package store

import (
	"crypto/sha1"
	"encoding/hex"
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"gitlab.celogeek.com/photos/api/internal/photoserrors"
)

type Store struct {
	Path string
}

type Chunk struct {
	*Store
	Sum   string
	Bytes []byte
}

func (s *Store) NewChunk(b []byte) *Chunk {
	sum := sha1.New()
	sum.Write(b)
	sumString := hex.EncodeToString(sum.Sum(nil))

	return &Chunk{s, sumString, b}
}

func (s *Store) LoadChunk(sum string) (*Chunk, error) {
	c := &Chunk{s, sum, nil}
	if !c.FileExists() {
		return nil, fmt.Errorf("chunk %s doesn't exists", sum)
	}
	b, err := os.ReadFile(c.Filename())
	if err != nil {
		return nil, err
	}
	c.Bytes = b
	return c, nil
}

func (c *Chunk) Dir() string {
	return filepath.Join(c.Path, "storage", c.Sum[0:1], c.Sum[1:2])
}

func (c *Chunk) Filename() string {
	return filepath.Join(c.Dir(), c.Sum)
}

func (c *Chunk) FileExists() bool {
	fs, err := os.Stat(c.Filename())
	if errors.Is(err, os.ErrNotExist) {
		return false
	}
	return !fs.IsDir()
}

func (c *Chunk) Mkdir() error {
	return os.MkdirAll(c.Dir(), 0755)
}

func (c *Chunk) Save() error {
	if c.FileExists() {
		return photoserrors.ErrStoreChunkAlreadyExists
	}

	if err := c.Mkdir(); err != nil {
		return err
	}

	fs, err := os.Create(c.Filename())
	if err != nil {
		return err
	}
	defer fs.Close()
	_, err = fs.Write(c.Bytes)
	return err
}

func (s *Store) Combine(sumb []string) (string, uint64, error) {
	sum := sha1.New()
	size := uint64(0)
	for _, sb := range sumb {
		c, err := s.LoadChunk(sb)
		if err != nil {
			return "", 0, err
		}
		sum.Write(c.Bytes)
		size += uint64(len(c.Bytes))
	}
	return hex.EncodeToString(sum.Sum(nil)), size, nil
}