World day against cyber censorship

1 files changed, 169 insertions, 0 deletions

diff --git a/public/inc/zensur.js b/public/inc/zensur.js
new file mode 100644
index 0000000..d6b4d29
--- /dev/null
+++ b/public/inc/zensur.js
@@ -0,0 +1,169 @@
+(function() {
+  // states
+  // 0: uncensored
+  // 1: start_censor
+  // 2: censored
+  // state transition probabilities:
+  var p_trans = [
+    // x     uncensored   -> uncensored
+    0.08, // uncensored   -> start_censor
+    // 0     uncensored   -> censored
+    // 0     start_censor -> uncensored
+    // 0     start_censor -> start_censor
+    // 1     start_censor -> censored
+    0.55, // censored   -> uncensored
+    // 0     censored   -> start_censor
+    // x     censored   -> censored
+  ];
+  var censored_tag = "span";
+  var censored_class = "censored";
+  var start_censor = "<" + censored_tag + " class=\"" + censored_class + "\">";
+  var stop_censor = "</" + censored_tag + ">";
+  var re_censor = /[0-9A-Za-z]/;
+  var isCensored = true;
+  var censoredElements = [];
+
+  function splitWords(text) {
+    // some older IEs don't suppport capturing parentheses
+    // return text.split(/([\t\n\r ])/);
+    if (text.length === 0) {
+      return [""];
+    }
+    var words = [];
+    var last_i = 0;
+    for (var i = 0; i < text.length; i++) {
+      switch(text[i]) {
+        case '\t':
+        case '\n':
+        case '\r':
+        case ' ':
+          if (last_i !== i) {
+            words.push(text.slice(last_i, i));
+          }
+          words.push(text[i]);
+          last_i = i + 1;
+      }
+    }
+    if (last_i !== text.length) {
+      words.push(text.slice(last_i));
+    }
+    return words;
+  }
+
+  function censorWord(state, word) {
+    // ignore words not containing letters (may be spaces only)
+    if (!word.match(re_censor)) {
+      return word;
+    }
+
+    var r = Math.random();
+    var prefix = "";
+    var suffix = "";
+
+    if (state.s === 1) {
+      // start_censor -> censored
+      state.s = 2;
+      prefix = start_censor;
+    }
+
+    if (state.s === 0 && r < p_trans[0]) {
+      // uncensored -> start_censor
+      state.s = 1;
+    }
+    else if (state.s === 2 && r < p_trans[1]) {
+      // censored -> uncensored
+      state.s = 0;
+      suffix = stop_censor;
+    }
+
+    return prefix + word + suffix;
+  }
+
+  function censorTextNode(node) {
+    var state = { s: 0 };
+    if (Math.random() < p_trans[0]) {
+      // start_censor
+      state.s = 1;
+    }
+    var words = splitWords(node.nodeValue);
+    for (var i in words) {
+      words[i] = censorWord(state, words[i]);
+    }
+    if (state.s === 2) {
+      words[words.length-1] = words[words.length-1] + stop_censor;
+    }
+    var newnode = document.createElement(censored_tag);
+    newnode.innerHTML = words.join("");
+    return newnode;
+  }
+
+  function censorElement(element, on) {
+    var childs = element.childNodes;
+    var uncensored = false;
+    for (var i in childs) {
+
+      if (childs[i].nodeType === 1 &&
+          childs[i].nodeName !== "OPTION" &&
+          childs[i].nodeName !== "SCRIPT" &&
+          childs[i].nodeName !== "SELECT" &&
+          childs[i].nodeName !== "STYLE" &&
+          childs[i].nodeName !== "TEXTAREA" &&
+          childs[i].nodeName !== "TITLE")
+      {
+        if (!on &&
+            childs[i].nodeName === censored_tag.toUpperCase() &&
+            childs[i].className === censored_class &&
+            childs[i].childNodes.length === 1)
+        {
+          uncensored = true;
+          element.replaceChild(childs[i].childNodes[0], childs[i]);
+        }
+
+        var childUncensored = censorElement(childs[i], on);
+        if (!on && childUncensored)
+        {
+          var newnode = document.createTextNode("");
+          for (var j in childs[i].childNodes) {
+            if (!childs[i].childNodes[j].nodeType === 3) {
+              return;
+            }
+            if (childs[i].childNodes[j].nodeValue) {
+              newnode.nodeValue += childs[i].childNodes[j].nodeValue;
+            }
+          }
+          element.replaceChild(newnode, childs[i]);
+        }
+      }
+
+      else if (on &&
+          childs[i].nodeType === 3 &&
+          childs[i].nodeValue.match(re_censor))
+      {
+        element.replaceChild(censorTextNode(childs[i]), childs[i]);
+      }
+
+    }
+
+    return uncensored;
+  }
+
+  function doCensor(on) {
+    for (var i in censoredElements) {
+      censorElement(censoredElements[i], on);
+    }
+  }
+
+  window.zensurjs = function(arg) {
+    if (arg === undefined) {
+      isCensored = !isCensored;
+      doCensor(isCensored);
+    }
+    else {
+      censoredElements.push(arg);
+      if (isCensored) {
+        censorElement(arg, true);
+      }
+    }
+    return isCensored;
+  };
+})();