use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};

use config::redis::{RedisConfig, RedisMode};
use redis::aio::{ConnectionManager, MultiplexedConnection};
use redis::cluster_async::ClusterConnection;
use redis::{ConnectionAddr, ConnectionInfo, Value};

use crate::error::ExportError;

#[derive(Clone)]
pub enum RedisConnection {
    Standalone(ConnectionManager),
    Cluster(ClusterConnection),
}

impl RedisConnection {
    pub fn is_cluster(&self) -> bool {
        matches!(self, RedisConnection::Cluster(_))
    }
}

#[derive(Clone)]
pub struct AppRedis {
    config: RedisConfig,
    /// One multiplexed connection per pool slot; every slot is an independent
    /// connection (not a clone of another slot) so requests spread over
    /// multiple sockets.
    connections: Vec<RedisConnection>,
    /// Round-robin cursor shared across clones of this handle.
    cursor: Arc<AtomicUsize>,
    /// Connection parameters (auth, tls) of the first configured node,
    /// reused to open per-node connections for cluster-wide operations.
    node_info: Option<ConnectionInfo>,
}

impl AppRedis {
    pub async fn connect(config: RedisConfig) -> Result<Self, ExportError> {
        let url = config.validate().map_err(ExportError::InvalidConfig)?;
        let pool_size = config.pool_size().max(1);

        let (connections, node_info) = match config.mode() {
            RedisMode::Cluster => {
                let nodes = url
                    .split(',')
                    .map(str::trim)
                    .filter(|node| !node.is_empty())
                    .map(String::from)
                    .collect::<Vec<_>>();

                let client =
                    redis::cluster::ClusterClient::new(nodes).map_err(ExportError::from)?;
                let node_info = connection_info(url)?;

                let mut connections = Vec::with_capacity(pool_size);
                for _ in 0..pool_size {
                    let connection = client
                        .get_async_connection()
                        .await
                        .map_err(ExportError::from)?;

                    connections.push(RedisConnection::Cluster(connection));
                }

                (connections, Some(node_info))
            }
            RedisMode::Standalone | RedisMode::Sentinel | RedisMode::ValkeyStandalone => {
                let mut connections = Vec::with_capacity(pool_size);
                for _ in 0..pool_size {
                    let client = redis::Client::open(url).map_err(ExportError::from)?;
                    let manager = ConnectionManager::new(client)
                        .await
                        .map_err(ExportError::from)?;

                    connections.push(RedisConnection::Standalone(manager));
                }

                let node_info = connection_info(url)?;

                (connections, Some(node_info))
            }
        };

        Ok(Self {
            config,
            connections,
            cursor: Arc::new(AtomicUsize::new(0)),
            node_info,
        })
    }

    pub fn config(&self) -> &RedisConfig {
        &self.config
    }

    pub fn mode(&self) -> RedisMode {
        self.config.mode()
    }

    pub fn is_cluster(&self) -> bool {
        self.config.mode() == RedisMode::Cluster
    }

    pub fn connection(&self) -> &RedisConnection {
        &self.connections[0]
    }

    pub fn connection_clone(&self) -> RedisConnection {
        let index = self.cursor.fetch_add(1, Ordering::Relaxed) % self.connections.len();

        self.connections[index].clone()
    }

    pub async fn publish(&self, channel: &str, payload: &str) -> Result<(), ExportError> {
        let mut conn = self.connection_clone();
        let result: Result<i64, redis::RedisError> = match &mut conn {
            RedisConnection::Standalone(c) => {
                redis::cmd("PUBLISH")
                    .arg(channel)
                    .arg(payload)
                    .query_async(c)
                    .await
            }
            RedisConnection::Cluster(c) => {
                redis::cmd("PUBLISH")
                    .arg(channel)
                    .arg(payload)
                    .query_async(c)
                    .await
            }
        };
        result.map(|_| ()).map_err(ExportError::from)
    }

    /// `SET key 1 NX EX ttl`; returns false when the key already exists
    /// (already consumed / inside an active window) or redis fails.
    pub async fn set_nx_ex(&self, key: &str, ttl_secs: u64) -> bool {
        let mut conn = self.connection_clone();
        let result: Result<Option<String>, redis::RedisError> = match &mut conn {
            RedisConnection::Standalone(c) => {
                redis::cmd("SET")
                    .arg(key)
                    .arg("1")
                    .arg("NX")
                    .arg("EX")
                    .arg(ttl_secs.max(1))
                    .query_async(c)
                    .await
            }
            RedisConnection::Cluster(c) => {
                redis::cmd("SET")
                    .arg(key)
                    .arg("1")
                    .arg("NX")
                    .arg("EX")
                    .arg(ttl_secs.max(1))
                    .query_async(c)
                    .await
            }
        };
        matches!(result, Ok(Some(_)))
    }

    /// `INCR key` with a window TTL set on first increment; returns the count.
    pub async fn incr_window(&self, key: &str, window_secs: u64) -> i64 {
        let mut conn = self.connection_clone();
        let result: Result<i64, redis::RedisError> = match &mut conn {
            RedisConnection::Standalone(c) => {
                let count: i64 = redis::cmd("INCR")
                    .arg(key)
                    .query_async(c)
                    .await
                    .unwrap_or(0);
                if count == 1 {
                    let _: Result<redis::Value, redis::RedisError> = redis::cmd("EXPIRE")
                        .arg(key)
                        .arg(window_secs)
                        .query_async(c)
                        .await;
                }
                Ok(count)
            }
            RedisConnection::Cluster(c) => {
                let count: i64 = redis::cmd("INCR")
                    .arg(key)
                    .query_async(c)
                    .await
                    .unwrap_or(0);
                if count == 1 {
                    let _: Result<redis::Value, redis::RedisError> = redis::cmd("EXPIRE")
                        .arg(key)
                        .arg(window_secs)
                        .query_async(c)
                        .await;
                }
                Ok(count)
            }
        };
        result.unwrap_or(0)
    }

    /// Rolling-window quota check; `max == 0` disables the quota.
    pub async fn quota_allow(&self, key: &str, max: i64, window_secs: u64) -> bool {
        if max <= 0 {
            return true;
        }
        self.incr_window(key, window_secs).await <= max
    }

    /// Opens a multiplexed connection to every master node of the cluster.
    ///
    /// Masters are discovered at call time via `CLUSTER SLOTS`, so this keeps
    /// working after topology changes. Returns an empty list for standalone
    /// connections.
    pub async fn cluster_master_connections(
        &self,
    ) -> Result<Vec<MultiplexedConnection>, ExportError> {
        let mut conn = self.connection_clone();
        let RedisConnection::Cluster(cluster) = &mut conn else {
            return Ok(Vec::new());
        };

        let slots: Value = redis::cmd("CLUSTER")
            .arg("SLOTS")
            .query_async(cluster)
            .await
            .map_err(ExportError::from)?;

        let node_info = self.node_info.clone().ok_or_else(|| {
            ExportError::InvalidConfig("cluster connection info is unavailable".into())
        })?;

        let mut seen = std::collections::HashSet::new();
        let mut connections = Vec::new();

        for (host, port) in cluster_master_addrs(&slots) {
            if !seen.insert((host.clone(), port)) {
                continue;
            }

            let addr = match node_info.addr() {
                ConnectionAddr::Tcp(_, _) => ConnectionAddr::Tcp(host.clone(), port),
                ConnectionAddr::TcpTls {
                    insecure,
                    tls_params,
                    ..
                } => ConnectionAddr::TcpTls {
                    host: host.clone(),
                    port,
                    insecure: *insecure,
                    tls_params: tls_params.clone(),
                },
                ConnectionAddr::Unix(_) => {
                    return Err(ExportError::InvalidConfig(
                        "unix sockets are not supported for cluster connections".into(),
                    ));
                }
                _ => {
                    return Err(ExportError::InvalidConfig(
                        "unsupported connection address type for cluster connections".into(),
                    ));
                }
            };

            let mut info = node_info.clone();
            info = info.set_addr(addr);

            let client = redis::Client::open(info).map_err(ExportError::from)?;
            // BRPOP 之类的阻塞命令会持有连接直到超时；必须关闭响应超时，
            // 否则默认超时会让阻塞读被误判为 timeout 错误。
            let conn_config = redis::AsyncConnectionConfig::new()
                .set_response_timeout(None)
                .set_connection_timeout(Some(self.config.connection_timeout()));
            let connection = client
                .get_multiplexed_async_connection_with_config(&conn_config)
                .await
                .map_err(ExportError::from)?;

            connections.push(connection);
        }

        Ok(connections)
    }

    /// Returns `(slot_start, slot_end, master_index)` triples where `master_index`
    /// matches the position of the owning connection in [`cluster_master_connections`].
    ///
    /// Empty for standalone connections. The ordering mirrors the dedup logic used
    /// when collecting master addresses, so callers can map a slot to the right
    /// pre-established connection without reconnecting.
    pub async fn cluster_slot_ranges(&self) -> Result<Vec<(i64, i64, usize)>, ExportError> {
        let mut conn = self.connection_clone();
        let RedisConnection::Cluster(cluster) = &mut conn else {
            return Ok(Vec::new());
        };

        let slots: Value = redis::cmd("CLUSTER")
            .arg("SLOTS")
            .query_async(cluster)
            .await
            .map_err(ExportError::from)?;

        Ok(cluster_slot_ranges(&slots))
    }
}

/// Extracts the host/port of every master from a `CLUSTER SLOTS` response.
///
/// Each slot group is `[start, end, [ip, port, node_id, ...], replicas...]`,
/// where the first entry of the node list is the master.
fn cluster_master_addrs(slots: &Value) -> Vec<(String, u16)> {
    let Value::Array(groups) = slots else {
        return Vec::new();
    };

    let mut masters = Vec::new();
    for group in groups {
        let Value::Array(fields) = group else {
            continue;
        };

        let Some(Value::Array(nodes)) = fields.get(2) else {
            continue;
        };

        let (Some(Value::BulkString(host)), Some(Value::Int(port))) = (nodes.first(), nodes.get(1))
        else {
            continue;
        };

        masters.push((String::from_utf8_lossy(host).into_owned(), *port as u16));
    }

    masters
}

/// Builds the connection info of the first configured node, used as a template
/// (scheme, auth, tls settings) for connections to other cluster nodes.
fn connection_info(urls: &str) -> Result<ConnectionInfo, ExportError> {
    let first = urls
        .split(',')
        .map(str::trim)
        .find(|node| !node.is_empty())
        .ok_or_else(|| ExportError::InvalidConfig("redis url contains no nodes".into()))?;

    Ok(redis::Client::open(first)?.get_connection_info().clone())
}

macro_rules! dispatch {
    ($conn:expr, |$c:ident| $body:expr) => {
        match &mut $conn {
            RedisConnection::Standalone($c) => $body,
            RedisConnection::Cluster($c) => $body,
        }
    };
}

pub async fn get_string(redis: &AppRedis, key: &str) -> Result<Option<String>, redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| redis::cmd("GET").arg(key).query_async(c).await)
}

pub async fn set_string(
    redis: &AppRedis,
    key: &str,
    value: &str,
    ttl_secs: u64,
) -> Result<(), redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| {
        redis::cmd("SET")
            .arg(key)
            .arg(value)
            .arg("EX")
            .arg(ttl_secs)
            .exec_async(c)
            .await
    })
}

pub async fn set_nx_ex(
    redis: &AppRedis,
    key: &str,
    value: &str,
    ttl_secs: u64,
) -> Result<bool, redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| {
        redis::cmd("SET")
            .arg(key)
            .arg(value)
            .arg("NX")
            .arg("EX")
            .arg(ttl_secs)
            .query_async(c)
            .await
    })
}

pub async fn delete(redis: &AppRedis, key: &str) -> Result<(), redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| redis::cmd("DEL").arg(key).exec_async(c).await)
}

pub async fn exists(redis: &AppRedis, key: &str) -> Result<bool, redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| redis::cmd("EXISTS").arg(key).query_async(c).await)
}

pub async fn getdel_string(
    redis: &AppRedis,
    key: &str,
) -> Result<Option<String>, redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| redis::cmd("GETDEL").arg(key).query_async(c).await)
}

const INCR_EXPIRE_SCRIPT: &str = r#"local c = redis.call('INCR', KEYS[1])
if c == 1 then
  redis.call('EXPIRE', KEYS[1], ARGV[1])
end
return c"#;

pub async fn incr_expire(
    redis: &AppRedis,
    key: &str,
    ttl_secs: u64,
) -> Result<i64, redis::RedisError> {
    let mut conn = redis.connection_clone();
    dispatch!(conn, |c| {
        redis::cmd("EVAL")
            .arg(INCR_EXPIRE_SCRIPT)
            .arg(1)
            .arg(key)
            .arg(ttl_secs)
            .query_async(c)
            .await
    })
}

/// Extracts `(start, end, master_index)` for every slot range.
///
/// `master_index` counts unique master addresses in first-seen order, matching
/// [`AppRedis::cluster_master_connections`].
fn cluster_slot_ranges(slots: &Value) -> Vec<(i64, i64, usize)> {
    let Value::Array(groups) = slots else {
        return Vec::new();
    };

    let mut seen: std::collections::HashMap<(String, u16), usize> =
        std::collections::HashMap::new();
    let mut ranges = Vec::new();

    for group in groups {
        let Value::Array(fields) = group else {
            continue;
        };

        let (Some(Value::Int(start)), Some(Value::Int(end))) = (fields.first(), fields.get(1))
        else {
            continue;
        };

        let Some(Value::Array(nodes)) = fields.get(2) else {
            continue;
        };

        let (Some(Value::BulkString(host)), Some(Value::Int(port))) = (nodes.first(), nodes.get(1))
        else {
            continue;
        };

        let addr = (String::from_utf8_lossy(host).to_string(), *port as u16);
        let next_index = seen.len();
        let index = *seen.entry(addr).or_insert(next_index);

        ranges.push((*start, *end, index));
    }

    ranges
}