Initial commit

contracts/governance/PolicyEngine.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.24;
+
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "../interfaces/IPolicyEngine.sol";
+import "../interfaces/IPolicyModule.sol";
+
+/**
+ * @title PolicyEngine
+ * @notice Aggregates policy decisions from multiple modules
+ * @dev All registered modules must approve an action for it to be allowed
+ */
+contract PolicyEngine is IPolicyEngine, Ownable {
+    // Registered policy modules
+    address[] private policyModules;
+    mapping(address => bool) private isRegisteredModule;
+
+    modifier onlyRegistered(address module) {
+        require(isRegisteredModule[module], "Module not registered");
+        _;
+    }
+
+    constructor(address initialOwner) Ownable(initialOwner) {}
+
+    /**
+     * @notice Register a policy module
+     */
+    function registerPolicyModule(address module) external override onlyOwner {
+        require(module != address(0), "Invalid module");
+        require(!isRegisteredModule[module], "Module already registered");
+        
+        // Verify it implements IPolicyModule
+        try IPolicyModule(module).name() returns (string memory) {
+            // Module is valid
+        } catch {
+            revert("Invalid policy module");
+        }
+
+        policyModules.push(module);
+        isRegisteredModule[module] = true;
+
+        emit PolicyModuleRegistered(module, IPolicyModule(module).name());
+    }
+
+    /**
+     * @notice Unregister a policy module
+     */
+    function unregisterPolicyModule(address module) external override onlyOwner onlyRegistered(module) {
+        // Remove from array
+        for (uint256 i = 0; i < policyModules.length; i++) {
+            if (policyModules[i] == module) {
+                policyModules[i] = policyModules[policyModules.length - 1];
+                policyModules.pop();
+                break;
+            }
+        }
+
+        delete isRegisteredModule[module];
+        emit PolicyModuleUnregistered(module);
+    }
+
+    /**
+     * @notice Evaluate all registered policy modules
+     * @return allowed True if ALL modules allow the action
+     * @return reason Reason from first denying module
+     */
+    function evaluateAll(
+        bytes32 actionType,
+        bytes memory actionData
+    ) external view override returns (bool allowed, string memory reason) {
+        // If no modules registered, allow by default
+        if (policyModules.length == 0) {
+            return (true, "");
+        }
+
+        // Check all modules
+        for (uint256 i = 0; i < policyModules.length; i++) {
+            address module = policyModules[i];
+            
+            // Skip if module is disabled
+            try IPolicyModule(module).isEnabled() returns (bool enabled) {
+                if (!enabled) {
+                    continue;
+                }
+            } catch {
+                continue; // Skip if check fails
+            }
+
+            // Get decision from module
+            IPolicyModule.PolicyDecision memory decision;
+            try IPolicyModule(module).evaluate(actionType, actionData) returns (IPolicyModule.PolicyDecision memory d) {
+                decision = d;
+            } catch {
+                // If evaluation fails, deny for safety
+                return (false, "Policy evaluation failed");
+            }
+
+            // If any module denies, return denial
+            if (!decision.allowed) {
+                return (false, decision.reason);
+            }
+        }
+
+        // All modules allowed
+        return (true, "");
+    }
+
+    /**
+     * @notice Get all registered policy modules
+     */
+    function getPolicyModules() external view override returns (address[] memory) {
+        return policyModules;
+    }
+
+    /**
+     * @notice Check if a module is registered
+     */
+    function isRegistered(address module) external view override returns (bool) {
+        return isRegisteredModule[module];
+    }
+
+    /**
+     * @notice Get number of registered modules
+     */
+    function getModuleCount() external view returns (uint256) {
+        return policyModules.length;
+    }
+}
+