From 82236b75f1a8d85610c2d9b78ce9c68c3f454b3e Mon Sep 17 00:00:00 2001
From: Nat Quayle Nelson <natquaylenelson@gmail.com>
Date: Wed, 9 Dec 2020 21:46:07 -0700
Subject: [PATCH] Refactor reader macros in AOC Day 8 pt 1

---
 src/kiss/Helpers.hx | 12 ++++++++++--
 src/kiss/Reader.hx  |  8 ++++++--
 src/kiss/Stream.hx  |  2 +-
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/kiss/Helpers.hx b/src/kiss/Helpers.hx
index f5fd135..0be308d 100644
--- a/src/kiss/Helpers.hx
+++ b/src/kiss/Helpers.hx
@@ -197,6 +197,7 @@ class Helpers {
         interp.variables.set("read", Reader.assertRead.bind(_, k.readTable));
         interp.variables.set("readExpArray", Reader.readExpArray.bind(_, _, k.readTable));
         interp.variables.set("ReaderExp", ReaderExpDef);
+        interp.variables.set("nextToken", Reader.nextToken.bind(_, "a token"));
         interp.variables.set("kiss", {
             Reader: {
                 ReaderExpDef: ReaderExpDef
@@ -247,8 +248,15 @@ class Helpers {
                 FieldExp(field, evalUnquotes(innerExp, k, args));
             case KeyValueExp(keyExp, valueExp):
                 KeyValueExp(evalUnquotes(keyExp, k, args), evalUnquotes(valueExp, k, args));
-            case Unquote(exp):
-                runAtCompileTime(exp, k, args).def;
+            case Unquote(innerExp):
+                var unquoteValue:Dynamic = runAtCompileTime(innerExp, k, args);
+                if (unquoteValue == null) {
+                    throw CompileError.fromExp(innerExp, "unquote evaluated to null");
+                } else if (Std.isOfType(unquoteValue, ReaderExpDef)) {
+                    unquoteValue;
+                } else {
+                    unquoteValue.def;
+                };
             default:
                 throw CompileError.fromExp(exp, 'unquote evaluation not implemented');
         };
diff --git a/src/kiss/Reader.hx b/src/kiss/Reader.hx
index 124b78b..45616fd 100644
--- a/src/kiss/Reader.hx
+++ b/src/kiss/Reader.hx
@@ -93,8 +93,12 @@ class Reader {
 
     public static final terminators = [")", "]", "/*", "\n", " "];
 
-    static function nextToken(stream:Stream, expect:String) {
-        return stream.expect(expect, () -> stream.takeUntilOneOf(terminators));
+    public static function nextToken(stream:Stream, expect:String) {
+        var tok = stream.expect(expect, () -> stream.takeUntilOneOf(terminators));
+        if (tok.length == 0) {
+            throw 'Expected token $expect at ${stream.position()}';
+        }
+        return tok;
     }
 
     public static function assertRead(stream:Stream, readTable:Map<String, ReadFunction>):ReaderExp {
diff --git a/src/kiss/Stream.hx b/src/kiss/Stream.hx
index 4531d99..7fc3175 100644
--- a/src/kiss/Stream.hx
+++ b/src/kiss/Stream.hx
@@ -158,7 +158,7 @@ class Stream {
         switch (f()) {
             case Some(s):
                 return s;
-            case None:
+            default:
                 throw 'Expected $whatToExpect at $position';
         }
     }