use crate::IpAddr;
use crate::Ipv6Addr;

// Convert a 256-bit hex hash into the reduced u64 value used by
// the mining difficulty comparison.
pub async fn hex_to_u64(hex_string: &str) -> Result<u64, String> {
    // The input must be one full 32-byte hash encoded as 64 hex characters.
    if hex_string.len() != 64 {
        return Err("Invalid hash length. Must be 64 characters.".to_string());
    }
    let mut extracted_string = String::new();

    // Sample across the whole hash instead of using only the front bytes.
    for i in (0..64).step_by(4) {
        extracted_string.push(hex_string.chars().nth(i).unwrap());
    }

    // Interpret the sampled hex characters as the mining comparison value.
    if let Ok(value) = u64::from_str_radix(&extracted_string, 16) {
        Ok(value)
    } else {
        Err("Failed to convert to u64.".to_string())
    }
}

// Convert raw bytes into UTF-8 text for command payloads that are
// expected to be plain strings.
pub fn binary_to_string(binary_data: Vec<u8>) -> String {
    match String::from_utf8(binary_data.clone()) {
        Ok(s) => s,
        Err(_) => {
            "Invalid UTF-8 Data".to_string()
        }
    }
}

pub fn ip_to_binary(ip_str: &str) -> Vec<u8> {
    // Parse the IP string into the standard IP enum before encoding it.
    match ip_str.parse::<IpAddr>() {
        Ok(IpAddr::V4(ipv4_addr)) => {
            // Store IPv4 addresses in the same 16-byte field by
            // prefixing the 4-byte address with twelve zero bytes.
            let mut bytes = vec![0u8; 12];
            bytes.extend_from_slice(&ipv4_addr.octets());
            bytes
        }
        Ok(IpAddr::V6(ipv6_addr)) => {
            // IPv6 already fits the fixed 16-byte network layout.
            ipv6_addr.octets().to_vec()
        }
        Err(_) => {
            // Invalid IP strings are rejected by returning no bytes.
            Vec::new()
        }
    }
}

// Convert the fixed 16-byte network IP layout back into visible text.
pub fn binary_to_ip(bytes: Vec<u8>) -> String {
    if bytes.len() != 16 {
        return "Invalid input length".to_string();
    }

    // Twelve leading zero bytes identify an IPv4 address stored in
    // the final four bytes of the fixed-width field.
    if bytes[0..12].iter().all(|&b| b == 0) {
        let ipv4_addr = (u32::from(bytes[12]) << 24
            | u32::from(bytes[13]) << 16
            | u32::from(bytes[14]) << 8
            | u32::from(bytes[15]))
        .into();
        format!("{}", IpAddr::V4(ipv4_addr))
    } else {
        // Non-IPv4 layouts are decoded as a full IPv6 address.
        let mut ipv6_bytes = [0u8; 16];
        ipv6_bytes.copy_from_slice(&bytes);
        format!("{}", IpAddr::V6(Ipv6Addr::from(ipv6_bytes)))
    }
}

// Convert the fixed 18-byte network endpoint layout into ip:port text.
pub fn binary_to_ip_port(bytes: &[u8]) -> String {
    if bytes.len() != 18 {
        return String::from("Error: Invalid binary length");
    }

    // The first 16 bytes are the IP address and the final two are the port.
    let ip_bytes = &bytes[..16];
    let port_bytes = &bytes[16..];
    let ip = binary_to_ip(ip_bytes.to_vec());
    let port_bytes: [u8; 2] = match port_bytes.try_into() {
        Ok(bytes) => bytes,
        Err(_) => {
            return String::from("Error: Invalid port_bytes length");
        }
    };
    let port = u16::from_le_bytes(port_bytes);
    format!("{ip}:{port}")
}

// Convert ip:port text into the fixed 18-byte endpoint layout used on the wire.
pub fn ip_port_to_binary(ip_port: &str) -> Result<Vec<u8>, String> {
    // Split from the right so IPv6 addresses with colons still parse correctly.
    let (ip_part, port_part) = ip_port
        .rsplit_once(':')
        .ok_or_else(|| String::from("Invalid format"))?;

    // Accept bracketed IPv6 endpoint strings such as [::1]:50000.
    let normalized_ip = ip_part
        .strip_prefix('[')
        .and_then(|ip| ip.strip_suffix(']'))
        .unwrap_or(ip_part);

    let ip: IpAddr = normalized_ip
        .parse()
        .map_err(|_| String::from("Invalid IP address"))?;
    let port: u16 = port_part
        .parse()
        .map_err(|_| String::from("Invalid port"))?;

    // Store IPv4 and IPv6 in the same fixed-width 16-byte address slot.
    let ip_bytes = match ip {
        IpAddr::V4(ipv4) => {
            let mut ipv6_bytes = [0u8; 16];
            ipv6_bytes[12..].copy_from_slice(&ipv4.octets());
            ipv6_bytes.to_vec()
        }
        IpAddr::V6(ipv6) => ipv6.octets().to_vec(),
    };

    // Ports are little-endian because the rest of the binary protocol
    // stores integer fields in little-endian order.
    let mut result = ip_bytes;
    result.extend_from_slice(&port.to_le_bytes());
    Ok(result)
}