Add initial support for interfacing with gnubg

pkg/server/server.go

@@ -1,14 +1,18 @@
 package server
 
 import (
+	"bufio"
 	"bytes"
 	"crypto/rand"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"log"
 	"math/big"
 	"net"
 	"net/http"
+	"os"
+	"os/exec"
 	"regexp"
 	"strconv"
 	"strings"
@@ -602,6 +606,46 @@ func (s *server) gameByClient(c *serverClient) *serverGame {
 	return nil
 }
 
+// Analyze returns match analysis information calculated by gnubg.
+func (s *server) Analyze(g *bgammon.Game) {
+	cmd := exec.Command("gnubg", "--tty")
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		log.Fatal(err)
+	}
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		log.Fatal(err)
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = cmd.Start()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	go func() {
+		scanner := bufio.NewScanner(stdout)
+		for scanner.Scan() {
+			log.Println("STDOUT", string(scanner.Bytes()))
+		}
+	}()
+
+	go func() {
+		scanner := bufio.NewScanner(stderr)
+		for scanner.Scan() {
+			log.Println("STDERR", string(scanner.Bytes()))
+		}
+	}()
+
+	stdin.Write([]byte(fmt.Sprintf("new game\nset board %s\nanalyze game\n", gnubgPosition(g))))
+
+	time.Sleep(2 * time.Second)
+	os.Exit(0)
+}
+
 func (s *server) handleCommands() {
 	var cmd serverCommand
 COMMANDS:
@@ -1917,6 +1961,89 @@ func RandInt(max int) int {
 	return int(i.Int64())
 }
 
+func gnubgPosition(g *bgammon.Game) string {
+	opponent := 2
+	start := 0
+	end := 25
+	boardStart := 1
+	boardEnd := 24
+	delta := 1
+	playerBarSpace := bgammon.SpaceBarPlayer
+	opponentBarSpace := bgammon.SpaceBarOpponent
+	switch g.Turn {
+	case 1:
+	case 2:
+		opponent = 1
+		start = 25
+		end = 0
+		boardStart = 24
+		boardEnd = 1
+		delta = -1
+		playerBarSpace = bgammon.SpaceBarOpponent
+		opponentBarSpace = bgammon.SpaceBarPlayer
+	default:
+		log.Fatalf("failed to analyze game: zero turn")
+	}
+
+	var buf []byte
+	for space := boardStart; space != end; space += delta {
+		playerCheckers := bgammon.PlayerCheckers(g.Board[space], g.Turn)
+		for i := 0; i < playerCheckers; i++ {
+			buf = append(buf, '1')
+		}
+		buf = append(buf, '0')
+	}
+	playerCheckers := bgammon.PlayerCheckers(g.Board[playerBarSpace], g.Turn)
+	for i := 0; i < playerCheckers; i++ {
+		buf = append(buf, '1')
+	}
+	buf = append(buf, '0')
+
+	for space := boardEnd; space != start; space -= delta {
+		opponentCheckers := bgammon.PlayerCheckers(g.Board[space], opponent)
+		for i := 0; i < opponentCheckers; i++ {
+			buf = append(buf, '1')
+		}
+		buf = append(buf, '0')
+	}
+	opponentCheckers := bgammon.PlayerCheckers(g.Board[opponentBarSpace], opponent)
+	for i := 0; i < opponentCheckers; i++ {
+		buf = append(buf, '1')
+	}
+	buf = append(buf, '0')
+
+	for i := len(buf); i < 80; i++ {
+		buf = append(buf, '0')
+	}
+
+	var out []byte
+	for i := 0; i < len(buf); i += 8 {
+		s := reverseString(string(buf[i : i+8]))
+		v, err := strconv.ParseUint(s, 2, 8)
+		if err != nil {
+			panic(err)
+		}
+		out = append(out, byte(v))
+	}
+
+	position := base64.StdEncoding.EncodeToString(out)
+	if len(position) == 0 {
+		return ""
+	}
+	for position[len(position)-1] == '=' {
+		position = position[:len(position)-1]
+	}
+	return position
+}
+
+func reverseString(s string) string {
+	runes := []rune(s)
+	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
+		runes[i], runes[j] = runes[j], runes[i]
+	}
+	return string(runes)
+}
+
 type ratingPlayer struct {
 	r       float64
 	rd      float64