//! Background tasks: CRDT-event bridge, auto-assign subscriber, unified tick
//! loop, gateway relay, and startup reconciliation.

use crate::agents::{AgentPool, ReconciliationEvent};
use crate::config;
use crate::gateway_relay;
use crate::http::context::AppContext;
use crate::http::mcp::dispatch::dispatch_tool_call;
use crate::io;
use crate::service;
use crate::service::event_triggers::store::EventTriggerStore;
use crate::service::event_triggers::{FireMode, TriggerAction};
use crate::service::status::StatusBroadcaster;
use crate::service::timer::scheduled::{
    ScheduledTimer, ScheduledTimerStore, TimerAction, TimerMode,
};
use std::path::PathBuf;
use std::sync::Arc;
use tokio::sync::broadcast;

/// Bridge CRDT state-transition events to the watcher broadcast channel and
/// spawn the auto-assign subscriber that triggers on active-stage transitions.
pub(crate) fn spawn_event_bridges(
    watcher_tx: broadcast::Sender<io::watcher::WatcherEvent>,
    project_root: Option<PathBuf>,
    agents: Arc<AgentPool>,
) {
    // Audit log subscriber: write one structured line per pipeline transition.
    crate::pipeline_state::spawn_audit_log_subscriber();

    // CRDT → watcher bridge: translate CRDT stage-transition events into
    // WatcherEvent::WorkItem so downstream consumers (WebSocket, auto-assign)
    // see a uniform stream regardless of whether the event originated from the
    // filesystem watcher or from a CRDT sync peer.
    {
        let crdt_watcher_tx = watcher_tx.clone();
        if let Some(mut crdt_rx) = crate::crdt_state::subscribe() {
            tokio::spawn(async move {
                while let Ok(evt) = crdt_rx.recv().await {
                    let (action, commit_msg) =
                        io::watcher::stage_metadata(&evt.to_stage, &evt.story_id);
                    let watcher_evt = io::watcher::WatcherEvent::WorkItem {
                        stage: evt.to_stage.dir_name().to_string(),
                        item_id: evt.story_id,
                        action: action.to_string(),
                        commit_msg,
                        from_stage: evt.from_stage.map(|s| s.dir_name().to_string()),
                    };
                    let _ = crdt_watcher_tx.send(watcher_evt);
                }
            });
        }
    }

    // Auto-assign: trigger `auto_assign_available_work` on every work-item
    // CRDT state-transition event.  auto_assign_available_work is idempotent
    // and noops where there is nothing to do, so firing on every transition
    // ensures that MergeFailure and other non-"active" stages are covered
    // without any per-stage special-casing.
    if let Some(root) = project_root {
        // Worktree lifecycle subscribers: create worktrees on Stage::Coding
        // and remove them on terminal stages (Done, Archived, Abandoned, Superseded).
        crate::agents::pool::worktree_lifecycle::spawn_worktree_create_subscriber(
            root.clone(),
            agents.port(),
        );
        crate::agents::pool::worktree_lifecycle::spawn_worktree_cleanup_subscriber(root.clone());

        // Mergemaster auto-spawn subscriber: reacts to TransitionFired events for
        // Stage::MergeFailure { kind: ConflictDetected } and spawns mergemaster
        // directly from the typed event, eliminating the predicate-mismatch
        // failure mode of the previous scan-loop approach (story 998).
        crate::agents::pool::auto_assign::spawn_merge_failure_subscriber(
            Arc::clone(&agents),
            root.clone(),
        );

        // Consecutive-failure auto-block subscriber: blocks stories after N
        // consecutive MergeFailure transitions (story 1018).  Bug 1025: takes
        // the agent pool so it can gate the counter on mergemaster presence —
        // failures during active recovery iteration do not count toward block.
        crate::agents::pool::auto_assign::spawn_merge_failure_block_subscriber(
            Arc::clone(&agents),
            root.clone(),
        );

        // Content-store GC subscriber: purges all ContentKey::* entries for a
        // story when it reaches a terminal stage, preventing zombie entries from
        // accumulating in the process heap (story 996).
        crate::db::gc::spawn_content_gc_subscriber();

        // Cost-rollup bootstrap: pre-populate the register from existing JSONL
        // so status renderers show correct costs after a server restart.
        crate::service::agents::cost_rollup::init_from_disk(&root);

        // Cost-rollup subscriber: snapshots per-story token costs into the
        // in-memory register whenever a story reaches a terminal stage.
        crate::agents::pool::cost_rollup_subscriber::spawn_cost_rollup_subscriber(root.clone());

        // Done→archived subscriber: archives Done stories after the configured
        // retention period. Fires on each Stage::Done TransitionFired event and
        // sleeps for the remaining retention time from merged_at before archiving.
        // Replaces the periodic sweep_done_to_archived scan that ran on every
        // sweep_interval_secs tick.
        {
            let done_retention = config::ProjectConfig::load(&root)
                .map(|c| std::time::Duration::from_secs(c.watcher.done_retention_secs))
                .unwrap_or_else(|_| std::time::Duration::from_secs(4 * 3600));
            io::watcher::spawn_done_to_archived_subscriber(done_retention);
        }

        let watcher_auto_rx = watcher_tx.subscribe();
        let watcher_auto_agents = Arc::clone(&agents);
        tokio::spawn(async move {
            let mut rx = watcher_auto_rx;
            while let Ok(event) = rx.recv().await {
                if let io::watcher::WatcherEvent::WorkItem { ref stage, .. } = event {
                    crate::slog!(
                        "[auto-assign] CRDT transition detected in {stage}/; \
                         triggering auto-assign."
                    );
                    watcher_auto_agents.auto_assign_available_work(&root).await;
                }
            }
        });
    }
}

/// Spawn the unified 1-second background tick loop.
///
/// Handles only genuinely time-based work:
/// - **Timer tick** (every second): fires due pipeline timers by comparing the
///   current wall-clock time against each timer's `due_at` field. Cannot be
///   reactive because timers encode absolute timestamps that only become
///   actionable when the clock reaches them.
/// - **Scheduled timer tick** (every second): fires generic scheduled timers
///   registered via the `schedule_timer` MCP tool.
/// - **Agent watchdog** (every 30 seconds): detects orphaned `Running` agents
///   by comparing elapsed time since the last heartbeat. Cannot be reactive
///   because the absence of an event (no heartbeat) is what signals a problem;
///   a `TransitionFired` subscriber would never fire for a silently crashed agent.
///
/// Stage-change-reactive work (done→archived archival, worktree cleanup) has
/// been moved to `TransitionFired` subscribers spawned from `spawn_event_bridges`.
pub(crate) fn spawn_tick_loop(
    agents: Arc<AgentPool>,
    timer_store: Arc<service::timer::TimerStore>,
    scheduled_timer_store: Arc<ScheduledTimerStore>,
    root: Option<PathBuf>,
    ctx: AppContext,
) {
    let pending_count = timer_store.list().len();
    let scheduled_count = scheduled_timer_store.list().len();
    crate::slog!(
        "[tick] Unified tick loop started; {pending_count} rate-limit timer(s), \
         {scheduled_count} scheduled timer(s)"
    );

    tokio::spawn(async move {
        let mut interval = tokio::time::interval(std::time::Duration::from_secs(1));
        let mut tick_count: u64 = 0;
        loop {
            interval.tick().await;
            tick_count = tick_count.wrapping_add(1);

            // Time-based: timers encode absolute due timestamps; only a
            // wall-clock comparison can determine when one is due.
            if let Some(ref r) = root {
                let result = service::timer::tick_once(&timer_store, &agents, r).await;
                if let Err(msg) = result {
                    crate::slog_error!("[tick] Timer tick panicked: {msg}");
                }
            }

            // Generic scheduled timer tick.
            tick_scheduled_timers(&scheduled_timer_store, &ctx).await;

            // Time-based: the watchdog detects silence (no heartbeat within a
            // timeout window). A `TransitionFired` subscriber cannot observe the
            // absence of events, so this must remain on a periodic tick.
            if tick_count.is_multiple_of(30) {
                let found = agents.run_watchdog_pass(root.as_deref());
                if found > 0 {
                    crate::slog!(
                        "[tick] {found} orphaned agent(s) detected; triggering auto-assign."
                    );
                    if let Some(ref r) = root {
                        agents.auto_assign_available_work(r).await;
                    }
                }
                agents.reap_stale_merge_jobs();
            }
        }
    });
}

/// Fire any due generic scheduled timers and re-arm recurring ones.
///
/// Called every second from the unified tick loop.  Catch-up semantics: timers
/// whose `fire_at` is already in the past fire on the next tick after boot.
async fn tick_scheduled_timers(store: &Arc<ScheduledTimerStore>, ctx: &AppContext) {
    let due = store.take_due(chrono::Utc::now());
    if due.is_empty() {
        return;
    }

    crate::slog!("[scheduled-timer] {} timer(s) due", due.len());

    for timer in due {
        fire_scheduled_timer(&timer, ctx).await;

        // Re-arm recurring timers.
        if let TimerMode::Recurring { interval_secs } = &timer.mode {
            let next_fire = timer.fire_at + chrono::Duration::seconds(*interval_secs as i64);
            let rearmed = ScheduledTimer {
                id: timer.id.clone(),
                label: timer.label.clone(),
                fire_at: next_fire,
                action: timer.action.clone(),
                mode: timer.mode.clone(),
                created_at: timer.created_at,
            };
            if let Err(e) = store.add(rearmed) {
                crate::slog_error!("[scheduled-timer] Failed to re-arm timer {}: {e}", timer.id);
            } else {
                crate::slog!(
                    "[scheduled-timer] Recurring timer {} re-armed for {}",
                    timer.id,
                    next_fire
                );
            }
        }
    }
}

/// Execute a single scheduled timer's action.
async fn fire_scheduled_timer(timer: &ScheduledTimer, ctx: &AppContext) {
    let label = timer.label.as_deref().unwrap_or(&timer.id);
    match &timer.action {
        TimerAction::Mcp { method, args } => {
            crate::slog!(
                "[scheduled-timer] Firing MCP action '{}' for timer {}",
                method,
                timer.id
            );
            match dispatch_tool_call(method, args.clone(), ctx).await {
                Ok(result) => {
                    crate::slog!(
                        "[scheduled-timer] Timer {} ('{}') fired OK: {}",
                        timer.id,
                        label,
                        result.chars().take(200).collect::<String>()
                    );
                }
                Err(e) => {
                    crate::slog_error!(
                        "[scheduled-timer] Timer {} ('{}') MCP call '{}' failed: {e}",
                        timer.id,
                        label,
                        method
                    );
                }
            }
        }
        TimerAction::Prompt { text } => {
            crate::slog!(
                "[scheduled-timer] Prompt timer {} ('{}') fired: {}",
                timer.id,
                label,
                text
            );
        }
    }
}

/// Spawn the gateway relay task if `gateway_url` is configured in
/// `project.toml` or the `HUSKIES_GATEWAY_URL` environment variable.
pub(crate) fn spawn_gateway_relay(startup_root: &Option<PathBuf>, status: Arc<StatusBroadcaster>) {
    let relay_gateway_url = startup_root
        .as_ref()
        .and_then(|r| config::ProjectConfig::load(r).ok())
        .and_then(|c| c.gateway_url)
        .or_else(|| std::env::var("HUSKIES_GATEWAY_URL").ok())
        .unwrap_or_default();

    if !relay_gateway_url.is_empty() {
        let relay_project_name = startup_root
            .as_ref()
            .and_then(|r| config::ProjectConfig::load(r).ok())
            .and_then(|c| c.gateway_project)
            .or_else(|| std::env::var("HUSKIES_GATEWAY_PROJECT").ok())
            .or_else(|| {
                startup_root
                    .as_ref()
                    .and_then(|r| r.file_name())
                    .map(|n| n.to_string_lossy().into_owned())
            })
            .unwrap_or_else(|| "project".to_string());

        gateway_relay::spawn_relay_task(
            relay_gateway_url,
            relay_project_name,
            status,
            reqwest::Client::new(),
        );
    }
}

/// Spawn the event-trigger subscriber.
///
/// Subscribes to [`crate::pipeline_state::subscribe_transitions`] and on each
/// [`crate::pipeline_state::TransitionFired`] checks every registered trigger's
/// predicate.  Matching triggers have their action executed:
///
/// - `Mcp`: dispatches the named MCP tool via the full `dispatch_tool_call` path.
/// - `Prompt`: creates an ephemeral story and starts an agent on it.
///
/// `Once` triggers are removed from the store after they fire; `Persistent`
/// triggers remain until explicitly cancelled via `cancel_event_trigger`.
pub(crate) fn spawn_event_trigger_subscriber(
    store: Arc<EventTriggerStore>,
    agents: Arc<AgentPool>,
    project_root: Option<PathBuf>,
    ctx: AppContext,
) {
    let mut rx = crate::pipeline_state::subscribe_transitions();
    tokio::spawn(async move {
        loop {
            let fired = match rx.recv().await {
                Ok(f) => f,
                Err(broadcast::error::RecvError::Lagged(n)) => {
                    crate::slog!(
                        "[event-triggers] Lagged {n} transition events; some triggers may have been skipped"
                    );
                    continue;
                }
                Err(broadcast::error::RecvError::Closed) => {
                    crate::slog!("[event-triggers] Transition channel closed; subscriber stopping");
                    break;
                }
            };

            let triggers = store.list();
            if triggers.is_empty() {
                continue;
            }

            let mut to_cancel: Vec<String> = Vec::new();

            for trigger in &triggers {
                if !trigger.predicate.matches(&fired) {
                    continue;
                }

                crate::slog!(
                    "[event-triggers] Trigger {} matched: story={} {}→{}",
                    trigger.id,
                    fired.story_id.0,
                    crate::pipeline_state::stage_label(&fired.before),
                    crate::pipeline_state::stage_label(&fired.after),
                );

                match &trigger.action {
                    TriggerAction::Mcp { method, args } => {
                        execute_mcp_action(method, args.clone(), &ctx).await;
                    }
                    TriggerAction::Prompt { text } => {
                        execute_prompt_action(
                            text,
                            &fired.story_id.0,
                            &agents,
                            project_root.as_deref(),
                        )
                        .await;
                    }
                }

                if trigger.mode == FireMode::Once {
                    to_cancel.push(trigger.id.clone());
                }
            }

            if !to_cancel.is_empty() {
                store.cancel_batch(&to_cancel);
            }
        }
    });
}

/// Execute an Mcp action by dispatching through the full MCP tool dispatch path.
async fn execute_mcp_action(method: &str, args: serde_json::Value, ctx: &AppContext) {
    match crate::http::mcp::dispatch::dispatch_tool_call(method, args, ctx).await {
        Ok(result) => {
            crate::slog!("[event-triggers] Mcp '{method}' succeeded: {result}");
        }
        Err(e) => {
            crate::slog!("[event-triggers] Mcp '{method}' failed: {e}");
        }
    }
}

/// Execute a Prompt action: create an ephemeral story and start an agent on it.
async fn execute_prompt_action(
    text: &str,
    triggering_story_id: &str,
    agents: &Arc<AgentPool>,
    project_root: Option<&std::path::Path>,
) {
    let Some(root) = project_root else {
        crate::slog!("[event-triggers] Prompt action skipped (no project root configured): {text}");
        return;
    };

    // Allocate a new story ID for the ephemeral agent task.
    let num = crate::db::ops::next_item_number();
    let story_id = format!("{num}_trigger_task");

    let content = format!(
        "---\nname: Trigger Task\n---\n\
         # Trigger Task\n\n\
         _Auto-created by event trigger (source story: {triggering_story_id})_\n\n\
         ## Task\n\n\
         {text}\n\n\
         ## Acceptance Criteria\n\n\
         - [ ] Complete the task described above and exit.\n"
    );

    crate::db::write_item_with_content(
        &story_id,
        "1_backlog",
        &content,
        crate::db::ItemMeta {
            name: Some("Trigger Task".to_string()),
            ..Default::default()
        },
    );

    if let Err(e) = crate::agents::lifecycle::move_story_to_current(&story_id) {
        crate::slog!("[event-triggers] Failed to move {story_id} to current: {e}");
        return;
    }

    match agents.start_agent(root, &story_id, None, None, None).await {
        Ok(info) => {
            crate::slog!(
                "[event-triggers] Started agent {} for prompt task {story_id}",
                info.agent_name
            );
        }
        Err(e) => {
            crate::slog!("[event-triggers] Failed to start agent for prompt task {story_id}: {e}");
        }
    }
}

/// Spawn the startup reconstruction task: replay the current pipeline state
/// through the [`TransitionFired`][crate::pipeline_state::TransitionFired]
/// broadcast channel so that all existing subscribers (worktree lifecycle,
/// merge-failure auto-spawn, auto-assign) react identically to a live
/// transition, then trigger a full auto-assign pass.
///
/// Replaces the legacy scan-based `reconcile_on_startup` approach.  The CRDT
/// is the durable source of truth; replaying it as synthetic self-transitions
/// is cheaper, simpler, and idempotent: a second replay produces another burst
/// of events that subscribers safely ignore for already-assigned stories.
pub(crate) fn spawn_startup_reconciliation(
    startup_root: Option<PathBuf>,
    startup_agents: Arc<AgentPool>,
    startup_reconciliation_tx: broadcast::Sender<ReconciliationEvent>,
) {
    if let Some(root) = startup_root {
        tokio::spawn(async move {
            // Purge content-store entries for stories that reached terminal
            // stages in a previous session (before the GC subscriber was active).
            crate::db::gc::sweep_zombie_content_on_startup();
            crate::slog!(
                "[startup] Replaying current pipeline state through TransitionFired channel."
            );
            crate::pipeline_state::replay_current_pipeline_state();
            crate::slog!("[auto-assign] Scanning pipeline stages for unassigned work.");
            startup_agents.auto_assign_available_work(&root).await;
            let _ = startup_reconciliation_tx.send(ReconciliationEvent {
                story_id: String::new(),
                status: "done".to_string(),
                message: "Startup event replay complete.".to_string(),
            });
        });
    }
}