ALTER TABLE topics ADD COLUMN icon_name TEXT NOT NULL DEFAULT '';

ALTER TABLE pieces ADD COLUMN deleted_at_utc TEXT;

ALTER TABLE piece_media ADD COLUMN removed_at_utc TEXT;

CREATE TABLE piece_presentation_media (
	piece_id TEXT PRIMARY KEY REFERENCES pieces(id) ON DELETE CASCADE,
	media_id TEXT NOT NULL UNIQUE REFERENCES piece_media(id) ON DELETE RESTRICT
);

CREATE TRIGGER validate_piece_presentation_media_insert
BEFORE INSERT ON piece_presentation_media
WHEN NOT EXISTS (
	SELECT 1 FROM piece_media
	WHERE id = NEW.media_id AND piece_id = NEW.piece_id AND removed_at_utc IS NULL
)
BEGIN
	SELECT RAISE(ABORT, 'presentation media does not belong to piece');
END;

CREATE TRIGGER validate_piece_presentation_media_update
BEFORE UPDATE ON piece_presentation_media
WHEN NOT EXISTS (
	SELECT 1 FROM piece_media
	WHERE id = NEW.media_id AND piece_id = NEW.piece_id AND removed_at_utc IS NULL
)
BEGIN
	SELECT RAISE(ABORT, 'presentation media does not belong to piece');
END;

ALTER TABLE usage_topic_snapshots ADD COLUMN icon_name TEXT NOT NULL DEFAULT '';

CREATE TABLE usage_media_snapshots (
	id TEXT PRIMARY KEY,
	usage_id TEXT NOT NULL REFERENCES piece_usages(id) ON DELETE CASCADE,
	original_media_id TEXT NOT NULL REFERENCES piece_media(id) ON DELETE RESTRICT,
	alt_text TEXT NOT NULL DEFAULT '',
	position INTEGER NOT NULL CHECK (position >= 0),
	is_presentation INTEGER NOT NULL DEFAULT 0 CHECK (is_presentation IN (0, 1)),
	UNIQUE (usage_id, position)
);

CREATE INDEX idx_pieces_deleted_at ON pieces(deleted_at_utc);
CREATE INDEX idx_piece_media_active ON piece_media(piece_id, position)
	WHERE removed_at_utc IS NULL;
CREATE INDEX idx_usage_media_usage ON usage_media_snapshots(usage_id, position);
CREATE UNIQUE INDEX idx_one_presentation_media_per_usage
	ON usage_media_snapshots(usage_id) WHERE is_presentation = 1;