refactor: move html_util into legacy core library

lib/dd3_legacy_core/include/dd3_legacy_core.h

@@ -0,0 +1,4 @@
+#pragma once
+
+// Include this header in legacy Unity tests to force-link dd3_legacy_core.
+void dd3_legacy_core_force_link();

lib/dd3_legacy_core/include/html_util.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <Arduino.h>
+
+String html_escape(const String &input);
+String url_encode_component(const String &input);
+bool sanitize_device_id(const String &input, String &out_device_id);

lib/dd3_legacy_core/src/dd3_legacy_core.cpp

@@ -0,0 +1,3 @@
+#include "dd3_legacy_core.h"
+
+void dd3_legacy_core_force_link() {}

lib/dd3_legacy_core/src/html_util.cpp

@@ -0,0 +1,98 @@
+#include "html_util.h"
+
+String html_escape(const String &input) {
+  String out;
+  out.reserve(input.length() + 8);
+  for (size_t i = 0; i < input.length(); ++i) {
+    char c = input[i];
+    switch (c) {
+      case '&':
+        out += "&amp;";
+        break;
+      case '<':
+        out += "&lt;";
+        break;
+      case '>':
+        out += "&gt;";
+        break;
+      case '"':
+        out += "&quot;";
+        break;
+      case '\'':
+        out += "&#39;";
+        break;
+      default:
+        out += c;
+        break;
+    }
+  }
+  return out;
+}
+
+String url_encode_component(const String &input) {
+  String out;
+  out.reserve(input.length() * 3);
+  const char *hex = "0123456789ABCDEF";
+  for (size_t i = 0; i < input.length(); ++i) {
+    unsigned char c = static_cast<unsigned char>(input[i]);
+    bool safe = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+        (c >= '0' && c <= '9') || c == '-' || c == '_' || c == '.' || c == '~';
+    if (safe) {
+      out += static_cast<char>(c);
+    } else {
+      out += '%';
+      out += hex[(c >> 4) & 0x0F];
+      out += hex[c & 0x0F];
+    }
+  }
+  return out;
+}
+
+static bool is_hex_char(char c) {
+  return (c >= '0' && c <= '9') ||
+      (c >= 'a' && c <= 'f') ||
+      (c >= 'A' && c <= 'F');
+}
+
+static String to_upper_hex4(const String &input) {
+  String out = input;
+  out.toUpperCase();
+  return out;
+}
+
+bool sanitize_device_id(const String &input, String &out_device_id) {
+  String trimmed = input;
+  trimmed.trim();
+  if (trimmed.length() == 0) {
+    return false;
+  }
+  if (trimmed.indexOf('/') >= 0 || trimmed.indexOf('\\') >= 0 || trimmed.indexOf("..") >= 0) {
+    return false;
+  }
+  if (trimmed.indexOf('%') >= 0) {
+    return false;
+  }
+
+  if (trimmed.length() == 4) {
+    for (size_t i = 0; i < 4; ++i) {
+      if (!is_hex_char(trimmed[i])) {
+        return false;
+      }
+    }
+    out_device_id = String("dd3-") + to_upper_hex4(trimmed);
+    return true;
+  }
+
+  if (trimmed.length() == 8 && trimmed.startsWith("dd3-")) {
+    String hex = trimmed.substring(4);
+    for (size_t i = 0; i < 4; ++i) {
+      if (!is_hex_char(hex[i])) {
+        return false;
+      }
+    }
+    out_device_id = String("dd3-") + to_upper_hex4(hex);
+    return true;
+  }
+
+  return false;
+}