use anyhow::Result;
use tokio::net::TcpStream;
use tokio::time::Duration;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum OutboundAction {
    Proxy,
    Direct,
}

#[derive(Debug, Clone)]
pub struct OutboundRule {
    pub domain_suffix: Vec<String>,
    pub ip_cidr: Vec<String>,
    pub action: OutboundAction,
}

#[derive(Debug, Clone)]
pub struct OutboundConfig {
    pub enabled: bool,
    pub protocol: String,
    pub address: String,
    pub port: u16,
    pub rules: Vec<OutboundRule>,
    pub default_action: OutboundAction,
}

// ── Target connection with outbound routing ──────────────────────────────────

pub async fn connect_target(
    target: &str,
    outbound: Option<&OutboundConfig>,
    debug: bool,
) -> Result<TcpStream> {
    let connect_timeout = Duration::from_secs(10);
    if let Some(outbound) = outbound {
        if outbound.enabled {
            let action = select_outbound_action(target, outbound, debug).await;
            if action == OutboundAction::Proxy {
                let proxy_addr = format!("{}:{}", outbound.address, outbound.port);
                return match outbound.protocol.as_str() {
                    "socks5" => connect_via_socks5(&proxy_addr, target).await,
                    "http" => connect_via_http(&proxy_addr, target).await,
                    _ => tokio::time::timeout(connect_timeout, TcpStream::connect(target))
                        .await
                        .map_err(|_| anyhow::anyhow!("connect timeout ({}s): {}", connect_timeout.as_secs(), target))?
                        .map_err(Into::into),
                };
            }
        }
    }

    tokio::time::timeout(connect_timeout, TcpStream::connect(target))
        .await
        .map_err(|_| anyhow::anyhow!("connect timeout ({}s): {}", connect_timeout.as_secs(), target))?
        .map_err(Into::into)
}

// ── Rule matching ────────────────────────────────────────────────────────────

async fn select_outbound_action(
    target: &str,
    outbound: &OutboundConfig,
    debug: bool,
) -> OutboundAction {
    let (host, port) = match split_host_port(target) {
        Some(v) => v,
        None => return outbound.default_action,
    };

    let mut matched = None;
    for rule in &outbound.rules {
        if rule.domain_suffix.is_empty() && rule.ip_cidr.is_empty() {
            continue;
        }
        if match_domain_rule(&host, &rule.domain_suffix) {
            matched = Some(rule.action);
            break;
        }
        if match_ip_rule(&host, port, &rule.ip_cidr).await {
            matched = Some(rule.action);
            break;
        }
    }

    let action = matched.unwrap_or(outbound.default_action);
    if debug {
        tracing::debug!("Outbound routing: target={target} action={action:?}");
    }
    action
}

fn match_domain_rule(host: &str, suffixes: &[String]) -> bool {
    if suffixes.is_empty() {
        return false;
    }
    let host = host.trim_end_matches('.').to_lowercase();
    suffixes.iter().any(|suffix| {
        let suffix = suffix.trim().trim_start_matches('.').to_lowercase();
        !suffix.is_empty() && (host == suffix || host.ends_with(&format!(".{suffix}")))
    })
}

async fn match_ip_rule(host: &str, port: u16, cidrs: &[String]) -> bool {
    if cidrs.is_empty() {
        return false;
    }
    let parsed: Vec<Cidr> = cidrs.iter().filter_map(|c| parse_cidr(c)).collect();
    if parsed.is_empty() {
        return false;
    }
    if let Ok(ip) = host.parse::<std::net::IpAddr>() {
        return parsed.iter().any(|cidr| cidr.contains(&ip));
    }

    match tokio::net::lookup_host((host, port)).await {
        Ok(addrs) => addrs.into_iter().any(|addr| parsed.iter().any(|cidr| cidr.contains(&addr.ip()))),
        Err(_) => false,
    }
}

// ── SOCKS5 / HTTP CONNECT upstream proxy ─────────────────────────────────────

async fn connect_via_socks5(proxy_addr: &str, target: &str) -> Result<TcpStream> {
    use tokio::io::{AsyncReadExt, AsyncWriteExt};

    let mut stream = TcpStream::connect(proxy_addr).await?;
    stream.write_all(&[0x05, 0x01, 0x00]).await?;
    let mut reply = [0u8; 2];
    stream.read_exact(&mut reply).await?;
    if reply != [0x05, 0x00] {
        anyhow::bail!("SOCKS5 auth not accepted");
    }

    let (host, port) = split_host_port(target).ok_or_else(|| anyhow::anyhow!("invalid target"))?;
    let mut req = Vec::new();
    req.extend_from_slice(&[0x05, 0x01, 0x00]);
    if let Ok(ip) = host.parse::<std::net::IpAddr>() {
        match ip {
            std::net::IpAddr::V4(v4) => {
                req.push(0x01);
                req.extend_from_slice(&v4.octets());
            }
            std::net::IpAddr::V6(v6) => {
                req.push(0x04);
                req.extend_from_slice(&v6.octets());
            }
        }
    } else {
        req.push(0x03);
        req.push(host.len() as u8);
        req.extend_from_slice(host.as_bytes());
    }
    req.extend_from_slice(&port.to_be_bytes());
    stream.write_all(&req).await?;

    let mut header = [0u8; 4];
    stream.read_exact(&mut header).await?;
    if header[1] != 0x00 {
        anyhow::bail!("SOCKS5 connect failed: 0x{:02x}", header[1]);
    }

    let addr_len = match header[3] {
        0x01 => 4,
        0x04 => 16,
        0x03 => {
            let mut len = [0u8; 1];
            stream.read_exact(&mut len).await?;
            len[0] as usize
        }
        _ => 0,
    };
    if addr_len > 0 {
        let mut skip = vec![0u8; addr_len + 2];
        stream.read_exact(&mut skip).await?;
    }

    Ok(stream)
}

async fn connect_via_http(proxy_addr: &str, target: &str) -> Result<TcpStream> {
    use tokio::io::{AsyncReadExt, AsyncWriteExt};

    let mut stream = TcpStream::connect(proxy_addr).await?;
    let request = format!("CONNECT {target} HTTP/1.1\r\nHost: {target}\r\n\r\n");
    stream.write_all(request.as_bytes()).await?;

    let mut buf = vec![0u8; 1024];
    let n = stream.read(&mut buf).await?;
    let response = String::from_utf8_lossy(&buf[..n]);
    if !response.starts_with("HTTP/1.1 200") && !response.starts_with("HTTP/1.0 200") {
        anyhow::bail!("HTTP CONNECT failed: {response}");
    }
    Ok(stream)
}

// ── CIDR utilities ───────────────────────────────────────────────────────────

enum Cidr {
    V4(u32, u8),
    V6(u128, u8),
}

impl Cidr {
    fn contains(&self, ip: &std::net::IpAddr) -> bool {
        match (self, ip) {
            (Cidr::V4(net, bits), std::net::IpAddr::V4(addr)) => {
                let mask = if *bits == 0 { 0 } else { u32::MAX << (32 - bits) };
                let ip = u32::from_be_bytes(addr.octets());
                (ip & mask) == (*net & mask)
            }
            (Cidr::V6(net, bits), std::net::IpAddr::V6(addr)) => {
                let mask = if *bits == 0 { 0 } else { u128::MAX << (128 - bits) };
                let ip = u128::from_be_bytes(addr.octets());
                (ip & mask) == (*net & mask)
            }
            _ => false,
        }
    }
}

fn parse_cidr(value: &str) -> Option<Cidr> {
    let value = value.trim();
    if value.is_empty() {
        return None;
    }
    if let Some((addr_str, bits_str)) = value.split_once('/') {
        let bits: u8 = bits_str.parse().ok()?;
        if let Ok(addr) = addr_str.parse::<std::net::IpAddr>() {
            return match addr {
                std::net::IpAddr::V4(v4) => Some(Cidr::V4(u32::from_be_bytes(v4.octets()), bits.min(32))),
                std::net::IpAddr::V6(v6) => Some(Cidr::V6(u128::from_be_bytes(v6.octets()), bits.min(128))),
            };
        }
    }
    if let Ok(addr) = value.parse::<std::net::IpAddr>() {
        return match addr {
            std::net::IpAddr::V4(v4) => Some(Cidr::V4(u32::from_be_bytes(v4.octets()), 32)),
            std::net::IpAddr::V6(v6) => Some(Cidr::V6(u128::from_be_bytes(v6.octets()), 128)),
        };
    }
    None
}

pub fn split_host_port(target: &str) -> Option<(String, u16)> {
    if let Some((host, port)) = target.rsplit_once(':') {
        if host.starts_with('[') && host.ends_with(']') {
            let host = host.trim_start_matches('[').trim_end_matches(']').to_string();
            let port = port.parse().ok()?;
            return Some((host, port));
        }
        if host.contains(':') {
            return None;
        }
        let port = port.parse().ok()?;
        return Some((host.to_string(), port));
    }
    None
}

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

    #[test]
    fn test_split_host_port() {
        assert_eq!(split_host_port("example.com:443"), Some(("example.com".to_string(), 443)));
        assert_eq!(split_host_port("127.0.0.1:80"), Some(("127.0.0.1".to_string(), 80)));
        assert_eq!(split_host_port("[::1]:8080"), Some(("::1".to_string(), 8080)));
        assert_eq!(split_host_port("noport"), None);
        assert_eq!(split_host_port("::1:8080"), None); // ambiguous IPv6 without brackets
    }

    #[test]
    fn test_parse_cidr_v4() {
        let cidr = parse_cidr("10.0.0.0/8").unwrap();
        assert!(cidr.contains(&"10.1.2.3".parse().unwrap()));
        assert!(cidr.contains(&"10.255.255.255".parse().unwrap()));
        assert!(!cidr.contains(&"11.0.0.1".parse().unwrap()));
    }

    #[test]
    fn test_parse_cidr_v4_exact() {
        let cidr = parse_cidr("192.168.1.1").unwrap();
        assert!(cidr.contains(&"192.168.1.1".parse().unwrap()));
        assert!(!cidr.contains(&"192.168.1.2".parse().unwrap()));
    }

    #[test]
    fn test_parse_cidr_v6() {
        let cidr = parse_cidr("::1/128").unwrap();
        assert!(cidr.contains(&"::1".parse().unwrap()));
        assert!(!cidr.contains(&"::2".parse().unwrap()));
    }

    #[test]
    fn test_parse_cidr_invalid() {
        assert!(parse_cidr("").is_none());
        assert!(parse_cidr("not-an-ip/24").is_none());
    }

    #[test]
    fn test_match_domain_rule() {
        assert!(match_domain_rule("example.com", &[".example.com".to_string()]));
        assert!(match_domain_rule("sub.example.com", &[".example.com".to_string()]));
        assert!(!match_domain_rule("notexample.com", &[".example.com".to_string()]));
        assert!(match_domain_rule("test.onion", &[".onion".to_string()]));
        assert!(!match_domain_rule("onion.com", &[".onion".to_string()]));
    }

    #[test]
    fn test_match_domain_rule_exact() {
        // Without dot prefix, the rule matches both exact and subdomains
        // because the implementation treats "example.com" as a suffix match
        assert!(match_domain_rule("example.com", &["example.com".to_string()]));
        assert!(match_domain_rule("sub.example.com", &["example.com".to_string()]));
    }

    #[test]
    fn test_match_domain_rule_empty() {
        assert!(!match_domain_rule("example.com", &[]));
    }
}