//! Utilities for managing database schema changes.
mod migration_schema_v10;
mod migration_schema_v6;
mod migration_schema_v7;
mod migration_schema_v8;
mod migration_schema_v9;
mod types;

use crate::beacon_chain::{BeaconChainTypes, FORK_CHOICE_DB_KEY};
use crate::persisted_fork_choice::{
    PersistedForkChoiceV1, PersistedForkChoiceV10, PersistedForkChoiceV7, PersistedForkChoiceV8,
};
use crate::types::ChainSpec;
use slog::{warn, Logger};
use std::path::Path;
use std::sync::Arc;
use store::hot_cold_store::{HotColdDB, HotColdDBError};
use store::metadata::{SchemaVersion, CURRENT_SCHEMA_VERSION};
use store::{Error as StoreError, StoreItem};

/// 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,
    log: Logger,
    spec: &ChainSpec,
) -> 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(()),
        // Upgrade 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, log.clone(), spec)?;
            migrate_schema::<T>(db, datadir, next, to, log, spec)
        }

        //
        // Migrations from before SchemaVersion(5) are deprecated.
        //

        // Migration for adding `execution_status` field to the fork choice store.
        (SchemaVersion(5), SchemaVersion(6)) => {
            // Database operations to be done atomically
            let mut ops = vec![];

            // The top-level `PersistedForkChoice` struct is still V1 but will have its internal
            // bytes for the fork choice updated to V6.
            let fork_choice_opt = db.get_item::<PersistedForkChoiceV1>(&FORK_CHOICE_DB_KEY)?;
            if let Some(mut persisted_fork_choice) = fork_choice_opt {
                migration_schema_v6::update_execution_statuses::<T>(&mut persisted_fork_choice)
                    .map_err(StoreError::SchemaMigrationError)?;

                // Store the converted fork choice store under the same key.
                ops.push(persisted_fork_choice.as_kv_store_op(FORK_CHOICE_DB_KEY));
            }

            db.store_schema_version_atomically(to, ops)?;

            Ok(())
        }
        // 1. Add `proposer_boost_root`.
        // 2. Update `justified_epoch` to `justified_checkpoint` and `finalized_epoch` to
        //  `finalized_checkpoint`.
        // 3. This migration also includes a potential update to the justified
        //  checkpoint in case the fork choice store's justified checkpoint and finalized checkpoint
        //  combination does not actually exist for any blocks in fork choice. This was possible in
        //  the consensus spec prior to v1.1.6.
        //
        // Relevant issues:
        //
        // https://github.com/sigp/lighthouse/issues/2741
        // https://github.com/ethereum/consensus-specs/pull/2727
        // https://github.com/ethereum/consensus-specs/pull/2730
        (SchemaVersion(6), SchemaVersion(7)) => {
            // Database operations to be done atomically
            let mut ops = vec![];

            let fork_choice_opt = db.get_item::<PersistedForkChoiceV1>(&FORK_CHOICE_DB_KEY)?;
            if let Some(persisted_fork_choice_v1) = fork_choice_opt {
                // This migrates the `PersistedForkChoiceStore`, adding the `proposer_boost_root` field.
                let mut persisted_fork_choice_v7 = persisted_fork_choice_v1.into();

                let result = migration_schema_v7::update_fork_choice::<T>(
                    &mut persisted_fork_choice_v7,
                    db.clone(),
                );

                // Fall back to re-initializing fork choice from an anchor state if necessary.
                if let Err(e) = result {
                    warn!(log, "Unable to migrate to database schema 7, re-initializing fork choice"; "error" => ?e);
                    migration_schema_v7::update_with_reinitialized_fork_choice::<T>(
                        &mut persisted_fork_choice_v7,
                        db.clone(),
                        spec,
                    )
                    .map_err(StoreError::SchemaMigrationError)?;
                }

                // Store the converted fork choice store under the same key.
                ops.push(persisted_fork_choice_v7.as_kv_store_op(FORK_CHOICE_DB_KEY));
            }

            db.store_schema_version_atomically(to, ops)?;

            Ok(())
        }
        // Migration to add an `epoch` key to the fork choice's balances cache.
        (SchemaVersion(7), SchemaVersion(8)) => {
            let mut ops = vec![];
            let fork_choice_opt = db.get_item::<PersistedForkChoiceV7>(&FORK_CHOICE_DB_KEY)?;
            if let Some(fork_choice) = fork_choice_opt {
                let updated_fork_choice =
                    migration_schema_v8::update_fork_choice::<T>(fork_choice, db.clone())?;

                ops.push(updated_fork_choice.as_kv_store_op(FORK_CHOICE_DB_KEY));
            }

            db.store_schema_version_atomically(to, ops)?;

            Ok(())
        }
        // Upgrade from v8 to v9 to separate the execution payloads into their own column.
        (SchemaVersion(8), SchemaVersion(9)) => {
            migration_schema_v9::upgrade_to_v9::<T>(db.clone(), log)?;
            db.store_schema_version(to)
        }
        // Downgrade from v9 to v8 to ignore the separation of execution payloads
        // NOTE: only works before the Bellatrix fork epoch.
        (SchemaVersion(9), SchemaVersion(8)) => {
            migration_schema_v9::downgrade_from_v9::<T>(db.clone(), log)?;
            db.store_schema_version(to)
        }
        (SchemaVersion(9), SchemaVersion(10)) => {
            let mut ops = vec![];
            let fork_choice_opt = db.get_item::<PersistedForkChoiceV8>(&FORK_CHOICE_DB_KEY)?;
            if let Some(fork_choice) = fork_choice_opt {
                let updated_fork_choice = migration_schema_v10::update_fork_choice(fork_choice)?;

                ops.push(updated_fork_choice.as_kv_store_op(FORK_CHOICE_DB_KEY));
            }

            db.store_schema_version_atomically(to, ops)?;

            Ok(())
        }
        (SchemaVersion(10), SchemaVersion(9)) => {
            let mut ops = vec![];
            let fork_choice_opt = db.get_item::<PersistedForkChoiceV10>(&FORK_CHOICE_DB_KEY)?;
            if let Some(fork_choice) = fork_choice_opt {
                let updated_fork_choice = migration_schema_v10::downgrade_fork_choice(fork_choice)?;

                ops.push(updated_fork_choice.as_kv_store_op(FORK_CHOICE_DB_KEY));
            }

            db.store_schema_version_atomically(to, ops)?;

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