-- 985_tracks_storage_backend.sql
-- v1.0.8 Phase 0 (MinIO upload migration) — prepare tracks schema for
-- multi-backend storage (local FS vs S3/MinIO). Schema-only change; Phase 1
-- will wire TrackService.UploadTrack() to actually route writes via the
-- storage_backend column.
--
-- Context: FUNCTIONAL_AUDIT §4 item 2 flagged "stockage local disque only"
-- as a multi-pod prod blocker. The S3 client exists but is never called on
-- the upload path. This migration makes it possible to gradually migrate
-- uploads without a big-bang switchover.
--
-- Columns added:
--   storage_backend — VARCHAR(16) NOT NULL DEFAULT 'local'
--     Which storage impl wrote this track. 'local' = file_path points at
--     veza-backend-api/uploads/tracks/... . 's3' = storage_key holds the
--     S3 object key inside config.S3Bucket. Check constraint limits values.
--
--   storage_key — VARCHAR(512) NULL
--     When storage_backend='s3', this is the S3 object key (e.g.
--     "tracks/<userID>/<uuid>.<ext>"). NULL when storage_backend='local'
--     (file_path carries the info in that case — kept for back-compat).
--
-- Index:
--   idx_tracks_storage_backend_s3 — partial index on s3-backed rows only.
--   Useful for the migration script (Phase 3) which sweeps local→s3 and
--   for monitoring queries (what % of tracks already migrated).

ALTER TABLE public.tracks
    ADD COLUMN storage_backend VARCHAR(16) NOT NULL DEFAULT 'local'
        CHECK (storage_backend IN ('local', 's3')),
    ADD COLUMN storage_key     VARCHAR(512);

-- Partial index: only indexes s3-backed rows (majority stay 'local' during
-- migration, so full index would be wasteful).
CREATE INDEX idx_tracks_storage_backend_s3
    ON public.tracks(storage_backend)
    WHERE storage_backend = 's3';

COMMENT ON COLUMN public.tracks.storage_backend IS
    'Storage impl that owns the file: local (disk) or s3 (MinIO/S3). v1.0.8 multi-backend prep.';

COMMENT ON COLUMN public.tracks.storage_key IS
    'S3 object key when storage_backend=s3. NULL when storage_backend=local (file_path carries the info).';