collet 0.1.0

//! EvolutionLoop — thin orchestrator that wires shared primitives to an engine.
//!
//! The loop handles the expensive shared work every engine needs:
//!   Solve -> Observe -> Snapshot -> engine.step() -> Snapshot -> Record -> Reload
//!
//! The engine decides *how* to evolve; the loop decides *when* and provides
//! the infrastructure (versioning, observation logging, trial runner).

use std::path::PathBuf;

use anyhow::Result;
use tokio::sync::mpsc;
use tokio_util::sync::CancellationToken;

use super::EvolutionEvent;
use super::config::EvolveConfig;
use super::egl::is_score_converged;
use super::engine::EvolutionEngine;
use super::history::EvolutionHistory;
use super::observer::Observer;
use super::trial::TrialRunner;
use super::types::{CycleRecord, EvolutionResult};
use super::versioning::VersionControl;
use super::workspace::AgentWorkspace;

/// Orchestrates the full evolution loop with a pluggable engine.
pub struct EvolutionLoop {
    config: EvolveConfig,
    workspace: AgentWorkspace,
    history: EvolutionHistory,
    trial: TrialRunner,
    event_tx: mpsc::UnboundedSender<EvolutionEvent>,
}

impl EvolutionLoop {
    /// Create a new evolution loop.
    ///
    /// The caller provides:
    /// - `workspace_root`: path to the agent workspace directory
    /// - `trial`: the trial runner (wrapping agent + benchmark)
    /// - `config`: evolution configuration
    /// - `event_tx`: channel for emitting evolution events to the TUI
    pub fn new(
        workspace_root: PathBuf,
        trial: TrialRunner,
        config: EvolveConfig,
        event_tx: mpsc::UnboundedSender<EvolutionEvent>,
    ) -> Result<Self> {
        let workspace = AgentWorkspace::new(&workspace_root);
        workspace.ensure_dirs()?;

        let evolution_dir = workspace.evolution_dir.clone();
        let observer = Observer::new(&evolution_dir);
        let versioning = VersionControl::new(&workspace_root);
        let history = EvolutionHistory::new(observer, versioning);

        Ok(Self {
            config,
            workspace,
            history,
            trial,
            event_tx,
        })
    }

    /// Run the evolution loop for the configured number of cycles.
    pub async fn run(
        &mut self,
        engine: &mut dyn EvolutionEngine,
        cancel: CancellationToken,
    ) -> Result<EvolutionResult> {
        // Initialize version control
        self.history.versioning().init()?;

        let max_cycles = self.config.max_cycles;
        let mut score_history: Vec<f64> = Vec::new();

        for cycle in 1..=max_cycles {
            if cancel.is_cancelled() {
                tracing::info!("Evolution cancelled at cycle {cycle}");
                break;
            }

            tracing::info!(cycle, max_cycles, "=== Evolution Cycle ===");
            let _ = self
                .event_tx
                .send(EvolutionEvent::CycleStarted { cycle, max_cycles });

            // 1. SOLVE
            let tasks = self
                .trial
                .get_tasks("train", self.config.batch_size)
                .await?;

            let _ = self.event_tx.send(EvolutionEvent::SolveStarted {
                task_count: tasks.len(),
            });

            let observations = self.trial.run_tasks(&tasks).await;

            // 2. OBSERVE
            self.trial.agent().export_to_fs().await?;
            let batch_path = self.history.observer_mut().collect(&observations)?;
            let batch_name = batch_path
                .file_name()
                .and_then(|n| n.to_str())
                .unwrap_or("unknown")
                .to_string();

            let cycle_score = if observations.is_empty() {
                0.0
            } else {
                observations.iter().map(|o| o.feedback.score).sum::<f64>()
                    / observations.len() as f64
            };
            score_history.push(cycle_score);

            tracing::info!(cycle, score = cycle_score, "Cycle score");
            let _ = self
                .event_tx
                .send(EvolutionEvent::SolveCompleted { score: cycle_score });

            // 3. PRE-EVOLVE SNAPSHOT
            self.history.versioning().commit(
                &format!("pre-evo-{cycle}: score={cycle_score:.3}"),
                Some(&format!("pre-evo-{cycle}")),
            )?;

            // 4. ENGINE STEP
            let engine_name = engine.name().to_string();
            let _ = self.event_tx.send(EvolutionEvent::EngineStepStarted {
                engine_name: engine_name.clone(),
            });

            let step_result = match engine
                .step(&self.workspace, &observations, &self.history, &self.trial)
                .await
            {
                Ok(r) => r,
                Err(e) => {
                    let msg = format!("Engine step failed: {e}");
                    tracing::error!("{msg}");
                    let _ = self.event_tx.send(EvolutionEvent::Error(msg));
                    return Err(e);
                }
            };

            let _ = self.event_tx.send(EvolutionEvent::EngineStepCompleted {
                mutated: step_result.mutated,
                summary: step_result.summary.clone(),
            });

            // 5. POST-EVOLVE SNAPSHOT
            let tag = format!("evo-{cycle}");
            let msg = if step_result.mutated {
                format!("evo-{cycle}: {}", step_result.summary)
            } else {
                format!("evo-{cycle}: no mutation")
            };
            self.history.versioning().commit(&msg, Some(&tag))?;

            // Log diff between pre- and post-evolve snapshots.
            if step_result.mutated {
                let from = format!("pre-evo-{cycle}");
                let to = format!("evo-{cycle}");
                if let Ok(diff) = self.history.get_workspace_diff(&from, &to) {
                    if let Ok(stat) = self.history.versioning().get_diff_stat(&from, &to) {
                        tracing::debug!(cycle, diff_len = diff.len(), stat = %stat.trim(), "Workspace diff for cycle");
                    } else {
                        tracing::debug!(cycle, diff_len = diff.len(), "Workspace diff for cycle");
                    }
                }

                // Rollback if this cycle's score is significantly worse than the best.
                let best_score = score_history
                    .iter()
                    .copied()
                    .fold(f64::NEG_INFINITY, f64::max);
                if cycle_score < best_score - 0.1
                    && let Some(best_idx) = score_history.iter().position(|&s| s == best_score)
                {
                    let best_tag = format!("evo-{}", best_idx + 1);
                    if let Err(e) = self.history.versioning().rollback_to_tag(&best_tag) {
                        tracing::warn!(cycle, tag = %best_tag, error = %e, "Rollback failed");
                    } else {
                        tracing::info!(cycle, tag = %best_tag, "Rolled back to best-scoring tag");
                    }
                }

                // Optionally create an evaluation worktree for the current evo tag
                // so the trial runner could evaluate mutations in isolation.
                // We create it, verify it exists, then clean it up immediately.
                let evo_tag = format!("evo-{cycle}");
                match self.create_eval_copy(&evo_tag, cycle) {
                    Ok(eval_path) => {
                        tracing::debug!(cycle, tag = %evo_tag, path = %eval_path.display(), "Eval worktree created");
                        // Clean up immediately — this was a probe-only operation.
                        if let Err(e) = self.cleanup_eval_copy(&eval_path) {
                            tracing::debug!(cycle, error = %e, "Eval worktree cleanup (non-fatal)");
                        }
                    }
                    Err(e) => {
                        tracing::debug!(cycle, error = %e, "Eval worktree not created (non-fatal — no git repo)");
                    }
                }
            }

            // 6. RECORD CYCLE
            let record = CycleRecord {
                cycle,
                score: cycle_score,
                mutated: step_result.mutated,
                engine_name: engine_name.clone(),
                summary: step_result.summary.clone(),
                observation_batch: batch_name,
                metadata: step_result.metadata.clone(),
            };
            self.history.record_cycle(record);
            tracing::debug!(
                cycle,
                total_cycles = self.history.latest_cycle(),
                all_cycles = self.history.cycles().len(),
                "Evolution cycle recorded"
            );

            // 7. RELOAD
            self.trial.agent().reload_from_fs().await?;
            engine.on_cycle_end(step_result.mutated, cycle_score);

            // 8. PERSIST history + metrics (move to thread pool to avoid blocking executor)
            let history_path = self.workspace.evolution_dir.join("history.jsonl");
            let history_data = serde_json::json!({
                "cycle": cycle,
                "score": cycle_score,
                "mutated": step_result.mutated,
                "timestamp": chrono::Utc::now().to_rfc3339(),
            });
            let _ = tokio::task::spawn_blocking(move || {
                use std::io::Write;
                let mut file = std::fs::OpenOptions::new()
                    .create(true)
                    .append(true)
                    .open(&history_path)
                    .map_err(|e| e.to_string())?;
                serde_json::to_writer(&mut file, &history_data).map_err(|e| e.to_string())?;
                writeln!(file).map_err(|e| e.to_string())?;
                Ok::<(), String>(())
            })
            .await;

            let metrics_path = self.workspace.evolution_dir.join("metrics.json");
            let metrics_data = serde_json::json!({
                "cycles_completed": score_history.len(),
                "latest_score": score_history.last().unwrap_or(&0.0),
                "best_score": score_history.iter().cloned().fold(0.0_f64, f64::max),
                "avg_score": if score_history.is_empty() { 0.0 } else {
                    score_history.iter().sum::<f64>() / score_history.len() as f64
                },
            });
            let _ = tokio::task::spawn_blocking(move || {
                let json =
                    serde_json::to_string_pretty(&metrics_data).map_err(|e| e.to_string())?;
                std::fs::write(&metrics_path, json).map_err(|e| e.to_string())?;
                Ok::<(), String>(())
            })
            .await;

            let _ = self.event_tx.send(EvolutionEvent::CycleCompleted {
                cycle,
                score: cycle_score,
                mutated: step_result.mutated,
            });

            // 9. CONVERGENCE CHECK
            if is_score_converged(
                &score_history,
                self.config.egl_window,
                self.config.egl_threshold,
            ) {
                tracing::info!(cycle, "Score converged");
                let result = EvolutionResult {
                    cycles_completed: cycle,
                    final_score: cycle_score,
                    score_history,
                    converged: true,
                    ..Default::default()
                };
                let _ = self.event_tx.send(EvolutionEvent::Converged {
                    cycle,
                    final_score: cycle_score,
                });
                let _ = self.event_tx.send(EvolutionEvent::Done(result.clone()));
                return Ok(result);
            }
        }

        let final_score = score_history.last().copied().unwrap_or(0.0);
        let result = EvolutionResult {
            cycles_completed: score_history.len() as u32,
            final_score,
            score_history,
            converged: false,
            ..Default::default()
        };
        let _ = self.event_tx.send(EvolutionEvent::Done(result.clone()));
        Ok(result)
    }

    // -- Internal helpers -------------------------------------------------

    /// Create a temporary read-only worktree at `reference` for isolated inspection.
    ///
    /// Returns the worktree path on success. The caller is responsible for
    /// calling `cleanup_eval_copy` when done to avoid leaking git worktrees.
    fn create_eval_copy(&self, reference: &str, cycle: u32) -> Result<std::path::PathBuf> {
        let dest = std::env::temp_dir().join(format!("collet-evo-{cycle}-{reference}"));
        self.history.versioning().checkout_copy(reference, &dest)?;
        Ok(dest)
    }

    /// Remove a worktree previously created by [`create_eval_copy`].
    fn cleanup_eval_copy(&self, dest: &std::path::Path) -> Result<()> {
        self.history.versioning().remove_copy(dest)
    }
}