Implement string interpolation.

Merge pull request #45 from haroldo-ok/string-interpolation
Now it is possible to use print a numeric variable in the middle of a text line by using `${expression}`.

examples/test/project/startup.choice

@@ -5,7 +5,6 @@
 * create boolVar, true
 * temp localInt, 2
 
-* set intVar, 3
 * set localInt, intVar + 3
 
 * create playingMusic, false
@@ -33,14 +32,16 @@
 		* image "Smiley.png", at(30, 3)
 		OK... showing a smiley!
 	# Fourth choice
-		You chose the last one
+		This is a test.
+		Second line.
+		Third line.
 		* choice
 			# Yet another choice
 				You chose this.
 			# One more choice
 				You chose that.
+	# Increment a number
+		* set intVar, intVar + 1
+		The value is now ${intVar}!
 	# Go to another scene
-		* goto_scene test
-This is a test.
-Second line.
-Third line.
+		* goto_scene test

examples/test/src/vn_engine.c

@@ -63,7 +63,7 @@ void VN_init() {
 	XGM_setLoopNumber(-1);
 	XGM_setForceDelayDMA(TRUE);
 
-	VDP_drawText("choice4genesis v0.4.0", 18, 27);
+	VDP_drawText("choice4genesis v0.5.0", 18, 27);
 }
 
 
@@ -117,11 +117,25 @@ void VN_clearWindow() {
 	VDP_clearTextAreaEx(BG_A, TILE_ATTR_FULL(PAL0, FALSE, FALSE, FALSE, 0x05A0), window.x, window.y, window.w, window.h, DMA);
 }
 
-void VN_text(char *text) {
+void VN_textStart() {
 	if (textBuffer[0]) strcat(textBuffer, "\n");
+}
+
+void VN_textString(char *text) {
 	strcat(textBuffer, text);
 }
 
+void VN_textInt(int number) {
+	char number_buffer[12];
+	sprintf(number_buffer, "%d", number);
+	VN_textString(number_buffer);
+}
+
+void VN_text(char *text) {
+	VN_textStart();
+	VN_textString(text);
+}
+
 void VN_flushText() {
 	if (!textBuffer[0]) return;
 

examples/test/src/vn_engine.h

@@ -19,6 +19,9 @@ extern void VN_music(const u8 *music);
 extern void VN_sound(const u8 *sound, const u16 length);
 extern void VN_stop(const u8 flags);
 
+extern void VN_textStart();
+extern void VN_textString(char *text);
+extern void VN_textInt(int number);
 extern void VN_text(char *text);
 extern void VN_flushText();
 extern void VN_wait(u16 duration);

generator/generator.js

@@ -276,6 +276,19 @@ const COMMAND_GENERATORS = {
 generateFromBody = (body, context) => 
 	compact((body || []).map(entity => {
 		if (entity.type === 'text') {
+			if (entity.expressions) {
+				return [
+					'VN_textStart();',
+					...entity.expressions.map(o => {
+						if (o.params && o.params.positional && o.params.positional.expression) {
+							const expr = getExpression(entity, o.params.positional.expression, context, 'Expression');
+							return `VN_textInt(${expr.code});`;
+						}
+						return `VN_textString("${o}");`;
+					})
+				].join('\n');
+			}
+
 			return `VN_text("${entity.text}");`
 		}
 		if (entity.type === 'option') {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "choice4genesis",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "description": "A ChoiceScript clone that generates SGDK-compatible C source for the Sega Genesis ",
   "main": "index.js",
   "scripts": {

parser/syntax-full.js

@@ -42,9 +42,23 @@ const COMMANDS = {
 
 const COMMAND_PARSERS = Object.fromEntries(Object.entries(COMMANDS).map(([command, config]) => [command, createExpressionParser(config)]));
 
+const stringInterpolationParser = createExpressionParser({ positional: ['expression'] });
+
 
 const checkOnlyAfter = (body, errors) => 
 	body.map((element, index) => {
+		if (element.type === 'text') {
+			const interpRegex = /\$\{(.*?)\}/g;
+			const parts = element.text.replace(interpRegex, a => '\n' + a + '\n').split('\n');
+			if (parts.length > 1 || interpRegex.test(parts[0] || '')) {
+				const expressions = parts.map(part => interpRegex.test(part) ? 
+					stringInterpolationParser(part.replace(interpRegex, '$1')) : 
+					part);
+				return { ...element, expressions };
+			}
+			return element;
+		}
+
 		if (element.type !== 'command') {
 			return element;
 		}