[MM-62427] Add message attachments validation (#30180)

* Add message attachments validation

* Add props validation

* Validate slack attachment fields

* Update tests and library usage

* Improve interactive dialog error for length checks

* Allow predefined colors for slack attachments

* Fix TestPostAction

* Use const for data source

* Add tests

* Cleanup unused props

* Add happy path tests

* lint fixes

* Add validation for PostActionOptions

server/public/model/slack_attachment.go

@@ -6,9 +6,15 @@ package model
 import (
 	"fmt"
 	"regexp"
+	"slices"
+
+	"github.com/hashicorp/go-multierror"
 )
 
-var linkWithTextRegex = regexp.MustCompile(`<([^<\|]+)\|([^>]+)>`)
+var (
+	linkWithTextRegex = regexp.MustCompile(`<([^<\|]+)\|([^>]+)>`)
+	hexColorRegex     = regexp.MustCompile(`^#[0-9a-fA-F]{6}$`)
+)
 
 type SlackAttachment struct {
 	Id         int64                   `json:"id"`
@@ -30,6 +36,78 @@ type SlackAttachment struct {
 	Actions    []*PostAction           `json:"actions,omitempty"`
 }
 
+func (s *SlackAttachment) IsValid() error {
+	var multiErr *multierror.Error
+
+	if s.Color != "" {
+		validStyles := []string{"good", "warning", "danger"}
+		// If not a predefined style, check if it's a hex color
+		if !slices.Contains(validStyles, s.Color) && !hexColorRegex.MatchString(s.Color) {
+			multiErr = multierror.Append(multiErr, fmt.Errorf("invalid style '%s' - must be one of [good, warning, danger] or a hex color", s.Color))
+		}
+	}
+
+	if s.AuthorLink != "" {
+		if s.AuthorName == "" {
+			multiErr = multierror.Append(multiErr, fmt.Errorf("author link cannot be set without author name"))
+		}
+
+		if !IsValidHTTPURL(s.AuthorLink) {
+			multiErr = multierror.Append(multiErr, fmt.Errorf("invalid author link URL"))
+		}
+	}
+
+	if s.AuthorIcon != "" && !IsValidHTTPURL(s.AuthorIcon) {
+		multiErr = multierror.Append(multiErr, fmt.Errorf("invalid author icon URL"))
+	}
+
+	if s.TitleLink != "" {
+		if s.Title == "" {
+			multiErr = multierror.Append(multiErr, fmt.Errorf("title link cannot be set without title"))
+		}
+
+		if !IsValidHTTPURL(s.TitleLink) {
+			multiErr = multierror.Append(multiErr, fmt.Errorf("invalid title link URL"))
+		}
+	}
+
+	for _, field := range s.Fields {
+		if err := field.IsValid(); err != nil {
+			multiErr = multierror.Append(multiErr, err)
+		}
+	}
+
+	if s.ImageURL != "" && !IsValidHTTPURL(s.ImageURL) {
+		multiErr = multierror.Append(multiErr, fmt.Errorf("invalid image URL"))
+	}
+
+	if s.ThumbURL != "" && !IsValidHTTPURL(s.ThumbURL) {
+		multiErr = multierror.Append(multiErr, fmt.Errorf("invalid thumb URL"))
+	}
+
+	if s.FooterIcon != "" && !IsValidHTTPURL(s.FooterIcon) {
+		multiErr = multierror.Append(multiErr, fmt.Errorf("invalid footer icon URL"))
+	}
+
+	// Validate timestamp is either string or int64
+	if s.Timestamp != nil {
+		switch s.Timestamp.(type) {
+		case string, int64:
+			// Valid types
+		default:
+			multiErr = multierror.Append(multiErr, fmt.Errorf("timestamp must be either a string or int64"))
+		}
+	}
+
+	for i, action := range s.Actions {
+		if err := action.IsValid(); err != nil {
+			multiErr = multierror.Append(multiErr, multierror.Prefix(err, fmt.Sprintf("action at index %d is invalid:", i)))
+		}
+	}
+
+	return multiErr.ErrorOrNil()
+}
+
 func (s *SlackAttachment) Equals(input *SlackAttachment) bool {
 	// Direct comparison of simple types
 
@@ -120,6 +198,21 @@ type SlackAttachmentField struct {
 	Short SlackCompatibleBool `json:"short"`
 }
 
+func (s *SlackAttachmentField) IsValid() error {
+	var multiErr *multierror.Error
+
+	if s.Value != nil {
+		switch s.Value.(type) {
+		case string, int:
+			// Valid types
+		default:
+			multiErr = multierror.Append(multiErr, fmt.Errorf("value must be either a string or int"))
+		}
+	}
+
+	return multiErr.ErrorOrNil()
+}
+
 func (s *SlackAttachmentField) Equals(input *SlackAttachmentField) bool {
 	if s.Title != input.Title {
 		return false
@@ -188,7 +281,7 @@ func ParseSlackAttachment(post *Post, attachments []*SlackAttachment) {
 		}
 		postAttachments = append(postAttachments, attachment)
 	}
-	post.AddProp("attachments", postAttachments)
+	post.AddProp(PostPropsAttachments, postAttachments)
 }
 
 func ParseSlackLinksToMarkdown(text string) string {