use std::process;

use export::{AppRedis, RedisConnection};
use uuid::Uuid;

use crate::sync::error::SyncResult;

const LOCK_KEY_PREFIX: &str = "git:sync:lock:";

const REFRESH_SCRIPT: &str = "local v = redis.call('GET', KEYS[1])\nif v == ARGV[1] then\n  redis.call('PEXPIRE', KEYS[1], ARGV[2])\n  return 1\nend\nreturn 0";

const RELEASE_SCRIPT: &str = "local v = redis.call('GET', KEYS[1])\nif v == ARGV[1] then\n  return redis.call('DEL', KEYS[1])\nend\nreturn 0";

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

pub struct SyncLock {
    redis: AppRedis,
    key: String,
    value: String,
}

impl SyncLock {
    #[must_use]
    pub fn value(&self) -> &str {
        &self.value
    }

    #[must_use]
    pub fn key(&self) -> &str {
        &self.key
    }

    pub async fn refresh(&self, ttl_secs: u64) -> SyncResult<bool> {
        let mut conn = self.redis.connection_clone();
        let n: i64 = dispatch!(conn, |c| {
            redis::cmd("EVAL")
                .arg(REFRESH_SCRIPT)
                .arg(1)
                .arg(&self.key)
                .arg(&self.value)
                .arg(ttl_secs.saturating_mul(1000))
                .query_async(c)
                .await
        })?;
        if n != 1 {
            tracing::warn!(key = %self.key, "sync lock heartbeat refresh lost ownership");
        }
        Ok(n == 1)
    }

    pub async fn release(&self) -> SyncResult<()> {
        let mut conn = self.redis.connection_clone();
        let _: i64 = dispatch!(conn, |c| {
            redis::cmd("EVAL")
                .arg(RELEASE_SCRIPT)
                .arg(1)
                .arg(&self.key)
                .arg(&self.value)
                .query_async(c)
                .await
        })?;
        tracing::debug!(key = %self.key, "sync lock released");
        Ok(())
    }
}

fn lock_key(repo_id: Uuid) -> String {
    format!("{LOCK_KEY_PREFIX}{repo_id}")
}

pub async fn acquire_lock(
    redis: &AppRedis,
    repo_id: Uuid,
    ttl_secs: u64,
) -> SyncResult<Option<SyncLock>> {
    let key = lock_key(repo_id);
    let value = format!("{}:{}", Uuid::now_v7(), process::id());

    let mut conn = redis.connection_clone();
    let acquired: bool = dispatch!(conn, |c| {
        redis::cmd("SET")
            .arg(&key)
            .arg(&value)
            .arg("NX")
            .arg("EX")
            .arg(ttl_secs)
            .query_async(c)
            .await
    })?;

    if !acquired {
        tracing::debug!(key = %key, repo_id = %repo_id, "sync lock busy; another sync in progress");
        return Ok(None);
    }

    tracing::debug!(key = %key, repo_id = %repo_id, ttl_secs, "sync lock acquired");
    Ok(Some(SyncLock {
        redis: redis.clone(),
        key,
        value,
    }))
}