package storage

import (
	"context"
	"errors"
	"fmt"
	"io"
	"mime"
	"net/http"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/google/uuid"
	"github.com/minio/minio-go/v7"
	"github.com/minio/minio-go/v7/pkg/credentials"
)

type Config struct {
	Endpoint  string
	AccessKey string
	SecretKey string
	Bucket    string
	UseSSL    bool
}

type Storage struct {
	cfg    Config
	client *minio.Client
}

type ObjectInfo struct {
	Size        int64
	ContentType string
}

func New(cfg Config) (*Storage, error) {
	if cfg.Endpoint == "" || cfg.AccessKey == "" || cfg.SecretKey == "" {
		return &Storage{cfg: cfg}, nil
	}
	cli, err := minio.New(cfg.Endpoint, &minio.Options{
		Creds:  credentials.NewStaticV4(cfg.AccessKey, cfg.SecretKey, ""),
		Secure: cfg.UseSSL,
	})
	if err != nil {
		return nil, fmt.Errorf("init minio client: %w", err)
	}
	return &Storage{cfg: cfg, client: cli}, nil
}

func (s *Storage) Configured() bool {
	return s.client != nil && s.cfg.Bucket != ""
}

func (s *Storage) EnsureBucket(ctx context.Context) error {
	if !s.Configured() {
		return nil
	}
	exists, err := s.client.BucketExists(ctx, s.cfg.Bucket)
	if err != nil {
		return fmt.Errorf("check bucket: %w", err)
	}
	if exists {
		return nil
	}
	return s.client.MakeBucket(ctx, s.cfg.Bucket, minio.MakeBucketOptions{})
}

func (s *Storage) Check(ctx context.Context) error {
	if !s.Configured() {
		return errors.New("storage not configured")
	}
	exists, err := s.client.BucketExists(ctx, s.cfg.Bucket)
	if err != nil {
		return fmt.Errorf("check bucket: %w", err)
	}
	if !exists {
		return fmt.Errorf("bucket %q does not exist", s.cfg.Bucket)
	}
	return nil
}

func GenerateKey(ownerID, filename string) string {
	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(filename), "."))
	if !AllowedExtension(ext) {
		ext = "bin"
	}
	return fmt.Sprintf("%s/%s.%s", ownerID, uuid.NewString(), ext)
}

func AllowedExtension(ext string) bool {
	switch strings.ToLower(ext) {
	case "doc", "docx", "xls", "xlsx", "xlsm", "ppt", "pptx", "ods", "odt", "odp",
		"pdf", "png", "jpg", "jpeg", "webp", "gif", "mp4", "webm", "mov", "m4v", "mp3", "wav", "ogg":
		return true
	default:
		return false
	}
}

func GuessContentType(filename, clientType string) string {
	if clientType != "" && clientType != "application/octet-stream" {
		return clientType
	}
	if ext := filepath.Ext(filename); ext != "" {
		if v := mime.TypeByExtension(ext); v != "" {
			return v
		}
	}
	return "application/octet-stream"
}

func (s *Storage) PutObject(ctx context.Context, key string, body io.Reader, size int64, contentType string) error {
	if !s.Configured() {
		return errors.New("storage not configured")
	}
	_, err := s.client.PutObject(ctx, s.cfg.Bucket, key, body, size, minio.PutObjectOptions{
		ContentType: contentType,
	})
	return err
}

func (s *Storage) Stat(ctx context.Context, key string) (*ObjectInfo, error) {
	if !s.Configured() {
		return nil, errors.New("storage not configured")
	}
	info, err := s.client.StatObject(ctx, s.cfg.Bucket, key, minio.StatObjectOptions{})
	if err != nil {
		return nil, err
	}
	return &ObjectInfo{Size: info.Size, ContentType: info.ContentType}, nil
}

func (s *Storage) GetObject(ctx context.Context, key string, rangeStart, rangeEnd int64) (io.ReadCloser, *ObjectInfo, error) {
	if !s.Configured() {
		return nil, nil, errors.New("storage not configured")
	}
	opts := minio.GetObjectOptions{}
	if rangeStart > 0 || rangeEnd > 0 {
		_ = opts.SetRange(rangeStart, rangeEnd)
	}
	obj, err := s.client.GetObject(ctx, s.cfg.Bucket, key, opts)
	if err != nil {
		return nil, nil, err
	}
	info, err := obj.Stat()
	if err != nil {
		_ = obj.Close()
		return nil, nil, err
	}
	return obj, &ObjectInfo{Size: info.Size, ContentType: info.ContentType}, nil
}

func (s *Storage) RemoveObject(ctx context.Context, key string) error {
	if !s.Configured() {
		return errors.New("storage not configured")
	}
	return s.client.RemoveObject(ctx, s.cfg.Bucket, key, minio.RemoveObjectOptions{})
}

func ParseRange(header string, totalSize int64) (start, end int64, ok bool) {
	if !strings.HasPrefix(header, "bytes=") {
		return 0, 0, false
	}
	parts := strings.SplitN(strings.TrimPrefix(header, "bytes="), "-", 2)
	if len(parts) != 2 {
		return 0, 0, false
	}
	if parts[0] == "" {
		n, err := strconv.ParseInt(parts[1], 10, 64)
		if err != nil || n <= 0 || n > totalSize {
			return 0, 0, false
		}
		return totalSize - n, totalSize - 1, true
	}
	start, err := strconv.ParseInt(parts[0], 10, 64)
	if err != nil || start < 0 || start >= totalSize {
		return 0, 0, false
	}
	if parts[1] == "" {
		return start, totalSize - 1, true
	}
	end, err = strconv.ParseInt(parts[1], 10, 64)
	if err != nil || end < start {
		return 0, 0, false
	}
	if end >= totalSize {
		end = totalSize - 1
	}
	return start, end, true
}

func WriteRangeResponse(w http.ResponseWriter, contentType string, totalSize, start, end int64, hasRange bool) {
	w.Header().Set("Content-Type", contentType)
	w.Header().Set("Accept-Ranges", "bytes")
	if hasRange {
		w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, totalSize))
		w.Header().Set("Content-Length", strconv.FormatInt(end-start+1, 10))
		w.WriteHeader(http.StatusPartialContent)
		return
	}
	w.Header().Set("Content-Length", strconv.FormatInt(totalSize, 10))
	w.WriteHeader(http.StatusOK)
}