//! Server messages (`server.slsknet.org:2242`), u32 codes.

use bytes::Bytes;
use md5::{Digest, Md5};
use std::net::{Ipv4Addr, SocketAddrV4};

use crate::wire::{Reader, Writer};
use crate::Result;

/// Client version fields sent at login. 160 is the protocol version spoken
/// by current clients (Nicotine+ uses the same).
pub const VERSION: u32 = 160;
pub const MINOR_VERSION: u32 = 1;

pub mod code {
    pub const LOGIN: u32 = 1;
    pub const SET_LISTEN_PORT: u32 = 2;
    pub const GET_PEER_ADDRESS: u32 = 3;
    pub const WATCH_USER: u32 = 5;
    pub const CONNECT_TO_PEER: u32 = 18;
    pub const FILE_SEARCH: u32 = 26;
    pub const PING: u32 = 32;
    pub const SHARED_FOLDERS_AND_FILES: u32 = 35;
    pub const HAVE_NO_PARENTS: u32 = 71;
    pub const PARENT_MIN_SPEED: u32 = 83;
    pub const PARENT_SPEED_RATIO: u32 = 84;
    pub const EMBEDDED_MESSAGE: u32 = 93; // wraps a distributed search
    pub const ACCEPT_CHILDREN: u32 = 100;
    pub const NET_INFO: u32 = 102;
    pub const WISHLIST_INTERVAL: u32 = 104;
    pub const BRANCH_LEVEL: u32 = 126;
    pub const BRANCH_ROOT: u32 = 127;
    pub const EXCLUDED_SEARCH_PHRASES: u32 = 160;
    pub const CANNOT_CONNECT: u32 = 1001;
}

// ---- outgoing ----

pub fn login(username: &str, password: &str) -> Vec<u8> {
    let hash = hex(Md5::digest(format!("{username}{password}").as_bytes()));
    Writer::new()
        .string(username)
        .string(password)
        .u32(VERSION)
        .string(&hash)
        .u32(MINOR_VERSION)
        .finish_u32(code::LOGIN)
}

pub fn set_listen_port(port: u32) -> Vec<u8> {
    Writer::new().u32(port).finish_u32(code::SET_LISTEN_PORT)
}

pub fn file_search(token: u32, query: &str) -> Vec<u8> {
    Writer::new()
        .u32(token)
        .string(query)
        .finish_u32(code::FILE_SEARCH)
}

pub fn shared_folders_and_files(dirs: u32, files: u32) -> Vec<u8> {
    Writer::new()
        .u32(dirs)
        .u32(files)
        .finish_u32(code::SHARED_FOLDERS_AND_FILES)
}

/// Tell the server whether we need a distributed parent.
pub fn accept_children(accept: bool) -> Vec<u8> {
    Writer::new().bool(accept).finish_u32(code::ACCEPT_CHILDREN)
}

pub fn branch_level(level: u32) -> Vec<u8> {
    Writer::new().u32(level).finish_u32(code::BRANCH_LEVEL)
}

pub fn branch_root(root: &str) -> Vec<u8> {
    Writer::new().string(root).finish_u32(code::BRANCH_ROOT)
}

pub fn ping() -> Vec<u8> {
    Writer::new().finish_u32(code::PING)
}

pub fn get_peer_address(username: &str) -> Vec<u8> {
    Writer::new()
        .string(username)
        .finish_u32(code::GET_PEER_ADDRESS)
}

/// Ask the server to have `username` connect to us (indirect connection).
pub fn connect_to_peer(token: u32, username: &str, conn_type: &str) -> Vec<u8> {
    Writer::new()
        .u32(token)
        .string(username)
        .string(conn_type)
        .finish_u32(code::CONNECT_TO_PEER)
}

pub fn have_no_parents(value: bool) -> Vec<u8> {
    Writer::new().bool(value).finish_u32(code::HAVE_NO_PARENTS)
}

// ---- incoming ----

#[derive(Debug, Clone)]
pub enum ServerEvent {
    LoginOk {
        greeting: String,
        own_ip: Ipv4Addr,
        is_supporter: bool,
    },
    LoginFailed {
        reason: String,
    },
    /// Another client wants a connection with us (or is answering our
    /// indirect request): connect to them and send PierceFirewall(token).
    ConnectToPeer {
        username: String,
        conn_type: String,
        addr: SocketAddrV4,
        token: u32,
        privileged: bool,
    },
    /// Our indirect connection request to `token` failed.
    CannotConnect {
        token: u32,
        username: Option<String>,
    },
    /// Answer to GetPeerAddress. A 0.0.0.0/port-0 address means offline.
    UserAddress {
        username: String,
        addr: SocketAddrV4,
    },
    ExcludedSearchPhrases(Vec<String>),
    /// Candidate distributed parents to connect to.
    NetInfo(Vec<(String, SocketAddrV4)>),
    /// A search relayed directly by the server (older path).
    ServerSearch {
        username: String,
        token: u32,
        query: String,
    },
    /// A distributed message wrapped by the server (code 93). The inner
    /// bytes are a distributed frame starting with its code byte — decode
    /// with `dist::decode`.
    Embedded(Bytes),
    Unhandled {
        code: u32,
    },
}

pub fn decode(code: u32, payload: Bytes) -> Result<ServerEvent> {
    let mut r = Reader::new(payload);
    Ok(match code {
        code::LOGIN => {
            if r.bool()? {
                let greeting = r.string()?;
                let own_ip = r.ipv4()?;
                // Trailing hash + supporter flag are absent on some servers.
                let _hash = r.string().unwrap_or_default();
                let is_supporter = r.bool().unwrap_or(false);
                ServerEvent::LoginOk {
                    greeting,
                    own_ip,
                    is_supporter,
                }
            } else {
                ServerEvent::LoginFailed {
                    reason: r.string()?,
                }
            }
        }
        code::CONNECT_TO_PEER => {
            let username = r.string()?;
            let conn_type = r.string()?;
            let ip = r.ipv4()?;
            let port = r.u32()?;
            let token = r.u32()?;
            let privileged = r.bool().unwrap_or(false);
            ServerEvent::ConnectToPeer {
                username,
                conn_type,
                addr: SocketAddrV4::new(ip, port as u16),
                token,
                privileged,
            }
        }
        code::GET_PEER_ADDRESS => {
            let username = r.string()?;
            let ip = r.ipv4()?;
            let port = r.u32()?;
            // Trailing obfuscation fields ignored.
            ServerEvent::UserAddress {
                username,
                addr: SocketAddrV4::new(ip, port as u16),
            }
        }
        code::CANNOT_CONNECT => {
            let token = r.u32()?;
            let username = r.string().ok();
            ServerEvent::CannotConnect { token, username }
        }
        code::NET_INFO => {
            let count = r.u32()?.min(1000);
            let mut parents = Vec::with_capacity(count as usize);
            for _ in 0..count {
                let username = r.string()?;
                let ip = r.ipv4()?;
                let port = r.u32()?;
                parents.push((username, SocketAddrV4::new(ip, port as u16)));
            }
            ServerEvent::NetInfo(parents)
        }
        code::FILE_SEARCH => {
            // Server-relayed search (same code we send): username, token, query.
            let username = r.string()?;
            let token = r.u32()?;
            let query = r.string()?;
            ServerEvent::ServerSearch {
                username,
                token,
                query,
            }
        }
        code::EMBEDDED_MESSAGE => ServerEvent::Embedded(r.rest()),
        code::EXCLUDED_SEARCH_PHRASES => {
            let count = r.u32()?.min(10_000);
            let mut phrases = Vec::with_capacity(count as usize);
            for _ in 0..count {
                phrases.push(r.string()?);
            }
            ServerEvent::ExcludedSearchPhrases(phrases)
        }
        other => ServerEvent::Unhandled { code: other },
    })
}

fn hex(digest: impl AsRef<[u8]>) -> String {
    digest.as_ref().iter().map(|b| format!("{b:02x}")).collect()
}

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

    #[test]
    fn login_message_layout() {
        let msg = login("user", "pass");
        let mut r = Reader::new(Bytes::copy_from_slice(&msg[8..]));
        assert_eq!(&msg[4..8], &1u32.to_le_bytes());
        assert_eq!(r.string().unwrap(), "user");
        assert_eq!(r.string().unwrap(), "pass");
        assert_eq!(r.u32().unwrap(), VERSION);
        // md5("userpass")
        assert_eq!(r.string().unwrap(), "63e780c3f321d13109c71bf81805476e");
        assert_eq!(r.u32().unwrap(), MINOR_VERSION);
    }

    #[test]
    fn decode_connect_to_peer() {
        let payload = Writer::new()
            .string("bob")
            .string("P")
            .u8(4)
            .u8(3)
            .u8(2)
            .u8(1) // 1.2.3.4 reversed on wire
            .u32(2234)
            .u32(99)
            .bool(false)
            .finish_u32(18);
        let ev = decode(18, Bytes::copy_from_slice(&payload[8..])).unwrap();
        match ev {
            ServerEvent::ConnectToPeer {
                username,
                conn_type,
                addr,
                token,
                ..
            } => {
                assert_eq!(username, "bob");
                assert_eq!(conn_type, "P");
                assert_eq!(addr, "1.2.3.4:2234".parse().unwrap());
                assert_eq!(token, 99);
            }
            other => panic!("wrong event: {other:?}"),
        }
    }
}