package file

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	"mime/multipart"
	"net/url"
	"path"
	"strings"
	"sync"
	"time"

	"hfb_sys/backend/internal/config"

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

type Storage struct {
	client      *minio.Client
	bucket      string
	bucketMu    sync.Mutex
	bucketReady bool
	mirror      *Storage
	mirrorErr   error
}

type Object struct {
	Reader      io.ReadCloser
	ContentType string
	Size        int64
}

func NewStorage(cfg config.StorageConfig) (*Storage, error) {
	client, err := NewStorageClient(cfg)
	if err != nil {
		return nil, err
	}
	storage := &Storage{client: client, bucket: cfg.Bucket}
	if err := storage.ensureBucket(context.Background()); err != nil {
		return storage, err
	}
	return storage, nil
}

// NewStorageClient 根据项目存储配置创建 S3 兼容客户端，供迁移工具复用。
func NewStorageClient(cfg config.StorageConfig) (*minio.Client, error) {
	endpoint, secure, err := normalizeEndpoint(cfg.Endpoint)
	if err != nil {
		return nil, err
	}
	lookup, err := parseBucketLookup(cfg.BucketLookup)
	if err != nil {
		return nil, err
	}
	return minio.New(endpoint, &minio.Options{
		Creds:        credentials.NewStaticV4(cfg.AccessKeyID, cfg.SecretAccessKey, ""),
		Secure:       secure,
		Region:       cfg.Region,
		BucketLookup: lookup,
	})
}

func parseBucketLookup(raw string) (minio.BucketLookupType, error) {
	switch strings.ToLower(strings.TrimSpace(raw)) {
	case "", "auto":
		return minio.BucketLookupAuto, nil
	case "dns":
		return minio.BucketLookupDNS, nil
	case "path":
		return minio.BucketLookupPath, nil
	default:
		return minio.BucketLookupAuto, fmt.Errorf("unsupported storage bucket lookup: %s", raw)
	}
}

// SetMirror 启用迁移期间的同步双写。镜像端不可用时上传会失败，避免出现未同步的业务文件。
func (s *Storage) SetMirror(mirror *Storage, err error) {
	s.mirror = mirror
	s.mirrorErr = err
}

func (s *Storage) Put(ctx context.Context, scene string, header *multipart.FileHeader, reader io.Reader, contentType string) (string, error) {
	key, err := newObjectKey(scene, header.Filename)
	if err != nil {
		return "", err
	}
	if err := s.PutObject(ctx, key, reader, header.Size, contentType, map[string]string{
		"original-filename": header.Filename,
	}); err != nil {
		return "", err
	}
	return key, nil
}

func (s *Storage) PutObject(ctx context.Context, key string, reader io.Reader, size int64, contentType string, metadata map[string]string) error {
	if s.mirrorErr != nil {
		return fmt.Errorf("storage mirror unavailable: %w", s.mirrorErr)
	}
	if s.mirror == nil {
		return s.putObject(ctx, key, reader, size, contentType, metadata)
	}

	// 当前文件上传大小被限制在 10MB；镜像写入前缓存在内存中，确保两个端点得到完全相同的字节流。
	data, err := io.ReadAll(reader)
	if err != nil {
		return err
	}
	if err := s.putObject(ctx, key, bytes.NewReader(data), int64(len(data)), contentType, metadata); err != nil {
		return err
	}
	if err := s.mirror.putObject(ctx, key, bytes.NewReader(data), int64(len(data)), contentType, metadata); err != nil {
		return fmt.Errorf("storage mirror upload failed: %w", err)
	}
	return nil
}

func (s *Storage) putObject(ctx context.Context, key string, reader io.Reader, size int64, contentType string, metadata map[string]string) error {
	if err := s.ensureBucketReady(ctx); err != nil {
		return err
	}
	_, err := s.client.PutObject(ctx, s.bucket, key, reader, size, minio.PutObjectOptions{
		ContentType:  contentType,
		UserMetadata: sanitizeObjectMetadata(metadata),
	})
	if isNoSuchBucketError(err) && rewindReader(reader) == nil {
		s.markBucketNotReady()
		if readyErr := s.ensureBucketReady(ctx); readyErr != nil {
			return readyErr
		}
		_, err = s.client.PutObject(ctx, s.bucket, key, reader, size, minio.PutObjectOptions{
			ContentType:  contentType,
			UserMetadata: sanitizeObjectMetadata(metadata),
		})
	}
	return err
}

func (s *Storage) Get(ctx context.Context, key string) (*Object, error) {
	object, err := s.client.GetObject(ctx, s.bucket, key, minio.GetObjectOptions{})
	if err != nil {
		return nil, err
	}
	info, err := object.Stat()
	if err != nil {
		_ = object.Close()
		return nil, err
	}
	return &Object{
		Reader:      object,
		ContentType: info.ContentType,
		Size:        info.Size,
	}, nil
}

func (s *Storage) ensureBucket(ctx context.Context) error {
	exists, err := s.client.BucketExists(ctx, s.bucket)
	if err != nil {
		errResp := minio.ToErrorResponse(err)
		if errResp.Code != "NoSuchBucket" && !strings.Contains(strings.ToLower(err.Error()), "bucket does not exist") {
			return err
		}
	}
	if exists {
		s.bucketReady = true
		return nil
	}
	if err := s.client.MakeBucket(ctx, s.bucket, minio.MakeBucketOptions{}); err != nil {
		return err
	}
	s.bucketReady = true
	return nil
}

func (s *Storage) ensureBucketReady(ctx context.Context) error {
	s.bucketMu.Lock()
	defer s.bucketMu.Unlock()
	if s.bucketReady {
		return nil
	}
	return s.ensureBucket(ctx)
}

func (s *Storage) markBucketNotReady() {
	s.bucketMu.Lock()
	defer s.bucketMu.Unlock()
	s.bucketReady = false
}

func isNoSuchBucketError(err error) bool {
	if err == nil {
		return false
	}
	errResp := minio.ToErrorResponse(err)
	if errResp.Code == "NoSuchBucket" {
		return true
	}
	return strings.Contains(strings.ToLower(err.Error()), "bucket does not exist")
}

func rewindReader(reader io.Reader) error {
	seeker, ok := reader.(io.Seeker)
	if !ok {
		return fmt.Errorf("reader cannot rewind")
	}
	_, err := seeker.Seek(0, io.SeekStart)
	return err
}

func sanitizeObjectMetadata(metadata map[string]string) map[string]string {
	if len(metadata) == 0 {
		return nil
	}
	sanitized := make(map[string]string, len(metadata))
	for key, value := range metadata {
		key = strings.TrimSpace(key)
		if key == "" {
			continue
		}
		// MinIO/S3 用户元数据会作为 HTTP header 发送，值统一转义为 ASCII，避免中文文件名导致上传失败。
		sanitized[key] = url.QueryEscape(value)
	}
	return sanitized
}

func normalizeEndpoint(raw string) (string, bool, error) {
	parsed, err := url.Parse(raw)
	if err != nil {
		return "", false, err
	}
	if parsed.Scheme == "" {
		return raw, false, nil
	}
	return parsed.Host, parsed.Scheme == "https", nil
}

func newObjectKey(scene string, filename string) (string, error) {
	if scene == "" {
		scene = "misc"
	}
	scene = strings.ToLower(scene)
	now := time.Now()
	token := make([]byte, 12)
	if _, err := rand.Read(token); err != nil {
		return "", err
	}
	ext := strings.ToLower(path.Ext(filename))
	return fmt.Sprintf("%s/%04d/%02d/%02d/%s%s", scene, now.Year(), now.Month(), now.Day(), hex.EncodeToString(token), ext), nil
}