CREATE SCHEMA "blocks";
CREATE TABLE "blocks"."block"
(
    uuid                UUID PRIMARY KEY   NOT NULL,
    settings_type       CHARACTER VARYING  NOT NULL,
    settings            JSONB              NOT NULL,
    title               CHARACTER VARYING,
    view_type           CHARACTER VARYING,
    enabled             BOOL DEFAULT TRUE  NOT NULL,
    visibility_settings JSONB
);

CREATE UNIQUE INDEX "block_uuid_uindex"
    ON "blocks"."block" (uuid);

CREATE INDEX "enabled_index"
    ON "blocks"."block" (enabled);

CREATE TABLE "blocks"."placement"
(
    location_name   CHARACTER VARYING   NOT NULL,
    index           INT                 NOT NULL,
    block_uuid      UUID                NOT NULL,
    scope_path      CHARACTER VARYING   NOT NULL,
    inherited       BOOL DEFAULT FALSE  NOT NULL,
    excluded_scopes CHARACTER VARYING [],

    -- NOTE: Because we UPDATE the primary (location_name, index) key on the placement-table,
    -- the constraint behavior on the primary key is set to DEFERRABLE and INITIALLY IMMEDIATE.
    --
    -- For more inforation, refer to this bug-report:
    --
    -- https://www.postgresql.org/message-id/flat/20170322123053.1421.55154%40wrigleys.postgresql.org

    CONSTRAINT placement_location_name_index_pk PRIMARY KEY (location_name, index) DEFERRABLE INITIALLY IMMEDIATE,
    CONSTRAINT placement_block_uuid_fk FOREIGN KEY (block_uuid) REFERENCES "blocks"."block" (uuid) ON DELETE CASCADE
);

CREATE INDEX "placement_location_name_index_index"
    ON "blocks".placement (location_name, index);

CREATE INDEX "placement_scope_path_index"
    ON "blocks".placement (scope_path);

CREATE INDEX "placement_index_index"
    ON "blocks".placement (index);

CREATE TABLE "blocks"."location_hash"
(
    location_name CHARACTER VARYING PRIMARY KEY  NOT NULL,
    hash          CHARACTER VARYING              NOT NULL
);

CREATE TABLE "blocks"."child_blocks"
(
    parent_uuid  UUID    NOT NULL,
    column_index INT     NOT NULL,
    child_uuids  UUID [] NOT NULL,
    CONSTRAINT child_blocks_parent_uuid_index_pk PRIMARY KEY (parent_uuid, column_index),
    CONSTRAINT child_blocks_block_uuid_fk FOREIGN KEY (parent_uuid) REFERENCES "blocks"."block" (uuid) ON DELETE CASCADE

    -- TODO add a trigger to sanitize child_uuids when a block record is deleted
);

CREATE INDEX "child_blocks_parent_uuid_index"
    ON "blocks"."child_blocks" (parent_uuid);

CREATE TABLE "blocks"."user_bucket"
(
    user_uuid   UUID PRIMARY KEY NOT NULL,
    block_uuids UUID []          NOT NULL
);

CREATE UNIQUE INDEX "user_bucket_user_uuid_uindex"
    ON "blocks"."user_bucket" (user_uuid);

CREATE VIEW "blocks"."block_count" AS
    SELECT
        b."uuid"                               AS "block_uuid",
        (
            (SELECT COUNT(*)
                FROM "blocks"."placement" p
                WHERE p."block_uuid" = b."uuid")
            +
            (SELECT COALESCE(SUM((SELECT COUNT(*)
                                    FROM unnest(c."child_uuids") cb
                                    WHERE cb = b."uuid")), 0)
                FROM "blocks"."child_blocks" c)
        )                                      AS "ref_count",
        (SELECT COUNT(*)
            FROM "blocks"."user_bucket" k
            WHERE "uuid" = ANY (k."block_uuids")) AS "user_count"
    FROM "blocks"."block" b;

CREATE OR REPLACE FUNCTION "blocks".delete_orphaned_blocks()
    RETURNS TRIGGER
AS $$
BEGIN
    LOOP
        -- Note that RETURN QUERY does not return from the function - it works
        -- more like the yield-statement in PHP, in that records from the
        -- DELETE..RETURNING statement are returned, and execution then
        -- resumes from the following statement.

        DELETE FROM "blocks"."block" b
        WHERE b.uuid IN (
            SELECT c.block_uuid
            FROM "blocks"."block_count" c
            WHERE c.ref_count = 0 AND c.user_count = 0
        );

        -- The FOUND flag is set TRUE/FALSE after executing a query - so we
        -- EXIT from the LOOP block when the DELETE..RETURNING statement does
        -- not delete and return any records.

        EXIT WHEN NOT FOUND;
    END LOOP;

    RETURN NULL;
END;
$$
LANGUAGE plpgsql;

CREATE TRIGGER delete_orphans
AFTER UPDATE OR DELETE
    ON "blocks"."user_bucket"
FOR EACH STATEMENT
EXECUTE PROCEDURE "blocks".delete_orphaned_blocks();

CREATE TRIGGER delete_orphans
AFTER UPDATE OR DELETE
    ON "blocks"."placement"
FOR EACH STATEMENT
EXECUTE PROCEDURE "blocks".delete_orphaned_blocks();

CREATE TRIGGER delete_orphans
AFTER UPDATE OR DELETE
    ON "blocks"."child_blocks"
FOR EACH STATEMENT
EXECUTE PROCEDURE "blocks".delete_orphaned_blocks();