//! Delivery handlers — enqueue, fetch, fetch_wait, peek, ack, batch_enqueue.

use std::sync::Arc;

use bytes::Bytes;
use prost::Message;
use quicprochat_proto::qpc::v1;
use quicprochat_rpc::error::RpcStatus;
use quicprochat_rpc::method::{HandlerResult, RequestContext};
use sha2::{Digest, Sha256};
use tokio::sync::Notify;

use crate::domain::delivery::DeliveryService;
use crate::domain::types::{AckReq, BatchEnqueueReq, EnqueueReq, FetchReq, PeekReq};
use crate::hooks::{HookAction, MessageEvent};

use super::{require_auth, ServerState};

/// Build a 96-byte delivery proof: `SHA-256(seq || recipient_key || timestamp_ms) || Ed25519(hash)`.
///
/// The sender stores this as cryptographic evidence that the server enqueued the message.
fn build_delivery_proof(
    signing_key: &quicprochat_core::IdentityKeypair,
    seq: u64,
    recipient_key: &[u8],
    timestamp_ms: u64,
) -> Vec<u8> {
    let mut hasher = Sha256::new();
    hasher.update(seq.to_le_bytes());
    hasher.update(recipient_key);
    hasher.update(timestamp_ms.to_le_bytes());
    let hash: [u8; 32] = hasher.finalize().into();

    let sig = signing_key.sign_raw(&hash);

    let mut proof = vec![0u8; 96];
    proof[..32].copy_from_slice(&hash);
    proof[32..].copy_from_slice(&sig);
    proof
}

pub async fn handle_enqueue(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::EnqueueRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    if req.recipient_key.is_empty() || req.payload.is_empty() {
        return HandlerResult::err(RpcStatus::BadRequest, "recipient_key and payload required");
    }

    // Rate limiting.
    if let Err(_e) = crate::auth::check_rate_limit(&state.rate_limits, &identity_key) {
        return HandlerResult::err(RpcStatus::RateLimited, "rate limit exceeded");
    }

    // Idempotency dedup: if message_id is provided and already seen, return the cached seq.
    if !req.message_id.is_empty() {
        if let Some(entry) = state.seen_message_ids.get(&req.message_id) {
            let (cached_seq, _ts) = *entry;
            let proto = v1::EnqueueResponse {
                seq: cached_seq,
                delivery_proof: Vec::new(),
                duplicate: true,
            };
            return HandlerResult::ok(Bytes::from(proto.encode_to_vec()));
        }
    }

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    let domain_req = EnqueueReq {
        recipient_key: req.recipient_key.clone(),
        payload: req.payload.clone(),
        channel_id: req.channel_id.clone(),
        ttl_secs: req.ttl_secs,
    };

    match svc.enqueue(domain_req) {
        Ok(resp) => {
            // Record message_id for dedup.
            if !req.message_id.is_empty() {
                let now = crate::auth::current_timestamp();
                state.seen_message_ids.insert(req.message_id, (resp.seq, now));
            }

            // Fire hook.
            let action = state.hooks.on_message_enqueue(&MessageEvent {
                sender_identity: Some(identity_key),
                recipient_key: req.recipient_key.clone(),
                channel_id: req.channel_id,
                payload_len: req.payload.len(),
                seq: resp.seq,
            });
            if let HookAction::Reject(reason) = action {
                return HandlerResult::err(RpcStatus::Forbidden, &reason);
            }

            // Build server-signed delivery proof.
            let timestamp_ms = crate::auth::current_timestamp();
            let delivery_proof = build_delivery_proof(
                &state.signing_key,
                resp.seq,
                &req.recipient_key,
                timestamp_ms,
            );

            let proto = v1::EnqueueResponse {
                seq: resp.seq,
                delivery_proof,
                duplicate: false,
            };
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("enqueue: {e}")),
    }
}

pub async fn handle_fetch(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::FetchRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    let base_key = if req.recipient_key.is_empty() {
        identity_key
    } else {
        req.recipient_key
    };
    let recipient_key = if req.device_id.is_empty() {
        base_key
    } else {
        DeliveryService::device_recipient_key(&base_key, &req.device_id)
    };

    let domain_req = FetchReq {
        recipient_key,
        channel_id: req.channel_id,
        limit: req.limit,
    };

    match svc.fetch(domain_req) {
        Ok(resp) => {
            let proto = v1::FetchResponse {
                payloads: resp
                    .payloads
                    .into_iter()
                    .map(|e| v1::Envelope {
                        seq: e.seq,
                        data: e.data,
                    })
                    .collect(),
            };
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}")),
    }
}

pub async fn handle_fetch_wait(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::FetchWaitRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    let base_key = if req.recipient_key.is_empty() {
        identity_key
    } else {
        req.recipient_key
    };
    let recipient_key = if req.device_id.is_empty() {
        base_key
    } else {
        DeliveryService::device_recipient_key(&base_key, &req.device_id)
    };

    let timeout_ms = if req.timeout_ms == 0 {
        30_000
    } else {
        req.timeout_ms.min(60_000)
    };

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    // Try immediate fetch first.
    let fetch_req = FetchReq {
        recipient_key: recipient_key.clone(),
        channel_id: req.channel_id.clone(),
        limit: req.limit,
    };

    match svc.fetch(fetch_req) {
        Ok(resp) if !resp.payloads.is_empty() => {
            let proto = v1::FetchWaitResponse {
                payloads: resp
                    .payloads
                    .into_iter()
                    .map(|e| v1::Envelope {
                        seq: e.seq,
                        data: e.data,
                    })
                    .collect(),
            };
            return HandlerResult::ok(Bytes::from(proto.encode_to_vec()));
        }
        Err(e) => {
            return HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}"));
        }
        _ => {}
    }

    // Long-poll: wait for notification or timeout.
    let notify = state
        .waiters
        .entry(recipient_key.clone())
        .or_insert_with(|| Arc::new(Notify::new()))
        .clone();

    let timeout = tokio::time::Duration::from_millis(timeout_ms);
    let _ = tokio::time::timeout(timeout, notify.notified()).await;

    // Re-fetch after wake or timeout.
    let fetch_req = FetchReq {
        recipient_key,
        channel_id: req.channel_id,
        limit: req.limit,
    };

    match svc.fetch(fetch_req) {
        Ok(resp) => {
            let proto = v1::FetchWaitResponse {
                payloads: resp
                    .payloads
                    .into_iter()
                    .map(|e| v1::Envelope {
                        seq: e.seq,
                        data: e.data,
                    })
                    .collect(),
            };
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}")),
    }
}

pub async fn handle_peek(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::PeekRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    let base_key = if req.recipient_key.is_empty() {
        identity_key
    } else {
        req.recipient_key
    };
    let recipient_key = if req.device_id.is_empty() {
        base_key
    } else {
        DeliveryService::device_recipient_key(&base_key, &req.device_id)
    };

    let domain_req = PeekReq {
        recipient_key,
        channel_id: req.channel_id,
        limit: req.limit,
    };

    match svc.peek(domain_req) {
        Ok(resp) => {
            let proto = v1::PeekResponse {
                payloads: resp
                    .payloads
                    .into_iter()
                    .map(|e| v1::Envelope {
                        seq: e.seq,
                        data: e.data,
                    })
                    .collect(),
            };
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("peek: {e}")),
    }
}

pub async fn handle_ack(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::AckRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    let base_key = if req.recipient_key.is_empty() {
        identity_key
    } else {
        req.recipient_key
    };
    let recipient_key = if req.device_id.is_empty() {
        base_key
    } else {
        DeliveryService::device_recipient_key(&base_key, &req.device_id)
    };

    let domain_req = AckReq {
        recipient_key,
        channel_id: req.channel_id,
        seq_up_to: req.seq_up_to,
    };

    match svc.ack(domain_req) {
        Ok(()) => {
            let proto = v1::AckResponse {};
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("ack: {e}")),
    }
}

pub async fn handle_batch_enqueue(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
    let identity_key = match require_auth(&state, &ctx) {
        Ok(ik) => ik,
        Err(e) => return e,
    };

    let req = match v1::BatchEnqueueRequest::decode(ctx.payload) {
        Ok(r) => r,
        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
    };

    if req.recipient_keys.is_empty() || req.payload.is_empty() {
        return HandlerResult::err(
            RpcStatus::BadRequest,
            "recipient_keys and payload required",
        );
    }

    // Rate limiting.
    if let Err(_e) = crate::auth::check_rate_limit(&state.rate_limits, &identity_key) {
        return HandlerResult::err(RpcStatus::RateLimited, "rate limit exceeded");
    }

    let svc = DeliveryService {
        store: Arc::clone(&state.store),
        waiters: Arc::clone(&state.waiters),
    };

    let domain_req = BatchEnqueueReq {
        recipient_keys: req.recipient_keys,
        payload: req.payload,
        channel_id: req.channel_id,
        ttl_secs: req.ttl_secs,
    };

    match svc.batch_enqueue(domain_req) {
        Ok(resp) => {
            let proto = v1::BatchEnqueueResponse { seqs: resp.seqs };
            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
        }
        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("batch_enqueue: {e}")),
    }
}