roll: Support more complex rolls.

1 files changed, 63 insertions, 24 deletions

diff --git a/roll.go b/roll.go
index 414b0d2..5a02138 100644
--- a/roll.go
+++ b/roll.go
@@ -8,10 +8,13 @@ import (
 	"os"
 	"regexp"
 	"strconv"
+	"strings"
 )
 
 func usage() {
-	fmt.Printf("Arguments are in the format [<COUNT>]d<SIZE>[+<MOD>]\n")
+	fmt.Printf("Usage: %s <SPECSLIST>...\n", os.Args[0])
+	fmt.Println("SPECLIST = [-]SPEC[<<+|->SPEC>...]")
+	fmt.Println("SPEC = [<COUNT>]d<SIZE> | <MOD>")
 }
 
 func rollDie(size int) int {
@@ -22,39 +25,75 @@ func rollDie(size int) int {
 	return int(num.Int64()) + 1
 }
 
-func roll(input string) {
-	parser := regexp.MustCompile("^([0-9]*)d([0-9]+)([+-][0-9]+)?$")
-	parts := parser.FindStringSubmatch(input)
-	if len(parts) < 2 {
+var parser = regexp.MustCompile("^(([0-9]*)d)?([0-9]+)$")
+
+func rollSpec(spec string) (string, int) {
+	parts := parser.FindStringSubmatch(spec)
+	if len(parts) < 4 {
 		usage()
-		return
-	}
-	dice, _ := strconv.Atoi(parts[1])
-	die_size, _ := strconv.Atoi(parts[2])
-	mod := 0
-	if len(parts) > 3 {
-		mod, _ = strconv.Atoi(parts[3])
+		os.Exit(1)
 	}
-	if dice < 1 {
-		dice = 1
+
+	var str string
+	var num int
+	if parts[1] == "" {
+		str = parts[3]
+		num, _ = strconv.Atoi(str)
+	} else {
+		dice, _ := strconv.Atoi(parts[2])
+		die_size, _ := strconv.Atoi(parts[3])
+		if dice < 1 {
+			dice = 1
+		}
+
+		var rolls []string
+		for i := 0; i < dice; i++ {
+			v := rollDie(die_size)
+			rolls = append(rolls, strconv.Itoa(v))
+			num += v
+		}
+		str = "(" + strings.Join(rolls, "+") + ")"
 	}
+	return str, num
+}
+
+func roll(speclist string) {
+	var strs []string
+	var total int
 
-	total := 0
-	for i := 0; i < dice; i++ {
-		v := rollDie(die_size)
-		fmt.Printf("%d+", v)
-		total += v
+	neg := strings.HasPrefix(speclist, "-")
+	speclist = strings.TrimPrefix(speclist, "-")
+	for {
+		sep := strings.IndexAny(speclist, "+-")
+		var spec string
+		if sep < 0 {
+			spec = speclist
+		} else {
+			spec = speclist[:sep]
+		}
+		str, num := rollSpec(spec)
+		if neg {
+			str = "-" + str
+			num = -num
+		}
+		strs = append(strs, str)
+		total += num
+
+		if sep < 0 {
+			break
+		}
+		neg = speclist[sep] == '-'
+		speclist = speclist[sep+1:]
 	}
-	total += mod
-	fmt.Printf("%d = %d\n", mod, total)
+
+	fmt.Printf("%s = %d\n", strings.Join(strs, " + "), total)
 }
 
 func main() {
-	if len(os.Args) == 1 {
+	if len(os.Args) < 2 {
 		usage()
 	}
-	args := os.Args[1:]
-	for _, arg := range args {
+	for _, arg := range os.Args[1:] {
 		roll(arg)
 	}
 }