package biz

import (
	"context"
	"crypto/md5"
	"encoding/hex"
	"errors"
	"fmt"
	"github.com/google/uuid"
	"io"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

type MediaFile struct {
	ID            uint
	CreatedAt     time.Time
	UpdatedAt     time.Time
	Name          string
	CategoryID    int
	URL, Tag, Key string
	Size          int64
	Mime, MD5     string
	UserID        uint
}
type AttachmentCategory struct {
	ID        uint
	CreatedAt time.Time
	UpdatedAt time.Time
	Name      string
	ParentID  uint
	Children  []*AttachmentCategory
}
type UploadSession struct {
	ID                  uint
	UserID              uint
	FileName, FileHash  string
	FileSize, ChunkSize int64
	ChunkTotal          int
	Status, StorageKey  string
	MediaID             uint
}
type UploadChunk struct {
	Index int
	Hash  string
	Size  int64
}
type MediaRepo interface {
	CreateMedia(context.Context, *MediaFile) error
	FindMedia(context.Context, uint) (*MediaFile, error)
	FindMediaByHash(context.Context, uint, string) (*MediaFile, error)
	ListMedia(context.Context, int, int, string, int, string, uint) ([]*MediaFile, int64, error)
	UpdateMediaName(context.Context, uint, string) error
	DeleteMedia(context.Context, uint) error
	MediaKeyReferences(context.Context, string) (int64, error)
	CreateMediaBatch(context.Context, []*MediaFile) error
	SaveCategory(context.Context, *AttachmentCategory) error
	DeleteCategory(context.Context, uint) error
	ListCategories(context.Context) ([]*AttachmentCategory, error)
	FindUploadingSession(context.Context, uint, string) (*UploadSession, error)
	CreateUploadSession(context.Context, *UploadSession) error
	FindUploadSession(context.Context, uint) (*UploadSession, error)
	CompleteUploadSession(context.Context, uint, string, uint) error
	DeleteUploadSession(context.Context, uint) error
	UpsertChunk(context.Context, uint, *UploadChunk) error
	ListChunks(context.Context, uint) ([]*UploadChunk, error)
	DeleteChunks(context.Context, uint) error
}
type MediaUsecase struct {
	repo  MediaRepo
	files FileStorage
}

func NewMediaUsecase(repo MediaRepo, files FileStorage) *MediaUsecase {
	return &MediaUsecase{repo: repo, files: files}
}
func (uc *MediaUsecase) Repo() MediaRepo { return uc.repo }

var blockedExtensions = map[string]bool{".exe": true, ".dll": true, ".bat": true, ".cmd": true, ".sh": true, ".php": true, ".jsp": true, ".asp": true, ".aspx": true, ".html": true, ".htm": true, ".svg": true}

func validateMediaName(name string) error {
	if name == "" || filepath.Base(name) != name {
		return errors.New("文件名不合法")
	}
	if blockedExtensions[strings.ToLower(filepath.Ext(name))] {
		return errors.New("文件类型不允许上传")
	}
	return nil
}
func (uc *MediaUsecase) Upload(ctx context.Context, userID uint, name, mime string, categoryID int, reader io.Reader, save bool) (*MediaFile, error) {
	if err := validateMediaName(name); err != nil {
		return nil, err
	}
	ext := strings.ToLower(filepath.Ext(name))
	key := time.Now().Format("20060102") + "/" + uuid.NewString() + ext
	hash := md5.New()
	stored, err := uc.files.Put(ctx, key, io.TeeReader(reader, hash))
	if err != nil {
		return nil, err
	}
	media := &MediaFile{Name: name, CategoryID: categoryID, URL: stored.URL, Tag: strings.TrimPrefix(ext, "."), Key: key, Size: stored.Size, Mime: mime, MD5: hex.EncodeToString(hash.Sum(nil)), UserID: userID}
	if save {
		if err = uc.repo.CreateMedia(ctx, media); err != nil {
			_ = uc.files.Delete(ctx, key)
			return nil, err
		}
	}
	return media, nil
}
func (uc *MediaUsecase) Delete(ctx context.Context, id uint) error {
	media, err := uc.repo.FindMedia(ctx, id)
	if err != nil {
		return err
	}
	count, err := uc.repo.MediaKeyReferences(ctx, media.Key)
	if err != nil {
		return err
	}
	if count <= 1 {
		if err = uc.files.Delete(ctx, media.Key); err != nil {
			return err
		}
	}
	return uc.repo.DeleteMedia(ctx, id)
}
func (uc *MediaUsecase) InitUpload(ctx context.Context, userID uint, name, hash string, size, chunkSize int64, total int) (*UploadSession, *MediaFile, []int, error) {
	if err := validateMediaName(name); err != nil {
		return nil, nil, nil, err
	}
	if size <= 0 || chunkSize <= 0 || total <= 0 {
		return nil, nil, nil, errors.New("上传参数不合法")
	}
	if media, err := uc.repo.FindMediaByHash(ctx, userID, hash); err == nil {
		copy := *media
		copy.ID = 0
		copy.Name = name
		if err = uc.repo.CreateMedia(ctx, &copy); err == nil {
			return nil, &copy, nil, nil
		}
	}
	session, err := uc.repo.FindUploadingSession(ctx, userID, hash)
	if err != nil {
		session = &UploadSession{UserID: userID, FileName: name, FileHash: hash, FileSize: size, ChunkSize: chunkSize, ChunkTotal: total, Status: "uploading"}
		if err = uc.repo.CreateUploadSession(ctx, session); err != nil {
			return nil, nil, nil, err
		}
	}
	chunks, err := uc.repo.ListChunks(ctx, session.ID)
	if err != nil {
		return nil, nil, nil, err
	}
	indices := make([]int, 0, len(chunks))
	for _, v := range chunks {
		indices = append(indices, v.Index)
	}
	sort.Ints(indices)
	return session, nil, indices, nil
}
func (uc *MediaUsecase) SaveChunk(ctx context.Context, userID, uploadID uint, index int, expected string, reader io.Reader) error {
	session, err := uc.repo.FindUploadSession(ctx, uploadID)
	if err != nil || session.UserID != userID {
		return errors.New("上传会话不存在或无权操作")
	}
	if session.Status != "uploading" || index < 0 || index >= session.ChunkTotal {
		return errors.New("上传会话状态或分片序号不合法")
	}
	hash := md5.New()
	key := fmt.Sprintf(".chunks/%d/%08d", uploadID, index)
	stored, err := uc.files.Put(ctx, key, io.TeeReader(reader, hash))
	if err != nil {
		return err
	}
	actual := hex.EncodeToString(hash.Sum(nil))
	if !strings.EqualFold(actual, expected) {
		_ = uc.files.Delete(ctx, key)
		return errors.New("分片校验失败")
	}
	return uc.repo.UpsertChunk(ctx, uploadID, &UploadChunk{Index: index, Hash: actual, Size: stored.Size})
}
func (uc *MediaUsecase) CompleteUpload(ctx context.Context, userID, uploadID uint, mime string) (*MediaFile, error) {
	session, err := uc.repo.FindUploadSession(ctx, uploadID)
	if err != nil || session.UserID != userID {
		return nil, errors.New("上传会话不存在或无权操作")
	}
	chunks, err := uc.repo.ListChunks(ctx, uploadID)
	if err != nil || len(chunks) != session.ChunkTotal {
		return nil, errors.New("分片不完整")
	}
	sort.Slice(chunks, func(i, j int) bool { return chunks[i].Index < chunks[j].Index })
	names := make([]string, 0, len(chunks))
	for index, chunk := range chunks {
		if chunk.Index != index {
			return nil, errors.New("分片序号不连续")
		}
		names = append(names, fmt.Sprintf(".chunks/%d/%08d", uploadID, index))
	}
	ext := strings.ToLower(filepath.Ext(session.FileName))
	key := time.Now().Format("20060102") + "/" + uuid.NewString() + ext
	stored, hash, err := uc.files.Compose(ctx, names, key)
	if err != nil {
		return nil, err
	}
	if !strings.EqualFold(hash, session.FileHash) {
		_ = uc.files.Delete(ctx, key)
		return nil, errors.New("整文件校验失败")
	}
	media := &MediaFile{Name: session.FileName, URL: stored.URL, Tag: strings.TrimPrefix(ext, "."), Key: key, Size: stored.Size, Mime: mime, MD5: hash, UserID: userID}
	if err = uc.repo.CreateMedia(ctx, media); err != nil {
		_ = uc.files.Delete(ctx, key)
		return nil, err
	}
	_ = uc.repo.CompleteUploadSession(ctx, uploadID, key, media.ID)
	_ = uc.repo.DeleteChunks(ctx, uploadID)
	_ = uc.files.DeletePrefix(ctx, fmt.Sprintf(".chunks/%d", uploadID))
	return media, nil
}
func (uc *MediaUsecase) CancelUpload(ctx context.Context, userID, uploadID uint) error {
	session, err := uc.repo.FindUploadSession(ctx, uploadID)
	if err != nil || session.UserID != userID {
		return errors.New("上传会话不存在或无权操作")
	}
	_ = uc.repo.DeleteChunks(ctx, uploadID)
	_ = uc.files.DeletePrefix(ctx, fmt.Sprintf(".chunks/%d", uploadID))
	return uc.repo.DeleteUploadSession(ctx, uploadID)
}
func (uc *MediaUsecase) ListStorage(ctx context.Context, prefix, cursor string, limit int) ([]*StoredFile, string, bool, error) {
	return uc.files.List(ctx, prefix, cursor, limit)
}