DayLimit first version

contracts/DayLimit.sol

+pragma solidity ^0.4.4;
+
+
+import './Shareable.sol';
+
+
+/*
+ * DayLimit
+ *
+ * inheritable "property" contract that enables methods to be protected by placing a linear limit (specifiable)
+ * on a particular resource per calendar day. is multiowned to allow the limit to be altered. resource that method
+ * uses is specified in the modifier.
+ */
+contract DayLimit is Shareable {
+  // FIELDS
+
+  uint public dailyLimit;
+  uint public spentToday;
+  uint public lastDay;
+
+
+  // MODIFIERS
+
+  // simple modifier for daily limit.
+  modifier limitedDaily(uint _value) {
+    if (underLimit(_value))
+      _;
+  }
+
+
+  // CONSTRUCTOR
+  // stores initial daily limit and records the present day's index.
+  function DayLimit(uint _limit) {
+    dailyLimit = _limit;
+    lastDay = today();
+  }
+
+
+  // METHODS
+
+  // (re)sets the daily limit. needs many of the owners to confirm. doesn't alter the amount already spent today.
+  function setDailyLimit(uint _newLimit) onlymanyowners(sha3(msg.data)) external {
+    dailyLimit = _newLimit;
+  }
+
+  // resets the amount already spent today. needs many of the owners to confirm
+  function resetSpentToday() onlymanyowners(sha3(msg.data)) external {
+    spentToday = 0;
+  }
+
+
+  // INTERNAL METHODS
+
+  // checks to see if there is at least `_value` left from the daily limit today. if there is, subtracts it and
+  // returns true. otherwise just returns false.
+  function underLimit(uint _value) internal onlyowner returns (bool) {
+    // reset the spend limit if we're on a different day to last time.
+    if (today() > lastDay) {
+      spentToday = 0;
+      lastDay = today();
+    }
+    // check to see if there's enough left - if so, subtract and return true.
+    // overflow protection                    // dailyLimit check  
+    if (spentToday + _value >= spentToday && spentToday + _value <= dailyLimit) {
+      spentToday += _value;
+      return true;
+    }
+    return false;
+  }
+
+  // determines today's index.
+  function today() private constant returns (uint) {
+    return now / 1 days;
+  }
+}