UPDATE platform_user_vehicle
SET valid_from = granted_at
WHERE valid_from IS NULL;

CREATE INDEX idx_platform_user_vehicle_active_time
    ON platform_user_vehicle(user_id, valid_from, valid_to, vin);

CREATE TABLE IF NOT EXISTS platform_user_vehicle_grant_history (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    user_id BIGINT UNSIGNED NOT NULL,
    vin VARCHAR(64) NOT NULL,
    valid_from DATETIME(3) NOT NULL,
    valid_to DATETIME(3) NULL,
    source_system VARCHAR(32) NOT NULL DEFAULT 'manual',
    external_ref VARCHAR(128) NOT NULL DEFAULT '',
    granted_by VARCHAR(96) NOT NULL,
    revoked_by VARCHAR(96) NOT NULL DEFAULT '',
    created_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
    updated_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
    INDEX idx_platform_vehicle_grant_user_time (user_id, valid_from, valid_to),
    INDEX idx_platform_vehicle_grant_vin_time (vin, valid_from, valid_to),
    CONSTRAINT fk_platform_vehicle_grant_user FOREIGN KEY (user_id) REFERENCES platform_user(id) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

INSERT INTO platform_user_vehicle_grant_history(
    user_id, vin, valid_from, valid_to, source_system, external_ref, granted_by, revoked_by
)
SELECT
    current_grant.user_id,
    current_grant.vin,
    COALESCE(current_grant.valid_from, current_grant.granted_at),
    current_grant.valid_to,
    current_grant.source_system,
    current_grant.external_ref,
    current_grant.granted_by,
    CASE WHEN current_grant.valid_to IS NULL THEN '' ELSE 'migration' END
FROM platform_user_vehicle current_grant
WHERE NOT EXISTS (
    SELECT 1
    FROM platform_user_vehicle_grant_history history
    WHERE history.user_id = current_grant.user_id
      AND history.vin = current_grant.vin
      AND history.valid_from = COALESCE(current_grant.valid_from, current_grant.granted_at)
);