Implement RNG format blocks in sentences

The RNG blocks follow a slightly different format than the word blocks.
They are wrapped in square brackets instead of curly braces.  The format
is as follows:

    [cmd:arguments]

`cmd` can be one of either "rng" or "hide".  "rng" takes a comma
separated list as its arguments and will choose one option from the
list.  Only raw words are accepted here (word blocks are not parsed).
"hide" will randomly hide its arguments in the output string.  The
arguments for this command *are* parsed, so {word} and {{new_word}}
blocks can be used.

english.go

@@ -30,22 +30,31 @@ func NewEnglish(db database.DB) (HackerQuotes, error) {
 }
 
 /*
-
 	Sentence format
 
+	bare words
 	{word_type:options}
 	{{word_type:new word:properties}}
 
+	[rng:random,choice,list]		// one word is chosen from the comma-separated list
+
+	// Randomly hide/show the enclosed definition
+	[hide:{word_type:options}]
+	[hide:{{word_type:new word:options}}]
+
 	{pronoun} can't {verb:i,present} {noun_phrase}, it {verb:it,future} {noun_phrase}!
 	{verb:you,present} {noun_phrase:indefinite}, then you can {verb:you,present} {noun_phrase:definite}!
 	{noun_phrase} {verb}. With {noun_phrase:indifinite,noadj,compound}!
 
 	{pronoun} {{verb:need:from_pronoun,present}} to {verb:i,present} {noun_phrase:definite}!
+
+	{pronoun} [rng:can,may] {verb:i,present} {noun_phrase} [hide:{noun_phrase:singlular}], it {verb:it,future} {noun_phrase:definite}.
 */
 
 func (g *english) Hack() (string, error) {
 	//var fmtString string = `{verb:you,present} {noun_phrase:definite} then you can {verb:you,present} {noun_phrase:definite}!`
 	//var str string = `{pronoun} {{verb:need:from_pronoun,present}} to {verb:i,present} {noun_phrase:definite}!`
+	//var str string = `{pronoun} [rng:can,may] {verb:i,present} {noun_phrase}[hide: {noun_phrase:singlular}], it {verb:it,future} {noun_phrase:definite}.`
 	str, err := g.randomSentence()
 	if err != nil {
 		return "", err
@@ -63,16 +72,15 @@ func (g *english) HackThis(fmtString string) (string, error) {
 
 	for idx < len(fmtString) {
 		if fmtString[idx] == '{' {
-			if fmtString[idx+1] == '{' {
+			nidx, err = g.consumeWord(fmtString, idx, output)
-				nidx, err = g.consumeNewWord(fmtString, idx, output)
 			if err != nil {
 				return "", err
 			}
 			idx = nidx
 			continue
-			}
 
-			nidx, err = g.consumeWord(fmtString, idx, output)
+		} else if fmtString[idx] == '[' {
+			nidx, err = g.consumeRng(fmtString, idx, output)
 			if err != nil {
 				return "", err
 			}
@@ -90,8 +98,57 @@ func (g *english) HackThis(fmtString string) (string, error) {
 	return toCap(output.String()), nil
 }
 
+func (g *english) consumeRng(fmtString string, idx int, output *strings.Builder) (int, error) {
+	idx++
+	def := strings.Index(fmtString[idx:], ":")
+	if def == -1 {
+		return 0, fmt.Errorf("Missing command separator in RNG block")
+	}
+	def += idx
+
+	end := strings.Index(fmtString[idx:], "]")
+	if end == -1 {
+		return 0, fmt.Errorf("Unclosed RNG block starting at offset %d", idx-1)
+	}
+	end += idx
+
+	if def > end {
+		return 0, fmt.Errorf("Missing command separator in RNG block")
+	}
+
+	switch fmtString[idx:def] {
+	case "rng":
+		choices := strings.Split(fmtString[def+1:end], ",")
+		ridx := rand.Intn(len(choices))
+		output.WriteString(choices[ridx])
+
+	case "hide":
+		if rand.Int() % 2 == 0 {
+			return end+1, nil
+		}
+
+		var newEnd int = def+1
+		var err error
+		for newEnd < end {
+			if fmtString[newEnd] == '{' {
+				newEnd, err = g.consumeWord(fmtString, newEnd, output)
+				if err != nil {
+					return 0, err
+				}
+			} else {
+				newEnd, err = g.consumeRaw(fmtString, newEnd, output)
+			}
+		}
+
+	default:
+		return 0, fmt.Errorf("RNG type %q is not implemented", fmtString[idx:def])
+	}
+
+	return end+1, nil
+}
+
 func (g *english) consumeRaw(fmtString string, idx int, output *strings.Builder) (int, error) {
-	end := strings.Index(fmtString[idx:], "{")
+	end := strings.IndexAny(fmtString[idx:], "{[")
 	if end == -1 {
 		output.WriteString(fmtString[idx:len(fmtString)])
 		return len(fmtString), nil
@@ -243,6 +300,10 @@ func (g *english) consumeNewWord(fmtString string, idx int, output *strings.Buil
 }
 
 func (g *english) consumeWord(fmtString string, idx int, output *strings.Builder) (int, error) {
+	if fmtString[idx+1] == '{' {
+		return g.consumeNewWord(fmtString, idx, output)
+	}
+
 	idx++
 	var wordtype string
 	var options string
@@ -275,7 +336,7 @@ func (g *english) consumeWord(fmtString string, idx int, output *strings.Builder
 		var plural bool = rand.Int() % 2 == 0
 		if sliceContains(opts, "plural") {
 			plural = true
-		} else if sliceContains(opts, "singular")
+		} else if sliceContains(opts, "singular") {
 			plural = false
 		}
 

word_lists.json

@@ -419,6 +419,7 @@
         "{pronoun} can't {verb:i,present} {noun_phrase}, it {verb:it,future} {noun_phrase}!",
         "{verb:you,present} {noun_phrase:definite}, then you can {verb:you,present} {noun_phrase:definite}!",
         "{noun_phrase:it,past} {verb}. With {noun_phrase:indifinite,noadj,compound}!",
-        "{pronoun} {{verb:need:from_pronoun,present}} to {verb:i,present} {noun_phrase:definite}!"
+        "{pronoun} {{verb:need:from_pronoun,present}} to {verb:i,present} {noun_phrase:definite}!",
+        "{pronoun} [rng:can,may] {verb:i,present} {noun_phrase} [hide:{noun_phrase:singlular}], it {verb:it,future} {noun_phrase:definite}."
     ]
 }