Convert from BoltDB to Maildir storage for emails

internal/imap/uidlist/uidlist.go

@@ -0,0 +1,233 @@
+// package uidlist implements Dovecot's `dovecot-uidlist` file format for
+// Maildir directories
+//
+// Reference: https://wiki.dovecot.org/MailboxFormat/Maildir
+package uidlist
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+const (
+	DefaultFilename = "dovecot-uidlist"
+)
+
+type List struct {
+	filename string
+	header   Header
+	entries  []Entry
+
+	mutex *sync.Mutex
+}
+
+func Create(dir string) (*List, error) {
+	return CreateFile(filepath.Join(dir, DefaultFilename))
+}
+
+// FIXME: on startup, we need to scan `cur/` in case any problems arose
+func Open(dir string) (*List, error) {
+	return OpenFile(filepath.Join(dir, DefaultFilename))
+}
+
+func CreateFile(filename string) (*List, error) {
+	list, err := handleFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC)
+	if err != nil {
+		return nil, err
+	}
+
+	hdr, err := GenerateHeader()
+	if err != nil {
+		return nil, err
+	}
+
+	list.header = hdr
+
+	// TODO: allow the dovecot-uidlist to be populated from scratch
+	// FIXME: in particular, NextUID and entries are wrong here
+
+	if err := list.save(); err != nil {
+		return nil, err
+	}
+
+	return list, nil
+}
+
+func OpenFile(filename string) (*List, error) {
+	list, err := handleFile(filename, os.O_RDWR|os.O_CREATE)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := list.parse(); err != nil {
+		return nil, err
+	}
+
+	return list, nil
+}
+
+func handleFile(filename string, flags int) (*List, error) {
+	file, err := os.OpenFile(filename, flags, 0600)
+	if err != nil {
+		return nil, err
+	}
+	file.Close()
+
+	return &List{
+		filename: filename,
+		mutex:    &sync.Mutex{},
+	}, nil
+}
+
+func (l *List) UIDValidity() uint64 {
+	return l.header.UIDValidity
+}
+
+func (l *List) GUID() string {
+	return l.header.GUID
+}
+
+func (l *List) Entries() []Entry {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	// FIXME: use copy() ?
+	return l.entries
+}
+
+func (l *List) EntriesInRange(start, end uint64) []Entry {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	// FIXME: this shouldn't need a full scan
+	var out []Entry
+
+	log.Printf("Checking range %d to %d in %#v", start, end, l.entries)
+
+	for _, e := range l.entries {
+		if e.UID >= start && (end == 0 || e.UID <= end) {
+			out = append(out, e)
+		}
+	}
+
+	return out
+}
+
+func (l *List) Entry(key string) *Entry {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	return nil
+}
+
+func (l *List) Append(filenames ...string) error {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	file, err := os.OpenFile(l.filename, os.O_APPEND|os.O_RDWR, 0600)
+	if err != nil {
+		return err
+	}
+
+	defer file.Close()
+
+	for _, filename := range filenames {
+		entry := Entry{
+			UID:               l.header.NextUID,
+			LastKnownFilename: filename,
+		}
+		log.Printf("Adding entry: %#v", entry)
+
+		l.entries = append(l.entries, entry)
+		l.header.NextUID = l.header.NextUID + 1
+
+		// Try to write them all, at least
+		// FIXME: we don't bubble up errors when we should
+		if _, err := fmt.Fprintln(file, entry.String()); err != nil {
+			log.Printf("failed to write UID %d to %s: %v", entry.UID, l.filename, err)
+		}
+	}
+	log.Printf("Appended %d entries", len(filenames))
+
+	return nil
+}
+
+func (l *List) save() (err error) {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	// FIXME: When rewriting the file, we're meant to:
+	//   * Take the dovecot-uidlist.lock file
+	//   * write to a temporary file then atomically rename onto -uidlist
+	// Unsure if the temporary file and the lock file are the same thing or not
+
+	file, err := os.OpenFile(l.filename, os.O_TRUNC|os.O_RDWR, 0600)
+	if err != nil {
+		return
+	}
+
+	defer func() { err = file.Close() }()
+
+	_, err = fmt.Fprintln(file, l.header.String())
+	if err != nil {
+		return
+	}
+
+	for _, e := range l.entries {
+		_, err = fmt.Fprintln(file, e.String())
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}
+
+func (l *List) parse() error {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+
+	file, err := os.Open(l.filename)
+	if err != nil {
+		return err
+	}
+
+	defer file.Close()
+
+	r := bufio.NewScanner(file)
+
+	// Get the header if present, which is the first line
+	if !r.Scan() {
+		return r.Err()
+	}
+
+	header, err := ParseHeader(r.Text())
+	if err != nil {
+		return err
+	}
+
+	// Now parse each additional line
+	entries := []Entry{}
+	for r.Scan() {
+		entry, err := ParseEntry(r.Text())
+		if err != nil {
+			return err
+		}
+		entries = append(entries, entry)
+
+		// If NextUID is out of date in the file, ignore it. We never want to
+		// re-use a seen UID
+		if entry.UID >= l.header.NextUID {
+			l.header.NextUID++
+		}
+	}
+
+	l.header = header
+	l.entries = entries
+
+	return nil
+}