use std::net::SocketAddr;
use std::path::Path;
use std::sync::Arc;

use anyhow::Context;
use quinn::{ClientConfig, Endpoint};
use quinn_proto::crypto::rustls::QuicClientConfig;
use rustls::pki_types::CertificateDer;
use rustls::{ClientConfig as RustlsClientConfig, RootCertStore};
use tokio_util::compat::{TokioAsyncReadCompatExt, TokioAsyncWriteCompatExt};
use capnp_rpc::{rpc_twoparty_capnp::Side, twoparty, RpcSystem};

use quicnprotochat_core::HybridPublicKey;
use quicnprotochat_proto::node_capnp::{auth, node_service};

use crate::AUTH_CONTEXT;

use super::retry::{
    anyhow_is_retriable, base_delay_ms_from_env, max_retries_from_env, retry_async,
};

/// Establish a QUIC/TLS connection and return a `NodeService` client.
///
/// Must be called from within a `LocalSet` because capnp-rpc is `!Send`.
pub async fn connect_node(
    server: &str,
    ca_cert: &Path,
    server_name: &str,
) -> anyhow::Result<node_service::Client> {
    let addr: SocketAddr = server
        .parse()
        .with_context(|| format!("server must be host:port, got {server}"))?;

    let cert_bytes = std::fs::read(ca_cert).with_context(|| format!("read ca_cert {ca_cert:?}"))?;
    let mut roots = RootCertStore::empty();
    roots
        .add(CertificateDer::from(cert_bytes))
        .context("add root cert")?;

    let mut tls = RustlsClientConfig::builder()
        .with_root_certificates(roots)
        .with_no_client_auth();
    tls.alpn_protocols = vec![b"capnp".to_vec()];

    let crypto = QuicClientConfig::try_from(tls)
        .map_err(|e| anyhow::anyhow!("invalid client TLS config: {e}"))?;

    let bind_addr: SocketAddr = "0.0.0.0:0".parse().context("parse client bind address")?;
    let mut endpoint = Endpoint::client(bind_addr)?;
    endpoint.set_default_client_config(ClientConfig::new(Arc::new(crypto)));

    let connection = endpoint
        .connect(addr, server_name)
        .context("quic connect init")?
        .await
        .context("quic connect failed")?;

    let (send, recv) = connection.open_bi().await.context("open bi stream")?;

    let network = twoparty::VatNetwork::new(
        recv.compat(),
        send.compat_write(),
        Side::Client,
        Default::default(),
    );

    let mut rpc_system = RpcSystem::new(Box::new(network), None);
    let client: node_service::Client = rpc_system.bootstrap(Side::Server);

    tokio::task::spawn_local(rpc_system);

    Ok(client)
}

pub fn set_auth(auth: &mut auth::Builder<'_>) -> anyhow::Result<()> {
    let ctx = AUTH_CONTEXT.get().ok_or_else(|| {
        anyhow::anyhow!("init_auth must be called with a non-empty token before RPCs")
    })?;
    auth.set_version(ctx.version);
    auth.set_access_token(&ctx.access_token);
    auth.set_device_id(&ctx.device_id);
    Ok(())
}

/// Upload a KeyPackage and verify the fingerprint echoed by the AS.
pub async fn upload_key_package(
    client: &node_service::Client,
    identity_key: &[u8],
    package: &[u8],
) -> anyhow::Result<()> {
    let mut req = client.upload_key_package_request();
    {
        let mut p = req.get();
        p.set_identity_key(identity_key);
        p.set_package(package);
        let mut auth = p.reborrow().init_auth();
        set_auth(&mut auth)?;
    }

    let resp = req
        .send()
        .promise
        .await
        .context("upload_key_package RPC failed")?;

    let server_fp = resp
        .get()
        .context("upload_key_package: bad response")?
        .get_fingerprint()
        .context("upload_key_package: missing fingerprint")?
        .to_vec();

    let local_fp = super::state::sha256(package);
    anyhow::ensure!(server_fp == local_fp, "fingerprint mismatch");
    Ok(())
}

/// Fetch a KeyPackage for `identity_key` from the AS.
pub async fn fetch_key_package(
    client: &node_service::Client,
    identity_key: &[u8],
) -> anyhow::Result<Vec<u8>> {
    let mut req = client.fetch_key_package_request();
    {
        let mut p = req.get();
        p.set_identity_key(identity_key);
        let mut auth = p.reborrow().init_auth();
        set_auth(&mut auth)?;
    }

    let resp = req
        .send()
        .promise
        .await
        .context("fetch_key_package RPC failed")?;

    let pkg = resp
        .get()
        .context("fetch_key_package: bad response")?
        .get_package()
        .context("fetch_key_package: missing package field")?
        .to_vec();

    Ok(pkg)
}

/// Enqueue an opaque payload to the DS for `recipient_key`.
/// Returns the per-inbox sequence number assigned by the server.
/// Retries on transient failures with exponential backoff.
pub async fn enqueue(
    client: &node_service::Client,
    recipient_key: &[u8],
    payload: &[u8],
) -> anyhow::Result<u64> {
    let client = client.clone();
    let recipient_key = recipient_key.to_vec();
    let payload = payload.to_vec();
    retry_async(
        || {
            let client = client.clone();
            let recipient_key = recipient_key.clone();
            let payload = payload.clone();
            async move {
                let mut req = client.enqueue_request();
                {
                    let mut p = req.get();
                    p.set_recipient_key(&recipient_key);
                    p.set_payload(&payload);
                    p.set_channel_id(&[]);
                    p.set_version(1);
                    let mut auth = p.reborrow().init_auth();
                    set_auth(&mut auth)?;
                }
                let resp = req.send().promise.await.context("enqueue RPC failed")?;
                let seq = resp.get().context("enqueue: bad response")?.get_seq();
                Ok(seq)
            }
        },
        max_retries_from_env(),
        base_delay_ms_from_env(),
        anyhow_is_retriable,
    )
    .await
}

/// Fetch and drain all payloads for `recipient_key`.
/// Returns `(seq, payload)` pairs — sort by `seq` before MLS processing.
/// Retries on transient failures with exponential backoff.
pub async fn fetch_all(
    client: &node_service::Client,
    recipient_key: &[u8],
) -> anyhow::Result<Vec<(u64, Vec<u8>)>> {
    let client = client.clone();
    let recipient_key = recipient_key.to_vec();
    retry_async(
        || {
            let client = client.clone();
            let recipient_key = recipient_key.clone();
            async move {
                let mut req = client.fetch_request();
                {
                    let mut p = req.get();
                    p.set_recipient_key(&recipient_key);
                    p.set_channel_id(&[]);
                    p.set_version(1);
                    p.set_limit(0); // fetch all
                    let mut auth = p.reborrow().init_auth();
                    set_auth(&mut auth)?;
                }

                let resp = req.send().promise.await.context("fetch RPC failed")?;

                let list = resp
                    .get()
                    .context("fetch: bad response")?
                    .get_payloads()
                    .context("fetch: missing payloads")?;

                let mut payloads = Vec::with_capacity(list.len() as usize);
                for i in 0..list.len() {
                    let entry = list.get(i);
                    let seq = entry.get_seq();
                    let data = entry
                        .get_data()
                        .context("fetch: envelope data read failed")?
                        .to_vec();
                    payloads.push((seq, data));
                }

                Ok(payloads)
            }
        },
        max_retries_from_env(),
        base_delay_ms_from_env(),
        anyhow_is_retriable,
    )
    .await
}

/// Long-poll for payloads with optional timeout (ms).
/// Returns `(seq, payload)` pairs — sort by `seq` before MLS processing.
/// Retries on transient failures with exponential backoff.
pub async fn fetch_wait(
    client: &node_service::Client,
    recipient_key: &[u8],
    timeout_ms: u64,
) -> anyhow::Result<Vec<(u64, Vec<u8>)>> {
    let client = client.clone();
    let recipient_key = recipient_key.to_vec();
    retry_async(
        || {
            let client = client.clone();
            let recipient_key = recipient_key.clone();
            let timeout_ms = timeout_ms;
            async move {
                let mut req = client.fetch_wait_request();
                {
                    let mut p = req.get();
                    p.set_recipient_key(&recipient_key);
                    p.set_timeout_ms(timeout_ms);
                    p.set_channel_id(&[]);
                    p.set_version(1);
                    p.set_limit(0); // fetch all
                    let mut auth = p.reborrow().init_auth();
                    set_auth(&mut auth)?;
                }

                let resp = req.send().promise.await.context("fetch_wait RPC failed")?;

                let list = resp
                    .get()
                    .context("fetch_wait: bad response")?
                    .get_payloads()
                    .context("fetch_wait: missing payloads")?;

                let mut payloads = Vec::with_capacity(list.len() as usize);
                for i in 0..list.len() {
                    let entry = list.get(i);
                    let seq = entry.get_seq();
                    let data = entry
                        .get_data()
                        .context("fetch_wait: envelope data read failed")?
                        .to_vec();
                    payloads.push((seq, data));
                }

                Ok(payloads)
            }
        },
        max_retries_from_env(),
        base_delay_ms_from_env(),
        anyhow_is_retriable,
    )
    .await
}

/// Upload a hybrid (X25519 + ML-KEM-768) public key for an identity.
pub async fn upload_hybrid_key(
    client: &node_service::Client,
    identity_key: &[u8],
    hybrid_pk: &HybridPublicKey,
) -> anyhow::Result<()> {
    let mut req = client.upload_hybrid_key_request();
    {
        let mut p = req.get();
        p.set_identity_key(identity_key);
        p.set_hybrid_public_key(&hybrid_pk.to_bytes());
        let mut auth = p.reborrow().init_auth();
        set_auth(&mut auth)?;
    }
    req.send()
        .promise
        .await
        .context("upload_hybrid_key RPC failed")?;
    Ok(())
}

/// Fetch a peer's hybrid public key from the server.
///
/// Returns `None` if the peer has not uploaded a hybrid key.
pub async fn fetch_hybrid_key(
    client: &node_service::Client,
    identity_key: &[u8],
) -> anyhow::Result<Option<HybridPublicKey>> {
    let mut req = client.fetch_hybrid_key_request();
    {
        let mut p = req.get();
        p.set_identity_key(identity_key);
        let mut auth = p.reborrow().init_auth();
        set_auth(&mut auth)?;
    }

    let resp = req
        .send()
        .promise
        .await
        .context("fetch_hybrid_key RPC failed")?;

    let pk_bytes = resp
        .get()
        .context("fetch_hybrid_key: bad response")?
        .get_hybrid_public_key()
        .context("fetch_hybrid_key: missing field")?
        .to_vec();

    if pk_bytes.is_empty() {
        return Ok(None);
    }

    let pk = HybridPublicKey::from_bytes(&pk_bytes).context("invalid hybrid public key")?;
    Ok(Some(pk))
}

/// Decrypt a hybrid envelope. Requires a hybrid key; no fallback to plaintext MLS.
pub fn try_hybrid_decrypt(
    hybrid_kp: Option<&quicnprotochat_core::HybridKeypair>,
    payload: &[u8],
) -> anyhow::Result<Vec<u8>> {
    let kp = hybrid_kp.ok_or_else(|| anyhow::anyhow!("hybrid key required for decryption"))?;
    quicnprotochat_core::hybrid_decrypt(kp, payload).map_err(|e| anyhow::anyhow!("{e}"))
}

/// Return the current Unix timestamp in milliseconds.
pub fn current_timestamp_ms() -> u64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap_or_default()
        .as_millis() as u64
}