Horrible hack for bad architecture

internal/imap/uidlist/uidlist.go

@@ -143,7 +143,10 @@ func (l *List) Append(filenames ...string) error {
 		log.Printf("Adding entry: %#v", entry)
 
 		l.entries = append(l.entries, entry)
-		l.header.NextUID = l.header.NextUID + 1
+
+		log.Printf("NextUID: %v", l.header.NextUID)
+		l.header.NextUID++
+		log.Printf("NextUID: %v", l.header.NextUID)
 
 		// Try to write them all, at least
 		// FIXME: we don't bubble up errors when we should
@@ -191,6 +194,9 @@ func (l *List) parse() error {
 	l.mutex.Lock()
 	defer l.mutex.Unlock()
 
+	log.Printf("Parsing %v", l.filename)
+	defer func() { log.Printf("Finished parsing %v", l.filename) }()
+
 	file, err := os.Open(l.filename)
 	if err != nil {
 		return err
@@ -212,6 +218,7 @@ func (l *List) parse() error {
 
 	// Now parse each additional line
 	entries := []Entry{}
+
 	for r.Scan() {
 		entry, err := ParseEntry(r.Text())
 		if err != nil {
@@ -221,13 +228,17 @@ func (l *List) parse() error {
 
 		// If NextUID is out of date in the file, ignore it. We never want to
 		// re-use a seen UID
+		log.Printf("l.header.NextUID: %v", l.header.NextUID)
 		if entry.UID >= l.header.NextUID {
-			l.header.NextUID++
+			log.Printf("Incrementing as entry with UID %v is greater", entry.UID)
+			l.header.NextUID = entry.UID + 1
 		}
+		log.Printf("l.header.NextUID: %v", l.header.NextUID)
 	}
 
 	l.header = header
 	l.entries = entries
+	log.Printf("list: %#v", l)
 
 	return nil
 }

internal/store/maildir.go

@@ -5,6 +5,7 @@ import (
 	"net/mail"
 	"os"
 	"path/filepath"
+	"sync"
 
 	"github.com/luksen/maildir"
 
@@ -55,21 +56,38 @@ func (c *concrete) CreateMaildir(m *Maildir) error {
 	}
 
 	if m.uids == nil {
+		uidsLock.Lock()
+		defer uidsLock.Unlock()
+
+		if uidsCache[m.Rel()] == nil {
+
 			uids, err := uidlist.Create(m.directory)
 			if err != nil {
 				// FIXME: this leaves a dangling Maildir
 				return err
 			}
+			uidsCache[m.Rel()] = uids
+		}
 
-		m.uids = uids
+		m.uids = uidsCache[m.Rel()]
 	}
 
 	return nil
 }
 
+// Ugh
+// FIXME: multiple sessions get different Maildir instances, so breaking any
+// hope at locking (sigh)
+var (
+	uidsLock  sync.Mutex
+	uidsCache map[string]*uidlist.List
+)
+
+func init() {
+	uidsCache = make(map[string]*uidlist.List)
+}
+
 func (c *concrete) FindMaildir(account Account, name string) (Maildir, error) {
-	// FIXME: multiple IMAP sessions get different Maildir instances, so breaking
-	// any hope at locking (sigh)
 	m := Maildir{
 		Account:   account,
 		Name:      name,
@@ -81,11 +99,17 @@ func (c *concrete) FindMaildir(account Account, name string) (Maildir, error) {
 		return Maildir{}, errors.New("not found")
 	}
 
+	uidsLock.Lock()
+	defer uidsLock.Unlock()
+	if uidsCache[m.Rel()] == nil {
 		uids, err := uidlist.Open(m.directory)
 		if err != nil {
 			return Maildir{}, err
 		}
-	m.uids = uids
+		uidsCache[m.Rel()] = uids
+	}
+
+	m.uids = uidsCache[m.Rel()]
 
 	return m, nil
 }