package tsdb

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/influxdb/influxdb/influxql"
	"github.com/influxdb/influxdb/models"
)

var (
	ErrShardNotFound = fmt.Errorf("shard not found")
	ErrStoreClosed   = fmt.Errorf("store is closed")
)

const (
	MaintenanceCheckInterval = time.Minute
)

type Store struct {
	mu   sync.RWMutex
	path string

	databaseIndexes map[string]*DatabaseIndex
	// shards is a map of shard IDs to Shards for *ALL DATABASES*.
	shards map[uint64]*Shard

	EngineOptions EngineOptions
	Logger        *log.Logger

	closing chan struct{}
	wg      sync.WaitGroup
	opened  bool
}

func NewStore(path string) *Store {
	opts := NewEngineOptions()
	opts.Config = NewConfig()

	return &Store{
		path:          path,
		EngineOptions: opts,
		Logger:        log.New(os.Stderr, "[store] ", log.LstdFlags),
	}
}

// Path returns the store's root path.
func (s *Store) Path() string { return s.path }

func (s *Store) Open() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.closing = make(chan struct{})

	s.shards = map[uint64]*Shard{}
	s.databaseIndexes = map[string]*DatabaseIndex{}

	s.Logger.Printf("Using data dir: %v", s.Path())

	// Create directory.
	if err := os.MkdirAll(s.path, 0777); err != nil {
		return err
	}

	// TODO: Start AE for Node
	if err := s.loadIndexes(); err != nil {
		return err
	}

	if err := s.loadShards(); err != nil {
		return err
	}

	go s.periodicMaintenance()
	s.opened = true

	return nil
}

func (s *Store) loadIndexes() error {
	dbs, err := ioutil.ReadDir(s.path)
	if err != nil {
		return err
	}
	for _, db := range dbs {
		if !db.IsDir() {
			s.Logger.Printf("Skipping database dir: %s. Not a directory", db.Name())
			continue
		}
		s.databaseIndexes[db.Name()] = NewDatabaseIndex()
	}
	return nil
}

func (s *Store) loadShards() error {
	// loop through the current database indexes
	for db := range s.databaseIndexes {
		rps, err := ioutil.ReadDir(filepath.Join(s.path, db))
		if err != nil {
			return err
		}

		for _, rp := range rps {
			// retention policies should be directories.  Skip anything that is not a dir.
			if !rp.IsDir() {
				s.Logger.Printf("Skipping retention policy dir: %s. Not a directory", rp.Name())
				continue
			}

			shards, err := ioutil.ReadDir(filepath.Join(s.path, db, rp.Name()))
			if err != nil {
				return err
			}
			for _, sh := range shards {
				path := filepath.Join(s.path, db, rp.Name(), sh.Name())
				walPath := filepath.Join(s.EngineOptions.Config.WALDir, db, rp.Name(), sh.Name())

				// Shard file names are numeric shardIDs
				shardID, err := strconv.ParseUint(sh.Name(), 10, 64)
				if err != nil {
					s.Logger.Printf("Skipping shard: %s. Not a valid path", rp.Name())
					continue
				}

				shard := NewShard(shardID, s.databaseIndexes[db], path, walPath, s.EngineOptions)
				err = shard.Open()
				if err != nil {
					return fmt.Errorf("failed to open shard %d: %s", shardID, err)
				}
				s.shards[shardID] = shard
			}
		}
	}

	return nil
}

func (s *Store) Close() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.opened {
		close(s.closing)
	}
	s.wg.Wait()

	for _, sh := range s.shards {
		if err := sh.Close(); err != nil {
			return err
		}
	}
	s.opened = false
	s.shards = nil
	s.databaseIndexes = nil

	return nil
}

// DatabaseIndexN returns the number of databases indicies in the store.
func (s *Store) DatabaseIndexN() int {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return len(s.databaseIndexes)
}

// Shard returns a shard by id.
func (s *Store) Shard(id uint64) *Shard {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.shards[id]
}

// Shards returns a list of shards by id.
func (s *Store) Shards(ids []uint64) []*Shard {
	s.mu.RLock()
	defer s.mu.RUnlock()
	a := make([]*Shard, 0, len(ids))
	for _, id := range ids {
		a = append(a, s.shards[id])
	}
	return a
}

// ShardN returns the number of shard in the store.
func (s *Store) ShardN() int {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return len(s.shards)
}

func (s *Store) CreateShard(database, retentionPolicy string, shardID uint64) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	select {
	case <-s.closing:
		return ErrStoreClosed
	default:
	}

	// shard already exists
	if _, ok := s.shards[shardID]; ok {
		return nil
	}

	// created the db and retention policy dirs if they don't exist
	if err := os.MkdirAll(filepath.Join(s.path, database, retentionPolicy), 0700); err != nil {
		return err
	}

	// create the WAL directory
	walPath := filepath.Join(s.EngineOptions.Config.WALDir, database, retentionPolicy, fmt.Sprintf("%d", shardID))
	if err := os.MkdirAll(walPath, 0700); err != nil {
		return err
	}

	// create the database index if it does not exist
	db, ok := s.databaseIndexes[database]
	if !ok {
		db = NewDatabaseIndex()
		s.databaseIndexes[database] = db
	}

	shardPath := filepath.Join(s.path, database, retentionPolicy, strconv.FormatUint(shardID, 10))
	shard := NewShard(shardID, db, shardPath, walPath, s.EngineOptions)
	if err := shard.Open(); err != nil {
		return err
	}

	s.shards[shardID] = shard

	return nil
}

// DeleteShard removes a shard from disk.
func (s *Store) DeleteShard(shardID uint64) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	// ensure shard exists
	sh, ok := s.shards[shardID]
	if !ok {
		return nil
	}

	if err := sh.Close(); err != nil {
		return err
	}

	if err := os.RemoveAll(sh.path); err != nil {
		return err
	}

	if err := os.RemoveAll(sh.walPath); err != nil {
		return err
	}

	delete(s.shards, shardID)

	return nil
}

// DeleteDatabase will close all shards associated with a database and remove the directory and files from disk.
func (s *Store) DeleteDatabase(name string, shardIDs []uint64) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	for _, id := range shardIDs {
		shard := s.shards[id]
		if shard != nil {
			shard.Close()
		}
		delete(s.shards, id)
	}

	if err := os.RemoveAll(filepath.Join(s.path, name)); err != nil {
		return err
	}
	if err := os.RemoveAll(filepath.Join(s.EngineOptions.Config.WALDir, name)); err != nil {
		return err
	}

	delete(s.databaseIndexes, name)

	return nil
}

// DeleteMeasurement removes a measurement and all associated series from a database.
func (s *Store) DeleteMeasurement(database, name string) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Find the database.
	db := s.databaseIndexes[database]
	if db == nil {
		return nil
	}

	// Find the measurement.
	m := db.Measurement(name)
	if m == nil {
		return ErrMeasurementNotFound(name)
	}

	// Remove measurement from index.
	db.DropMeasurement(m.Name)

	// Remove underlying data.
	for _, sh := range s.shards {
		if sh.index != db {
			continue
		}
		if err := sh.DeleteMeasurement(m.Name, m.SeriesKeys()); err != nil {
			return err
		}
	}

	return nil
}

// ShardIDs returns a slice of all ShardIDs under management.
func (s *Store) ShardIDs() []uint64 {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.shardIDs()
}

func (s *Store) shardIDs() []uint64 {
	a := make([]uint64, 0, len(s.shards))
	for shardID, _ := range s.shards {
		a = append(a, shardID)
	}
	return a
}

// shardsSlice returns an ordered list of shards.
func (s *Store) shardsSlice() []*Shard {
	a := make([]*Shard, 0, len(s.shards))
	for _, sh := range s.shards {
		a = append(a, sh)
	}
	sort.Sort(Shards(a))
	return a
}

func (s *Store) DatabaseIndex(name string) *DatabaseIndex {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.databaseIndexes[name]
}

// Databases returns all the databases in the indexes
func (s *Store) Databases() []string {
	s.mu.RLock()
	defer s.mu.RUnlock()
	databases := []string{}
	for db := range s.databaseIndexes {
		databases = append(databases, db)
	}
	return databases
}

func (s *Store) Measurement(database, name string) *Measurement {
	s.mu.RLock()
	db := s.databaseIndexes[database]
	s.mu.RUnlock()
	if db == nil {
		return nil
	}
	return db.Measurement(name)
}

// DiskSize returns the size of all the shard files in bytes.  This size does not include the WAL size.
func (s *Store) DiskSize() (int64, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	var size int64
	for _, shardID := range s.ShardIDs() {
		shard := s.Shard(shardID)
		sz, err := shard.DiskSize()
		if err != nil {
			return 0, err
		}
		size += sz
	}
	return size, nil
}

// BackupShard will get the shard and have the engine backup since the passed in time to the writer
func (s *Store) BackupShard(id uint64, since time.Time, w io.Writer) error {
	shard := s.Shard(id)
	if shard == nil {
		return fmt.Errorf("shard %d doesn't exist on this server", id)
	}

	path, err := relativePath(s.path, shard.path)
	if err != nil {
		return err
	}

	return shard.engine.Backup(w, path, since)
}

// ShardRelativePath will return the relative path to the shard. i.e. <database>/<retention>/<id>
func (s *Store) ShardRelativePath(id uint64) (string, error) {
	shard := s.Shard(id)
	if shard == nil {
		return "", fmt.Errorf("shard %d doesn't exist on this server", id)
	}
	return relativePath(s.path, shard.path)
}

// DeleteSeries loops through the local shards and deletes the series data and metadata for the passed in series keys
func (s *Store) DeleteSeries(database string, seriesKeys []string) error {
	s.mu.RLock()
	defer s.mu.RUnlock()

	db, ok := s.databaseIndexes[database]
	if !ok {
		return ErrDatabaseNotFound(database)
	}

	for _, sh := range s.shards {
		if sh.index != db {
			continue
		}
		if err := sh.DeleteSeries(seriesKeys); err != nil {
			return err
		}
	}
	return nil
}

// periodicMaintenance is the method called in a goroutine on the opening of the store
// to perform periodic maintenance of the shards.
func (s *Store) periodicMaintenance() {
	t := time.NewTicker(MaintenanceCheckInterval)
	for {
		select {
		case <-t.C:
			s.performMaintenance()
		case <-s.closing:
			t.Stop()
			return
		}
	}
}

// performMaintenance will loop through the shars and tell them
// to perform any maintenance tasks. Those tasks should kick off
// their own goroutines if it's anything that could take time.
func (s *Store) performMaintenance() {
	s.mu.Lock()
	defer s.mu.Unlock()
	for _, sh := range s.shards {
		s.performMaintenanceOnShard(sh)
	}
}

func (s *Store) performMaintenanceOnShard(shard *Shard) {
	defer func() {
		if r := recover(); r != nil {
			s.Logger.Printf("recovered eror in maintenance on shard %d", shard.id)
		}
	}()
	shard.PerformMaintenance()
}

// ExpandSources expands regex sources and removes duplicates.
// NOTE: sources must be normalized (db and rp set) before calling this function.
func (s *Store) ExpandSources(sources influxql.Sources) (influxql.Sources, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Use a map as a set to prevent duplicates.
	set := map[string]influxql.Source{}

	// Iterate all sources, expanding regexes when they're found.
	for _, source := range sources {
		switch src := source.(type) {
		case *influxql.Measurement:
			// Add non-regex measurements directly to the set.
			if src.Regex == nil {
				set[src.String()] = src
				continue
			}

			// Lookup the database.
			db := s.databaseIndexes[src.Database]
			if db == nil {
				return nil, nil
			}

			// Loop over matching measurements.
			for _, m := range db.measurementsByRegex(src.Regex.Val) {
				other := &influxql.Measurement{
					Database:        src.Database,
					RetentionPolicy: src.RetentionPolicy,
					Name:            m.Name,
				}
				set[other.String()] = other
			}

		default:
			return nil, fmt.Errorf("expandSources: unsupported source type: %T", source)
		}
	}

	// Convert set to sorted slice.
	names := make([]string, 0, len(set))
	for name := range set {
		names = append(names, name)
	}
	sort.Strings(names)

	// Convert set to a list of Sources.
	expanded := make(influxql.Sources, 0, len(set))
	for _, name := range names {
		expanded = append(expanded, set[name])
	}

	return expanded, nil
}

func (s *Store) WriteToShard(shardID uint64, points []models.Point) error {
	s.mu.RLock()
	defer s.mu.RUnlock()

	select {
	case <-s.closing:
		return ErrStoreClosed
	default:
	}

	sh, ok := s.shards[shardID]
	if !ok {
		return ErrShardNotFound
	}

	return sh.WritePoints(points)
}

// IsRetryable returns true if this error is temporary and could be retried
func IsRetryable(err error) bool {
	if err == nil {
		return true
	}

	if strings.Contains(err.Error(), "field type conflict") {
		return false
	}
	return true
}

// relativePath will expand out the full paths passed in and return
// the relative shard path from the store
func relativePath(storePath, shardPath string) (string, error) {
	path, err := filepath.Abs(storePath)
	if err != nil {
		return "", fmt.Errorf("store abs path: %s", err)
	}

	fp, err := filepath.Abs(shardPath)
	if err != nil {
		return "", fmt.Errorf("file abs path: %s", err)
	}

	name, err := filepath.Rel(path, fp)
	if err != nil {
		return "", fmt.Errorf("file rel path: %s", err)
	}

	return name, nil
}