// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package rawdb

import (
	"encoding/json"
	"fmt"
	"time"

	"github.com/ledgerwatch/turbo-geth/common/dbutils"
	"github.com/ledgerwatch/turbo-geth/ethdb"

	"github.com/ledgerwatch/turbo-geth/common"
	"github.com/ledgerwatch/turbo-geth/log"
	"github.com/ledgerwatch/turbo-geth/params"
	"github.com/ledgerwatch/turbo-geth/rlp"
)

// ReadChainConfig retrieves the consensus settings based on the given genesis hash.
func ReadChainConfig(db ethdb.KVGetter, hash common.Hash) (*params.ChainConfig, error) {
	data, err := db.GetOne(dbutils.ConfigPrefix, hash[:])
	if err != nil {
		return nil, err
	}
	if len(data) == 0 {
		return nil, nil
	}
	var config params.ChainConfig
	if err := json.Unmarshal(data, &config); err != nil {
		return nil, fmt.Errorf("invalid chain config JSON: %x, %w", hash, err)
	}
	return &config, nil
}

// WriteChainConfig writes the chain config settings to the database.
func WriteChainConfig(db ethdb.Putter, hash common.Hash, cfg *params.ChainConfig) error {
	if cfg == nil {
		return nil
	}
	data, err := json.Marshal(cfg)
	if err != nil {
		return fmt.Errorf("failed to JSON encode chain config: %w", err)
	}
	if err := db.Put(dbutils.ConfigPrefix, hash[:], data); err != nil {
		return fmt.Errorf("failed to store chain config: %w", err)
	}
	return nil
}

// crashList is a list of unclean-shutdown-markers, for rlp-encoding to the
// database
type crashList struct {
	Discarded uint64   // how many ucs have we deleted
	Recent    []uint64 // unix timestamps of 10 latest unclean shutdowns
}

const crashesToKeep = 10

// PushUncleanShutdownMarker appends a new unclean shutdown marker and returns
// the previous data
// - a list of timestamps
// - a count of how many old unclean-shutdowns have been discarded
func PushUncleanShutdownMarker(db ethdb.Database) ([]uint64, uint64, error) {
	var uncleanShutdowns crashList
	// Read old data
	if data, err := db.Get(dbutils.UncleanShutdown, []byte(dbutils.UncleanShutdown)); err != nil {
		log.Warn("Error reading unclean shutdown markers", "error", err)
	} else if err := rlp.DecodeBytes(data, &uncleanShutdowns); err != nil {
		return nil, 0, err
	}
	var discarded = uncleanShutdowns.Discarded
	var previous = make([]uint64, len(uncleanShutdowns.Recent))
	copy(previous, uncleanShutdowns.Recent)
	// Add a new (but cap it)
	uncleanShutdowns.Recent = append(uncleanShutdowns.Recent, uint64(time.Now().Unix()))
	if count := len(uncleanShutdowns.Recent); count > crashesToKeep+1 {
		numDel := count - (crashesToKeep + 1)
		uncleanShutdowns.Recent = uncleanShutdowns.Recent[numDel:]
		uncleanShutdowns.Discarded += uint64(numDel)
	}
	// And save it again
	data, _ := rlp.EncodeToBytes(uncleanShutdowns)
	if err := db.Put(dbutils.UncleanShutdown, []byte(dbutils.UncleanShutdown), data); err != nil {
		log.Warn("Failed to write unclean-shutdown marker", "err", err)
		return nil, 0, err
	}
	return previous, discarded, nil
}

// PopUncleanShutdownMarker removes the last unclean shutdown marker
func PopUncleanShutdownMarker(db ethdb.Database) {
	var uncleanShutdowns crashList
	// Read old data
	if data, err := db.Get(dbutils.UncleanShutdown, []byte(dbutils.UncleanShutdown)); err != nil {
		log.Warn("Error reading unclean shutdown markers", "error", err)
	} else if err := rlp.DecodeBytes(data, &uncleanShutdowns); err != nil {
		log.Error("Error decoding unclean shutdown markers", "error", err) // Should mos def _not_ happen
	}
	if l := len(uncleanShutdowns.Recent); l > 0 {
		uncleanShutdowns.Recent = uncleanShutdowns.Recent[:l-1]
	}
	data, _ := rlp.EncodeToBytes(uncleanShutdowns)
	if err := db.Put(dbutils.UncleanShutdown, []byte(dbutils.UncleanShutdown), data); err != nil {
		log.Warn("Failed to clear unclean-shutdown marker", "err", err)
	}
}