mem: Initial in-memory store implementation for #88

- Reduce default retention sleep, change description.

pkg/storage/mem/message.go

@@ -0,0 +1,51 @@
+package mem
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"net/mail"
+	"time"
+
+	"github.com/jhillyerd/inbucket/pkg/storage"
+)
+
+// Message is a memory store message.
+type Message struct {
+	index   int
+	mailbox string
+	id      string
+	from    *mail.Address
+	to      []*mail.Address
+	date    time.Time
+	subject string
+	source  []byte
+}
+
+var _ storage.Message = &Message{}
+
+// Mailbox returns the mailbox name.
+func (m *Message) Mailbox() string { return m.mailbox }
+
+// ID the message ID.
+func (m *Message) ID() string { return m.id }
+
+// From returns the from address.
+func (m *Message) From() *mail.Address { return m.from }
+
+// To returns the to address list.
+func (m *Message) To() []*mail.Address { return m.to }
+
+// Date returns the date received.
+func (m *Message) Date() time.Time { return m.date }
+
+// Subject returns the subject line.
+func (m *Message) Subject() string { return m.subject }
+
+// Source returns a reader for the message source.
+func (m *Message) Source() (io.ReadCloser, error) {
+	return ioutil.NopCloser(bytes.NewReader(m.source)), nil
+}
+
+// Size returns the message size in bytes.
+func (m *Message) Size() int64 { return int64(len(m.source)) }