From 52b787d8b7bcb024cbd7b33bc41f613a2c22d265 Mon Sep 17 00:00:00 2001
From: Hauke D <haukex@zero-g.net>
Date: Mon, 13 Aug 2018 15:53:52 +0200
Subject: [PATCH] Autoload WebPerl for <script> tags

---
 Changes.md     |  1 +
 web/webperl.js | 20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Changes.md b/Changes.md
index 0d2c3b8..e48447e 100644
--- a/Changes.md
+++ b/Changes.md
@@ -9,6 +9,7 @@ Not yet released: v0.03-beta
 - Fixed an issue with WebPerl::JSObject::toperl()
   where JS objects were not being converted properly.
 - Added AJAX demo
+- Added WebPerl autoloading for script tags
 - ...
 
 
diff --git a/web/webperl.js b/web/webperl.js
index f99320e..b01877a 100644
--- a/web/webperl.js
+++ b/web/webperl.js
@@ -94,8 +94,24 @@ window.addEventListener("load", function () {
 	}
 	else if (scripts.length) {
 		console.debug("Perl: Found",scripts.length,"embedded script(s), autorunning...");
-		//TODO: should we maybe prefix "use warnings; use 5.028;"? or at least "use WebPerl qw/js/;"?
-		Perl._saveAndRun( scripts.join(";\n") );
+		var code = scripts.join(";\n");
+		
+		// get the first five lines of code
+		var n = 5 + 1; // the contents of the <script> tag will usually begin with a newline
+		var i = -1;
+		while (n-- && i++ < code.length) {
+			i = code.indexOf("\n", i);
+			if (i < 0) break;
+		}
+		var head = i<0 ? code : code.substring(0,i);
+		// look for a "use WebPerl"
+		const regex = /^\s*use\s+WebPerl(\s|;)/m;
+		if (!regex.exec(head)) { // load WebPerl unless the user loaded it
+			console.debug("Perl: Autoloading WebPerl");
+			code = "use WebPerl 'js';\n" + code;
+		}
+		
+		Perl._saveAndRun(code);
 	}
 	else console.debug("Perl: No embedded scripts");
 });