forge-guard 0.3.6

//! On-chain contract verification — verifies deployed contracts against
//! their source code via block explorers (Etherscan, Basescan, etc.) and
//! RPC bytecode matching.
//!
//! # Explorer URL Registry
//!
//! Maps chain names to their block explorer API URLs for all 17 supported chains.
//! Used by [`forge verify-contract`] and direct API calls.

use std::time::{Duration, Instant};

// ─────────────────────────────────────────────────────────────
// Explorer API URL Registry
// ─────────────────────────────────────────────────────────────

/// Returns the block explorer API base URL for a given chain name.
///
/// These are the standard Etherscan-compatible API endpoints used by
/// `forge verify-contract`. Returns `None` for unknown chains.
pub fn explorer_api_url(chain: &str) -> Option<&'static str> {
    match chain.to_lowercase().as_str() {
        "ethereum" | "eth" | "mainnet" => Some("https://api.etherscan.io/api"),
        "base" => Some("https://api.basescan.org/api"),
        "arbitrum" | "arb" => Some("https://api.arbiscan.io/api"),
        "optimism" | "op" => Some("https://api-optimistic.etherscan.io/api"),
        "polygon" | "matic" => Some("https://api.polygonscan.com/api"),
        "bnb" | "bsc" => Some("https://api.bscscan.com/api"),
        "avalanche" | "avax" => Some("https://api.snowtrace.io/api"),
        "scroll" => Some("https://api.scrollscan.com/api"),
        "linea" => Some("https://api.lineascan.build/api"),
        "zksync" | "zk" => Some("https://api-era.zksync.network/api"),
        "blast" => Some("https://api.blastscan.io/api"),
        "mantle" => Some("https://api.mantlescan.xyz/api"),
        "robinhood" => Some("https://api.robinhoodscan.com/api"),
        _ => None,
    }
}

/// Returns the block explorer front-end URL for a given chain name.
/// Used for providing clickable links in reports.
pub fn explorer_base_url(chain: &str) -> Option<&'static str> {
    match chain.to_lowercase().as_str() {
        "ethereum" | "eth" | "mainnet" => Some("https://etherscan.io"),
        "base" => Some("https://basescan.org"),
        "arbitrum" | "arb" => Some("https://arbiscan.io"),
        "optimism" | "op" => Some("https://optimistic.etherscan.io"),
        "polygon" | "matic" => Some("https://polygonscan.com"),
        "bnb" | "bsc" => Some("https://bscscan.com"),
        "avalanche" | "avax" => Some("https://snowtrace.io"),
        "scroll" => Some("https://scrollscan.com"),
        "linea" => Some("https://lineascan.build"),
        "unichain" => Some("https://uniscan.xyz"),
        "zksync" | "zk" => Some("https://explorer.zksync.io"),
        "hyperevm" | "hyperliquid" => Some("https://hyperscan.xyz"),
        "monad" => Some("https://monadscan.xyz"),
        "sonic" => Some("https://sonicscan.org"),
        "blast" => Some("https://blastscan.io"),
        "mantle" => Some("https://mantlescan.xyz"),
        "robinhood" => Some("https://robinhoodscan.com"),
        _ => None,
    }
}

/// Get the environment variable name for the explorer API key.
pub fn explorer_api_key_env(chain: &str) -> &'static str {
    match chain.to_lowercase().as_str() {
        "ethereum" | "eth" | "mainnet" => "ETHERSCAN_API_KEY",
        "base" => "BASESCAN_API_KEY",
        "arbitrum" | "arb" => "ARBISCAN_API_KEY",
        "optimism" | "op" => "OPTIMISTIC_ETHERSCAN_API_KEY",
        "polygon" | "matic" => "POLYGONSCAN_API_KEY",
        "bnb" | "bsc" => "BSCSCAN_API_KEY",
        "avalanche" | "avax" => "SNOWTRACE_API_KEY",
        "scroll" => "SCROLLSCAN_API_KEY",
        "linea" => "LINEASCAN_API_KEY",
        "zksync" | "zk" => "ZKSYNC_API_KEY",
        "blast" => "BLASTSCAN_API_KEY",
        "mantle" => "MANTLESCAN_API_KEY",
        _ => "ETHERSCAN_API_KEY",
    }
}

// ─────────────────────────────────────────────────────────────
// Verification Types
// ─────────────────────────────────────────────────────────────

/// The result of a verification attempt.
#[derive(Debug, Clone)]
pub struct VerificationResult {
    /// Whether the contract was successfully verified.
    pub verified: bool,
    /// The method used for verification.
    pub method: VerificationMethod,
    /// Human-readable details about the result.
    pub details: String,
    /// Duration of the verification attempt.
    pub duration: Duration,
}

/// The method used for contract verification.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VerificationMethod {
    /// Verified via block explorer API (Etherscan, Basescan, etc.)
    Explorer,
    /// Verified by comparing local bytecode with on-chain bytecode via RPC
    BytecodeMatch,
    /// Verified via Sourcify
    Sourcify,
    /// Not yet verified
    Pending,
}

impl std::fmt::Display for VerificationMethod {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Explorer => write!(f, "Block Explorer"),
            Self::BytecodeMatch => write!(f, "Bytecode Match"),
            Self::Sourcify => write!(f, "Sourcify"),
            Self::Pending => write!(f, "Pending"),
        }
    }
}

// ─────────────────────────────────────────────────────────────
// Verification Engine
// ─────────────────────────────────────────────────────────────

/// Handles on-chain contract verification via explorer APIs and RPC bytecode matching.
pub struct ContractVerifier {
    /// Explorer API key.
    api_key: String,
}

impl ContractVerifier {
    /// Create a new verifier for the given chain.
    ///
    /// `api_key` — optional explorer API key. Reads the chain-specific env var when empty.
    pub fn new(chain: &str, api_key: Option<String>) -> Self {
        let key = api_key
            .filter(|k| !k.is_empty())
            .or_else(|| std::env::var(explorer_api_key_env(chain)).ok())
            .unwrap_or_default();

        Self { api_key: key }
    }

    /// Verify a contract using `forge verify-contract`.
    ///
    /// This delegates to Foundry's built-in Etherscan integration.
    pub fn forge_verify(
        &self,
        address: &str,
        contract_name: &str,
        chain: &str,
        constructor_args: Option<&str>,
    ) -> VerificationResult {
        let start = Instant::now();

        if self.api_key.is_empty() {
            return VerificationResult {
                verified: false,
                method: VerificationMethod::Explorer,
                details: format!(
                    "No API key set. Set {} or pass --explorer-api-key.",
                    explorer_api_key_env(chain)
                ),
                duration: start.elapsed(),
            };
        }

        let mut cmd = std::process::Command::new("forge");
        cmd.arg("verify-contract")
            .arg(address)
            .arg(contract_name)
            .arg("--chain")
            .arg(chain)
            .arg("--etherscan-api-key")
            .arg(&self.api_key);

        if let Some(args) = constructor_args {
            cmd.arg("--constructor-args").arg(args);
        }

        match cmd.output() {
            Ok(output) => {
                let _stdout = String::from_utf8_lossy(&output.stdout);
                let stderr = String::from_utf8_lossy(&output.stderr);

                if output.status.success() {
                    VerificationResult {
                        verified: true,
                        method: VerificationMethod::Explorer,
                        details: "Contract verified successfully on block explorer.".into(),
                        duration: start.elapsed(),
                    }
                } else {
                    let msg = if stderr.contains("Already Verified") {
                        "Contract already verified on block explorer.".to_string()
                    } else {
                        format!("Verification failed: {}", stderr.trim())
                    };
                    VerificationResult {
                        verified: msg.contains("Already Verified"),
                        method: VerificationMethod::Explorer,
                        details: msg,
                        duration: start.elapsed(),
                    }
                }
            }
            Err(e) => VerificationResult {
                verified: false,
                method: VerificationMethod::Explorer,
                details: format!("Failed to run forge verify-contract: {e}"),
                duration: start.elapsed(),
            },
        }
    }

    /// Compare locally compiled bytecode with on-chain bytecode via RPC.
    ///
    /// This method:
    /// 1. Runs `forge build` to compile the contract
    /// 2. Extracts the deployed bytecode from `out/`
    /// 3. Calls `eth_getCode` via RPC
    /// 4. Compares the two (stripping metadata hash)
    pub fn verify_bytecode_match(
        &self,
        address: &str,
        contract_name: &str,
        rpc_url: &str,
    ) -> VerificationResult {
        let start = Instant::now();

        // Step 1: Compile the contract
        let _build_output = match std::process::Command::new("forge")
            .arg("build")
            .arg("--silent")
            .output()
        {
            Ok(o) if o.status.success() => o,
            Ok(o) => {
                let stderr = String::from_utf8_lossy(&o.stderr);
                return VerificationResult {
                    verified: false,
                    method: VerificationMethod::BytecodeMatch,
                    details: format!("Compilation failed: {}", stderr.trim()),
                    duration: start.elapsed(),
                };
            }
            Err(e) => {
                return VerificationResult {
                    verified: false,
                    method: VerificationMethod::BytecodeMatch,
                    details: format!("Failed to run forge build: {e}"),
                    duration: start.elapsed(),
                };
            }
        };

        // Step 2: Parse bytecode from compilation output
        // Forge outputs to out/{contract}.sol/{contract}.json with deployedBytecode field
        let out_path = format!("out/{contract_name}.sol/{contract_name}.json");
        let bytecode = match std::fs::read_to_string(&out_path) {
            Ok(content) => {
                let parsed: serde_json::Value =
                    serde_json::from_str(&content).unwrap_or(serde_json::Value::Null);
                parsed["deployedBytecode"]["object"]
                    .as_str()
                    .map(|s| s.trim_start_matches("0x").to_lowercase())
                    .unwrap_or_default()
            }
            Err(_) => {
                // Try alternate path: flattened contract name
                let alt_path = format!("out/{contract_name}.json");
                match std::fs::read_to_string(&alt_path) {
                    Ok(content) => {
                        let parsed: serde_json::Value =
                            serde_json::from_str(&content).unwrap_or(serde_json::Value::Null);
                        parsed["deployedBytecode"]["object"]
                            .as_str()
                            .map(|s| s.trim_start_matches("0x").to_lowercase())
                            .unwrap_or_default()
                    }
                    Err(_) => String::new(),
                }
            }
        };

        if bytecode.is_empty() {
            return VerificationResult {
                verified: false,
                method: VerificationMethod::BytecodeMatch,
                details: format!(
                    "Could not find compiled bytecode at out/{contract_name}.sol/{contract_name}.json"
                ),
                duration: start.elapsed(),
            };
        }

        // Step 3: Fetch on-chain bytecode via RPC
        let onchain_bytecode = match self.fetch_onchain_bytecode(rpc_url, address) {
            Some(code) => code.trim_start_matches("0x").to_lowercase(),
            None => {
                return VerificationResult {
                    verified: false,
                    method: VerificationMethod::BytecodeMatch,
                    details: format!("Could not fetch on-chain bytecode for {address}"),
                    duration: start.elapsed(),
                };
            }
        };

        // Step 4: Compare (strip metadata hash — last 53 bytes / 106 hex chars)
        let local_stripped = strip_metadata(&bytecode);
        let onchain_stripped = strip_metadata(&onchain_bytecode);

        if local_stripped == onchain_stripped {
            VerificationResult {
                verified: true,
                method: VerificationMethod::BytecodeMatch,
                details: format!(
                    "Local bytecode matches on-chain bytecode at {address} ({} bytes matched)",
                    local_stripped.len() / 2
                ),
                duration: start.elapsed(),
            }
        } else {
            // Find where they diverge
            let diff_pos = local_stripped
                .chars()
                .zip(onchain_stripped.chars())
                .position(|(a, b)| a != b);

            VerificationResult {
                verified: false,
                method: VerificationMethod::BytecodeMatch,
                details: format!(
                    "Bytecode mismatch at address {address}. Local: {} bytes, On-chain: {} bytes{}",
                    local_stripped.len() / 2,
                    onchain_stripped.len() / 2,
                    diff_pos
                        .map(|p| format!(", first difference at hex position {p}"))
                        .unwrap_or_default()
                ),
                duration: start.elapsed(),
            }
        }
    }

    /// Check whether the `forge` CLI is available on the system.
    /// Delegates to the free function [`forge_available()`].
    pub fn forge_available(&self) -> bool {
        forge_available()
    }

    /// Fetch on-chain bytecode using `eth_getCode` RPC call.
    fn fetch_onchain_bytecode(&self, rpc_url: &str, address: &str) -> Option<String> {
        let client = reqwest::blocking::Client::builder()
            .timeout(Duration::from_secs(30))
            .build()
            .ok()?;

        let body = serde_json::json!({
            "jsonrpc": "2.0",
            "method": "eth_getCode",
            "params": [address, "latest"],
            "id": 1
        });

        let resp = client
            .post(rpc_url)
            .header("Content-Type", "application/json")
            .json(&body)
            .send()
            .ok()?;

        let text = resp.text().ok()?;
        let parsed: serde_json::Value = serde_json::from_str(&text).ok()?;
        parsed["result"].as_str().map(String::from)
    }
}

/// Strip the Solidity metadata hash from the end of a bytecode string.
///
/// Solidity appends a CBOR-encoded metadata hash (ipfs/Swarm) to the end of
/// deployed bytecode. This hash differs between compilations even when the
/// source code is identical, so we strip it before comparing.
///
/// The metadata is encoded in the last 53 bytes (106 hex chars) of bytecode
/// and always ends with the CBOR tag `0xa264` for IPFS or `0xa265` for Swarm.
fn strip_metadata(bytecode: &str) -> &str {
    // The metadata section is at the end. Solidity 0.8+ uses last 53 bytes.
    // We look for the CBOR metadata marker at the tail.
    let len = bytecode.len();
    if len < 106 {
        return bytecode;
    }

    // Check for the CBOR end-of-encoding marker patterns
    // The last byte of valid bytecode before metadata is the end of the contract code.
    // Metadata starts with 0xa2 (IPFS) or 0xa2 (CBOR map of 2 items) or 0xa3 (CBOR map of 3 items)
    let metadata_start_candidates = [106, 110, 114, 118]; // common metadata lengths

    for &offset in &metadata_start_candidates {
        if offset > len {
            continue;
        }
        let start = len - offset;
        // Check if this looks like metadata by examining the tail pattern
        // Valid metadata ends with 0x00 0x29 (empty string CBOR)
        if bytecode[start..].ends_with("0029") {
            return &bytecode[..start];
        }
    }

    // Fallback: strip the last 106 hex chars (53 bytes)
    &bytecode[..len - 106]
}

/// Check whether `forge` CLI is available on the system.
pub fn forge_available() -> bool {
    std::process::Command::new("forge")
        .arg("--version")
        .output()
        .map(|o| o.status.success())
        .unwrap_or(false)
}

/// Get the RPC URL for a chain from environment or return a default.
pub fn rpc_url_for_chain(chain: &str) -> String {
    // Check chain-specific env vars first
    let env_var = match chain.to_lowercase().as_str() {
        "ethereum" | "eth" | "mainnet" => "ETH_RPC_URL",
        "base" => "BASE_RPC_URL",
        "arbitrum" | "arb" => "ARBITRUM_RPC_URL",
        "optimism" | "op" => "OPTIMISM_RPC_URL",
        "polygon" | "matic" => "POLYGON_RPC_URL",
        "bnb" | "bsc" => "BSC_RPC_URL",
        _ => "ETH_RPC_URL",
    };

    std::env::var(env_var)
        .or_else(|_| std::env::var("ETH_RPC_URL"))
        .unwrap_or_else(|_| "http://localhost:8545".into())
}

// ── Tests ────────────────────────────────────────────────────
#[cfg(test)]
mod tests {
    use super::*;
    use std::time::Duration;

    #[test]
    fn test_explorer_api_url_ethereum() {
        assert_eq!(
            explorer_api_url("ethereum"),
            Some("https://api.etherscan.io/api")
        );
        assert_eq!(
            explorer_api_url("eth"),
            Some("https://api.etherscan.io/api")
        );
        assert_eq!(
            explorer_api_url("mainnet"),
            Some("https://api.etherscan.io/api")
        );
    }

    #[test]
    fn test_explorer_api_url_base() {
        assert_eq!(
            explorer_api_url("base"),
            Some("https://api.basescan.org/api")
        );
    }

    #[test]
    fn test_explorer_api_url_arbitrum() {
        assert_eq!(explorer_api_url("arb"), Some("https://api.arbiscan.io/api"));
    }

    #[test]
    fn test_explorer_api_url_unknown() {
        assert_eq!(explorer_api_url("unknown-chain"), None);
    }

    #[test]
    fn test_explorer_base_url() {
        assert_eq!(explorer_base_url("ethereum"), Some("https://etherscan.io"));
        assert_eq!(explorer_base_url("base"), Some("https://basescan.org"));
        assert_eq!(explorer_base_url("arbitrum"), Some("https://arbiscan.io"));
    }

    #[test]
    fn test_explorer_api_key_env() {
        assert_eq!(explorer_api_key_env("ethereum"), "ETHERSCAN_API_KEY");
        assert_eq!(explorer_api_key_env("base"), "BASESCAN_API_KEY");
        assert_eq!(explorer_api_key_env("arb"), "ARBISCAN_API_KEY");
        assert_eq!(explorer_api_key_env("polygon"), "POLYGONSCAN_API_KEY");
    }

    #[test]
    fn test_verifier_no_api_key() {
        let verifier = ContractVerifier::new("ethereum", None);
        let result = verifier.forge_verify("0x1234", "MyContract", "ethereum", None);
        assert!(!result.verified);
        assert!(result.details.contains("API key"));
    }

    #[test]
    fn test_verifier_explicit_api_key() {
        let verifier = ContractVerifier::new("ethereum", Some("test_key".into()));
        // This will fail because forge isn't available or the address doesn't exist,
        // but it proves the API key was used.
        let result = verifier.forge_verify("0x1234", "MyContract", "ethereum", None);
        // It should try to run forge, not fail on API key
        assert!(result.details.contains("failed") || result.details.contains("forge"));
    }

    #[test]
    fn test_strip_metadata_short_bytecode() {
        // Bytecode shorter than metadata section — return as-is
        let short = "0x1234";
        assert_eq!(strip_metadata(short), short);
    }

    #[test]
    fn test_strip_metadata_with_cbor_tail() {
        // Simulated bytecode of sufficient length
        let mut bytecode = "608060405260008054".to_string();
        // Pad to 200 chars
        while bytecode.len() < 200 {
            bytecode.push_str("00");
        }
        // Add CBOR tail ending with 0029
        bytecode.push_str("a2646970667358221220");
        while bytecode.len() % 2 != 0 {
            bytecode.push('0');
        }
        // End with 0029
        if !bytecode.ends_with("0029") {
            bytecode.push_str("0029");
        }

        let stripped = strip_metadata(&bytecode);
        assert!(
            stripped.len() < bytecode.len(),
            "should strip metadata bytes"
        );
        assert!(stripped.ends_with("00"), "should end with valid opcode");
    }

    #[test]
    fn test_verification_method_display() {
        assert_eq!(VerificationMethod::Explorer.to_string(), "Block Explorer");
        assert_eq!(
            VerificationMethod::BytecodeMatch.to_string(),
            "Bytecode Match"
        );
        assert_eq!(VerificationMethod::Pending.to_string(), "Pending");
    }

    #[test]
    fn test_verification_result_creation() {
        let result = VerificationResult {
            verified: true,
            method: VerificationMethod::Explorer,
            details: "Success".into(),
            duration: Duration::from_secs(2),
        };
        assert!(result.verified);
        assert_eq!(result.method, VerificationMethod::Explorer);
    }

    #[test]
    fn test_rpc_url_from_env() {
        // Should return default when no env vars are set
        let url = rpc_url_for_chain("ethereum");
        assert!(!url.is_empty());
        assert!(url.contains("localhost") || url.contains("http"));
    }

    #[test]
    fn test_forge_available() {
        // This test verifies forge detection — forge might not be installed
        // in the test environment, so we just check it doesn't panic
        let _available = forge_available();
    }

    #[test]
    fn test_bytecode_verify_no_forge() {
        let verifier = ContractVerifier::new("ethereum", None);
        let result = verifier.verify_bytecode_match(
            "0xdead000000000000000000000000000000000000",
            "Nonexistent",
            "http://localhost:8545",
        );
        // Should fail gracefully, not panic
        assert!(!result.verified, "should fail without forge build");
        assert!(!result.details.is_empty());
    }
}