From fd6465aad222a00d4c805043b7c0cf3b2d0f3c6b Mon Sep 17 00:00:00 2001
From: Danny van Kooten <dannyvankooten@users.noreply.github.com>
Date: Thu, 19 Mar 2020 20:05:39 +0100
Subject: add operator precedence

---
 src/template.c        | 28 ++++++++++++----------------
 tests/test_template.c | 22 ++++++++++++++++++++++
 2 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/src/template.c b/src/template.c
index 3d336d0..7b0d65b 100644
--- a/src/template.c
+++ b/src/template.c
@@ -92,9 +92,9 @@ mpc_parser_t *parser_init() {
         " string    : '\"' /([^\"])*/ '\"' ;"
         " op        : '+' | '-' | '*' | '/' | '>' | '<';"
         " factor    : '(' <expression> ')' | <symbol> | <number> | <string> ;"
-        " term      : <spaces> <factor> <spaces> (('*' | '/' | '%') <spaces> <factor> <spaces>)* ;"
-        " expression: <term> (('+' | '-') <term>)* ;"
-        " print     : /{{2}-?/ <expression> /-?}}/ ;"
+        " term      :  <factor> (<spaces> ('*' | '/' | '%') <spaces> <factor>)* ;"
+        " expression: <term> (<spaces> ('+' | '-' | '>' | '<') <spaces> <term>)* ;"
+        " print     : /{{2}-? */ <expression> / *-?}}/ ;"
         " comment   : \"{#\" /[^#][^#}]*/ \"#}\" ;"
         " statement_open: /{\%-? */;"
         " statement_close: / *-?\%}/;"
@@ -385,24 +385,24 @@ struct unja_object *eval_infix_expression(struct unja_object *left, char *op, st
 struct unja_object *eval_expression(mpc_ast_t* expr, struct context *ctx) {
 
     /* singular term */
-    if (strstr(expr->tag, "term")) {
-        return eval_expression_value(expr->children[1], ctx);
+    if (expr->children_num == 0 || strstr(expr->tag, "string|")) {
+        return eval_expression_value(expr, ctx);
     }
 
     /* otherwise: with operator */
     int offset = 0; 
-    struct object *result;
-    mpc_ast_t *left_node = expr->children[0]->children[1];
-    struct unja_object *left = eval_expression_value(left_node, ctx);
+    struct unja_object *result;
+    mpc_ast_t *left_node = expr->children[0];
+    struct unja_object *left = eval_expression(left_node, ctx);
 
     while (offset < expr->children_num - 1) {
-        mpc_ast_t *op = expr->children[offset+1];
-        mpc_ast_t *right_node = expr->children[offset+2]->children[1];
-        struct unja_object *right = eval_expression_value(right_node, ctx);
+        mpc_ast_t *op = expr->children[offset+2];
+        mpc_ast_t *right_node = expr->children[offset+4];
+        struct unja_object *right = eval_expression(right_node, ctx);
         result = eval_infix_expression(left, op->contents, right);
 
         left = result;
-        offset += 2;
+        offset += 4;
     }
 
     return result;
@@ -412,10 +412,6 @@ struct unja_object *eval_expression(mpc_ast_t* expr, struct context *ctx) {
 int eval(struct buffer *buf, mpc_ast_t* t, struct context *ctx) {
     static int trim_whitespace = 0;
 
-    #if DEBUG
-    printf("Node: %s = %s\n", t->tag, t->contents);
-    #endif
-
     // maybe eat whitespace going backward
     if (t->children_num > 0 && strstr(t->children[0]->contents, "-")) {
         buf->string = trim_trailing_whitespace(buf->string);
diff --git a/tests/test_template.c b/tests/test_template.c
index cb23dbf..4521d6c 100644
--- a/tests/test_template.c
+++ b/tests/test_template.c
@@ -89,6 +89,27 @@ TEST(expr_add) {
     hashmap_free(ctx);
 }
 
+
+TEST(expr_op_precedence) {
+    struct {
+        char *input;
+        char *expected_output;
+    } tests[] = {
+        {"{{ 5 * 2 + 1 }}.", "11."},
+        {"{{ 1 +  5 * 2 }}.", "11."},
+        {"{{ 10 / 2 + 1 }}.", "6."},
+        {"{{ 1 + 10 / 2 }}.", "6."},
+    };
+
+    struct hashmap *ctx = hashmap_new();
+    for (int i=0; i < ARRAY_SIZE(tests); i++) {
+        char *output = template_string(tests[i].input, ctx);
+        assert_str(output, tests[i].expected_output);
+        free(output);
+    }
+    hashmap_free(ctx);
+}
+
 TEST(expr_subtract) {
     char *input = "Hello {{ 5 - 5 }}.";
     char *output = template_string(input, NULL);
@@ -211,6 +232,7 @@ TEST(if_block) {
         {"{% if foobar %}1{% endif %}.", "."},
         {"{% if name %}1{% endif %}.", "1."},
         {"{% if age > 10 %}1{% endif %}.", "1."},
+        {"{% if 10+1 > 10 %}1{% endif %}.", "1."},
     };
 
     struct hashmap *ctx = hashmap_new();
-- 
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