//! Main-loop operations: heartbeat, claim scanning, conflict detection, and branch pushing.

use std::collections::HashMap;
use std::path::Path;

use crate::agents::AgentPool;
use crate::crdt_state;
use crate::slog;

use super::claim::{CLAIM_TIMEOUT_SECS, should_self_claim};

/// Write this node's heartbeat to the CRDT `nodes` list.
pub(super) fn write_heartbeat(rendezvous_url: &str, port: u16) {
    let Some(node_id) = crdt_state::our_node_id() else {
        return;
    };
    let now = chrono::Utc::now().timestamp() as f64;
    let now_ms = chrono::Utc::now().timestamp_millis() as f64;
    // Advertise our crdt-sync endpoint.
    let address = format!("ws://0.0.0.0:{port}/crdt-sync");
    crdt_state::write_node_presence(&node_id, &address, now, true);
    // Write millisecond-precision timestamp via LWW register.
    crdt_state::write_node_metadata(&node_id, "", None, now_ms);
    slog!(
        "[agent-mode] Heartbeat written: node={:.12}… rendezvous={rendezvous_url}",
        &node_id
    );
}

/// Scan CRDT pipeline for unclaimed stories and claim them.
pub(super) async fn scan_and_claim(
    agents: &AgentPool,
    project_root: &Path,
    our_claims: &mut HashMap<String, f64>,
) {
    let Some(items) = crdt_state::read_all_items() else {
        return;
    };
    let Some(our_node) = crdt_state::our_node_id() else {
        return;
    };

    for item in &items {
        // Only claim stories in execution stages (Coding, Qa, Merge).
        if !matches!(
            item.stage(),
            crate::pipeline_state::Stage::Coding { .. }
                | crate::pipeline_state::Stage::Qa
                | crate::pipeline_state::Stage::Merge { .. }
        ) {
            continue;
        }

        // Skip blocked stories (story 945: `Stage::Blocked` is the source of truth).
        if matches!(
            item.stage(),
            crate::pipeline_state::Stage::Blocked { .. }
                | crate::pipeline_state::Stage::MergeFailure { .. }
                | crate::pipeline_state::Stage::MergeFailureFinal { .. }
                | crate::pipeline_state::Stage::Archived {
                    reason: crate::pipeline_state::ArchiveReason::Blocked { .. },
                    ..
                }
        ) {
            continue;
        }

        let item_claim = match item.stage() {
            crate::pipeline_state::Stage::Coding { claim, .. } => claim.as_ref(),
            crate::pipeline_state::Stage::Merge { claim, .. } => claim.as_ref(),
            _ => None,
        };

        // If already claimed by us, skip.
        if item_claim.is_some_and(|c| c.agent.0 == our_node) {
            continue;
        }

        // If claimed by another node, respect the claim while it is fresh.
        // Once the TTL expires the claim is considered stale regardless of
        // whether the holder appears alive — displacement is purely TTL-driven.
        if let Some(claim) = item_claim
            && claim.agent.0 != our_node
        {
            let now = chrono::Utc::now().timestamp() as u64;
            let age = now.saturating_sub(claim.claimed_at.timestamp() as u64) as f64;
            if age < CLAIM_TIMEOUT_SECS {
                // Claim is still fresh — respect it.
                continue;
            }
            // Claim TTL has expired: displace the stale holder.
            slog!(
                "[agent-mode] Displacing stale claim on '{}' held by {:.12}… \
                 (age {}s > TTL {}s)",
                item.story_id(),
                claim.agent.0,
                age as u64,
                CLAIM_TIMEOUT_SECS as u64,
            );
        }

        // Pre-spawn hash-based tie-break: only the node whose
        // SHA-256(node_id || story_id) is strictly lowest among all alive
        // candidates should write the CRDT claim.  This eliminates the
        // thundering-herd of simultaneous LWW conflicts while keeping the
        // existing LWW + reclaim-stale logic as a safety net for clock skew
        // and partial alive-list views.
        let alive_peers: Vec<String> = crdt_state::read_all_node_presence()
            .unwrap_or_default()
            .into_iter()
            .filter(|n| {
                let now_ms = chrono::Utc::now().timestamp_millis() as f64;
                let last_ms = n.last_seen_ms.unwrap_or(n.last_seen * 1000.0);
                n.alive && (now_ms - last_ms) / 1000.0 < CLAIM_TIMEOUT_SECS
            })
            .map(|n| n.node_id)
            .collect();
        if !should_self_claim(&our_node, item.story_id(), &alive_peers) {
            slog!(
                "[agent-mode] Hash tie-break: deferring claim on '{}' to lower-hash peer",
                item.story_id()
            );
            continue;
        }

        // Try to claim this story.
        slog!(
            "[agent-mode] Claiming story '{}' for this node",
            item.story_id()
        );
        if crdt_state::write_claim(item.story_id()) {
            let now = chrono::Utc::now().timestamp() as f64;
            our_claims.insert(item.story_id().to_string(), now);
        }
    }

    // Trigger auto-assign to start agents for newly claimed work.
    agents.auto_assign_available_work(project_root).await;
}

/// Detect if another node overwrote our claims (CRDT conflict resolution).
/// If so, stop our local agent for that story.
pub(super) async fn detect_conflicts(
    agents: &AgentPool,
    project_root: &Path,
    our_claims: &mut HashMap<String, f64>,
) {
    let lost: Vec<String> = our_claims
        .keys()
        .filter(|story_id| !crdt_state::is_claimed_by_us(story_id))
        .cloned()
        .collect();

    for story_id in lost {
        slog!(
            "[agent-mode] Lost claim on '{}' to another node; stopping local agent.",
            story_id
        );
        our_claims.remove(&story_id);

        // Stop any local agent for this story by looking up its name.
        if let Ok(agent_list) = agents.list_agents() {
            for info in agent_list {
                if info.story_id == story_id {
                    let _ = agents
                        .stop_agent(project_root, &story_id, &info.agent_name)
                        .await;
                    break;
                }
            }
        }

        // Release our claim (in case it wasn't fully overwritten).
        crdt_state::release_claim(&story_id);
    }
}

/// Reclaim work from nodes that have timed out (stale heartbeat).
pub(super) fn reclaim_timed_out_work(_project_root: &Path) {
    let Some(items) = crdt_state::read_all_items() else {
        return;
    };
    let now = chrono::Utc::now().timestamp() as f64;

    for item in &items {
        if !matches!(
            item.stage(),
            crate::pipeline_state::Stage::Coding { .. }
                | crate::pipeline_state::Stage::Qa
                | crate::pipeline_state::Stage::Merge { .. }
        ) {
            continue;
        }

        // Release the claim if the TTL has expired — regardless of whether the
        // holder is still alive.  A node actively working should refresh its
        // claim before the TTL window closes.
        let reclaim_claim = match item.stage() {
            crate::pipeline_state::Stage::Coding { claim, .. } => claim.as_ref(),
            crate::pipeline_state::Stage::Merge { claim, .. } => claim.as_ref(),
            _ => None,
        };
        if let Some(claim) = reclaim_claim {
            let claim_ts = claim.claimed_at.timestamp() as u64;
            let age = now as u64 - claim_ts.min(now as u64);
            if age as f64 >= CLAIM_TIMEOUT_SECS {
                slog!(
                    "[agent-mode] Releasing stale claim on '{}' held by {:.12}… (age {}s)",
                    item.story_id(),
                    claim.agent.0,
                    age,
                );
                crdt_state::release_claim(item.story_id());
            }
        }
    }
}

/// Check for completed agents, push their feature branches to the remote,
/// and report completion via CRDT.
pub(super) async fn check_completions_and_push(agents: &AgentPool, _project_root: &Path) {
    let Ok(agent_list) = agents.list_agents() else {
        return;
    };

    for info in agent_list {
        if !matches!(
            info.status,
            crate::agents::AgentStatus::Completed | crate::agents::AgentStatus::Failed
        ) {
            continue;
        }

        let story_id = &info.story_id;

        // Only push if this node still owns the claim.
        if !crdt_state::is_claimed_by_us(story_id) {
            continue;
        }

        slog!(
            "[agent-mode] Agent {} for '{}'; pushing feature branch.",
            if matches!(info.status, crate::agents::AgentStatus::Completed) {
                "completed"
            } else {
                "failed"
            },
            story_id
        );

        // Push the feature branch to the remote.
        if let Some(ref wt) = info.worktree_path {
            let push_result = push_feature_branch(wt, story_id);
            match push_result {
                Ok(()) => {
                    slog!("[agent-mode] Pushed feature branch for '{story_id}' to remote.");
                }
                Err(e) => {
                    slog!("[agent-mode] Failed to push '{story_id}': {e}");
                }
            }
        }

        // Release the claim now that work is done.
        crdt_state::release_claim(story_id);
    }
}

/// Push the feature branch of a worktree to the git remote.
pub(super) fn push_feature_branch(worktree_path: &str, story_id: &str) -> Result<(), String> {
    let branch = format!("feature/story-{story_id}");

    // Try to push to 'origin'. If origin doesn't exist, try the first remote.
    let output = std::process::Command::new("git")
        .args(["push", "origin", &branch])
        .current_dir(worktree_path)
        .output()
        .map_err(|e| format!("Failed to run git push: {e}"))?;

    if output.status.success() {
        Ok(())
    } else {
        let stderr = String::from_utf8_lossy(&output.stderr);
        // If 'origin' doesn't exist, try to find any remote.
        if stderr.contains("does not appear to be a git repository")
            || stderr.contains("No such remote")
        {
            let remotes = std::process::Command::new("git")
                .args(["remote"])
                .current_dir(worktree_path)
                .output()
                .map_err(|e| format!("Failed to list remotes: {e}"))?;

            let remote_list = String::from_utf8_lossy(&remotes.stdout);
            let first_remote = remote_list.lines().next();

            if let Some(remote) = first_remote {
                let retry = std::process::Command::new("git")
                    .args(["push", remote.trim(), &branch])
                    .current_dir(worktree_path)
                    .output()
                    .map_err(|e| format!("Failed to push to {remote}: {e}"))?;

                if retry.status.success() {
                    return Ok(());
                }
                return Err(format!(
                    "git push to '{remote}' failed: {}",
                    String::from_utf8_lossy(&retry.stderr)
                ));
            }

            // No remotes configured — not an error in agent mode, just skip.
            slog!("[agent-mode] No git remote configured; skipping push for '{story_id}'.");
            Ok(())
        } else {
            Err(format!("git push failed: {stderr}"))
        }
    }
}

// ── Tests ────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn push_feature_branch_handles_missing_worktree() {
        let result = push_feature_branch("/nonexistent/path", "test_story");
        assert!(result.is_err());
    }
}