//! Utilities for managing database schema changes.
use crate::beacon_chain::{BeaconChainTypes, OP_POOL_DB_KEY};
use crate::validator_pubkey_cache::ValidatorPubkeyCache;
use operation_pool::{PersistedOperationPool, PersistedOperationPoolBase};
use ssz::{Decode, Encode};
use ssz_derive::{Decode, Encode};
use std::fs;
use std::path::Path;
use std::sync::Arc;
use store::config::OnDiskStoreConfig;
use store::hot_cold_store::{HotColdDB, HotColdDBError};
use store::metadata::{SchemaVersion, CONFIG_KEY, CURRENT_SCHEMA_VERSION};
use store::{DBColumn, Error as StoreError, ItemStore, StoreItem};

const PUBKEY_CACHE_FILENAME: &str = "pubkey_cache.ssz";

/// Migrate the database from one schema version to another, applying all requisite mutations.
pub fn migrate_schema<T: BeaconChainTypes>(
    db: Arc<HotColdDB<T::EthSpec, T::HotStore, T::ColdStore>>,
    datadir: &Path,
    from: SchemaVersion,
    to: SchemaVersion,
) -> Result<(), StoreError> {
    match (from, to) {
        // Migrating from the current schema version to iself is always OK, a no-op.
        (_, _) if from == to && to == CURRENT_SCHEMA_VERSION => Ok(()),
        // Migrate across multiple versions by recursively migrating one step at a time.
        (_, _) if from.as_u64() + 1 < to.as_u64() => {
            let next = SchemaVersion(from.as_u64() + 1);
            migrate_schema::<T>(db.clone(), datadir, from, next)?;
            migrate_schema::<T>(db, datadir, next, to)
        }
        // Migration from v0.3.0 to v0.3.x, adding the temporary states column.
        // Nothing actually needs to be done, but once a DB uses v2 it shouldn't go back.
        (SchemaVersion(1), SchemaVersion(2)) => {
            db.store_schema_version(to)?;
            Ok(())
        }
        // Migration for removing the pubkey cache.
        (SchemaVersion(2), SchemaVersion(3)) => {
            let pk_cache_path = datadir.join(PUBKEY_CACHE_FILENAME);

            // Load from file, store to DB.
            ValidatorPubkeyCache::<T>::load_from_file(&pk_cache_path)
                .and_then(|cache| ValidatorPubkeyCache::convert(cache, db.clone()))
                .map_err(|e| StoreError::SchemaMigrationError(format!("{:?}", e)))?;

            db.store_schema_version(to)?;

            // Delete cache file now that keys are stored in the DB.
            fs::remove_file(&pk_cache_path).map_err(|e| {
                StoreError::SchemaMigrationError(format!(
                    "unable to delete {}: {:?}",
                    pk_cache_path.display(),
                    e
                ))
            })?;

            Ok(())
        }
        // Migration for adding sync committee contributions to the persisted op pool.
        (SchemaVersion(3), SchemaVersion(4)) => {
            // Deserialize from what exists in the database using the `PersistedOperationPoolBase`
            // variant and convert it to the Altair variant.
            let pool_opt = db
                .get_item::<PersistedOperationPoolBase<T::EthSpec>>(&OP_POOL_DB_KEY)?
                .map(PersistedOperationPool::Base)
                .map(PersistedOperationPool::base_to_altair);

            if let Some(pool) = pool_opt {
                // Store the converted pool under the same key.
                db.put_item::<PersistedOperationPool<T::EthSpec>>(&OP_POOL_DB_KEY, &pool)?;
            }

            db.store_schema_version(to)?;

            Ok(())
        }
        // Migration for weak subjectivity sync support and clean up of `OnDiskStoreConfig` (#1784).
        (SchemaVersion(4), SchemaVersion(5)) => {
            if let Some(OnDiskStoreConfigV4 {
                slots_per_restore_point,
                ..
            }) = db.hot_db.get(&CONFIG_KEY)?
            {
                let new_config = OnDiskStoreConfig {
                    slots_per_restore_point,
                };
                db.hot_db.put(&CONFIG_KEY, &new_config)?;
            }

            db.store_schema_version(to)?;

            Ok(())
        }
        // Anything else is an error.
        (_, _) => Err(HotColdDBError::UnsupportedSchemaVersion {
            target_version: to,
            current_version: from,
        }
        .into()),
    }
}

// Store config used in v4 schema and earlier.
#[derive(Debug, Clone, PartialEq, Eq, Encode, Decode)]
pub struct OnDiskStoreConfigV4 {
    pub slots_per_restore_point: u64,
    pub _block_cache_size: usize,
}

impl StoreItem for OnDiskStoreConfigV4 {
    fn db_column() -> DBColumn {
        DBColumn::BeaconMeta
    }

    fn as_store_bytes(&self) -> Vec<u8> {
        self.as_ssz_bytes()
    }

    fn from_store_bytes(bytes: &[u8]) -> Result<Self, StoreError> {
        Ok(Self::from_ssz_bytes(bytes)?)
    }
}