staskobzar / goagi

import (

	"bufio"

	"strings"

	"time"

)

// ErrAGI goagi error

var ErrAGI = newError("AGI session")

const rwDefaultTimeout = time.Second * 1

// Reader interface for AGI object. Can be net.Conn, os.File or crafted

type Reader interface {

	Read(b []byte) (int, error)

	SetReadDeadline(t time.Time) error

}

// Writer interface for AGI object. Can be net.Conn, os.File or crafted

type Writer interface {

	SetWriteDeadline(t time.Time) error

	Write(b []byte) (int, error)

}

/*

Debugger for AGI instance. Any interface that provides Printf method.

Usage example:

```go

	dbg := logger.New(os.Stdout, "myagi:", log.Lmicroseconds)

	r, w := net.Pipe()

	agi, err := goagi.New(r, w, dbg)

```

It should be used only for debugging as it give lots of output.

*/

type Debugger interface {

	Printf(format string, v ...interface{})

}

// AGI object

type AGI struct {

	env      map[string]string

	arg      []string

	reader   Reader

	writer   Writer

	isHUP    bool

	debugger Debugger

	rwtout   time.Duration

}

const (

	codeUnknown int = 0

	codeEarly       = 100

	codeSucc        = 200

	codeE503        = 503

	codeE510        = 510

	codeE511        = 511

	codeE520        = 520

)

var codeMap = map[string]int{

	"100 ": codeEarly,

	"200 ": codeSucc,

	"503 ": codeE503,

	"510 ": codeE510,

	"511 ": codeE511,

	"520 ": codeE520,

}

/*

New creates and returns AGI object.

Can be used to create agi and fastagi sessions.

Example for agi:

```go

	import (

		"github.com/staskobzar/goagi"

		"os"

	)

	agi, err := goagi.New(os.Stdin, os.Stdout, nil)

	if err != nil {

		panic(err)

	}

	agi.Verbose("Hello World!")

```

Fast agi example:

```go

	ln, err := net.Listen("tcp", "127.0.0.1:4573")

	if err != nil {

		panic(err)

	}

	for {

		conn, err := ln.Accept()

		if err != nil {

			panic(err)

		}

		go func(conn net.Conn) {

			agi, err := goagi.New(conn, conn, nil)

			if err != nil {

				panic(err)

			}

			agi.Verbose("Hello World!")

		}(conn)

	}

```

*/

func New(r Reader, w Writer, dbg Debugger) (*AGI, error) {

	agi := &AGI{

		reader:   r,

		writer:   w,

		debugger: dbg,

		rwtout:   rwDefaultTimeout,

	}

	agi.dbg("[>] New AGI")

	sessData, err := agi.sessionInit()

	if err != nil {

		return nil, ErrAGI.Msg("Failed to read setup: %s", err)

	}

	agi.sessionSetup(sessData)

	return agi, nil

}

// Env returns AGI environment variable by key

// EnvArgs returns list of environment arguments

func (agi *AGI) EnvArgs() []string {

	agi.dbg("[>] EnvArgs")

	return agi.arg

}

func (agi *AGI) sessionInit() ([]string, error) {

	agi.dbg("[>] sessionInit")

	buf := bufio.NewReader(agi.reader)

	data := make([]string, 0)

	for {

		tout := time.Now().Add(agi.rwtout)

		if err := agi.reader.SetReadDeadline(tout); err != nil {

			return nil, err

		}

		line, err := buf.ReadString('\n')

		if err != nil {

			return nil, err

		}

		if line == "\n" {

			break

		}

		agi.dbg(" [v] read line: %q", line)

		data = append(data, line[:len(line)-1])

	}

	return data, nil

}

func (agi *AGI) dbg(pattern string, vargs ...interface{}) {

	if agi.debugger != nil {

		pattern += "\n"

	}

}

// low level response from device and response as string, matched response

// code, true if channel reported as hangup and error.

// if timeout > 0 then will read with timeout

func (agi *AGI) read(timeout time.Duration) (resp string, code int, err error) {

	agi.dbg("[>] readResponse")

	buf := bufio.NewReader(agi.reader)

	var builder strings.Builder

	moreInputExpected := false

	for {

		if timeout > 0 {

			tout := time.Now().Add(timeout)

			if fail := agi.reader.SetReadDeadline(tout); fail != nil {

				err = fail

				return

			}

		}

		line, fail := buf.ReadString('\n')

		if fail != nil {

			err = fail

			return

		}

		agi.dbg(" [v] got line: %q", line)

		builder.WriteString(line)

		resp = builder.String()

		if codeMatch, ok := matchCode(line); ok {

			code = codeMatch

			return

		}

		if matchPrefix(line, "520-") {

			moreInputExpected = true

		}

		if matchPrefix(line, "HANGUP") {

			agi.isHUP = true

			builder.Reset()

			continue

		}

		if !moreInputExpected {

			err = ErrAGI.Msg("Invalid input while reading response: %q", resp)

			return

		}

	}

}

func matchPrefix(line, pattern string) bool {

	if len(line) < len(pattern) {

		return false

	}

	return line[:len(pattern)] == pattern

}

func matchCode(data string) (int, bool) {

	if len(data) < 4 {

		return 0, false

	}

	if codeMatch, ok := codeMap[data[:4]]; ok {

		return codeMatch, true

	}

	return 0, false

}

func (agi *AGI) write(command []byte) error {

	agi.dbg("[>] readResponse")

	if agi.rwtout > 0 {

		tout := time.Now().Add(agi.rwtout)

		agi.dbg(" [v] set write timeout: %dns", tout)

		if err := agi.writer.SetWriteDeadline(tout); err != nil {

			return err

		}

	}

	agi.dbg(" [v] write command: %q\n", string(command))

	_, err := agi.writer.Write(command)

	if err != nil {

		return err

	}

	return nil

}

// write command, read and parse response

func (agi *AGI) execute(cmd string, timeout bool) (Response, error) {

	agi.dbg("[>] execute cmd: %q", cmd)

	if err := agi.write([]byte(cmd)); err != nil {

		return nil, err

	}

	var tout time.Duration

	if timeout {

		tout = agi.rwtout

	}

	agi.dbg(" [v] read timeout=%d", tout)

	resp, code, err := agi.read(tout)

	if err != nil {

		return nil, err

	}

	return agi.parseResponse(resp, code)

}