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// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.
package model
import (
"encoding/binary"
"encoding/json"
"fmt"
"hash/fnv"
"net/http"
"time"
"unicode/utf8"
"github.com/dyatlov/go-opengraph/opengraph"
)
const (
LINK_METADATA_TYPE_IMAGE LinkMetadataType = "image"
LINK_METADATA_TYPE_NONE LinkMetadataType = "none"
LINK_METADATA_TYPE_OPENGRAPH LinkMetadataType = "opengraph"
MAX_IMAGES int = 5
)
type LinkMetadataType string
// LinkMetadata stores arbitrary data about a link posted in a message. This includes dimensions of linked images
// and OpenGraph metadata.
type LinkMetadata struct {
// Hash is a value computed from the URL and Timestamp for use as a primary key in the database.
Hash int64
URL string
Timestamp int64
Type LinkMetadataType
// Data is the actual metadata for the link. It should contain data of one of the following types:
// - *model.PostImage if the linked content is an image
// - *opengraph.OpenGraph if the linked content is an HTML document
// - nil if the linked content has no metadata
Data interface{}
}
// truncateText ensure string is 300 chars, truncate and add ellipsis
// if it was bigger.
func truncateText(original string) string {
if utf8.RuneCountInString(original) > 300 {
return fmt.Sprintf("%.300s[...]", original)
}
return original
}
func firstNImages(images []*opengraph.Image, maxImages int) []*opengraph.Image {
if maxImages < 0 { // dont break stuff, if it's weird, go for sane defaults
maxImages = MAX_IMAGES
}
numImages := len(images)
if numImages > maxImages {
return images[0:maxImages]
}
return images
}
// TruncateOpenGraph ensure OpenGraph metadata doesn't grow too big by
// shortening strings, trimming fields and reducing the number of
// images.
func TruncateOpenGraph(ogdata *opengraph.OpenGraph) *opengraph.OpenGraph {
if ogdata != nil {
empty := &opengraph.OpenGraph{}
ogdata.Title = truncateText(ogdata.Title)
ogdata.Description = truncateText(ogdata.Description)
ogdata.SiteName = truncateText(ogdata.SiteName)
ogdata.Article = empty.Article
ogdata.Book = empty.Book
ogdata.Profile = empty.Profile
ogdata.Determiner = empty.Determiner
ogdata.Locale = empty.Locale
ogdata.LocalesAlternate = empty.LocalesAlternate
ogdata.Images = firstNImages(ogdata.Images, MAX_IMAGES)
ogdata.Audios = empty.Audios
ogdata.Videos = empty.Videos
}
return ogdata
}
func (o *LinkMetadata) PreSave() {
o.Hash = GenerateLinkMetadataHash(o.URL, o.Timestamp)
}
func (o *LinkMetadata) IsValid() *AppError {
if o.URL == "" {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.url.app_error", nil, "", http.StatusBadRequest)
}
if o.Timestamp == 0 || !isRoundedToNearestHour(o.Timestamp) {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.timestamp.app_error", nil, "", http.StatusBadRequest)
}
switch o.Type {
case LINK_METADATA_TYPE_IMAGE:
if o.Data == nil {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.data.app_error", nil, "", http.StatusBadRequest)
}
if _, ok := o.Data.(*PostImage); !ok {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.data_type.app_error", nil, "", http.StatusBadRequest)
}
case LINK_METADATA_TYPE_NONE:
if o.Data != nil {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.data_type.app_error", nil, "", http.StatusBadRequest)
}
case LINK_METADATA_TYPE_OPENGRAPH:
if o.Data == nil {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.data.app_error", nil, "", http.StatusBadRequest)
}
if _, ok := o.Data.(*opengraph.OpenGraph); !ok {
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.data_type.app_error", nil, "", http.StatusBadRequest)
}
default:
return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.type.app_error", nil, "", http.StatusBadRequest)
}
return nil
}
// DeserializeDataToConcreteType converts o.Data from JSON into properly structured data. This is intended to be used
// after getting a LinkMetadata object that has been stored in the database.
func (o *LinkMetadata) DeserializeDataToConcreteType() error {
var b []byte
switch t := o.Data.(type) {
case []byte:
// MySQL uses a byte slice for JSON
b = t
case string:
// Postgres uses a string for JSON
b = []byte(t)
}
if b == nil {
// Data doesn't need to be fixed
return nil
}
var data interface{}
var err error
switch o.Type {
case LINK_METADATA_TYPE_IMAGE:
image := &PostImage{}
err = json.Unmarshal(b, &image)
data = image
case LINK_METADATA_TYPE_OPENGRAPH:
og := &opengraph.OpenGraph{}
json.Unmarshal(b, &og)
data = og
}
if err != nil {
return err
}
o.Data = data
return nil
}
// FloorToNearestHour takes a timestamp (in milliseconds) and returns it rounded to the previous hour in UTC.
func FloorToNearestHour(ms int64) int64 {
t := time.Unix(0, ms*int64(1000*1000)).UTC()
return time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, time.UTC).UnixNano() / int64(time.Millisecond)
}
// isRoundedToNearestHour returns true if the given timestamp (in milliseconds) has been rounded to the nearest hour in UTC.
func isRoundedToNearestHour(ms int64) bool {
return FloorToNearestHour(ms) == ms
}
// GenerateLinkMetadataHash generates a unique hash for a given URL and timestamp for use as a database key.
func GenerateLinkMetadataHash(url string, timestamp int64) int64 {
hash := fnv.New32()
// Note that we ignore write errors here because the Hash interface says that its Write will never return an error
binary.Write(hash, binary.LittleEndian, timestamp)
hash.Write([]byte(url))
return int64(hash.Sum32())
}
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