-- Photo versions (#191): an AI restoration, upscale or edit that sits on
-- disk near its original and is shown as the *same photo*.
--
-- The link is hash-keyed like every other derived table (CLAUDE.md →
-- "Multi-library data model"): a version records the blake3
-- `content_hash` of its primary original, so the link survives moves,
-- renames and an archive handoff. File name and location are hints only.
-- The version keeps its own `image_exif` row, so it still downloads and
-- thumbnails on its own; listings hide it while its original is reachable
-- in the current view (same rule as `duplicate_of_hash`).

-- A file is a version of at most one original.
CREATE TABLE photo_versions (
    version_hash  TEXT PRIMARY KEY NOT NULL,
    original_hash TEXT NOT NULL,
    kind          TEXT NOT NULL,      -- restored | upscale | edit
    source        TEXT NOT NULL,      -- xmp | name | backfill | api
    created_at    BIGINT NOT NULL,
    -- Denormalized back-ref to a live image_exif row for the version, kept
    -- current by the back-ref refresh pass (same pattern as face_detections).
    library_id    INTEGER NOT NULL,
    rel_path      TEXT NOT NULL
);
CREATE INDEX idx_photo_versions_original ON photo_versions(original_hash);

-- Reference photos (extra context fed to the model). Provenance only: a
-- reference is never hidden or grouped because of the version.
CREATE TABLE photo_version_references (
    version_hash   TEXT NOT NULL,
    reference_hash TEXT NOT NULL,
    PRIMARY KEY (version_hash, reference_hash)
);
CREATE INDEX idx_photo_version_references_ref ON photo_version_references(reference_hash);

-- The global (not per-user) choice of which file represents a photo.
-- No row = show the original.
CREATE TABLE photo_version_display (
    original_hash TEXT PRIMARY KEY NOT NULL,
    display_hash  TEXT NOT NULL,
    decided_at    BIGINT NOT NULL
);