// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.

package api

import (
	"bytes"
	"image"
	"image/color"
	"image/draw"
	_ "image/gif"
	"image/jpeg"
	"io"
	"net/http"
	"net/url"
	"path/filepath"
	"strconv"
	"strings"

	l4g "github.com/alecthomas/log4go"
	"github.com/disintegration/imaging"
	"github.com/gorilla/mux"
	"github.com/mattermost/platform/app"
	"github.com/mattermost/platform/model"
	"github.com/mattermost/platform/utils"
	"github.com/rwcarlsen/goexif/exif"
	_ "golang.org/x/image/bmp"
)

const (
	/*
	  EXIF Image Orientations
	  1        2       3      4         5            6           7          8

	  888888  888888      88  88      8888888888  88                  88  8888888888
	  88          88      88  88      88  88      88  88          88  88      88  88
	  8888      8888    8888  8888    88          8888888888  8888888888          88
	  88          88      88  88
	  88          88  888888  888888
	*/
	Upright            = 1
	UprightMirrored    = 2
	UpsideDown         = 3
	UpsideDownMirrored = 4
	RotatedCWMirrored  = 5
	RotatedCCW         = 6
	RotatedCCWMirrored = 7
	RotatedCW          = 8

	MaxImageSize = 6048 * 4032 // 24 megapixels, roughly 36MB as a raw image
)

func InitFile() {
	l4g.Debug(utils.T("api.file.init.debug"))

	BaseRoutes.TeamFiles.Handle("/upload", ApiUserRequired(uploadFile)).Methods("POST")

	BaseRoutes.NeedFile.Handle("/get", ApiUserRequiredTrustRequester(getFile)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_thumbnail", ApiUserRequiredTrustRequester(getFileThumbnail)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_preview", ApiUserRequiredTrustRequester(getFilePreview)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_info", ApiUserRequired(getFileInfo)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_public_link", ApiUserRequired(getPublicLink)).Methods("GET")

	BaseRoutes.Public.Handle("/files/{file_id:[A-Za-z0-9]+}/get", ApiAppHandlerTrustRequesterIndependent(getPublicFile)).Methods("GET")
	BaseRoutes.Public.Handle("/files/get/{team_id:[A-Za-z0-9]+}/{channel_id:[A-Za-z0-9]+}/{user_id:[A-Za-z0-9]+}/{filename:([A-Za-z0-9]+/)?.+(\\.[A-Za-z0-9]{3,})?}", ApiAppHandlerTrustRequesterIndependent(getPublicFileOld)).Methods("GET")
}

func uploadFile(c *Context, w http.ResponseWriter, r *http.Request) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		c.Err = model.NewLocAppError("uploadFile", "api.file.upload_file.storage.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	if r.ContentLength > *utils.Cfg.FileSettings.MaxFileSize {
		c.Err = model.NewLocAppError("uploadFile", "api.file.upload_file.too_large.app_error", nil, "")
		c.Err.StatusCode = http.StatusRequestEntityTooLarge
		return
	}

	if err := r.ParseMultipartForm(*utils.Cfg.FileSettings.MaxFileSize); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	m := r.MultipartForm

	props := m.Value
	if len(props["channel_id"]) == 0 {
		c.SetInvalidParam("uploadFile", "channel_id")
		return
	}
	channelId := props["channel_id"][0]
	if len(channelId) == 0 {
		c.SetInvalidParam("uploadFile", "channel_id")
		return
	}

	if !HasPermissionToChannelContext(c, channelId, model.PERMISSION_UPLOAD_FILE) {
		return
	}

	resStruct := &model.FileUploadResponse{
		FileInfos: []*model.FileInfo{},
		ClientIds: []string{},
	}

	previewPathList := []string{}
	thumbnailPathList := []string{}
	imageDataList := [][]byte{}

	for i, fileHeader := range m.File["files"] {
		file, fileErr := fileHeader.Open()
		defer file.Close()
		if fileErr != nil {
			http.Error(w, fileErr.Error(), http.StatusInternalServerError)
			return
		}

		buf := bytes.NewBuffer(nil)
		io.Copy(buf, file)
		data := buf.Bytes()

		info, err := doUploadFile(c.TeamId, channelId, c.Session.UserId, fileHeader.Filename, data)
		if err != nil {
			c.Err = err
			return
		}

		if info.PreviewPath != "" || info.ThumbnailPath != "" {
			previewPathList = append(previewPathList, info.PreviewPath)
			thumbnailPathList = append(thumbnailPathList, info.ThumbnailPath)
			imageDataList = append(imageDataList, data)
		}

		resStruct.FileInfos = append(resStruct.FileInfos, info)

		if len(m.Value["client_ids"]) > 0 {
			resStruct.ClientIds = append(resStruct.ClientIds, m.Value["client_ids"][i])
		}
	}

	handleImages(previewPathList, thumbnailPathList, imageDataList)

	w.Write([]byte(resStruct.ToJson()))
}

func doUploadFile(teamId string, channelId string, userId string, rawFilename string, data []byte) (*model.FileInfo, *model.AppError) {
	filename := filepath.Base(rawFilename)

	info, err := model.GetInfoForBytes(filename, data)
	if err != nil {
		err.StatusCode = http.StatusBadRequest
		return nil, err
	}

	info.Id = model.NewId()
	info.CreatorId = userId

	pathPrefix := "teams/" + teamId + "/channels/" + channelId + "/users/" + userId + "/" + info.Id + "/"
	info.Path = pathPrefix + filename

	if info.IsImage() {
		// Check dimensions before loading the whole thing into memory later on
		if info.Width*info.Height > MaxImageSize {
			err := model.NewLocAppError("uploadFile", "api.file.upload_file.large_image.app_error", map[string]interface{}{"Filename": filename}, "")
			err.StatusCode = http.StatusBadRequest
			return nil, err
		}

		nameWithoutExtension := filename[:strings.LastIndex(filename, ".")]
		info.PreviewPath = pathPrefix + nameWithoutExtension + "_preview.jpg"
		info.ThumbnailPath = pathPrefix + nameWithoutExtension + "_thumb.jpg"
	}

	if err := app.WriteFile(data, info.Path); err != nil {
		return nil, err
	}

	if result := <-app.Srv.Store.FileInfo().Save(info); result.Err != nil {
		return nil, result.Err
	}

	return info, nil
}

func handleImages(previewPathList []string, thumbnailPathList []string, fileData [][]byte) {
	for i, data := range fileData {
		go func(i int, data []byte) {
			img, width, height := prepareImage(fileData[i])
			if img != nil {
				go generateThumbnailImage(*img, thumbnailPathList[i], width, height)
				go generatePreviewImage(*img, previewPathList[i], width)
			}
		}(i, data)
	}
}

func prepareImage(fileData []byte) (*image.Image, int, int) {
	// Decode image bytes into Image object
	img, imgType, err := image.Decode(bytes.NewReader(fileData))
	if err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.decode.error"), err)
		return nil, 0, 0
	}

	width := img.Bounds().Dx()
	height := img.Bounds().Dy()

	// Fill in the background of a potentially-transparent png file as white
	if imgType == "png" {
		dst := image.NewRGBA(img.Bounds())
		draw.Draw(dst, dst.Bounds(), image.NewUniform(color.White), image.Point{}, draw.Src)
		draw.Draw(dst, dst.Bounds(), img, img.Bounds().Min, draw.Over)
		img = dst
	}

	// Flip the image to be upright
	orientation, _ := getImageOrientation(fileData)

	switch orientation {
	case UprightMirrored:
		img = imaging.FlipH(img)
	case UpsideDown:
		img = imaging.Rotate180(img)
	case UpsideDownMirrored:
		img = imaging.FlipV(img)
	case RotatedCWMirrored:
		img = imaging.Transpose(img)
	case RotatedCCW:
		img = imaging.Rotate270(img)
	case RotatedCCWMirrored:
		img = imaging.Transverse(img)
	case RotatedCW:
		img = imaging.Rotate90(img)
	}

	return &img, width, height
}

func getImageOrientation(imageData []byte) (int, error) {
	if exifData, err := exif.Decode(bytes.NewReader(imageData)); err != nil {
		return Upright, err
	} else {
		if tag, err := exifData.Get("Orientation"); err != nil {
			return Upright, err
		} else {
			orientation, err := tag.Int(0)
			if err != nil {
				return Upright, err
			} else {
				return orientation, nil
			}
		}
	}
}

func generateThumbnailImage(img image.Image, thumbnailPath string, width int, height int) {
	thumbWidth := float64(utils.Cfg.FileSettings.ThumbnailWidth)
	thumbHeight := float64(utils.Cfg.FileSettings.ThumbnailHeight)
	imgWidth := float64(width)
	imgHeight := float64(height)

	var thumbnail image.Image
	if imgHeight < thumbHeight && imgWidth < thumbWidth {
		thumbnail = img
	} else if imgHeight/imgWidth < thumbHeight/thumbWidth {
		thumbnail = imaging.Resize(img, 0, utils.Cfg.FileSettings.ThumbnailHeight, imaging.Lanczos)
	} else {
		thumbnail = imaging.Resize(img, utils.Cfg.FileSettings.ThumbnailWidth, 0, imaging.Lanczos)
	}

	buf := new(bytes.Buffer)
	if err := jpeg.Encode(buf, thumbnail, &jpeg.Options{Quality: 90}); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.encode_jpeg.error"), thumbnailPath, err)
		return
	}

	if err := app.WriteFile(buf.Bytes(), thumbnailPath); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.upload_thumb.error"), thumbnailPath, err)
		return
	}
}

func generatePreviewImage(img image.Image, previewPath string, width int) {
	var preview image.Image
	if width > int(utils.Cfg.FileSettings.PreviewWidth) {
		preview = imaging.Resize(img, utils.Cfg.FileSettings.PreviewWidth, utils.Cfg.FileSettings.PreviewHeight, imaging.Lanczos)
	} else {
		preview = img
	}

	buf := new(bytes.Buffer)

	if err := jpeg.Encode(buf, preview, &jpeg.Options{Quality: 90}); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.encode_preview.error"), previewPath, err)
		return
	}

	if err := app.WriteFile(buf.Bytes(), previewPath); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.upload_preview.error"), previewPath, err)
		return
	}
}

func getFile(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if data, err := app.ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, info.MimeType, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileThumbnail(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if info.ThumbnailPath == "" {
		c.Err = model.NewLocAppError("getFileThumbnail", "api.file.get_file_thumbnail.no_thumbnail.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := app.ReadFile(info.ThumbnailPath); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, "", data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFilePreview(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if info.PreviewPath == "" {
		c.Err = model.NewLocAppError("getFilePreview", "api.file.get_file_preview.no_preview.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := app.ReadFile(info.PreviewPath); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, "", data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileInfo(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	w.Header().Set("Cache-Control", "max-age=2592000, public")

	w.Write([]byte(info.ToJson()))
}

func getPublicFile(c *Context, w http.ResponseWriter, r *http.Request) {
	if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	info, err := getFileInfoForRequest(c, r, false)
	if err != nil {
		c.Err = err
		return
	}

	hash := r.URL.Query().Get("h")

	if len(hash) > 0 {
		correctHash := app.GeneratePublicLinkHash(info.Id, *utils.Cfg.FileSettings.PublicLinkSalt)

		if hash != correctHash {
			c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
			c.Err.StatusCode = http.StatusBadRequest
			return
		}
	} else {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := app.ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, info.MimeType, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileInfoForRequest(c *Context, r *http.Request, requireFileVisible bool) (*model.FileInfo, *model.AppError) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		err := model.NewLocAppError("getFileInfoForRequest", "api.file.get_file_info_for_request.storage.app_error", nil, "")
		err.StatusCode = http.StatusNotImplemented
		return nil, err
	}

	params := mux.Vars(r)

	fileId := params["file_id"]
	if len(fileId) != 26 {
		return nil, NewInvalidParamError("getFileInfoForRequest", "file_id")
	}

	var info *model.FileInfo
	if result := <-app.Srv.Store.FileInfo().Get(fileId); result.Err != nil {
		return nil, result.Err
	} else {
		info = result.Data.(*model.FileInfo)
	}

	// only let users access files visible in a channel, unless they're the one who uploaded the file
	if info.CreatorId != c.Session.UserId {
		if len(info.PostId) == 0 {
			err := model.NewLocAppError("getFileInfoForRequest", "api.file.get_file_info_for_request.no_post.app_error", nil, "file_id="+fileId)
			err.StatusCode = http.StatusBadRequest
			return nil, err
		}

		if requireFileVisible {
			if !HasPermissionToChannelByPostContext(c, info.PostId, model.PERMISSION_READ_CHANNEL) {
				return nil, c.Err
			}
		}
	}

	return info, nil
}

func getPublicFileOld(c *Context, w http.ResponseWriter, r *http.Request) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_public_file_old.storage.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	} else if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	params := mux.Vars(r)

	teamId := params["team_id"]
	channelId := params["channel_id"]
	userId := params["user_id"]
	filename := params["filename"]

	hash := r.URL.Query().Get("h")

	if len(hash) > 0 {
		correctHash := app.GeneratePublicLinkHash(filename, *utils.Cfg.FileSettings.PublicLinkSalt)

		if hash != correctHash {
			c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
			c.Err.StatusCode = http.StatusBadRequest
			return
		}
	} else {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	path := "teams/" + teamId + "/channels/" + channelId + "/users/" + userId + "/" + filename

	var info *model.FileInfo
	if result := <-app.Srv.Store.FileInfo().GetByPath(path); result.Err != nil {
		c.Err = result.Err
		return
	} else {
		info = result.Data.(*model.FileInfo)
	}

	if len(info.PostId) == 0 {
		c.Err = model.NewLocAppError("getPublicFileOld", "api.file.get_public_file_old.no_post.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := app.ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, info.MimeType, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func writeFileResponse(filename string, contentType string, bytes []byte, w http.ResponseWriter, r *http.Request) *model.AppError {
	w.Header().Set("Cache-Control", "max-age=2592000, public")
	w.Header().Set("Content-Length", strconv.Itoa(len(bytes)))

	if contentType != "" {
		w.Header().Set("Content-Type", contentType)
	} else {
		w.Header().Del("Content-Type") // Content-Type will be set automatically by the http writer
	}

	w.Header().Set("Content-Disposition", "attachment;filename=\""+filename+"\"; filename*=UTF-8''"+url.QueryEscape(filename))

	// prevent file links from being embedded in iframes
	w.Header().Set("X-Frame-Options", "DENY")
	w.Header().Set("Content-Security-Policy", "Frame-ancestors 'none'")

	w.Write(bytes)

	return nil
}

func getPublicLink(c *Context, w http.ResponseWriter, r *http.Request) {
	if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicLink", "api.file.get_public_link.disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if len(info.PostId) == 0 {
		c.Err = model.NewLocAppError("getPublicLink", "api.file.get_public_link.no_post.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	w.Write([]byte(model.StringToJson(app.GeneratePublicLink(c.GetSiteURL(), info))))
}