test: add gas usage tests for updateMiddlewareDataHash (fixes #1)

contracts/GAS_FINDINGS.md

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+# Gas Usage Analysis for `updateMiddlewareDataHash` Function
+
+## Executive Summary
+
+**Issue #1**: Check that `updateMiddlewareDataHash` function won't pass gas block limit
+
+**Finding**: The function WILL exceed block gas limits under realistic operating conditions.
+
+## Test Results
+
+### 1. Operator Count Scaling
+With fixed history length (10 entries):
+- 10 operators: 517K gas (1% of block limit) ✅
+- 25 operators: 1.06M gas (3% of block limit) ✅
+- 50 operators: 2.13M gas (7% of block limit) ✅
+- 100 operators: 4.58M gas (15% of block limit) ✅
+- 250 operators: 14.29M gas (47% of block limit) ⚠️
+- **500 operators: 38.46M gas (128% of block limit)** ❌ **EXCEEDS LIMIT**
+
+### 2. History Length Scaling
+With fixed operator count (100 operators):
+- 5 history entries: 2.99M gas (9% of block limit) ✅
+- 10 history entries: 4.58M gas (15% of block limit) ✅
+- 25 history entries: 9.18M gas (30% of block limit) ⚠️
+- 50 history entries: 20.51M gas (68% of block limit) ⚠️
+- **100 history entries: 52.58M gas (175% of block limit)** ❌ **EXCEEDS LIMIT**
+
+### 3. Growth Rate Analysis
+- **Operator count has super-linear growth**: 2x operators = 2.09x gas usage
+- **History length has super-linear growth**: 2x history = 1.58x gas usage
+- Combined scaling: 2x both = 3.54x gas usage
+
+### 4. Critical Thresholds
+Based on 80% safety margin (24M gas):
+- **Maximum safe configuration**: ~400 operators with minimal history OR ~80 history entries with 100 operators
+- **Realistic danger zone**: 250+ operators with 50+ history entries
+
+## Risk Assessment
+
+### HIGH RISK Scenarios:
+1. **Large operator sets** (>400 operators) will fail regardless of history length
+2. **Long history** (>80 entries) with moderate operator counts (100+) will fail
+3. **Combined moderate values** (250 operators + 50 history) exceed limits
+
+### Current Code Acknowledgments:
+The code already contains TODO comments acknowledging this issue:
+- Line 22: `// TODO: what to do if getMiddlewareData passes the block gas limit?`
+- Line 125 & 145: Notes about optimizing operator ID recomputation
+
+## Recommendations
+
+### Immediate Actions:
+1. **Implement gas limit checks** before calling the function
+2. **Add circuit breakers** for operator count and history length
+3. **Document maximum safe operating parameters**
+
+### Long-term Solutions:
+1. **Multi-step updates**: Break `updateMiddlewareDataHash` into multiple transactions
+   - Update operator keys in one transaction
+   - Update APK history in another
+   - Update stake history separately
+
+2. **History trimming**: Implement automatic pruning of old history entries
+   - Keep only recent N entries
+   - Archive old data off-chain if needed
+
+3. **Pagination**: Process operators in batches
+   - Update subset of operators per transaction
+   - Maintain partial state updates
+
+4. **Optimization opportunities**:
+   - Cache operator IDs instead of recomputing (noted in TODOs)
+   - Use more efficient data structures
+   - Consider merkle trees for large datasets
+
+## Conclusion
+
+Issue #1 is **CONFIRMED** as a valid concern. The `updateMiddlewareDataHash` function will exceed block gas limits with:
+- 500+ operators (regardless of history)
+- 100+ history entries (with 100 operators)
+- Combined moderate values (250 operators + 50 history)
+
+This is a **CRITICAL** issue that needs to be addressed before mainnet deployment with large operator sets.