feat: make re2 an optional peer dependency

Author: aldenquimby

.gitignore

@@ -6,3 +6,5 @@ node_modules/
 package-lock.json
 
 .npm
+
+.idea/

lib/regex.js

@@ -1,7 +1,22 @@
-var RE2 = require("re2");
+let RE2;
+let hasRE2;
 
 class RegexList {
   constructor() {
+    // inspiration: https://github.com/spamscanner/url-regex-safe/blob/6c1e2c3b5557709633a2cc971d599469ea395061/src/index.js#L37-L49
+    this.SafeRegExp = hasRE2 !== false
+        ? (() => {
+          if (typeof RE2 === 'function') return RE2;
+          try {
+            RE2 = require('re2');
+            return typeof RE2 === 'function' ? RE2 : RegExp;
+          } catch {
+            hasRE2 = false;
+            return RegExp;
+          }
+        })()
+        : RegExp;
+
     this.quoteHeadersRegex = this.buildRe2([
       /^-*\s*(On\s.+\s.+\n?wrote:{0,1})\s{0,1}-*$/m, // On DATE, NAME <EMAIL> wrote:
       /^-*\s*(Le\s.+\s.+\n?écrit\s?:{0,1})\s{0,1}-*$/m, // Le DATE, NAME <EMAIL> a écrit :
@@ -75,9 +90,7 @@ class RegexList {
   }
 
   buildRe2(regexList) {
-    return regexList.map((regex) => {
-      return new RE2(regex);
-    });
+    return regexList.map((regex) => new this.SafeRegExp(regex));
   }
 }