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//! Migrations to version [`2.0.0`], as denoted by the changelog.

use frame_support::{
  traits::{Get, StorageVersion},
  weights::Weight,
};

/// The old prefix.
pub const OLD_PREFIX: &[u8] = b"Template";

/// Some checks prior to migration. This can be linked to
/// [`frame_support::traits::OnRuntimeUpgrade::pre_upgrade`] for further testing.
///
/// Panics if anything goes wrong.
pub fn pre_migration<T: crate::Config, N: AsRef<str>>(new: N) {
  let new = new.as_ref();
  log::info!("pre-migration for the template pallet v2 = {}", new);

  // ensure storage version is 3.
  assert_eq!(StorageVersion::get::<crate::Pallet<T>>(), 1);
}

/// Migrate the entire storage of this pallet to a new prefix.
///
/// This new prefix must be the same as the one set in construct_runtime. For safety, use
/// `PalletInfo` to get it, as:
/// `<Runtime as frame_system::Config>::PalletInfo::name::<Template>`.
///
/// The old storage prefix, `Template` is hardcoded in the migration code.
pub fn migrate<T: crate::Config, N: AsRef<str>>(new_pallet_name: N) -> Weight {
  if new_pallet_name.as_ref().as_bytes() == OLD_PREFIX {
    log::info!(
      target: "runtime::template",
      "New pallet name is equal to the old prefix. No migration needs to be done.",
    );
    return Weight::zero();
  }
  let storage_version = StorageVersion::get::<crate::Pallet<T>>();
  log::info!(
    target: "runtime::template",
    "Running migration to v2 for template with storage version {:?}",
    storage_version,
  );

  if storage_version <= 1 {
    log::info!("new prefix: {}", new_pallet_name.as_ref());
    frame_support::storage::migration::move_pallet(OLD_PREFIX, new_pallet_name.as_ref().as_bytes());

    StorageVersion::new(2).put::<crate::Pallet<T>>();

    <T as frame_system::Config>::BlockWeights::get().max_block
  } else {
    log::warn!(
      target: "runtime::template",
      "Attempted to apply migration to v2 but failed because storage version is {:?}",
      storage_version,
    );
    Weight::zero()
  }
}

/// Some checks for after migration. This can be linked to
/// [`frame_support::traits::OnRuntimeUpgrade::post_upgrade`] for further testing.
///
/// Panics if anything goes wrong.
pub fn post_migration<T: crate::Config>() {
  log::info!("post-migration for the template pallet v2");
  // ensure we've been updated to v4 by the automatic write of crate version -> storage version.
  assert_eq!(StorageVersion::get::<crate::Pallet<T>>(), 2);
}