package raftbbolt

import (
	"errors"

	"git.giftfish.de/ston1th/raftbbolt/msgpack"
	"github.com/hashicorp/raft"
	"go.etcd.io/bbolt"
)

const (
	// Permissions to use on the db file. This is only used if the
	// database file does not exist and needs to be created.
	dbFileMode = 0600
)

var (
	// Bucket names we perform transactions in
	dbLogs = []byte("logs")
	dbConf = []byte("conf")

	// An error indicating a given key does not exist
	ErrKeyNotFound = errors.New("not found")
)

// Store provides access to BoltDB for Raft to store and retrieve
// log entries. It also provides key/value storage, and can be used as
// a LogStore and StableStore.
type Store struct {
	// conn is the underlying handle to the db.
	db *bbolt.DB

	// The path to the Bolt database file
	path string
}

// Options contains all the configuration used to open the BoltDB
type Options struct {
	// Path is the file path to the BoltDB to use
	Path string

	// BoltOptions contains any specific BoltDB options you might
	// want to specify [e.g. open timeout]
	BoltOptions *bbolt.Options

	// NoSync causes the database to skip fsync calls after each
	// write to the log. This is unsafe, so it should be used
	// with caution.
	NoSync bool
}

// readOnly returns true if the contained bolt options say to open
// the DB in readOnly mode [this can be useful to tools that want
// to examine the log]
func (o *Options) readOnly() bool {
	return o != nil && o.BoltOptions != nil && o.BoltOptions.ReadOnly
}

// NewStore takes a file path and returns a connected Raft backend.
func NewStore(path string) (*Store, error) {
	return New(Options{Path: path})
}

// New uses the supplied options to open the BoltDB and prepare it for use as a raft backend.
func New(options Options) (*Store, error) {
	db, err := bbolt.Open(options.Path, dbFileMode, options.BoltOptions)
	if err != nil {
		return nil, err
	}
	db.NoSync = options.NoSync

	// Create the new store
	store := &Store{
		db:   db,
		path: options.Path,
	}

	// If the store was opened read-only, don't try and create buckets
	if !options.readOnly() {
		// Set up our buckets
		if err := store.initialize(); err != nil {
			store.Close()
			return nil, err
		}
	}
	return store, nil
}

// initialize is used to set up all of the buckets.
func (s *Store) initialize() error {
	return s.db.Update(func(tx *bbolt.Tx) error {
		if _, err := tx.CreateBucketIfNotExists(dbLogs); err != nil {
			return err
		}
		_, err := tx.CreateBucketIfNotExists(dbConf)
		return err
	})
}

// Close is used to gracefully close the DB connection.
func (s *Store) Close() error {
	return s.db.Close()
}

// FirstIndex returns the first known index from the Raft log.
func (s *Store) FirstIndex() (n uint64, err error) {
	err = s.db.View(func(tx *bbolt.Tx) error {
		c := tx.Bucket(dbLogs).Cursor()
		first, _ := c.First()
		if first == nil {
			return nil
		}
		n = bytesToUint64(first)
		return nil
	})
	return
}

// LastIndex returns the last known index from the Raft log.
func (s *Store) LastIndex() (n uint64, err error) {
	err = s.db.View(func(tx *bbolt.Tx) error {
		c := tx.Bucket(dbLogs).Cursor()
		last, _ := c.Last()
		if last == nil {
			return nil
		}
		n = bytesToUint64(last)
		return nil
	})
	return
}

// GetLog is used to retrieve a log from BoltDB at a given index.
func (s *Store) GetLog(idx uint64, log *raft.Log) error {
	return s.db.View(func(tx *bbolt.Tx) error {
		b := tx.Bucket(dbLogs).Get(uint64ToBytes(idx))
		if b == nil {
			return raft.ErrLogNotFound
		}
		return msgpack.Unmarshal(b, log)
	})
}

// StoreLog is used to store a single raft log
func (s *Store) StoreLog(log *raft.Log) error {
	return s.StoreLogs([]*raft.Log{log})
}

// StoreLogs is used to store a set of raft logs
func (s *Store) StoreLogs(logs []*raft.Log) error {
	return s.db.Update(func(tx *bbolt.Tx) error {
		bucket := tx.Bucket(dbLogs)
		for _, log := range logs {
			b, err := msgpack.Marshal(log)
			if err != nil {
				return err
			}
			if err := bucket.Put(uint64ToBytes(log.Index), b); err != nil {
				return err
			}
		}
		return nil
	})
}

// DeleteRange is used to delete logs within a given range inclusively.
func (s *Store) DeleteRange(min, max uint64) error {
	return s.db.Update(func(tx *bbolt.Tx) error {
		c := tx.Bucket(dbLogs).Cursor()
		minKey := uint64ToBytes(min)
		for k, _ := c.Seek(minKey); k != nil; k, _ = c.Next() {
			// Handle out-of-range log index
			if bytesToUint64(k) > max {
				break
			}
			// Delete in-range log index
			if err := c.Delete(); err != nil {
				return err
			}
		}
		return nil
	})
}

// Set is used to set a key/value set outside of the raft log
func (s *Store) Set(k, v []byte) error {
	return s.db.Update(func(tx *bbolt.Tx) error {
		return tx.Bucket(dbConf).Put(k, v)
	})
}

// Get is used to retrieve a value from the k/v store by key
func (s *Store) Get(k []byte) (b []byte, err error) {
	err = s.db.View(func(tx *bbolt.Tx) error {
		b = tx.Bucket(dbConf).Get(k)
		if b == nil {
			return ErrKeyNotFound
		}
		return nil
	})
	return
}

// SetUint64 is like Set, but handles uint64 values
func (s *Store) SetUint64(k []byte, v uint64) error {
	return s.Set(k, uint64ToBytes(v))
}

// GetUint64 is like Get, but handles uint64 values
func (s *Store) GetUint64(k []byte) (uint64, error) {
	b, err := s.Get(k)
	if err != nil {
		return 0, err
	}
	return bytesToUint64(b), nil
}

// Sync performs an fsync on the database file handle. This is not necessary
// under normal operation unless NoSync is enabled, in which this forces the
// database file to sync against the disk.
func (s *Store) Sync() error {
	return s.db.Sync()
}