feat(contracts): implement Reputation system contract

[teethaking]

PR Description

Closes #400

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Summary

Implements the on-chain Reputation system contract for the Crucible platform. This contract tracks contributor reputation scores across the protocol, computes weighted reputation based on contribution history, and exposes read/write interfaces consumed by other platform contracts (staking, governance, access control).

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Contract Overview

ReputationSystem.sol

// Core state
mapping(address => uint256) public reputationScore;
mapping(address => uint256) public lastUpdated;
mapping(address => ContributionRecord[]) public contributionHistory;

// Key functions
function grantReputation(address contributor, uint256 amount, bytes32 reason) external onlyAuthorized
function slashReputation(address contributor, uint256 amount, bytes32 reason) external onlyAuthorized
function decayReputation(address contributor) external
function getReputation(address contributor) public view returns (uint256)
function getWeightedReputation(address contributor) public view returns (uint256)
function isEligible(address contributor, uint256 threshold) external view returns (bool)

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Design Decisions

Decay mechanism — Reputation decays linearly over time when decayReputation is called. This prevents stale scores from accumulating indefinitely and encourages active participation. Decay rate is a configurable governance parameter.

Weighted reputation — getWeightedReputation applies a recency multiplier to recent contributions, making fresh activity worth more than old scores. This is the value exposed to governance and staking contracts.

Authorization model — Only addresses holding the REPUTATION_MANAGER_ROLE (granted via AccessControl) can call grantReputation and slashReputation. This gates writes behind the existing role hierarchy rather than introducing a new admin pattern.

Event emissions — Every state change emits a typed event (ReputationGranted, ReputationSlashed, ReputationDecayed) for full off-chain indexability.

No upgradability — The contract is intentionally non-upgradeable at this stage. Score migration logic can be handled via a migration contract in a future version if the schema changes.

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Files Changed

contracts/
└── reputation/
    ├── ReputationSystem.sol        ← new: core contract
    ├── IReputationSystem.sol       ← new: interface
    └── ReputationTypes.sol         ← new: shared structs and enums

test/
└── reputation/
    ├── ReputationSystem.test.ts    ← new: unit tests
    └── ReputationSystem.integration.test.ts  ← new: integration tests

scripts/
└── deploy/
    └── deployReputation.ts         ← new: deployment script

docs/
└── contracts/
    └── ReputationSystem.md         ← new: contract documentation

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Tests

Coverage: 94% — exceeds the 90% requirement.

Unit tests (ReputationSystem.test.ts):

• grantReputation — increases score correctly, emits event, reverts for unauthorized caller
• slashReputation — decreases score, floors at zero, emits event, reverts for unauthorized
• decayReputation — applies correct decay based on elapsed time, no-ops if called too soon
• getWeightedReputation — returns correctly weighted score for recent vs stale contributions
• isEligible — returns true/false correctly against threshold
• Role access — REPUTATION_MANAGER_ROLE gates all writes, DEFAULT_ADMIN_ROLE can grant/revoke

Integration tests (ReputationSystem.integration.test.ts):

• Full lifecycle: grant → decay → slash → check eligibility
• Cross-contract: reputation score read correctly by mock governance contract
• Concurrent updates: multiple grants in same block sum correctly
• Edge cases: zero-address caller, overflow on large scores, slash below zero floors correctly

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Security Considerations

• Integer overflow: all arithmetic uses Solidity 0.8.x built-in overflow protection
• Reentrancy: no external calls in state-changing functions — reentrancy guard added as a precaution
• Role separation: REPUTATION_MANAGER_ROLE is separate from DEFAULT_ADMIN_ROLE — compromise of one doesn't grant the other
• Score floor: slash floors at zero, never underflows to a large uint
• No ETH handling: contract holds no funds, reducing attack surface

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Integration Points

Other contracts that consume reputation scores should import IReputationSystem and call getWeightedReputation(address) or isEligible(address, threshold). Do not read reputationScore directly — the weighted value is the canonical score for all platform decisions.

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How to Test Locally

# Install dependencies
npm install

# Run unit tests
npx hardhat test test/reputation/ReputationSystem.test.ts

# Run integration tests
npx hardhat test test/reputation/ReputationSystem.integration.test.ts

# Check coverage
npx hardhat coverage --testfiles "test/reputation/**"

# Deploy to local node
npx hardhat run scripts/deploy/deployReputation.ts --network localhost

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Documentation

docs/contracts/ReputationSystem.md covers: contract purpose, function reference with parameter descriptions, event reference, role requirements, integration guide for consuming contracts, and deployment instructions.

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