package file

import (
	"errors"
	"fmt"
	"mime/multipart"
	"net/http"
	"net/url"

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

	"rill/internal/auth"
	"rill/internal/config"
	"rill/internal/httpx"
	"rill/internal/model"
	"rill/internal/utils"
)

// multipartOverhead 预留 multipart 边界与头部体积。
const multipartOverhead = 1 << 20

// ReadUpload 按配置限制请求体大小并读取 multipart 字段 file，失败时已写入响应。
func ReadUpload(c *gin.Context, cfg *config.Config) (*multipart.FileHeader, bool) {
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, cfg.MaxUploadBytes()+multipartOverhead)
	header, err := c.FormFile("file")
	if err != nil {
		var maxErr *http.MaxBytesError
		if errors.As(err, &maxErr) {
			c.JSON(http.StatusRequestEntityTooLarge, httpx.ErrorResponse{Error: "file too large"})
			return nil, false
		}
		c.JSON(http.StatusBadRequest, httpx.ErrorResponse{Error: "invalid request: file is required"})
		return nil, false
	}
	return header, true
}

// RespondSaveError 将存储错误映射为 HTTP 响应。
func RespondSaveError(c *gin.Context, err error) {
	switch {
	case errors.Is(err, ErrTooLarge):
		c.JSON(http.StatusRequestEntityTooLarge, httpx.ErrorResponse{Error: err.Error()})
	case errors.Is(err, ErrEmpty):
		c.JSON(http.StatusBadRequest, httpx.ErrorResponse{Error: err.Error()})
	default:
		httpx.RespondDBError(c, err)
	}
}

// OperatorOf 构造操作人快照。
func OperatorOf(c *gin.Context, user model.User) Operator {
	name := user.Nickname
	if name == "" {
		name = user.Username
	}
	return Operator{ID: &user.ID, Name: name, IP: utils.ClientIP(c)}
}

// @Summary      Upload a file
// @Description  Upload a file (multipart field file). Content is deduplicated by sha256; the returned file has ref_count 0 until a business reference is acquired. Size limit from storage.max_size_mb.
// @Tags         user
// @Accept       mpfd
// @Produce      json
// @Param        file  formData  file  true  "File content"
// @Success      201   {object}  model.File
// @Failure      400   {object}  httpx.ErrorResponse  "invalid request or empty file"
// @Failure      413   {object}  httpx.ErrorResponse  "file too large"
// @Security     BearerAuth
// @Failure      401  {object}  httpx.ErrorResponse  "unauthorized or session expired"
// @Failure      403  {object}  httpx.ErrorResponse  "account disabled"
// @Failure      500  {object}  httpx.ErrorResponse
// @Router       /files [post]
func Upload(db *gorm.DB, cfg *config.Config) gin.HandlerFunc {
	return func(c *gin.Context) {
		current, ok := auth.CurrentUser(c)
		if !ok {
			httpx.RespondUnauthorized(c)
			return
		}
		header, ok := ReadUpload(c, cfg)
		if !ok {
			return
		}
		src, err := header.Open()
		if err != nil {
			httpx.RespondServerError(c, err, "打开上传文件失败")
			return
		}
		defer src.Close()

		saved, err := Save(c.Request.Context(), db, cfg, OperatorOf(c, current), header.Filename, src)
		if err != nil {
			RespondSaveError(c, err)
			return
		}
		c.JSON(http.StatusCreated, saved)
	}
}

// @Summary      Delete a file
// @Description  Delete a file physically and keep the record with status 0; uploader or admin only. Files still referenced (ref_count > 0) return 409.
// @Tags         user
// @Produce      json
// @Param        id  path  int  true  "File ID"  example(1)
// @Success      204  "Deleted"
// @Failure      400  {object}  httpx.ErrorResponse  "invalid id"
// @Failure      403  {object}  httpx.ErrorResponse  "permission denied or account disabled"
// @Failure      404  {object}  httpx.ErrorResponse  "record not found"
// @Failure      409  {object}  httpx.ErrorResponse  "file is in use"
// @Security     BearerAuth
// @Failure      401  {object}  httpx.ErrorResponse  "unauthorized or session expired"
// @Failure      500  {object}  httpx.ErrorResponse
// @Router       /files/{id} [delete]
func Delete(db *gorm.DB, cfg *config.Config) gin.HandlerFunc {
	return func(c *gin.Context) {
		current, ok := auth.CurrentUser(c)
		if !ok {
			httpx.RespondUnauthorized(c)
			return
		}
		id, ok := httpx.ParseID(c)
		if !ok {
			return
		}

		ctx := c.Request.Context()
		var record model.File
		if err := db.WithContext(ctx).First(&record, id).Error; err != nil {
			httpx.RespondGetError(c, err)
			return
		}
		if record.UploaderID == nil || *record.UploaderID != current.ID {
			if !current.IsAdmin() {
				c.JSON(http.StatusForbidden, httpx.ErrorResponse{Error: "permission denied"})
				return
			}
		}
		if err := DeleteFile(ctx, db, cfg, record, OperatorOf(c, current)); err != nil {
			if errors.Is(err, ErrFileInUse) {
				c.JSON(http.StatusConflict, httpx.ErrorResponse{Error: err.Error()})
				return
			}
			httpx.RespondDBError(c, err)
			return
		}
		c.Status(http.StatusNoContent)
	}
}

// @Summary      Get file content
// @Description  Public file content. Images, videos, audio, PDF and plain text are served inline; other types are served as attachments. Disabled files return 404.
// @Tags         public
// @Produce      application/octet-stream
// @Param        id  path  int  true  "File ID"  example(1)
// @Success      200  {file}    binary
// @Failure      400  {object}  httpx.ErrorResponse  "invalid id"
// @Failure      404  {object}  httpx.ErrorResponse  "record not found"
// @Failure      500  {object}  httpx.ErrorResponse
// @Router       /files/{id} [get]
func View(db *gorm.DB, cfg *config.Config) gin.HandlerFunc {
	return func(c *gin.Context) {
		id, ok := httpx.ParseID(c)
		if !ok {
			return
		}

		var record model.File
		if err := db.WithContext(c.Request.Context()).First(&record, id).Error; err != nil {
			httpx.RespondGetError(c, err)
			return
		}
		if record.Status != model.FileStatusEnabled {
			c.JSON(http.StatusNotFound, httpx.ErrorResponse{Error: "record not found"})
			return
		}

		handle, err := Open(cfg.Storage.Dir, record)
		if err != nil {
			if errors.Is(err, ErrFileNotFound) {
				c.JSON(http.StatusNotFound, httpx.ErrorResponse{Error: "record not found"})
				return
			}
			httpx.RespondDBError(c, err)
			return
		}
		defer handle.Close()

		contentType := record.MimeType
		if contentType == "" {
			contentType = "application/octet-stream"
		}
		disposition := "attachment"
		if CanInline(contentType) {
			disposition = "inline"
		}
		c.Header("Content-Disposition", fmt.Sprintf("%s; filename*=UTF-8''%s", disposition, url.PathEscape(record.Name)))
		c.Header("X-Content-Type-Options", "nosniff")
		c.Header("Content-Security-Policy", cspHeader)
		c.Header("Cache-Control", viewCacheControl)
		c.DataFromReader(http.StatusOK, record.Size, contentType, handle, nil)
	}
}