message.go

// vim: ts=8 noexpandtab ai

package mbox

import "io"

// A Message represents a single message in the file.
type Message struct {
	mbox           *MboxStream
	headers        map[string][]string
	sendingAddress string
}

// A bodyReader implements an io.Reader, confined to the current message to
// which this instance is bound.
type bodyReader struct {
	msg    *Message
	mbox   *MboxStream
	where  int
	srcErr error
}

// Sender() tells who sent the message.  This corresponds to the e-mail address
// following the From marker that identifies the start of the current message.
// Note that this field may not necessarily match any "From" header as indicated
// in the set of headers returned by Headers().
func (m *Message) Sender() string {
	return m.sendingAddress
}

// The Headers method provides raw access to the headers of a message.
// Applications identify headers by a name string.  Each header contains one or
// more value strings, each string corresponding to a line in the MIME header
// text.  For example, given the following two headers:
//
//     Subject: Code Review
//     X-Trace-Token: DEADBEEF-FEED-FACE-0123-45-67-89-AB-CD-EF;
//             user_id=sfalvo
//
// then we would find the following truths:
//
//     // hs := msg.Headers()
//     len(hs) == 2
//     len(hs["Subject"]) == 1
//     len(hs["X-Trace-Token"]) == 2
//     hs["Subject"] == []string{"Code Review"}
//     hs["X-Trace-Token"] == []string{
//             "DEADBEEF-FEED-FACE-0123-45-67-89-AB-CD-EF;",
//             "\tuser_id=sfalvo"
//     }
//
// Observe that the header values that continue onto subsequent lines preserve
// any whitespace used.  Again, this is a conscious decision to preserve as
// much of the MBOX file details as feasible.  The user may wish to pass the
// data through strings.TrimSpace before relying on any values if whitespace is
// to be ignored.
func (m *Message) Headers() map[string][]string {
	return m.headers
}

// BodyReader() provides an io.Reader compatible object that will read the body
// of the message.  It will return io.EOF if you attempt to read beyond the end
// of the message.
func (m *Message) BodyReader() io.Reader {
	br := &bodyReader{
		msg:  m,
		mbox: m.mbox,
	}

	return br
}

func (r *bodyReader) Read(bs []byte) (n int, err error) {
	if r.srcErr != nil {
		return 0, r.srcErr
	}

	if (len(r.mbox.prefetch) > 5) && (string(r.mbox.prefetch[0:5]) == "From ") {
		return 0, io.EOF
	}

	n = copy(bs, r.mbox.prefetch[r.where:])
	r.where = r.where + n
	if r.where >= len(r.mbox.prefetch) {
		r.where = 0
		r.srcErr = r.mbox.nextLine()
	}
	return
}