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package cnp
import (
"bufio"
"bytes"
"io"
"io/ioutil"
"strings"
)
// Message represents a CNP message.
type Message struct {
Header Header
Body io.Reader
closer io.Closer
}
// NewMessage creates a new CNP message.
//
// This method also calls Message.TryComputeLength().
func NewMessage(intent string, body io.Reader) *Message {
msg := &Message{
Header: NewHeader(intent, nil),
Body: body,
}
msg.TryComputeLength()
return msg
}
// ParseMessage parses a CNP message.
//
// The message's Body field is set to a bufio.Reader wrapping r. If r is a
// io.Closer, it is also stored separately for usage with Message.Close().
func ParseMessage(r io.Reader) (*Message, error) {
br := bufio.NewReader(r)
line, err := readLimitedLine(br, MaxHeaderLength)
if err != nil {
return nil, err
}
h, err := ParseHeader(line)
if err != nil {
return nil, err
}
msg := &Message{
Header: h,
Body: br,
}
if rc, ok := r.(io.Closer); ok {
msg.closer = rc
}
return msg, nil
}
// Close attempts to close the message body reader.
//
// If the message's Body field is an io.Closer, its Close() method is called.
// If Body is not an io.Closer and the message was created with ParseMessage
// provided with an io.Closer, the Close() method on the original reader will
// be called.
// Otherwise, this function does nothing.
func (msg *Message) Close() error {
if rc, ok := msg.Body.(io.Closer); ok {
return rc.Close()
}
if msg.closer != nil {
return msg.closer.Close()
}
return nil
}
// ComputeLength sets the length header parameter based on the message body.
// First, msg.TryComputeLength() is attempted; if that fails, the request is
// fully read into a buffer and msg.Body is set to a bytes.Reader.
func (msg *Message) ComputeLength() error {
if !msg.TryComputeLength() {
buf, err := ioutil.ReadAll(msg.Body)
if len(buf) > 0 {
msg.Body = bytes.NewReader(buf)
msg.SetLength(int64(len(buf)))
}
if err != nil {
return err
}
}
return nil
}
// TryComputeLength sets the length header parameter to the length of the
// message body if it's one of *bytes.Buffer, *bytes.Reader or *strings.Reader
// and returns true. If msg.Body is nil, the length parameter is unset and the
// function returns true. Otherwise, false is returned.
func (msg *Message) TryComputeLength() bool {
switch v := msg.Body.(type) {
case *bytes.Buffer:
msg.SetLength(int64(v.Len()))
case *bytes.Reader:
msg.SetLength(int64(v.Len()))
case *strings.Reader:
msg.SetLength(int64(v.Len()))
case nil:
msg.SetLength(0)
default:
return false
}
return true
}
// SetLength sets the length header parameter to n.
func (msg *Message) SetLength(n int64) {
if n == 0 {
msg.SetParam("length", "")
} else {
setInt(msg, "length", n)
}
}
// Length gets the length header parameter (or 0 if it's not set or invalid).
func (msg *Message) Length() int64 {
n, err := getInt(msg, "length")
if err != nil {
return 0
}
return n
}
// Param retrieves a header parameter.
func (msg *Message) Param(key string) string {
return msg.Header.Parameters[key]
}
// SetParam sets a header parameter. If the value is empty, the parameter is
// unset.
func (msg *Message) SetParam(key, value string) {
if len(value) == 0 {
delete(msg.Header.Parameters, key)
} else {
msg.Header.Parameters[key] = value
}
}
// Intent retrieves the message header intent.
func (msg *Message) Intent() string {
return msg.Header.Intent
}
// SetIntent sets the message header intent.
func (msg *Message) SetIntent(s string) {
msg.Header.Intent = s
}
// Validate validates the message header parameter value format (length).
func (msg *Message) Validate() error {
_, err := getInt(msg, "length")
return err
}
// Write writes the message header and body to w.
func (msg *Message) Write(w io.Writer) error {
if err := msg.Header.Write(w); err != nil {
return err
}
if msg.Body != nil {
if _, err := io.Copy(w, msg.Body); err != nil {
return err
}
}
return nil
}
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