espat: implement MQTT subscribe functionality via blocking select/channels.

also refactor response processing for greater speed and efficiency.

Signed-off-by: Ron Evans <ron@hybridgroup.com>

espat/espat.go

@@ -19,6 +19,7 @@
 package espat // import "tinygo.org/x/drivers/espat"
 
 import (
+	"errors"
 	"machine"
 	"strconv"
 	"strings"
@@ -54,11 +55,11 @@ func (d *Device) Connected() bool {
 	d.Execute(Test)
 
 	// handle response here, should include "OK"
-	r := d.Response(100)
-	if strings.Contains(string(r), "OK") {
-		return true
+	_, err := d.Response(100)
+	if err != nil {
+		return false
 	}
-	return false
+	return true
 }
 
 // Write raw bytes to the UART.
@@ -72,7 +73,7 @@ func (d *Device) Read(b []byte) (n int, err error) {
 }
 
 // how long in milliseconds to pause after sending AT commands
-const pause = 100
+const pause = 300
 
 // Execute sends an AT command to the ESP8266/ESP32.
 func (d Device) Execute(cmd string) error {
@@ -97,7 +98,11 @@ func (d Device) Set(cmd, params string) error {
 // Version returns the ESP8266/ESP32 firmware version info.
 func (d Device) Version() []byte {
 	d.Execute(Version)
-	return d.Response(100)
+	r, err := d.Response(100)
+	if err != nil {
+		return []byte("unknown")
+	}
+	return r
 }
 
 // Echo sets the ESP8266/ESP32 echo setting.
@@ -122,7 +127,7 @@ func (d Device) Reset() {
 // ReadSocket returns the data that has already been read in from the responses.
 func (d *Device) ReadSocket(b []byte) (n int, err error) {
 	// make sure no data in buffer
-	d.Response(100)
+	d.Response(300)
 
 	count := len(b)
 	if len(b) >= len(d.socketdata) {
@@ -142,118 +147,73 @@ func (d *Device) ReadSocket(b []byte) (n int, err error) {
 
 // Response gets the next response bytes from the ESP8266/ESP32.
 // The call will retry for up to timeout milliseconds before returning nothing.
-func (d *Device) Response(timeout int) []byte {
-	var i int
-	pause := 10 // pause to wait for 10 ms
+func (d *Device) Response(timeout int) ([]byte, error) {
+	// read data
+	var size int
+	var start, end int
+	pause := 100 // pause to wait for 100 ms
 	retries := timeout / pause
 
-	header := make([]byte, 2)
 	for {
-		for d.bus.Buffered() > 0 {
-			// get the first 2 bytes
-			header[0], _ = d.bus.ReadByte()
-			header[1], _ = d.bus.ReadByte()
+		size = d.bus.Buffered()
 
-			if d.isLeadingCRLF(header) {
-				// skip it
-				header[0], _ = d.bus.ReadByte()
-				header[1], _ = d.bus.ReadByte()
+		if size > 0 {
+			end += size
+			d.bus.Read(d.response[start:end])
+
+			// if "+IPD" then read socket data
+			if strings.Contains(string(d.response[:end]), "+IPD") {
+				// handle socket data
+				return nil, d.parseIPD(end)
 			}
 
-			if d.isIPD(header) {
-				// is socket data packet
-				d.parseIPD()
-			} else {
-				// no, so put into response
-				d.response[i] = header[0]
-				i++
-				d.response[i] = header[1]
-				i++
+			// if "OK" then the command worked
+			if strings.Contains(string(d.response[:end]), "OK") {
+				return d.response[start:end], nil
 			}
 
-			// read the rest of normal command response
-			for d.bus.Buffered() > 0 {
-				data, err := d.bus.ReadByte()
-				if err != nil {
-					return nil
-				}
-				d.response[i] = data
-				i++
+			// if "Error" then the command failed
+			if strings.Contains(string(d.response[:end]), "ERROR") {
+				return d.response[start:end], errors.New("response error:" + string(d.response[start:end]))
 			}
+
+			// if anything else, then keep reading data in?
+			start = end
 		}
+
+		// wait longer?
 		retries--
 		if retries == 0 {
-			break
+			return nil, errors.New("response timeout error:" + string(d.response[start:end]))
 		}
 
-		// pause to make sure is no more data to be read
 		time.Sleep(time.Duration(pause) * time.Millisecond)
 	}
-	return d.response[:i]
 }
 
-func (d *Device) isLeadingCRLF(b []byte) bool {
-	if len(b) < 2 {
-		return false
-	}
-	if b[0] == 13 && b[1] == 10 {
-		return true
-	}
-	return false
-}
+func (d *Device) parseIPD(end int) error {
+	// find the "+IPD," to get length
+	s := strings.Index(string(d.response[:end]), "+IPD,")
 
-func (d *Device) isIPD(b []byte) bool {
-	if len(b) < 2 {
-		return false
-	}
-	if b[0] == '+' && b[1] == 'I' {
-		return true
-	}
-	return false
-}
+	// find the ":"
+	e := strings.Index(string(d.response[:end]), ":")
 
-func (d *Device) parseIPD() bool {
-	data, _ := d.bus.ReadByte()
-	if data != 'P' {
-		// error
-		return false
-	}
-	data, _ = d.bus.ReadByte()
-	if data != 'D' {
-		// error
-		return false
-	}
-	data, _ = d.bus.ReadByte()
-	if data != ',' {
-		// error
-		return false
-	}
+	// find the data length
+	val := string(d.response[s+5 : e])
 
-	// get the expected data length
-	// skip remaining header up to the ":"
-	buf := []byte{}
-	data, _ = d.bus.ReadByte()
-	for data != ':' {
-		// put into the buffer with int value here
-		buf = append(buf, data)
-
-		// read next value
-		data, _ = d.bus.ReadByte()
-	}
-
-	val := string(buf)
-	count, err := strconv.Atoi(val)
+	// TODO: verify count
+	_, err := strconv.Atoi(val)
 	if err != nil {
 		// not expected data here. what to do?
-		return false
+		return err
 	}
 
 	// load up the socket data
-	// only read the expected amount of data
-	for m := 0; m < count; m++ {
-		data, _ = d.bus.ReadByte()
-		d.socketdata = append(d.socketdata, data)
-	}
-
-	return true
+	d.socketdata = append(d.socketdata, d.response[e+1:end]...)
+	return nil
+}
+
+// IsSocketDataAvailable returns of there is socket data available
+func (d *Device) IsSocketDataAvailable() bool {
+	return len(d.socketdata) > 0 || d.bus.Buffered() > 0
 }