package api

import (
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"

	"fileshare/internal/middleware"
	"fileshare/internal/model"
	"fileshare/internal/response"
	"fileshare/internal/storage"
)

// presignSessionExpires 预签名会话有效期（对齐参考 PRESIGN_SESSION_EXPIRES=900 秒）。
const presignSessionExpires = 900

// getValidSession 校验并返回预签名会话（对齐参考 _get_valid_session）：
// 不存在 404、已过期删除后 404、mode 不符 400。
func (d *Deps) getValidSession(c *gin.Context, uploadID, expectedMode string) (*model.PresignUploadSession, error) {
	ctx := c.Request.Context()
	var session model.PresignUploadSession
	err := d.DB.WithContext(ctx).
		Where("upload_id = ?", uploadID).First(&session).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, errNotFound("上传会话不存在")
	}
	if err != nil {
		return nil, errInternal("查询上传会话失败: " + err.Error())
	}
	if session.IsExpired(time.Now()) {
		_ = d.DB.WithContext(ctx).Where("upload_id = ?", uploadID).
			Delete(&model.PresignUploadSession{}).Error
		releaseStorage(ctx, d.DB, "presign:"+uploadID)
		return nil, errNotFound("上传会话已过期")
	}
	if expectedMode != "" && session.Mode != expectedMode {
		return nil, errBadRequest("此会话不支持" + expectedMode + "模式")
	}
	return &session, nil
}

// ============ POST /presign/upload/init 初始化预签名上传 ============

// presignInitRequest init 请求体（对齐参考 PresignUploadInitRequest）。
type presignInitRequest struct {
	FileName    string `json:"file_name" form:"file_name"`
	FileSize    int64  `json:"file_size" form:"file_size"`
	ExpireValue int    `json:"expire_value" form:"expire_value"`
	ExpireStyle string `json:"expire_style" form:"expire_style"`
	Code        string `json:"code" form:"code"` // 26.9：自定义提取码（init 时校验，完成时落库）
}

// presignInit 初始化预签名上传（对齐参考 presign_upload_init）：
// 引擎支持直链（S3）返回 direct + 预签名 PUT URL；否则返回 proxy + 代理地址。
func (d *Deps) presignInit(c *gin.Context) {
	if !d.requireShareLogin(c) {
		return
	}
	if !requireUploadLimit(c, d.Limiter) {
		return
	}
	var req presignInitRequest
	if err := bindJSONOrForm(c, &req); err != nil {
		respondError(c, err)
		return
	}
	safeName := storage.SanitizeFileName(req.FileName)
	if safeName == "" {
		auditRecordFailed(c, d.AuditSvc, "文件名非法")
		response.Fail(c, http.StatusBadRequest, "文件名非法")
		return
	}
	// 26.9：自定义提取码提前校验（init 时快速失败；完成请求须再次携带）
	if err := validatePickupCode(req.Code); err != nil {
		auditRecordFailed(c, d.AuditSvc, "提取码非法")
		respondError(c, err)
		return
	}
	if err := validateFileMagic(d.Cfg, safeName, "", nil); err != nil {
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件类型被拒绝")
		respondError(c, err)
		return
	}
	// 26.9 需求 ④⑩：动态策略校验（max_file_size，0=回落 uploadSize）
	if err := d.CurrentUploadPolicy().CheckSize(req.FileSize); err != nil {
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件大小超过限制")
		respondError(c, err)
		return
	}
	// M2：直传 confirm 的实际大小校验依赖真实对象，0/负值声明直接拒绝
	if req.FileSize <= 0 {
		auditRecordFailed(c, d.AuditSvc, "file_size 非法")
		response.Fail(c, http.StatusBadRequest, "file_size 必须大于 0")
		return
	}
	if req.ExpireValue <= 0 {
		req.ExpireValue = 1
	}
	if req.ExpireStyle == "" {
		req.ExpireStyle = "day"
	}
	if _, err := resolveExpire(d.Cfg, req.ExpireValue, req.ExpireStyle); err != nil {
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "过期策略非法")
		respondError(c, err)
		return
	}

	ctx := c.Request.Context()
	uploadID := uuidHex()
	resToken := "presign:" + uploadID
	if err := reserveStorage(ctx, d.DB, d.Cfg, resToken, req.FileSize, presignSessionExpires*time.Second); err != nil {
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "容量预留失败")
		respondError(c, err)
		return
	}

	dirPath, _, _, _, savePath := buildSavePath(d.Cfg, safeName, uploadID)
	mode := "proxy"
	uploadURL := "/presign/upload/proxy/" + uploadID
	putURL, err := d.Store.PresignPutURL(ctx, savePath, presignSessionExpires)
	switch {
	case err == nil:
		mode = "direct"
		uploadURL = putURL
	case errors.Is(err, storage.ErrNotSupported):
		// 引擎不支持直传：代理模式
	default:
		releaseStorage(ctx, d.DB, resToken)
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "生成预签名失败")
		respondError(c, mapStorageError(err))
		return
	}

	session := model.PresignUploadSession{
		UploadID:    uploadID,
		FileName:    safeName,
		FileSize:    req.FileSize,
		SavePath:    savePath,
		Mode:        mode,
		Engine:      d.Store.CurrentName(), // 26.9：会话归属引擎
		ExpireValue: req.ExpireValue,
		ExpireStyle: req.ExpireStyle,
		ExpiresAt:   time.Now().Add(presignSessionExpires * time.Second),
	}
	if err := d.DB.WithContext(ctx).Create(&session).Error; err != nil {
		releaseStorage(ctx, d.DB, resToken)
		auditUploadEntry(c, "", safeName, req.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "会话创建失败")
		respondError(c, errInternal("创建上传会话失败: "+err.Error()))
		return
	}

	d.Limiter.Add(c, middleware.LimitUpload)
	auditUploadEntry(c, uploadID, safeName, req.FileSize, 0)
	auditRecordSuccess(c, d.AuditSvc)
	detail := gin.H{
		"upload_id":  uploadID,
		"upload_url": uploadURL,
		"mode":       mode,
		"expires_in": presignSessionExpires,
		"file_path":  dirPath,
	}
	if mode == "proxy" {
		detail["proxy_upload_url"] = uploadURL
		detail["legacy_proxy_upload_url"] = "/api" + uploadURL
	}
	response.OK(c, detail)
}

// ============ PUT /presign/upload/proxy/{uploadID} 代理上传 ============

// presignProxy 代理模式上传（对齐参考 presign_upload_proxy）：
// 服务器接收文件并转存到存储引擎，随后立即创建分享记录。
func (d *Deps) presignProxy(c *gin.Context) {
	if !d.requireShareLogin(c) {
		return
	}
	if !requireUploadLimit(c, d.Limiter) {
		return
	}
	uploadID := c.Param("uploadID")
	session, err := d.getValidSession(c, uploadID, "proxy")
	if err != nil {
		auditUploadEntry(c, uploadID, "", 0, 0)
		auditRecordFailed(c, d.AuditSvc, err.Error())
		respondError(c, err)
		return
	}
	// 26.9：自定义提取码随代理上传表单携带（init 时已预校验）
	if err := validatePickupCode(c.PostForm("code")); err != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "提取码非法")
		respondError(c, err)
		return
	}
	ctx := c.Request.Context()
	if err := reserveStorage(ctx, d.DB, d.Cfg, "presign:"+uploadID, session.FileSize, presignSessionExpires*time.Second); err != nil {
		respondError(c, err)
		return
	}

	fh, err := c.FormFile("file")
	if err != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "缺少 file 字段")
		response.Fail(c, http.StatusBadRequest, "缺少上传文件 file 字段")
		return
	}
	// 动态策略快照（与 share/chunk 上传路径一致，消除会话窗口内的策略滞后）
	maxSize := d.CurrentUploadPolicy().MaxFileSize
	if maxSize > 0 && fh.Size > maxSize {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "大小超过限制")
		response.Fail(c, http.StatusForbidden, fmt.Sprintf("大小超过限制,最大为%s", humanSize(maxSize)))
		return
	}
	// 文件大小与声明不符（±1KB 容差，对齐参考）
	if abs64(fh.Size-session.FileSize) > 1024 {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件大小与声明不符")
		response.Fail(c, http.StatusBadRequest, "文件大小与声明不符")
		return
	}
	f, err := fh.Open()
	if err == nil {
		defer func() { _ = f.Close() }()
		if err = validateFileMagic(d.Cfg, session.FileName, fh.Header.Get("Content-Type"), readMultipartHeader(f, 64)); err == nil {
			// 26.9：落盘走会话归属引擎
			var ps storage.Storage
			ps, sErr := d.storeFor(session.Engine)
			if sErr != nil {
				err = sErr
			} else if _, err = ps.SaveFile(ctx, f, session.SavePath); err != nil {
				// 落盘失败，err 交给统一错误处理
			}
		}
	}
	if err != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件保存失败")
		if isStorageErr(err) {
			respondError(c, mapStorageError(err))
		} else {
			respondError(c, errInternal("文件保存失败: "+err.Error()))
		}
		return
	}

	code, err := d.createRecordFromSession(c, session, c.PostForm("code"))
	releaseStorage(ctx, d.DB, "presign:"+uploadID)
	if err != nil {
		if ps, sErr := d.storeFor(session.Engine); sErr == nil {
			_ = ps.DeleteFile(ctx, session.SavePath) // 26.9：清理走归属引擎
		}
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "创建分享失败")
		respondError(c, err)
		return
	}
	_ = d.DB.WithContext(ctx).Where("upload_id = ?", uploadID).
		Delete(&model.PresignUploadSession{}).Error
	d.Limiter.Add(c, middleware.LimitUpload)
	auditUploadEntry(c, code, session.FileName, session.FileSize, fh.Size)
	auditRecordSuccess(c, d.AuditSvc)
	response.OK(c, gin.H{"code": code, "name": session.FileName})
}

// ============ POST /presign/upload/confirm/{uploadID} 直传确认 ============

// presignConfirm 直传确认（对齐参考 presign_upload_confirm）：
// 客户端完成 S3 直传后调用，校验文件已存在并创建分享记录。
func (d *Deps) presignConfirm(c *gin.Context) {
	if !d.requireShareLogin(c) {
		return
	}
	if !requireUploadLimit(c, d.Limiter) {
		return
	}
	uploadID := c.Param("uploadID")
	session, err := d.getValidSession(c, uploadID, "direct")
	if err != nil {
		auditUploadEntry(c, uploadID, "", 0, 0)
		auditRecordFailed(c, d.AuditSvc, err.Error())
		respondError(c, err)
		return
	}
	ctx := c.Request.Context()
	if err := reserveStorage(ctx, d.DB, d.Cfg, "presign:"+uploadID, session.FileSize, presignSessionExpires*time.Second); err != nil {
		respondError(c, err)
		return
	}

	// 26.9：直传文件存在性按会话归属引擎检查（直传可能落在旧引擎）
	psCheck, sErr := d.storeFor(session.Engine)
	if sErr != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "存储引擎不可用: "+sErr.Error())
		respondError(c, mapStorageError(sErr))
		return
	}
	// 26.9：自定义提取码随确认请求携带（query 或 JSON/form body，均可选）
	customCode := c.Query("code")
	if customCode == "" && c.Request.Body != nil && c.Request.ContentLength != 0 {
		var fin struct {
			Code string `json:"code" form:"code"`
		}
		if err := bindJSONOrForm(c, &fin); err != nil {
			respondError(c, err)
			return
		}
		customCode = fin.Code
	}

	exists, err := psCheck.FileExists(ctx, session.SavePath)
	if err == nil && !exists {
		err = errNotFound("文件未上传或上传失败")
	}
	if err != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件未上传或上传失败")
		respondError(c, err)
		return
	}

	// M2 修复：直传内容不经过服务器，confirm 必须核实实际大小与内容类型。
	meta, head, hErr := psCheck.HeadMeta(ctx, session.SavePath, 64)
	if hErr != nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件信息读取失败")
		respondError(c, mapStorageError(hErr))
		return
	}
	if meta == nil {
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件未上传或上传失败")
		respondError(c, errNotFound("文件未上传或上传失败"))
		return
	}
	// 大小上限：实际大小超过策略上限 → 删除对象并 403（防绕过 max_file_size / storageLimit）
	maxSize := d.CurrentUploadPolicy().MaxFileSize
	if maxSize > 0 && meta.Size > maxSize {
		_ = psCheck.DeleteFile(ctx, session.SavePath)
		releaseStorage(ctx, d.DB, "presign:"+uploadID)
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "实际文件大小超过限制")
		respondError(c, errForbidden(fmt.Sprintf("大小超过限制,最大为%s", humanSize(maxSize))))
		return
	}
	// 大小与声明不符（±1KB 容差，对齐 proxy 模式）：超差删除对象并 400
	if abs64(meta.Size-session.FileSize) > 1024 {
		_ = psCheck.DeleteFile(ctx, session.SavePath)
		releaseStorage(ctx, d.DB, "presign:"+uploadID)
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件大小与声明不符")
		respondError(c, errBadRequest("文件大小与声明不符"))
		return
	}
	// 内容类型防伪造（对齐 proxy 模式 magic bytes 校验）
	if err := validateFileMagic(d.Cfg, session.FileName, "", head); err != nil {
		_ = psCheck.DeleteFile(ctx, session.SavePath)
		releaseStorage(ctx, d.DB, "presign:"+uploadID)
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "文件内容校验失败")
		respondError(c, err)
		return
	}

	code, err := d.createRecordFromSession(c, session, customCode)
	releaseStorage(ctx, d.DB, "presign:"+uploadID)
	if err != nil {
		if ps, sErr := d.storeFor(session.Engine); sErr == nil {
			_ = ps.DeleteFile(ctx, session.SavePath) // 26.9：清理走归属引擎
		}
		auditUploadEntry(c, uploadID, session.FileName, session.FileSize, 0)
		auditRecordFailed(c, d.AuditSvc, "创建分享失败")
		respondError(c, err)
		return
	}
	_ = d.DB.WithContext(ctx).Where("upload_id = ?", uploadID).
		Delete(&model.PresignUploadSession{}).Error
	d.Limiter.Add(c, middleware.LimitUpload)
	auditUploadEntry(c, code, session.FileName, session.FileSize, session.FileSize)
	auditRecordSuccess(c, d.AuditSvc)
	response.OK(c, gin.H{"code": code, "name": session.FileName})
}

// createRecordFromSession 依据预签名会话创建分享记录（对齐参考 create_file_record）。
func (d *Deps) createRecordFromSession(c *gin.Context, session *model.PresignUploadSession, customCode string) (string, error) {
	exp, err := resolveExpire(d.Cfg, session.ExpireValue, session.ExpireStyle)
	if err != nil {
		return "", err
	}
	// 26.9：完成请求的自定义提取码兜底校验（init 已验，防只发完成请求绕过）
	if err := validatePickupCode(customCode); err != nil {
		return "", err
	}
	ctx := c.Request.Context()
	code, err := pickCustomCode(ctx, d.DB, d.Cfg, customCode)
	if err != nil {
		return "", err
	}
	dir, name := splitDirBase(session.SavePath)
	ext := baseExt(name)
	fc := model.FileCodes{
		Code:         code,
		Prefix:       trimExt(name),
		Suffix:       ext,
		UUIDFileName: &name,
		FilePath:     &dir,
		Size:         session.FileSize,
		ExpiredAt:    exp.ExpiredAt,
		ExpiredCount: exp.ExpiredCount,
		UsedCount:    exp.UsedCount,
		Engine:       session.Engine, // 26.9：归属引擎戳
	}
	if err := d.DB.WithContext(ctx).Create(&fc).Error; err != nil {
		return "", mapCodeConflict(err) // 26.9：并发占用自定义码 → 友好 400
	}
	return code, nil
}

// ============ GET /presign/upload/status/{uploadID} ============

// presignStatus 查询预签名会话状态（对齐参考 presign_upload_status）。
func (d *Deps) presignStatus(c *gin.Context) {
	if !d.requireShareLogin(c) {
		return
	}
	uploadID := c.Param("uploadID")
	ctx := c.Request.Context()
	var session model.PresignUploadSession
	if err := d.DB.WithContext(ctx).
		Where("upload_id = ?", uploadID).First(&session).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			response.Fail(c, http.StatusNotFound, "上传会话不存在")
			return
		}
		respondError(c, errInternal("查询上传会话失败: "+err.Error()))
		return
	}
	response.OK(c, gin.H{
		"upload_id":  session.UploadID,
		"file_name":  session.FileName,
		"file_size":  session.FileSize,
		"mode":       session.Mode,
		"created_at": session.CreatedAt.Format(time.RFC3339),
		"expires_at": session.ExpiresAt.Format(time.RFC3339),
		"is_expired": session.IsExpired(time.Now()),
	})
}

// ============ DELETE /presign/upload/{uploadID} 取消会话 ============

// presignCancel 取消预签名上传会话（对齐参考 presign_upload_cancel）：
// 直传模式尽力清理已直传的文件。
func (d *Deps) presignCancel(c *gin.Context) {
	if !d.requireShareLogin(c) {
		return
	}
	uploadID := c.Param("uploadID")
	ctx := c.Request.Context()
	session, err := d.getValidSession(c, uploadID, "")
	if err != nil {
		respondError(c, err)
		return
	}
	if session.Mode == "direct" {
		// 26.9：清理走会话归属引擎
		if ps, sErr := d.storeFor(session.Engine); sErr == nil {
			if exists, eErr := ps.FileExists(ctx, session.SavePath); eErr == nil && exists {
				_ = ps.DeleteFile(ctx, session.SavePath)
			}
		}
	}
	if err := d.DB.WithContext(ctx).Where("upload_id = ?", uploadID).
		Delete(&model.PresignUploadSession{}).Error; err != nil {
		respondError(c, errInternal("取消上传会话失败: "+err.Error()))
		return
	}
	releaseStorage(ctx, d.DB, "presign:"+uploadID)
	response.OK(c, gin.H{"message": "上传会话已取消"})
}

// ============ 杂项 ============

// abs64 绝对值。
func abs64(n int64) int64 {
	if n < 0 {
		return -n
	}
	return n
}

// isStorageErr 判断是否为存储层哨兵错误（含 %w 包装）。
func isStorageErr(err error) bool {
	return err != nil && (errors.Is(err, storage.ErrNotFound) ||
		errors.Is(err, storage.ErrInvalidPath) ||
		errors.Is(err, storage.ErrUnavailable) ||
		errors.Is(err, storage.ErrNotSupported) ||
		errors.Is(err, storage.ErrRangeNotSatisfiable) ||
		errors.Is(err, storage.ErrHashMismatch))
}