\set ON_ERROR_STOP on
BEGIN ISOLATION LEVEL REPEATABLE READ READ ONLY;
SET LOCAL TIME ZONE 'UTC';

-- 只读导出本地内容，防止误把另一环境的数据当作本次内容来源。
DO $$
BEGIN
    IF current_database() <> 'doodle_dev' THEN
        RAISE EXCEPTION '导出只允许读取 doodle_dev';
    END IF;
    IF EXISTS (
        SELECT 1 FROM public._prisma_migrations
        WHERE finished_at IS NULL AND rolled_back_at IS NULL
    ) THEN
        RAISE EXCEPTION '源库存在未完成迁移，请先核查';
    END IF;
END $$;

WITH asset_ids AS (
    SELECT preview_asset_id AS id FROM public.worksheets
    UNION
    SELECT icon_asset_id FROM public.categories WHERE icon_asset_id IS NOT NULL
)
SELECT jsonb_build_object(
    'format', 'doodle-content-v1',
    'source_database', current_database(),
    'exported_at', transaction_timestamp(),
    'migration_history', (
        SELECT COALESCE(jsonb_agg(jsonb_build_object(
            'name', migration_name, 'checksum', checksum
        ) ORDER BY migration_name), '[]'::jsonb)
        FROM public._prisma_migrations
        WHERE finished_at IS NOT NULL AND rolled_back_at IS NULL
    ),
    -- 按字段名比较签名，兼容经旧 SQL 初始化、字段物理顺序不同的本地库。
    'column_signature', (
        SELECT jsonb_agg(jsonb_build_object(
            'table', c.relname, 'column', a.attname,
            'type', format_type(a.atttypid, a.atttypmod), 'not_null', a.attnotnull
        ) ORDER BY c.relname, a.attname)
        FROM pg_attribute a
        JOIN pg_class c ON c.oid = a.attrelid
        JOIN pg_namespace n ON n.oid = c.relnamespace
        WHERE n.nspname = 'public' AND c.relname IN ('assets', 'categories', 'worksheets')
            AND a.attnum > 0 AND NOT a.attisdropped
    ),
    'excluded_relations', jsonb_build_object(
        'worksheet_grades', (SELECT count(*) FROM public.worksheet_grades),
        'worksheet_resources', (SELECT count(*) FROM public.worksheet_resources),
        'worksheet_resource_assets', (SELECT count(*) FROM public.worksheet_resource_assets)
    ),
    'assets', (
        SELECT COALESCE(jsonb_agg(to_jsonb(a) ORDER BY a.id), '[]'::jsonb)
        FROM public.assets a JOIN asset_ids r ON r.id = a.id
    ),
    'categories', (
        SELECT COALESCE(jsonb_agg(to_jsonb(c) ORDER BY c.id), '[]'::jsonb)
        FROM public.categories c
    ),
    'worksheets', (
        SELECT COALESCE(jsonb_agg(to_jsonb(w) ORDER BY w.id), '[]'::jsonb)
        FROM public.worksheets w
    )
);
COMMIT;