-- Folder rollup ETag: introduce `storage.folders.tree_modified_at`,
-- which is bumped whenever any descendant (file or folder) changes.
--
-- Motivation: WebDAV / NextCloud sync clients use a collection's ETag
-- to decide "did anything change inside this folder since I last
-- looked?". Until now `Folder::etag()` returned the folder UUID
-- (constant for the row's life), which made the answer always "no" —
-- forcing clients to do periodic deep PROPFIND walks to discover new
-- files. With this column, `Folder::etag()` becomes
-- `{id_short}-{tree_modified_at}` and clients can do O(changed)
-- recursion instead of O(tree).
--
-- The two triggers cascade an update timestamp up the ltree ancestor
-- chain on every file write and every folder mutation. Performance
-- ceiling: O(depth) row updates per mutation; deep concurrent writes
-- to the same root subtree can contend on the root row.
--
-- Idempotency note: this migration was originally numbered
-- `20260625000000` and collided with `files_user_size_index` from a
-- parallel branch. Both files were renamed to disjoint versions, and
-- this body uses `IF NOT EXISTS` / `CREATE OR REPLACE` /
-- `DROP TRIGGER IF EXISTS` throughout so the migration is safe to
-- re-run against databases that already applied it under the old
-- version number. An orphan row for `20260625000000` may remain in
-- `_sqlx_migrations` on such databases — sqlx ignores rows whose
-- version no longer maps to a source file.

-- Gate the entire column-add + backfill block on column absence.
-- A naive `ADD COLUMN IF NOT EXISTS` paired with an unconditional
-- backfill `UPDATE` would clobber trigger-bumped values back to
-- `updated_at` on databases that already deployed this migration
-- under the old `20260625000000` version — every folder NC clients
-- have synced since first deploy would suddenly look "modified",
-- triggering a one-time re-walk. The DO block keeps the migration
-- a true no-op for those databases: column exists → skip both
-- statements → preserve the live trigger-maintained values.
DO $$
BEGIN
    IF NOT EXISTS (
        SELECT 1 FROM information_schema.columns
         WHERE table_schema = 'storage'
           AND table_name = 'folders'
           AND column_name = 'tree_modified_at'
    ) THEN
        ALTER TABLE storage.folders
            ADD COLUMN tree_modified_at TIMESTAMPTZ NOT NULL DEFAULT NOW();
        -- Backfill on first-deploy: collapse to per-folder updated_at.
        -- Clients re-walking after deploy will see one batch of
        -- "looks new to me" responses, handled as
        -- content-match-no-download — the expected one-time resync.
        UPDATE storage.folders SET tree_modified_at = updated_at;
    END IF;
END $$;


-- File-side trigger: any INSERT/UPDATE/DELETE on storage.files
-- bumps the file's parent folder + all its ancestors in the ltree.
-- Root-level files (folder_id IS NULL) have no ancestors and do not
-- trigger any folder bump — the root listing isn't an etag-emitting
-- collection in OxiCloud's model (no virtual root folder row).
CREATE OR REPLACE FUNCTION storage.bump_folder_tree_from_file()
RETURNS TRIGGER LANGUAGE plpgsql AS $$
DECLARE
    target_folder_id UUID;
    target_lpath ltree;
BEGIN
    target_folder_id := COALESCE(NEW.folder_id, OLD.folder_id);
    IF target_folder_id IS NULL THEN
        RETURN COALESCE(NEW, OLD);
    END IF;

    SELECT lpath INTO target_lpath
      FROM storage.folders
     WHERE id = target_folder_id;

    IF target_lpath IS NULL THEN
        RETURN COALESCE(NEW, OLD);
    END IF;

    -- `lpath @> target_lpath` matches the target folder AND every
    -- ancestor up to the root. The GiST index on lpath keeps this
    -- to an index range scan even on deep trees.
    UPDATE storage.folders
       SET tree_modified_at = NOW()
     WHERE lpath @> target_lpath;

    RETURN COALESCE(NEW, OLD);
END;
$$;

-- PG 13 doesn't support `CREATE OR REPLACE TRIGGER` (added in PG 14),
-- so use the DROP-then-CREATE pattern to stay re-runnable on the
-- minimum supported version.
DROP TRIGGER IF EXISTS files_bump_folder_tree_etag ON storage.files;
CREATE TRIGGER files_bump_folder_tree_etag
    AFTER INSERT OR UPDATE OR DELETE ON storage.files
    FOR EACH ROW EXECUTE FUNCTION storage.bump_folder_tree_from_file();


-- Folder-side trigger: covers creates, deletes, renames, and moves.
-- A folder move changes its lpath — the OLD chain and NEW chain
-- both need bumping (old parents lost a child, new parents gained
-- one). Self-exclusion (id <> the changed row) avoids the row
-- bumping itself, which is meaningless and would amplify
-- contention on hot paths.
--
-- The `pg_trigger_depth() > 1` guard breaks recursion: when this
-- trigger UPDATEs ancestor rows below, those UPDATEs would fire
-- the same trigger again. Without the guard, a single child
-- creation would cascade an unbounded number of upward writes.
CREATE OR REPLACE FUNCTION storage.bump_folder_tree_from_folder()
RETURNS TRIGGER LANGUAGE plpgsql AS $$
BEGIN
    IF pg_trigger_depth() > 1 THEN
        RETURN COALESCE(NEW, OLD);
    END IF;

    IF TG_OP IN ('DELETE', 'UPDATE') AND OLD.lpath IS NOT NULL THEN
        UPDATE storage.folders
           SET tree_modified_at = NOW()
         WHERE lpath @> OLD.lpath AND id <> OLD.id;
    END IF;

    IF TG_OP IN ('INSERT', 'UPDATE') AND NEW.lpath IS NOT NULL THEN
        UPDATE storage.folders
           SET tree_modified_at = NOW()
         WHERE lpath @> NEW.lpath AND id <> NEW.id;
    END IF;

    RETURN COALESCE(NEW, OLD);
END;
$$;

DROP TRIGGER IF EXISTS folders_bump_folder_tree_etag ON storage.folders;
CREATE TRIGGER folders_bump_folder_tree_etag
    AFTER INSERT OR UPDATE OR DELETE ON storage.folders
    FOR EACH ROW EXECUTE FUNCTION storage.bump_folder_tree_from_folder();