package store

import (
	"io"
	"os"

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

type StoreReaderChunk struct {
	Filename string
	Size     int64
}

type StoreReader struct {
	current *os.File
	chunk   int
	chunks  []StoreReaderChunk
	Size    int64
}

func (s *Store) NewStoreReader(chunks []string) (*StoreReader, error) {
	sr := &StoreReader{nil, 0, make([]StoreReaderChunk, len(chunks)), 0}
	for i, chunk := range chunks {
		c := s.Chunk(chunk)
		name := c.Filename()
		size := c.Size()
		if size < 0 {
			return nil, photoserrors.ErrStoreMissingChunks
		}
		sr.chunks[i] = StoreReaderChunk{name, size}
		sr.Size += size
	}
	return sr, nil
}

func (s *StoreReader) Read(p []byte) (n int, err error) {
	if s.current == nil {
		f, err := os.Open(s.chunks[s.chunk].Filename)
		if err != nil {
			return -1, err
		}
		s.current = f
	}

	n, err = s.current.Read(p)
	if err == io.EOF {
		s.chunk++
		if s.chunk > len(s.chunks)-1 {
			return
		}
		s.Close()
		return s.Read(p)
	}
	return
}

func (s *StoreReader) Close() {
	if s.current != nil {
		s.current.Close()
		s.current = nil
	}
}

// func (s *StoreReader) Seek(offset int64, whence int) (int64, error) {

// }