//! Upstream table: cmdline parsing and MANIFEST entry construction.

use crate::frame::{UpstreamEntry, PROTO_TCP, PROTO_UDP};

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Proto {
    Tcp,
    Udp,
}
impl Proto {
    pub fn as_u8(self) -> u8 {
        match self {
            Proto::Tcp => PROTO_TCP,
            Proto::Udp => PROTO_UDP,
        }
    }
}

#[derive(Clone, Debug)]
pub struct Upstream {
    pub id: u8,
    pub proto: Proto,
    pub port: u16,
    pub label: Option<String>,
}

pub struct UpstreamTable(pub Vec<Upstream>);

impl UpstreamTable {
    pub fn get(&self, id: u8) -> Option<&Upstream> {
        self.0.iter().find(|u| u.id == id)
    }
    pub fn entries(&self) -> Vec<UpstreamEntry> {
        self.0
            .iter()
            .map(|u| UpstreamEntry {
                id: u.id,
                proto: u.proto.as_u8(),
                port: u.port,
                label: u.label.clone(),
            })
            .collect()
    }
}

/// Parse a single `PORT[:label]` argument. v1 only accepts bare integers or
/// `int:label`; an explicit `proto:` prefix is reserved for the UDP extension.
pub fn parse_port_arg(id: u8, s: &str) -> Result<Upstream, String> {
    let (port_str, label) = match s.split_once(':') {
        Some((p, l)) => (p, Some(l.to_string())),
        None => (s, None),
    };
    let port: u16 = port_str
        .parse()
        .map_err(|_| format!("invalid port value: {port_str}"))?;
    if port == 0 {
        return Err(format!("port must be > 0: {s}"));
    }
    if let Some(l) = &label {
        if l.is_empty() {
            return Err(format!("empty label: {s}"));
        }
        if l.len() > 255 {
            return Err(format!("label too long (max 255 bytes): {s}"));
        }
    }
    Ok(Upstream { id, proto: Proto::Tcp, port, label })
}

pub fn build_table(args: &[String]) -> Result<UpstreamTable, String> {
    if args.is_empty() {
        return Err("at least one PORT is required".into());
    }
    if args.len() > 255 {
        return Err("too many upstreams (max 255)".into());
    }
    let mut v = Vec::with_capacity(args.len());
    for (i, a) in args.iter().enumerate() {
        let id = (i + 1) as u8;
        v.push(parse_port_arg(id, a)?);
    }
    Ok(UpstreamTable(v))
}