use crate::error::GitError;
use crate::hook::pool::types::HookTask;
use deadpool_redis::cluster::Connection as RedisConn;
use slog::Logger;

/// Redis List consumer using BLMOVE for atomic move-from-queue-to-work pattern.
/// Compatible with Redis Cluster via hash tags in key names.
pub struct RedisConsumer {
    pool: deadpool_redis::cluster::Pool,
    /// Hash-tag-prefixed key prefix, e.g. "{hook}".
    /// Full queue key: "{hook}:{task_type}"
    /// Full work key: "{hook}:{task_type}:work"
    prefix: String,
    block_timeout_secs: u64,
    logger: Logger,
}

impl RedisConsumer {
    pub fn new(
        pool: deadpool_redis::cluster::Pool,
        prefix: String,
        block_timeout_secs: u64,
        logger: Logger,
    ) -> Self {
        Self {
            pool,
            prefix,
            block_timeout_secs,
            logger,
        }
    }

    /// Atomically moves a task from the main queue to the work queue using BLMOVE.
    /// Blocks up to `block_timeout_secs` waiting for a task.
    ///
    /// Returns `Some((HookTask, task_json))` where `task_json` is the raw JSON string
    /// needed for LREM on ACK. Returns `None` if the blocking timed out.
    pub async fn next(&self, task_type: &str) -> Result<Option<(HookTask, String)>, GitError> {
        let queue_key = format!("{}:{}", self.prefix, task_type);
        let work_key = format!("{}:{}:work", self.prefix, task_type);

        let redis = self
            .pool
            .get()
            .await
            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;

        let mut conn: RedisConn = redis;

        // BLMOVE source destination <LEFT|RIGHT> <LEFT|RIGHT> timeout
        // RIGHT LEFT = BRPOPLPUSH equivalent (pop from right of src, push to left of dst)
        let task_json: Option<String> = redis::cmd("BLMOVE")
            .arg(&queue_key)
            .arg(&work_key)
            .arg("RIGHT")
            .arg("LEFT")
            .arg(self.block_timeout_secs)
            .query_async(&mut conn)
            .await
            .map_err(|e| GitError::Internal(format!("BLMOVE failed: {}", e)))?;

        match task_json {
            Some(json) => {
                match serde_json::from_str::<HookTask>(&json) {
                    Ok(task) => {
                        slog::debug!(self.logger, "task dequeued";
                            "task_id" => %task.id,
                            "task_type" => %task.task_type,
                            "queue" => %queue_key
                        );
                        Ok(Some((task, json)))
                    }
                    Err(e) => {
                        // Malformed task — remove from work queue and discard
                        slog::warn!(self.logger, "malformed task JSON, discarding";
                            "error" => %e,
                            "queue" => %work_key
                        );
                        let _ = self.ack_raw(&work_key, &json).await;
                        Ok(None)
                    }
                }
            }
            None => {
                // Timed out, no task available
                Ok(None)
            }
        }
    }

    /// Acknowledge a task: remove it from the work queue (LREM).
    pub async fn ack(&self, work_key: &str, task_json: &str) -> Result<(), GitError> {
        self.ack_raw(work_key, task_json).await
    }

    async fn ack_raw(&self, work_key: &str, task_json: &str) -> Result<(), GitError> {
        let redis = self
            .pool
            .get()
            .await
            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;

        let mut conn: RedisConn = redis;

        let _: i64 = redis::cmd("LREM")
            .arg(work_key)
            .arg(-1) // remove all occurrences
            .arg(task_json)
            .query_async(&mut conn)
            .await
            .map_err(|e| GitError::Internal(format!("LREM failed: {}", e)))?;

        Ok(())
    }

    /// Negative acknowledge (retry): remove from work queue and push back to main queue.
    pub async fn nak(
        &self,
        work_key: &str,
        queue_key: &str,
        task_json: &str,
    ) -> Result<(), GitError> {
        // First remove from work queue
        self.ack_raw(work_key, task_json).await?;

        // Then push back to main queue for retry
        let redis = self
            .pool
            .get()
            .await
            .map_err(|e| GitError::Internal(format!("redis pool get failed: {}", e)))?;

        let mut conn: RedisConn = redis;

        let _: i64 = redis::cmd("LPUSH")
            .arg(queue_key)
            .arg(task_json)
            .query_async(&mut conn)
            .await
            .map_err(|e| GitError::Internal(format!("LPUSH retry failed: {}", e)))?;

        slog::warn!(self.logger, "task nack'd and requeued"; "queue" => %queue_key);

        Ok(())
    }

    pub fn pool(&self) -> &deadpool_redis::cluster::Pool {
        &self.pool
    }

    pub fn prefix(&self) -> &str {
        &self.prefix
    }
}

impl Clone for RedisConsumer {
    fn clone(&self) -> Self {
        Self {
            pool: self.pool.clone(),
            prefix: self.prefix.clone(),
            block_timeout_secs: self.block_timeout_secs,
            logger: self.logger.clone(),
        }
    }
}