//! Webhook security helpers for HMAC verification and validation

use hmac::{Hmac, Mac};
use sha2::{Sha256, Sha512};
use sha1::Sha1;

/// Verify HMAC signature for webhook payload
pub fn verify_hmac_signature(
    payload: &[u8],
    signature: &str,
    secret: &str,
    algorithm: &str,
) -> Result<bool, String> {
    // Parse signature format (e.g., "sha256=abc123..." or just "abc123...")
    let (algo_from_sig, hex_signature) = if signature.contains('=') {
        let parts: Vec<&str> = signature.splitn(2, '=').collect();
        if parts.len() != 2 {
            return Err("Invalid signature format".to_string());
        }
        (Some(parts[0]), parts[1])
    } else {
        (None, signature)
    };

    // Verify algorithm matches if specified in signature
    if let Some(sig_algo) = algo_from_sig {
        if sig_algo != algorithm {
            return Err(format!(
                "Algorithm mismatch: expected {}, got {}",
                algorithm, sig_algo
            ));
        }
    }

    // Decode hex signature
    let expected_signature = hex::decode(hex_signature)
        .map_err(|e| format!("Invalid hex signature: {}", e))?;

    // Compute HMAC based on algorithm
    let is_valid = match algorithm {
        "sha256" => verify_hmac_sha256(payload, &expected_signature, secret),
        "sha512" => verify_hmac_sha512(payload, &expected_signature, secret),
        "sha1" => verify_hmac_sha1(payload, &expected_signature, secret),
        _ => return Err(format!("Unsupported algorithm: {}", algorithm)),
    };

    Ok(is_valid)
}

/// Verify HMAC-SHA256 signature
fn verify_hmac_sha256(payload: &[u8], expected: &[u8], secret: &str) -> bool {
    type HmacSha256 = Hmac<Sha256>;

    let mut mac = match HmacSha256::new_from_slice(secret.as_bytes()) {
        Ok(m) => m,
        Err(_) => return false,
    };

    mac.update(payload);

    // Use constant-time comparison
    mac.verify_slice(expected).is_ok()
}

/// Verify HMAC-SHA512 signature
fn verify_hmac_sha512(payload: &[u8], expected: &[u8], secret: &str) -> bool {
    type HmacSha512 = Hmac<Sha512>;

    let mut mac = match HmacSha512::new_from_slice(secret.as_bytes()) {
        Ok(m) => m,
        Err(_) => return false,
    };

    mac.update(payload);

    mac.verify_slice(expected).is_ok()
}

/// Verify HMAC-SHA1 signature (legacy, not recommended)
fn verify_hmac_sha1(payload: &[u8], expected: &[u8], secret: &str) -> bool {
    type HmacSha1 = Hmac<Sha1>;

    let mut mac = match HmacSha1::new_from_slice(secret.as_bytes()) {
        Ok(m) => m,
        Err(_) => return false,
    };

    mac.update(payload);

    mac.verify_slice(expected).is_ok()
}

/// Generate HMAC signature for testing
pub fn generate_hmac_signature(payload: &[u8], secret: &str, algorithm: &str) -> Result<String, String> {
    let signature = match algorithm {
        "sha256" => {
            type HmacSha256 = Hmac<Sha256>;
            let mut mac = HmacSha256::new_from_slice(secret.as_bytes())
                .map_err(|e| format!("Invalid key length: {}", e))?;
            mac.update(payload);
            let result = mac.finalize();
            hex::encode(result.into_bytes())
        }
        "sha512" => {
            type HmacSha512 = Hmac<Sha512>;
            let mut mac = HmacSha512::new_from_slice(secret.as_bytes())
                .map_err(|e| format!("Invalid key length: {}", e))?;
            mac.update(payload);
            let result = mac.finalize();
            hex::encode(result.into_bytes())
        }
        "sha1" => {
            type HmacSha1 = Hmac<Sha1>;
            let mut mac = HmacSha1::new_from_slice(secret.as_bytes())
                .map_err(|e| format!("Invalid key length: {}", e))?;
            mac.update(payload);
            let result = mac.finalize();
            hex::encode(result.into_bytes())
        }
        _ => return Err(format!("Unsupported algorithm: {}", algorithm)),
    };

    Ok(format!("{}={}", algorithm, signature))
}

/// Check if IP address matches a CIDR block
pub fn check_ip_in_cidr(ip: &str, cidr: &str) -> Result<bool, String> {
    use std::net::IpAddr;

    let ip_addr: IpAddr = ip.parse()
        .map_err(|e| format!("Invalid IP address: {}", e))?;

    // If CIDR doesn't contain '/', treat it as a single IP
    if !cidr.contains('/') {
        let cidr_addr: IpAddr = cidr.parse()
            .map_err(|e| format!("Invalid CIDR notation: {}", e))?;
        return Ok(ip_addr == cidr_addr);
    }

    // Parse CIDR notation
    let parts: Vec<&str> = cidr.split('/').collect();
    if parts.len() != 2 {
        return Err("Invalid CIDR format".to_string());
    }

    let network_addr: IpAddr = parts[0].parse()
        .map_err(|e| format!("Invalid network address: {}", e))?;
    let prefix_len: u8 = parts[1].parse()
        .map_err(|e| format!("Invalid prefix length: {}", e))?;

    // Convert to bytes for comparison
    match (ip_addr, network_addr) {
        (IpAddr::V4(ip), IpAddr::V4(network)) => {
            if prefix_len > 32 {
                return Err("IPv4 prefix length must be <= 32".to_string());
            }
            let ip_bits = u32::from(ip);
            let network_bits = u32::from(network);
            let mask = if prefix_len == 0 { 0 } else { !0u32 << (32 - prefix_len) };
            Ok((ip_bits & mask) == (network_bits & mask))
        }
        (IpAddr::V6(ip), IpAddr::V6(network)) => {
            if prefix_len > 128 {
                return Err("IPv6 prefix length must be <= 128".to_string());
            }
            let ip_bits = u128::from(ip);
            let network_bits = u128::from(network);
            let mask = if prefix_len == 0 { 0 } else { !0u128 << (128 - prefix_len) };
            Ok((ip_bits & mask) == (network_bits & mask))
        }
        _ => Err("IP address and CIDR must be same version (IPv4 or IPv6)".to_string()),
    }
}

/// Check if IP is in any of the CIDR blocks in the whitelist
pub fn check_ip_in_whitelist(ip: &str, whitelist: &[String]) -> Result<bool, String> {
    for cidr in whitelist {
        match check_ip_in_cidr(ip, cidr) {
            Ok(true) => return Ok(true),
            Ok(false) => continue,
            Err(e) => return Err(format!("Error checking CIDR {}: {}", cidr, e)),
        }
    }
    Ok(false)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_generate_and_verify_hmac_sha256() {
        let payload = b"test payload";
        let secret = "my-secret-key";
        let signature = generate_hmac_signature(payload, secret, "sha256").unwrap();

        assert!(verify_hmac_signature(payload, &signature, secret, "sha256").unwrap());
    }

    #[test]
    fn test_verify_hmac_wrong_secret() {
        let payload = b"test payload";
        let secret = "my-secret-key";
        let wrong_secret = "wrong-key";
        let signature = generate_hmac_signature(payload, secret, "sha256").unwrap();

        assert!(!verify_hmac_signature(payload, &signature, wrong_secret, "sha256").unwrap());
    }

    #[test]
    fn test_verify_hmac_wrong_payload() {
        let payload = b"test payload";
        let wrong_payload = b"wrong payload";
        let secret = "my-secret-key";
        let signature = generate_hmac_signature(payload, secret, "sha256").unwrap();

        assert!(!verify_hmac_signature(wrong_payload, &signature, secret, "sha256").unwrap());
    }

    #[test]
    fn test_verify_hmac_sha512() {
        let payload = b"test payload";
        let secret = "my-secret-key";
        let signature = generate_hmac_signature(payload, secret, "sha512").unwrap();

        assert!(verify_hmac_signature(payload, &signature, secret, "sha512").unwrap());
    }

    #[test]
    fn test_verify_hmac_without_algorithm_prefix() {
        let payload = b"test payload";
        let secret = "my-secret-key";
        let signature = generate_hmac_signature(payload, secret, "sha256").unwrap();

        // Remove the "sha256=" prefix
        let hex_only = signature.split('=').nth(1).unwrap();

        assert!(verify_hmac_signature(payload, hex_only, secret, "sha256").unwrap());
    }

    #[test]
    fn test_check_ip_in_cidr_single_ip() {
        assert!(check_ip_in_cidr("192.168.1.1", "192.168.1.1").unwrap());
        assert!(!check_ip_in_cidr("192.168.1.2", "192.168.1.1").unwrap());
    }

    #[test]
    fn test_check_ip_in_cidr_block() {
        assert!(check_ip_in_cidr("192.168.1.100", "192.168.1.0/24").unwrap());
        assert!(check_ip_in_cidr("192.168.1.1", "192.168.1.0/24").unwrap());
        assert!(check_ip_in_cidr("192.168.1.254", "192.168.1.0/24").unwrap());
        assert!(!check_ip_in_cidr("192.168.2.1", "192.168.1.0/24").unwrap());
    }

    #[test]
    fn test_check_ip_in_cidr_ipv6() {
        assert!(check_ip_in_cidr("2001:db8::1", "2001:db8::/32").unwrap());
        assert!(!check_ip_in_cidr("2001:db9::1", "2001:db8::/32").unwrap());
    }

    #[test]
    fn test_check_ip_in_whitelist() {
        let whitelist = vec![
            "192.168.1.0/24".to_string(),
            "10.0.0.0/8".to_string(),
            "172.16.5.10".to_string(),
        ];

        assert!(check_ip_in_whitelist("192.168.1.100", &whitelist).unwrap());
        assert!(check_ip_in_whitelist("10.20.30.40", &whitelist).unwrap());
        assert!(check_ip_in_whitelist("172.16.5.10", &whitelist).unwrap());
        assert!(!check_ip_in_whitelist("8.8.8.8", &whitelist).unwrap());
    }
}