func (d *Document) CalculateEdit() {
text := d.GetText()
// Calculate differences.
diffs := dmp.DiffMain(d.Shadow.Content, text, false)
diffs = dmp.DiffCleanupEfficiency(diffs)
// Calculate patch.
patches := dmp.PatchMake(d.Shadow.Content, diffs)
if len(patches) < 1 {
// No differences.
return
}
patchesText := dmp.PatchToText(patches)
// Increment shadow.
d.Shadow.Content = text
d.Shadow.LocalVersion++
// Add edit to edit queue.
edit := Edit{Version: d.Shadow.LocalVersion, Patch: patchesText, MD5: checksum.MD5(d.Shadow.Content)}
d.Edits.Enqueue(edit)
}
func (d *Document) ApplyEdits(version int, edits []Edit) error {
if version < d.Shadow.LocalVersion && version == d.Backup.LocalVersion {
// Edits are based on an old version. Use the backup shadow.
d.RestoreBackup()
} else if version < d.Shadow.LocalVersion && version != d.Backup.LocalVersion {
// Edits are based on an old version, but somehow the backup is out of sync. Reinitialize and accept loss.
return fmt.Errorf("patch failed: version mismatch (backup out of sync: client remote %d, backup local %d)", version, d.Backup.LocalVersion)
} else if version > d.Shadow.LocalVersion {
// Somehow, the client received a version we never had. Reinitialize and accept loss.
return fmt.Errorf("patch failed: version mismatch (client ahead of source: client remote %d, server local %d)", version, d.Shadow.LocalVersion)
}
// Versions match - apply patch
for _, edit := range edits {
if edit.Version <= d.Shadow.RemoteVersion {
// Already handled
continue
} else if edit.Version > d.Shadow.RemoteVersion+1 {
// Somehow we've skipped one version. Reinitialize and accept loss.
return fmt.Errorf("patch failed: version mismatch (missing version)")
}
// Versions match - apply patch
patch, _ := dmp.PatchFromText(edit.Patch)
// Apply to shadow (strict)
newShadow := *d.Shadow
newShadow.Content, _ = dmp.PatchApply(patch, d.Shadow.Content)
newShadow.RemoteVersion = edit.Version
if checksum.MD5(newShadow.Content) != edit.MD5 {
// Strict patch unsuccessful. Reinitialize and accept loss.
return fmt.Errorf("patch failed: strict patch unsuccessful")
}
// Strict patch successful.
d.Shadow = &newShadow
// Copy shadow to backup.
d.TakeBackup()
// Apply to text (fuzzy).
newText, _ := dmp.PatchApply(patch, d.GetText())
d.SetText(newText)
}
return nil
}