Check operation context on returned errors

[onechat] / log.go

diff --git a/log.go b/log.go
index d34f459ad09909af9213f0cfc58c542e41d3732c..75080f9912c7bd7479d125689372b2a959c371ea 100644 (file)
--- a/log.go
+++ b/log.go
@@ -58,9 +58,9 @@ func openLog(ctx context.Context, root string, clock func() time.Time) (*Log, er
 }
 
 // Log is the append-only message log of one chat. It writes one JSON line for
-// each message to main/YYYY-MM-DD.jsonl, named for the local day of the write.
-// It never edits or deletes a line. Each line goes to the operating system
-// before Append returns, so a crash of the process loses no message. An
+// each message to main/YYYY-MM-DD.jsonl, named for the local day of the
+// message. It never edits or deletes a line. Each line goes to the operating
+// system before Append returns, so a crash of the process loses no message. An
 // exclusive lock on the lock file makes sure that only one process writes the
 // log. After a failed write, the end of the file is not known, so the log
 // refuses all writes until it is opened again. The caller serializes all calls.
@@ -96,26 +96,44 @@ func (l *Log) Close() error {
 // Append writes a new message to the log and returns it with its ID, size, and
 // date.
 func (l *Log) Append(kind, text string) (Message, error) {
+       return l.AppendDated(kind, text, "")
+}
+
+// AppendDated writes a message with date in RFC 3339 format. An empty date uses
+// the clock. The day file uses the local day of the given date.
+func (l *Log) AppendDated(kind, text, date string) (Message, error) {
        if l.lock == nil {
-               return Message{}, os.ErrClosed
+               return Message{}, fmt.Errorf("append dated message: %w", os.ErrClosed)
        }
 
        if l.failure != nil {
                return Message{}, fmt.Errorf("log needs a reopen after a failed write: %w", l.failure)
        }
 
+       var err error
        now := l.clock()
+       if date == "" {
+               date = now.Format(time.RFC3339Nano)
+       } else {
+               now, err = time.Parse(time.RFC3339Nano, date)
+               if err != nil {
+                       return Message{}, fmt.Errorf("parse message date: %w", err)
+               }
+
+               now = now.In(time.Local)
+       }
+
        message := Message{
                ID:   l.index.count,
                Kind: kind,
                Text: text,
                Size: len(text),
-               Date: now.Format(time.RFC3339Nano),
+               Date: date,
        }
 
-       err := logValidateMessage(message)
+       err = logValidateMessage(message)
        if err != nil {
-               return Message{}, err
+               return Message{}, fmt.Errorf("validate dated message: %w", err)
        }
 
        line, err := json.Marshal(message)
@@ -190,7 +208,7 @@ func (l *Log) catchUp(ctx context.Context) error {
                var message Message
                err := json.Unmarshal(line, &message)
                if err != nil {
-                       return err
+                       return fmt.Errorf("decode log message: %w", err)
                }
 
                if message.ID != l.index.count {
@@ -213,9 +231,10 @@ func (l *Log) addIndex(place Position) error {
        return l.index.Append(record)
 }
 
-// Message is one entry of the chat log. ID is the permanent position of the
-// message in the chat, from 0. Size is the UTF-8 byte length of Text. Date is
-// the time of the write in RFC 3339 format.
+// Message is one entry of the chat log. ID is its position in the log, from 0.
+// A rebuild assigns positions in the merged log. Size is the UTF-8 byte length
+// of Text. Date is the message time in RFC 3339 format, supplied at append or
+// taken from the clock.
 type Message struct {
        ID   int    `json:"i"`
        Kind string `json:"kind"`