feat(hmpl): render simple placeholder with memory leak of course

package/c/hmpl/hmpl.c

@@ -3,7 +3,8 @@
 #include <string.h>
 #include <unistd.h>
 //#include "libhmpl.h"
-#include "libhectic.h"
+#include "chectic.h"
+#include "cjson/cJSON.h"
 
 #define KB128 131072
 
@@ -47,7 +48,7 @@
 //       _offset := simple_start + start_pattern_length;
 //       RAISE LOG '% := % + %', _offset, simple_start, start_pattern_length;
 //       IF _offset = 0 THEN
-//         RAISE EXCEPTION 'Malformed template: offcet cannot be 0';
+//         RAISE EXCEPTION 'Malformed template: offset cannot be 0';
 //       END IF;
 //       CONTINUE;
 //     END IF;
@@ -59,8 +60,62 @@
 // 
 //   RETURN result;
 // END $$;
+char *eval(cJSON *context, const char *key) {
+    if (!context || !key) return NULL;
+    char *key_copy = strdup(key);
+    char *token, *rest = key_copy;
+    cJSON *res = context;
 
-void render_template_placeholders(char *text, char *context, char prefix[1]) {
+    while ((token = strtok_r(rest, ".", &rest))) {
+        res = cJSON_GetObjectItemCaseSensitive(res, token);
+        if (!res) {
+            free(key_copy);
+            return NULL;
+        }
+    }
+    free(key_copy);
+
+    if (cJSON_IsString(res) && res->valuestring)
+        return strdup(res->valuestring);
+    else if (cJSON_IsNumber(res)) {
+        char buf[64];
+        snprintf(buf, sizeof(buf), "%g", res->valuedouble);
+        return strdup(buf);
+    }
+    return cJSON_PrintUnformatted(res);
+}
+
+void substring(const char *src, char *dest, size_t start, size_t len) {
+    raise_debug("substring %s from %d to %d", src, start, len);
+    size_t srclen = strlen(src);
+    if (start >= srclen) {
+        dest[0] = '\0';
+        return;
+    }
+    if (start + len > srclen)
+        len = srclen - start;
+    strncpy(dest, src + start, len);
+    dest[len] = '\0';
+}
+
+char* replace_substring(const char* src, int start, int end, const char* replacement) {
+    raise_debug("replace_substring");
+    int src_len = strlen(src);
+    int rep_len = strlen(replacement);
+    int new_len = src_len - (end - start + 1) + rep_len;
+
+    char* new_str = malloc(new_len + 1);
+    if (!new_str) return NULL;
+
+    memcpy(new_str, src, start); // copy before
+    memcpy(new_str + start, replacement, rep_len); // insert replacement
+    strcpy(new_str + start + rep_len, src + end + 1); // copy after
+
+    return new_str;
+}
+
+void render_template_placeholders(char *text, cJSON *context, char prefix[1]) {
+  raise_debug("render_template_placeholders");
   // start
   char start_pattern[4];
   sprintf(&start_pattern[0], "{{%s", prefix);
@@ -71,35 +126,68 @@ void render_template_placeholders(char *text, char *context, char prefix[1]) {
   while (1) {
     // find tag start
     char *placeholder_start = strstr(text + offset, start_pattern);
-    if (!placeholder_start) {
-      break;
+    if (!placeholder_start) { break; }
+    char *releative_start = (size_t)placeholder_start - (size_t)text + start_pattern_length;
+    raise_debug("start: %d", releative_start);
+
+    if (offset != 0) {
+      placeholder_start += offset - 1;
     }
+
+    char* placeholder_end = strstr(placeholder_start, "}}");
+    // TODO: user error instead exaption
+    if (!placeholder_end) { raise_exception("Malformed template: missing closing braces for placeholder start"); };
+    raise_debug("end: %d", (size_t)placeholder_end - (size_t)text);
+
+    int len = (size_t)placeholder_end - (size_t)placeholder_start - start_pattern_length;
+    char* placeholder_key = malloc(len + 1);;
+    substring(text, placeholder_key, releative_start, len);
+    raise_debug("key: %s", placeholder_key);
+    char* replacement = eval(context, placeholder_key);
+    raise_debug("%s = eval(%s, %s)", replacement, context, placeholder_key);
+    if (!replacement) {
+      offset = placeholder_start + start_pattern_length;
+      raise_log("offset is %s = %s + %s", offset, placeholder_start, start_pattern_length);
+      if (offset = 0) {
+        raise_exception("offset cannot be 0 here");
+      };
+      continue;
+    }
+    text = replace_substring(text, releative_start - start_pattern_length, releative_start + len + 2 - 1, replacement);
+    raise_info(text);
   };
 }
 
-void render_template(char *text, char *context) {
+void render_template(char *text, cJSON *context) {
   render_template_placeholders(text, context, "");
 }
 
 int main(int argc, char *argv[]) {
-    char *text = NULL;
-    char *context = strdup(argc > 1 ? argv[1] : "{}");
+  init_logger();
+  raise_info("start");
 
-    if (argc > 2) {
-        text = strdup(argv[2]);
-    } else if (!isatty(fileno(stdin))) {
-        size_t size = 0;
-        ssize_t len = getdelim(&text, &size, '\0', stdin);
-        if (len < 0) {
-            perror("read stdin");
-            free(context);
-            return 1;
-        }
-    }
+  char *text = NULL;
+  cJSON *context = cJSON_Parse(strdup(argc > 1 ? argv[1] : "{}"));
 
+  if (argc > 2) {
+      text = strdup(argv[2]);
+  } else if (!isatty(fileno(stdin))) {
+      size_t size = 0;
+      ssize_t len = getdelim(&text, &size, '\0', stdin);
+      if (len < 0) {
+          perror("read stdin");
+          free(context);
+          return 1;
+      }
+  }
+
+  if (text) {
     render_template(text, context);
+  }
 
-    free(text);
-    free(context);
-    return 0;
+  printf("%s", text);
+
+  free(text);
+  free(context);
+  return 0;
 }