package rpl

import (
	"fmt"
	"io/ioutil"
	"os"
	"sort"
	"sync"
	"time"

	"github.com/ledisdb/ledisdb/config"
	"github.com/siddontang/go/log"
	"github.com/siddontang/go/num"
)

const (
	defaultMaxLogFileSize = int64(256 * 1024 * 1024)

	maxLogFileSize = int64(1024 * 1024 * 1024)

	defaultLogNumInFile = int64(1024 * 1024)
)

/*
	File Store:
	00000001.data
	00000001.meta
	00000002.data
	00000002.meta

	data: log1 data | log2 data | magic data

	if data has no magic data, it means that we don't close replication gracefully.
	so we must repair the log data
	log data: id (bigendian uint64), create time (bigendian uint32), compression (byte), data len(bigendian uint32), data
	split data = log0 data + [padding 0] -> file % pagesize() == 0

	meta: log1 offset | log2 offset
	log offset: bigendian uint32 | bigendian uint32

	//sha1 of github.com/ledisdb/ledisdb 20 bytes
	magic data = "\x1c\x1d\xb8\x88\xff\x9e\x45\x55\x40\xf0\x4c\xda\xe0\xce\x47\xde\x65\x48\x71\x17"

	we must guarantee that the log id is monotonic increment strictly.
	if log1's id is 1, log2 must be 2
*/

type FileStore struct {
	LogStore

	cfg *config.Config

	base string

	rm sync.RWMutex
	wm sync.Mutex

	rs tableReaders
	w  *tableWriter

	quit chan struct{}
}

func NewFileStore(base string, cfg *config.Config) (*FileStore, error) {
	s := new(FileStore)

	s.quit = make(chan struct{})

	var err error

	if err = os.MkdirAll(base, 0755); err != nil {
		return nil, err
	}

	s.base = base

	if cfg.Replication.MaxLogFileSize == 0 {
		cfg.Replication.MaxLogFileSize = defaultMaxLogFileSize
	}

	cfg.Replication.MaxLogFileSize = num.MinInt64(cfg.Replication.MaxLogFileSize, maxLogFileSize)

	s.cfg = cfg

	if err = s.load(); err != nil {
		return nil, err
	}

	index := int64(1)
	if len(s.rs) != 0 {
		index = s.rs[len(s.rs)-1].index + 1
	}

	s.w = newTableWriter(s.base, index, cfg.Replication.MaxLogFileSize, cfg.Replication.UseMmap)
	s.w.SetSyncType(cfg.Replication.SyncLog)

	go s.checkTableReaders()

	return s, nil
}

func (s *FileStore) GetLog(id uint64, l *Log) error {
	//first search in table writer
	if err := s.w.GetLog(id, l); err == nil {
		return nil
	} else if err != ErrLogNotFound {
		return err
	}

	s.rm.RLock()
	t := s.rs.Search(id)

	if t == nil {
		s.rm.RUnlock()

		return ErrLogNotFound
	}

	err := t.GetLog(id, l)
	s.rm.RUnlock()

	return err
}

func (s *FileStore) FirstID() (uint64, error) {
	id := uint64(0)

	s.rm.RLock()
	if len(s.rs) > 0 {
		id = s.rs[0].first
	} else {
		id = 0
	}
	s.rm.RUnlock()

	if id > 0 {
		return id, nil
	}

	//if id = 0,

	return s.w.First(), nil
}

func (s *FileStore) LastID() (uint64, error) {
	id := s.w.Last()
	if id > 0 {
		return id, nil
	}

	//if table writer has no last id, we may find in the last table reader

	s.rm.RLock()
	if len(s.rs) > 0 {
		id = s.rs[len(s.rs)-1].last
	}
	s.rm.RUnlock()

	return id, nil
}

func (s *FileStore) StoreLog(l *Log) error {
	s.wm.Lock()
	err := s.storeLog(l)
	s.wm.Unlock()
	return err
}

func (s *FileStore) storeLog(l *Log) error {
	err := s.w.StoreLog(l)
	if err == nil {
		return nil
	} else if err != errTableNeedFlush {
		return err
	}

	var r *tableReader
	r, err = s.w.Flush()

	if err != nil {
		log.Fatalf("write table flush error %s, can not store!!!", err.Error())

		s.w.Close()

		return err
	}

	s.rm.Lock()
	s.rs = append(s.rs, r)
	s.rm.Unlock()

	err = s.w.StoreLog(l)

	return err
}

func (s *FileStore) PurgeExpired(n int64) error {
	s.rm.Lock()

	var purges []*tableReader

	t := uint32(time.Now().Unix() - int64(n))

	for i, r := range s.rs {
		if r.lastTime > t {
			purges = append([]*tableReader{}, s.rs[0:i]...)
			n := copy(s.rs, s.rs[i:])
			s.rs = s.rs[0:n]
			break
		}
	}

	s.rm.Unlock()

	s.purgeTableReaders(purges)

	return nil
}

func (s *FileStore) Sync() error {
	return s.w.Sync()
}

func (s *FileStore) Clear() error {
	s.wm.Lock()
	s.rm.Lock()

	defer func() {
		s.rm.Unlock()
		s.wm.Unlock()
	}()

	s.w.Close()

	for i := range s.rs {
		s.rs[i].Close()
	}

	s.rs = tableReaders{}

	if err := os.RemoveAll(s.base); err != nil {
		return err
	}

	if err := os.MkdirAll(s.base, 0755); err != nil {
		return err
	}

	s.w = newTableWriter(s.base, 1, s.cfg.Replication.MaxLogFileSize, s.cfg.Replication.UseMmap)

	return nil
}

func (s *FileStore) Close() error {
	close(s.quit)

	s.wm.Lock()
	s.rm.Lock()

	if r, err := s.w.Flush(); err != nil {
		if err != errNilHandler {
			log.Errorf("close err: %s", err.Error())
		}
	} else {
		r.Close()
		s.w.Close()
	}

	for i := range s.rs {
		s.rs[i].Close()
	}

	s.rs = tableReaders{}

	s.rm.Unlock()
	s.wm.Unlock()

	return nil
}

func (s *FileStore) checkTableReaders() {
	t := time.NewTicker(60 * time.Second)
	defer t.Stop()
	for {
		select {
		case <-t.C:
			s.rm.Lock()

			for _, r := range s.rs {
				if !r.Keepalived() {
					r.Close()
				}
			}

			purges := []*tableReader{}
			maxNum := s.cfg.Replication.MaxLogFileNum
			num := len(s.rs)
			if num > maxNum {
				purges = s.rs[:num-maxNum]
				s.rs = s.rs[num-maxNum:]
			}

			s.rm.Unlock()

			s.purgeTableReaders(purges)

		case <-s.quit:
			return
		}
	}
}

func (s *FileStore) purgeTableReaders(purges []*tableReader) {
	for _, r := range purges {
		dataName := fmtTableDataName(r.base, r.index)
		metaName := fmtTableMetaName(r.base, r.index)
		r.Close()
		if err := os.Remove(dataName); err != nil {
			log.Errorf("purge table data %s err: %s", dataName, err.Error())
		}
		if err := os.Remove(metaName); err != nil {
			log.Errorf("purge table meta %s err: %s", metaName, err.Error())
		}

	}
}

func (s *FileStore) load() error {
	fs, err := ioutil.ReadDir(s.base)
	if err != nil {
		return err
	}

	s.rs = make(tableReaders, 0, len(fs))

	var r *tableReader
	var index int64
	for _, f := range fs {
		if _, err := fmt.Sscanf(f.Name(), "%08d.data", &index); err == nil {
			if r, err = newTableReader(s.base, index, s.cfg.Replication.UseMmap); err != nil {
				log.Errorf("load table %s err: %s", f.Name(), err.Error())
			} else {
				s.rs = append(s.rs, r)
			}
		}
	}

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

	return nil
}

type tableReaders []*tableReader

func (ts tableReaders) Len() int {
	return len(ts)
}

func (ts tableReaders) Swap(i, j int) {
	ts[i], ts[j] = ts[j], ts[i]
}

func (ts tableReaders) Less(i, j int) bool {
	return ts[i].first < ts[j].first
}

func (ts tableReaders) Search(id uint64) *tableReader {
	i, j := 0, len(ts)-1

	for i <= j {
		h := i + (j-i)/2

		if ts[h].first <= id && id <= ts[h].last {
			return ts[h]
		} else if ts[h].last < id {
			i = h + 1
		} else {
			j = h - 1
		}
	}

	return nil
}

func (ts tableReaders) check() error {
	if len(ts) == 0 {
		return nil
	}

	sort.Sort(ts)

	first := ts[0].first
	last := ts[0].last
	index := ts[0].index

	if first == 0 || first > last {
		return fmt.Errorf("invalid log in table %s", ts[0])
	}

	for i := 1; i < len(ts); i++ {
		if ts[i].first <= last {
			return fmt.Errorf("invalid first log id %d in table %s", ts[i].first, ts[i])
		}

		if ts[i].index <= index {
			return fmt.Errorf("invalid index %d in table %s", ts[i].index, ts[i])
		}

		first = ts[i].first
		last = ts[i].last
		index = ts[i].index
	}
	return nil
}