package api

import (
	"bytes"
	"crypto/sha1"
	"encoding/hex"
	"fmt"
	"io"
	"io/fs"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strconv"

	"github.com/gin-gonic/gin"
)

var CHUNK_SIZE int64 = 1 << 20

func (s *Service) PrepareStore() {
	d, err := os.Stat(s.Config.StorePath)
	if err != nil {
		s.LogErr.Fatal("Store", err)
	}
	if !d.IsDir() {
		s.LogErr.Fatal("Store", ErrStorePathNotADirectory)
	}
}

func (s *Service) StoreDir(checksum string) (string, error) {
	dir := filepath.Join(s.Config.StorePath, "original", checksum[0:0], checksum[1:1], checksum[2:])
	err := os.MkdirAll(dir, 0755)
	return dir, err
}

func (s *Service) TempDir(checksum string) (string, error) {
	dir := filepath.Join(s.Config.StorePath, "tmp", checksum)
	err := os.MkdirAll(dir, 0755)
	return dir, err
}

type FileChunks struct {
	N    uint64
	Path fs.FS
	Name string
}

func (s *Service) FileChunks(checksum string) ([]FileChunks, error) {
	base := filepath.Join(s.Config.StorePath, "tmp", checksum)
	baseDir := os.DirFS(base)
	dir, err := os.Open(base)
	if err != nil {
		return nil, err
	}
	defer dir.Close()

	files, err := dir.Readdirnames(-1)
	if err != nil {
		return nil, err
	}
	parts := []FileChunks{}
	for _, f := range files {
		n, err := strconv.ParseUint(f, 10, 64)
		if err != nil {
			continue
		}
		parts = append(parts, FileChunks{n, baseDir, f})
	}

	sort.Slice(parts, func(i, j int) bool {
		return parts[i].N < parts[j].N
	})
	return parts, nil
}

func (s *Service) FileCreate(c *gin.Context) {
	var originalChecksum = c.Param("original_checksum")
	files, err := s.FileChunks(originalChecksum)
	if err != nil {
		s.Error(c, http.StatusInternalServerError, err)
		return
	}

	sum := sha1.New()
	size := uint64(0)
	for _, f := range files {
		b, err := fs.ReadFile(f.Path, f.Name)
		if err != nil {
			s.Error(c, http.StatusInternalServerError, err)
			return
		}
		sum.Write(b)
		size += uint64(len(b))
	}
	r := hex.EncodeToString(sum.Sum(nil))
	if r != originalChecksum {
		fmt.Printf("R=%s, O=%s\n", r, originalChecksum)
		s.Error(c, http.StatusExpectationFailed, ErrStoreMismatchChecksum)
		return
	}

	c.JSON(http.StatusOK, gin.H{
		"status":   "success",
		"checksum": originalChecksum,
		"nbParts":  len(files),
		"size":     size,
	})
}

func (s *Service) FileChunk(c *gin.Context) {
	var (
		originalChecksum = c.Param("original_checksum")
		part             = c.Param("part")
		partChecksum     = c.Param("part_checksum")
	)
	if len(originalChecksum) != 40 || len(partChecksum) != 40 {
		s.Error(c, http.StatusBadRequest, ErrStoreBadChecksum)
		return
	}

	if c.Request.ContentLength > CHUNK_SIZE {
		s.Error(c, http.StatusBadRequest, ErrStoreBadChunkSize)
		return
	}

	p, err := strconv.ParseUint(part, 10, 64)
	if err != nil || p < 1 {
		s.Error(c, http.StatusBadRequest, ErrStoreBadPartNumber)
		return
	}

	b := bytes.NewBuffer([]byte{})
	io.Copy(b, c.Request.Body)
	c.Request.Body.Close()

	sum := sha1.New()
	sum.Write(b.Bytes())
	r := hex.EncodeToString(sum.Sum(nil))

	if partChecksum != r {
		s.Error(c, http.StatusBadRequest, ErrStoreWrongPartChecksum)
		return
	}

	dir, err := s.TempDir(originalChecksum)
	if err != nil {
		s.Error(c, http.StatusInternalServerError, err)
		return
	}

	f, err := os.Create(filepath.Join(dir, part))
	if err != nil {
		s.Error(c, http.StatusInternalServerError, err)
		return
	}
	f.Write(b.Bytes())
	f.Close()

	c.JSON(http.StatusOK, gin.H{
		"status": "success",
	})
}