package cachefile

import (
	"net/netip"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/sagernet/sing-box/adapter"

	"go.etcd.io/bbolt"
)

var bucketSelected = []byte("selected")

var _ adapter.ClashCacheFile = (*CacheFile)(nil)

type CacheFile struct {
	DB                *bbolt.DB
	cacheID           []byte
	saveAccess        sync.RWMutex
	saveDomain        map[netip.Addr]string
	saveAddress4      map[string]netip.Addr
	saveAddress6      map[string]netip.Addr
	saveMetadataTimer *time.Timer
}

func Open(path string, cacheID string) (*CacheFile, error) {
	const fileMode = 0o666
	options := bbolt.Options{Timeout: time.Second}
	db, err := bbolt.Open(path, fileMode, &options)
	switch err {
	case bbolt.ErrInvalid, bbolt.ErrChecksum, bbolt.ErrVersionMismatch:
		if err = os.Remove(path); err != nil {
			break
		}
		db, err = bbolt.Open(path, 0o666, &options)
	}
	if err != nil {
		return nil, err
	}
	var cacheIDBytes []byte
	if cacheID != "" {
		cacheIDBytes = append([]byte{0}, []byte(cacheID)...)
	}
	err = db.Batch(func(tx *bbolt.Tx) error {
		return tx.ForEach(func(name []byte, b *bbolt.Bucket) error {
			if name[0] == 0 {
				return b.ForEachBucket(func(k []byte) error {
					bucketName := string(k)
					if !(bucketName == string(bucketSelected)) {
						delErr := b.DeleteBucket(name)
						if delErr != nil {
							return delErr
						}
					}
					return nil
				})
			} else {
				bucketName := string(name)
				if !(bucketName == string(bucketSelected) || strings.HasPrefix(bucketName, fakeipBucketPrefix)) {
					delErr := tx.DeleteBucket(name)
					if delErr != nil {
						return delErr
					}
				}
			}
			return nil
		})
	})
	if err != nil {
		return nil, err
	}
	return &CacheFile{
		DB:           db,
		cacheID:      cacheIDBytes,
		saveDomain:   make(map[netip.Addr]string),
		saveAddress4: make(map[string]netip.Addr),
		saveAddress6: make(map[string]netip.Addr),
	}, nil
}

func (c *CacheFile) bucket(t *bbolt.Tx, key []byte) *bbolt.Bucket {
	if c.cacheID == nil {
		return t.Bucket(key)
	}
	bucket := t.Bucket(c.cacheID)
	if bucket == nil {
		return nil
	}
	return bucket.Bucket(key)
}

func (c *CacheFile) createBucket(t *bbolt.Tx, key []byte) (*bbolt.Bucket, error) {
	if c.cacheID == nil {
		return t.CreateBucketIfNotExists(key)
	}
	bucket, err := t.CreateBucketIfNotExists(c.cacheID)
	if bucket == nil {
		return nil, err
	}
	return bucket.CreateBucketIfNotExists(key)
}

func (c *CacheFile) LoadSelected(group string) string {
	var selected string
	c.DB.View(func(t *bbolt.Tx) error {
		bucket := c.bucket(t, bucketSelected)
		if bucket == nil {
			return nil
		}
		selectedBytes := bucket.Get([]byte(group))
		if len(selectedBytes) > 0 {
			selected = string(selectedBytes)
		}
		return nil
	})
	return selected
}

func (c *CacheFile) StoreSelected(group, selected string) error {
	return c.DB.Batch(func(t *bbolt.Tx) error {
		bucket, err := c.createBucket(t, bucketSelected)
		if err != nil {
			return err
		}
		return bucket.Put([]byte(group), []byte(selected))
	})
}

func (c *CacheFile) Close() error {
	return c.DB.Close()
}