text)              TO knoe;
GRANT EXECUTE ON FUNCTION knoe.ekosystem_kind(text)                      TO knoe;
GRANT EXECUTE ON FUNCTION knoe.grant_object(text, text, smallint, text[], timestamptz)
                                                                         TO knoe;
GRANT EXECUTE ON FUNCTION knoe.revoke_object(text, text, smallint)       TO knoe;
GRANT EXECUTE ON FUNCTION knoe.can_access(text, text, smallint)          TO knoe;
GRANT EXECUTE ON FUNCTION knoe.my_grants(smallint)                       TO knoe;