// SPDX-License-Identifier: MIT
pragma solidity ^0.8.25;

import "./IStarkVerifier.sol";

/// @title BeliefAttestationVerifier
/// @notice RISC Zero STARK-based verifier for Vaultfire belief attestation proofs
///
/// @dev ╔══════════════════════════════════════════════════════════════════╗
/// @dev ║  ⚠️  DEVELOPMENT-MODE VERIFIER — DO NOT DEPLOY TO PRODUCTION  ⚠️  ║
/// @dev ║                                                                ║
/// @dev ║  This contract contains a PLACEHOLDER proof verifier that      ║
/// @dev ║  accepts ANY non-empty proof ≥ 32 bytes. It is restricted to   ║
/// @dev ║  Hardhat/local chains (ID 31337 / 1337) via multiple guards,   ║
/// @dev ║  but MUST be replaced with a real STARK verifier before any    ║
/// @dev ║  production deployment.                                        ║
/// @dev ║                                                                ║
/// @dev ║  Production replacement: ProductionBeliefAttestationVerifier   ║
/// @dev ╚══════════════════════════════════════════════════════════════════╝
///
/// @dev **RISC Zero Integration:**
///      This verifier accepts proofs generated by RISC Zero's zkVM, which allows
///      writing zero-knowledge programs in Rust using normal logic. Perfect for
///      proving complex behaviors like GitHub activity, NS3 logins, Base wallet
///      interactions where behavior = belief.
///
///      **Circuit Verification Logic:**
///      1. Prover knows secret belief without revealing it
///      2. Belief meets protocol-defined thresholds (80% loyalty)
///      3. Belief is authentic (originated through behavior, not fraud)
///      4. Activity-linked proof: GitHub commits, NS3 sessions, Base txs
///
///      **ZK Circuit Specification:**
///      - Public Inputs: [beliefHash, proverAddress, epoch, moduleID]
///      - Private Inputs: [beliefMessage, signature, loyaltyProof]
///      - Output: Proof that "This person is loyal, meets belief threshold,
///        and passed Vaultfire's moral integrity check — without revealing how."
///
///      **RISC Zero STARK Benefits:**
///      - No trusted setup (transparency with privacy)
///      - Post-quantum secure (future-proof)
///      - Fully programmable in Rust (creative expression stays intact)
///      - Built for ZK VMs (ideal for belief-based proof engines)
///
///      **Guest Program Location:** /risc0-guest/src/main.rs
///      **Proof Generation:** /scripts/generate-risc0-proof.js
contract BeliefAttestationVerifier is IStarkVerifier {
    /// @notice Proof system version identifier
    string public constant PROOF_SYSTEM_ID = "RISC0-STARK-BeliefAttestation-v1.0";

    /// @notice Number of public inputs expected by this verifier
    /// @dev [0]: beliefHash, [1]: proverAddress, [2]: epoch (optional), [3]: moduleID (optional)
    uint256 public constant PUBLIC_INPUTS_COUNT = 4;

    /// @notice Minimum belief threshold (basis points, 10000 = 100%)
    /// @dev Beliefs must meet this alignment threshold to be valid
    uint256 public constant MIN_BELIEF_THRESHOLD = 8000; // 80% alignment

    /// @notice Maximum epoch value (for campaign locking)
    uint256 public constant MAX_EPOCH = type(uint32).max;

    /// @notice Emitted when a proof is verified successfully
    /// @param beliefHash The belief hash that was verified
    /// @param proverAddress The address of the prover
    /// @param epoch The epoch/campaign ID (0 if not used)
    /// @param moduleID The Vaultfire module ID (0 if not used)
    event ProofVerified(
        bytes32 indexed beliefHash,
        address indexed proverAddress,
        uint256 epoch,
        uint256 moduleID
    );

    /// @notice Emitted every time the dev verifier is invoked as a warning signal.
    /// @dev Monitoring tools SHOULD alert on this event. Its presence on any
    ///      chain other than a local devnet indicates a critical misconfiguration.
    event DevVerifierUsed(
        address indexed caller,
        bytes32 indexed beliefHash,
        uint256 chainId,
        uint256 timestamp
    );

    /// @notice Verifies a STARK proof for belief attestation
    /// @dev This is the main verification function called by DilithiumAttestor
    ///
    ///      **Circuit Logic (what the STARK proof verifies):**
    ///      1. hash(beliefMessage) == publicInput[0] (beliefHash)
    ///      2. recover(signature, beliefHash) == publicInput[1] (proverAddress)
    ///      3. computeBeliefScore(beliefMessage, loyaltyProof) >= MIN_BELIEF_THRESHOLD
    ///      4. verifyLoyaltyProof(loyaltyProof, publicInput[3]) == true (moduleID check)
    ///      5. publicInput[2] <= MAX_EPOCH (epoch validity)
    ///
    ///      **Security Properties:**
    ///      - Zero-knowledge: beliefMessage and loyaltyProof remain private
    ///      - Soundness: Cannot forge proof without valid private inputs
    ///      - Completeness: Valid beliefs always verify successfully
    ///
    /// @param proofBytes The STARK proof (serialized via proof generation tool)
    /// @param publicInputs Array of public inputs [beliefHash, proverAddress, epoch, moduleID]
    /// @return True if proof is valid and all circuit constraints are satisfied
    function verifyProof(
        bytes calldata proofBytes,
        uint256[] calldata publicInputs
    ) external override returns (bool) {
        // Validate public inputs count
        require(publicInputs.length == PUBLIC_INPUTS_COUNT, "Invalid public inputs count");

        // Extract public inputs
        bytes32 beliefHash = bytes32(publicInputs[0]);
        address proverAddress = address(uint160(publicInputs[1]));
        uint256 epoch = publicInputs[2];
        uint256 moduleID = publicInputs[3];

        // Validate public input ranges
        require(beliefHash != bytes32(0), "Invalid belief hash");
        require(proverAddress != address(0), "Invalid prover address");
        require(epoch <= MAX_EPOCH, "Invalid epoch");

        // **STARK PROOF VERIFICATION**
        // In production, this would call into StarkWare's verifier contract
        // or a custom STARK verifier implementation. For now, we implement
        // the verification logic inline.
        //
        // The proof verifies that the prover knows:
        // - Private beliefMessage such that hash(beliefMessage) == beliefHash
        // - Private signature that recovers to proverAddress
        // - Private loyaltyProof that satisfies threshold and moduleID constraints
        //
        // Without revealing any of these private inputs.

        bool proofValid = _verifyStarkProof(proofBytes, beliefHash, proverAddress, epoch, moduleID);

        if (proofValid) {
            emit ProofVerified(beliefHash, proverAddress, epoch, moduleID);
        }

        return proofValid;
    }

    /// @notice Internal STARK proof verification logic
    ///
    /// @dev ╔══════════════════════════════════════════════════════════════╗
    /// @dev ║  ⚠️  PLACEHOLDER — ALWAYS RETURNS TRUE ON LOCAL CHAINS  ⚠️   ║
    /// @dev ║  This function MUST be replaced with a real STARK verifier  ║
    /// @dev ║  before any non-local deployment.                          ║
    /// @dev ╚══════════════════════════════════════════════════════════════╝
    ///
    ///      **Current Implementation:** Placeholder for STARK verifier integration
    ///      **Production Path:** Deploy StarkWare verifier, call via interface
    ///
    /// @param proofBytes The STARK proof data
    /// @param beliefHash Public input: hash of belief
    /// @param proverAddress Public input: prover's address
    /// @param epoch Public input: campaign/era identifier
    /// @param moduleID Public input: Vaultfire module (NS3, GitHub, etc.)
    /// @return True if STARK proof is valid
    function _verifyStarkProof(
        bytes calldata proofBytes,
        bytes32 beliefHash,
        address proverAddress,
        uint256 epoch,
        uint256 moduleID
    ) internal returns (bool) {
        // ══════════════════════════════════════════════════════════════════
        // DEFENSE-IN-DEPTH: Redundant chain-ID guard inside the internal
        // function itself, so even if the outer `verifyProof` entry point
        // is somehow called on a non-local chain, this will still revert.
        // ══════════════════════════════════════════════════════════════════
        require(
            block.chainid == 31337 || block.chainid == 1337,
            "DEV_VERIFIER: forbidden on non-local chain"
        );

        // Emit a warning event so monitoring tools can detect dev-verifier usage.
        emit DevVerifierUsed(msg.sender, beliefHash, block.chainid, block.timestamp);

        // Validate proof is non-empty
        require(proofBytes.length > 0, "Empty proof");

        // Validate proof structure (basic sanity checks)
        // Real STARK proofs are typically 100-200 KB
        require(proofBytes.length >= 32, "Proof too short");

        // **PLACEHOLDER IMPLEMENTATION - TESTNET/DEVELOPMENT ONLY**
        // Currently returns true for any non-empty proof with valid public inputs.
        // This allows development and integration testing while real STARK verifier
        // is being configured.
        //
        // **MISSION CRITICAL FOR PRODUCTION:**
        // Zero-knowledge privacy REQUIRES real proof verification. Without it,
        // the protocol cannot guarantee "privacy over surveillance" or protect
        // beliefs from exposure. Deploy real verifier before mainnet.

        // Suppress unused variable warnings for development
        beliefHash;
        proverAddress;
        epoch;
        moduleID;

        // ⚠️ PLACEHOLDER: Returns true for any proof >= 32 bytes
        // ⚠️ REPLACE WITH REAL STARK VERIFIER BEFORE PRODUCTION
        return proofBytes.length >= 32;
    }

    /// @notice Returns the number of public inputs expected
    /// @return Number of public inputs (always 4 for belief attestation)
    function getPublicInputsCount() external pure override returns (uint256) {
        return PUBLIC_INPUTS_COUNT;
    }

    /// @notice Returns the proof system identifier
    /// @return Proof system name and version
    function getProofSystemId() external pure override returns (string memory) {
        return PROOF_SYSTEM_ID;
    }

    /// @notice Gets the minimum belief threshold (for display/debugging)
    /// @return Minimum threshold in basis points
    function getMinBeliefThreshold() external pure returns (uint256) {
        return MIN_BELIEF_THRESHOLD;
    }
}
