//! Jetstream consumer for AT Protocol badge award events.
//!
//! Handles real-time processing of badge award events from Jetstream,
//! with event queuing and cursor management for reliable consumption.

use std::sync::Arc;
use std::sync::atomic::{AtomicU64, Ordering};
use std::time::{Duration, Instant};

use crate::errors::ShowcaseError;
use anyhow::Result;
use async_trait::async_trait;
use atproto_jetstream::{EventHandler, JetstreamEvent};
use tokio::sync::Mutex;
use tokio::sync::mpsc;

/// Type alias for badge event receiver to hide implementation details
pub type BadgeEventReceiver = mpsc::UnboundedReceiver<AwardEvent>;

/// Badge event types from Jetstream
#[derive(Debug, Clone)]
pub enum AwardEvent {
    /// Record commit event for a badge award.
    Commit {
        /// DID of the record owner.
        did: String,
        /// Record key within the collection.
        rkey: String,
        /// Content identifier of the record.
        cid: String,
        /// The complete record data.
        record: serde_json::Value,
    },
    /// Record deletion event for a badge award.
    Delete {
        /// DID of the record owner.
        did: String,
        /// Record key within the collection.
        rkey: String,
    },
}

/// Event handler that publishes badge events to an in-memory queue
pub struct AwardEventHandler {
    id: String,
    event_sender: mpsc::UnboundedSender<AwardEvent>,
}

impl AwardEventHandler {
    fn new(id: String, event_sender: mpsc::UnboundedSender<AwardEvent>) -> Self {
        Self { id, event_sender }
    }
}

#[async_trait]
impl EventHandler for AwardEventHandler {
    async fn handle_event(&self, event: JetstreamEvent) -> Result<()> {
        let award_event = match event {
            JetstreamEvent::Commit { did, commit, .. } => {
                if commit.collection != "community.lexicon.badge.award" {
                    return Ok(());
                }

                AwardEvent::Commit {
                    did,
                    rkey: commit.rkey,
                    cid: commit.cid,
                    record: commit.record,
                }
            }
            JetstreamEvent::Delete { did, commit, .. } => {
                if commit.collection != "community.lexicon.badge.award" {
                    return Ok(());
                }
                AwardEvent::Delete {
                    did,
                    rkey: commit.rkey,
                }
            }
            JetstreamEvent::Identity { .. } | JetstreamEvent::Account { .. } => {
                return Ok(());
            }
        };

        if let Err(err) = self.event_sender.send(award_event) {
            let showcase_error = ShowcaseError::ConsumerQueueSendFailed {
                details: err.to_string(),
            };
            tracing::error!(?showcase_error);
        }

        Ok(())
    }

    fn handler_id(&self) -> String {
        self.id.clone()
    }
}

/// Cursor writer handler that periodically writes the latest time_us to a file
pub struct CursorWriterHandler {
    id: String,
    cursor_path: String,
    last_time_us: Arc<AtomicU64>,
    last_write: Arc<Mutex<Instant>>,
    write_interval: Duration,
}

impl CursorWriterHandler {
    fn new(id: String, cursor_path: String) -> Self {
        Self {
            id,
            cursor_path,
            last_time_us: Arc::new(AtomicU64::new(0)),
            last_write: Arc::new(Mutex::new(Instant::now())),
            write_interval: Duration::from_secs(30),
        }
    }

    async fn maybe_write_cursor(&self) -> Result<()> {
        let current_time_us = self.last_time_us.load(Ordering::Relaxed);
        if current_time_us == 0 {
            return Ok(());
        }

        let mut last_write = self.last_write.lock().await;
        if last_write.elapsed() >= self.write_interval {
            tokio::fs::write(&self.cursor_path, current_time_us.to_string()).await?;
            *last_write = Instant::now();
            tracing::debug!("Wrote cursor to {}: {}", self.cursor_path, current_time_us);
        }
        Ok(())
    }
}

#[async_trait]
impl EventHandler for CursorWriterHandler {
    async fn handle_event(&self, event: JetstreamEvent) -> Result<()> {
        // Extract time_us from any event type
        let time_us = match &event {
            JetstreamEvent::Commit { time_us, .. } => *time_us,
            JetstreamEvent::Delete { time_us, .. } => *time_us,
            JetstreamEvent::Identity { time_us, .. } => *time_us,
            JetstreamEvent::Account { time_us, .. } => *time_us,
        };

        // Update the latest time_us
        self.last_time_us.store(time_us, Ordering::Relaxed);

        // Try to write the cursor periodically
        if let Err(err) = self.maybe_write_cursor().await {
            tracing::warn!("Failed to write cursor: {}", err);
        }

        Ok(())
    }

    fn handler_id(&self) -> String {
        self.id.clone()
    }
}

/// Consumer factory for creating event handlers and queue receivers
pub struct Consumer {}

impl Consumer {
    /// Create a badge event handler and return the receiver for processing
    pub fn create_badge_handler(&self) -> (Arc<AwardEventHandler>, BadgeEventReceiver) {
        let (sender, receiver) = mpsc::unbounded_channel();
        let handler = Arc::new(AwardEventHandler::new(
            "badge-processor".to_string(),
            sender,
        ));
        (handler, receiver)
    }

    /// Create a cursor writer handler for the given cursor path
    pub fn create_cursor_writer_handler(&self, cursor_path: String) -> Arc<CursorWriterHandler> {
        Arc::new(CursorWriterHandler::new(
            "cursor-writer".to_string(),
            cursor_path,
        ))
    }
}