PLT-4839 Split too-long Slack messages on import. (#4679)

* PLT-4839 Split too-long Slack messages on import.

This PR also takes the opportunity to make the max values for Post
properties into constants for easier use elsewhere, as has previously
been done for Channel properties.

* Only count runes once.

2 files changed, 28 insertions, 8 deletions

diff --git a/api/import.go b/api/import.go
index 570444464..63dfb033d 100644
--- a/api/import.go
+++ b/api/import.go
@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"io"
 	"regexp"
+	"unicode/utf8"
 
 	l4g "github.com/alecthomas/log4go"
 	"github.com/mattermost/platform/model"
@@ -19,10 +20,24 @@ import (
 //
 
 func ImportPost(post *model.Post) {
-	post.Hashtags, _ = model.ParseHashtags(post.Message)
+	for messageRuneCount := utf8.RuneCountInString(post.Message); messageRuneCount > 0; messageRuneCount = utf8.RuneCountInString(post.Message) {
+		var remainder string
+		if messageRuneCount > model.POST_MESSAGE_MAX_RUNES {
+			remainder = string(([]rune(post.Message))[model.POST_MESSAGE_MAX_RUNES:])
+			post.Message = truncateRunes(post.Message, model.POST_MESSAGE_MAX_RUNES)
+		} else {
+			remainder = ""
+		}
+
+		post.Hashtags, _ = model.ParseHashtags(post.Message)
+
+		if result := <-Srv.Store.Post().Save(post); result.Err != nil {
+			l4g.Debug(utils.T("api.import.import_post.saving.debug"), post.UserId, post.Message)
+		}
 
-	if result := <-Srv.Store.Post().Save(post); result.Err != nil {
-		l4g.Debug(utils.T("api.import.import_post.saving.debug"), post.UserId, post.Message)
+		post.Id = ""
+		post.CreateAt++
+		post.Message = remainder
 	}
 }
 
diff --git a/model/post.go b/model/post.go
index b5dcc4539..cffe8e342 100644
--- a/model/post.go
+++ b/model/post.go
@@ -19,6 +19,11 @@ const (
 	POST_HEADER_CHANGE         = "system_header_change"
 	POST_CHANNEL_DELETED       = "system_channel_deleted"
 	POST_EPHEMERAL             = "system_ephemeral"
+	POST_FILEIDS_MAX_RUNES     = 150
+	POST_FILENAMES_MAX_RUNES   = 4000
+	POST_HASHTAGS_MAX_RUNES    = 1000
+	POST_MESSAGE_MAX_RUNES     = 4000
+	POST_PROPS_MAX_RUNES       = 8000
 )
 
 type Post struct {
@@ -103,11 +108,11 @@ func (o *Post) IsValid() *AppError {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.original_id.app_error", nil, "")
 	}
 
-	if utf8.RuneCountInString(o.Message) > 4000 {
+	if utf8.RuneCountInString(o.Message) > POST_MESSAGE_MAX_RUNES {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.msg.app_error", nil, "id="+o.Id)
 	}
 
-	if utf8.RuneCountInString(o.Hashtags) > 1000 {
+	if utf8.RuneCountInString(o.Hashtags) > POST_HASHTAGS_MAX_RUNES {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.hashtags.app_error", nil, "id="+o.Id)
 	}
 
@@ -116,15 +121,15 @@ func (o *Post) IsValid() *AppError {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.type.app_error", nil, "id="+o.Type)
 	}
 
-	if utf8.RuneCountInString(ArrayToJson(o.Filenames)) > 4000 {
+	if utf8.RuneCountInString(ArrayToJson(o.Filenames)) > POST_FILENAMES_MAX_RUNES {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.filenames.app_error", nil, "id="+o.Id)
 	}
 
-	if utf8.RuneCountInString(ArrayToJson(o.FileIds)) > 150 {
+	if utf8.RuneCountInString(ArrayToJson(o.FileIds)) > POST_FILEIDS_MAX_RUNES {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.file_ids.app_error", nil, "id="+o.Id)
 	}
 
-	if utf8.RuneCountInString(StringInterfaceToJson(o.Props)) > 8000 {
+	if utf8.RuneCountInString(StringInterfaceToJson(o.Props)) > POST_PROPS_MAX_RUNES {
 		return NewLocAppError("Post.IsValid", "model.post.is_valid.props.app_error", nil, "id="+o.Id)
 	}