use std::path::PathBuf;
use std::sync::mpsc::{Receiver, Sender, TryRecvError};

use anyhow::Result;

use crate::app::{AppEvent, ControlCommand};
use crate::controller::{executor, goal_checker, planner, verifier};
use crate::model::{
    ControllerPhase, GoalStatus, PlannerResponse, SessionEntry, SessionSource, SessionStream,
    StepStatus, TaskConfig,
};
use crate::prompt;
use crate::repo;
use crate::storage::toon;

pub fn runtime_loop(
    repo_root: PathBuf,
    config: TaskConfig,
    control_rx: Receiver<ControlCommand>,
    event_tx: Sender<AppEvent>,
) -> Result<()> {
    toon::ensure_controller_files(&config)?;
    let _ = event_tx.send(AppEvent::Session(SessionEntry {
        source: SessionSource::Controller,
        stream: SessionStream::Status,
        title: "Session".to_string(),
        tag: Some(config.controller_id()),
        body: format!("Controller task loaded from {}", config.plan_file.display()),
        run_id: repo::next_run_id(),
    }));

    loop {
        let mut plan = toon::read_plan(&config.plan_file)?;
        let mut state = toon::read_state(&config.state_file)?;
        if recover_stale_execution_state(&config, &mut plan, &mut state, &event_tx)? {
            continue;
        }
        let goal_md = toon::read_markdown(&config.goal_file)?;
        let standards_md = toon::read_markdown(&config.standards_file)?;
        refresh_usage_state(&mut state);
        if matches!(state.phase, ControllerPhase::Planning)
            && state.planning_session.pending_input.is_some()
        {
            let pending_input = state
                .planning_session
                .pending_input
                .as_deref()
                .unwrap_or_default()
                .to_string();
            process_planning_submission(&repo_root, &config, &pending_input, &event_tx)?;
            continue;
        }
        emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);

        match control_rx.try_recv() {
            Ok(ControlCommand::Quit) => break,
            Ok(ControlCommand::Pause) => {
                crate::controller::state::pause(&mut state);
                toon::write_state(&config.state_file, &state)?;
                emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
                continue;
            }
            Ok(ControlCommand::Resume) => {
                crate::controller::state::resume(&mut state);
                toon::write_state(&config.state_file, &state)?;
                emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
                continue;
            }
            Ok(ControlCommand::Stop) => {
                state.phase = ControllerPhase::Blocked;
                state.goal_status = GoalStatus::Blocked;
                state.set_stop_reason("Stopped by user.");
                let reason = state
                    .phase_notice()
                    .unwrap_or_else(|| "Stopped by user.".to_string());
                toon::write_state(&config.state_file, &state)?;
                emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
                let _ = event_tx.send(AppEvent::Session(SessionEntry {
                    source: SessionSource::Warning,
                    stream: SessionStream::Status,
                    title: "Notice".to_string(),
                    tag: Some(config.controller_id()),
                    body: reason,
                    run_id: repo::next_run_id(),
                }));
                continue;
            }
            Ok(ControlCommand::Submit(_text)) => {
                if matches!(state.phase, ControllerPhase::Planning) {
                    let persisted_state = toon::read_state(&config.state_file)?;
                    if let Some(pending_input) =
                        persisted_state.planning_session.pending_input.as_deref()
                    {
                        process_planning_submission(
                            &repo_root,
                            &config,
                            pending_input,
                            &event_tx,
                        )?;
                    }
                } else {
                    let _ = event_tx.send(AppEvent::Session(SessionEntry {
                        source: SessionSource::Warning,
                        stream: SessionStream::Status,
                        title: "Execution".to_string(),
                        tag: Some(config.controller_id()),
                        body: "Execution is autonomous. Use /pause, /resume, /stop, /status, /diff, /tests, or /goal update."
                            .to_string(),
                        run_id: repo::next_run_id(),
                    }));
                }
                continue;
            }
            Err(TryRecvError::Disconnected) => break,
            Err(TryRecvError::Empty) => {}
        }

        match state.phase {
            ControllerPhase::Planning
            | ControllerPhase::Paused
            | ControllerPhase::Blocked
            | ControllerPhase::Done => {
                std::thread::sleep(std::time::Duration::from_millis(100));
                continue;
            }
            ControllerPhase::Executing => {}
        }

        if goal_checker::is_done(&plan, &state)? {
            state.phase = ControllerPhase::Done;
            state.clear_stop_reason();
            state.goal_status = GoalStatus::Done;
            let completion_summary = build_completion_summary(&plan);
            state.set_completion_summary(completion_summary.clone());
            state.history.push(crate::model::HistoryEvent {
                timestamp: repo::now_timestamp(),
                kind: "goal-complete".to_string(),
                detail: completion_summary.clone(),
            });
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            let _ = event_tx.send(AppEvent::Session(SessionEntry {
                source: SessionSource::Controller,
                stream: SessionStream::Status,
                title: "Goal".to_string(),
                tag: Some(config.controller_id()),
                body: completion_summary,
                run_id: repo::next_run_id(),
            }));
            continue;
        }

        let resumable_step = resumable_step(&plan, &state);
        if resumable_step.is_none() && (state.replan_required || plan.has_no_actionable_steps()) {
            let _ = event_tx.send(AppEvent::Session(SessionEntry {
                source: SessionSource::Planner,
                stream: SessionStream::Status,
                title: "Planner".to_string(),
                tag: Some(config.controller_id()),
                body: "Refining plan".to_string(),
                run_id: repo::next_run_id(),
            }));
            plan =
                planner::refine_without_user_input(&repo_root, &config, &plan, &state, &event_tx)?;
            state.replan_required = false;
            toon::write_plan(&config.plan_file, &plan)?;
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            continue;
        }

        let Some(step) = resumable_step.or_else(|| planner::next_step(&plan, &state)) else {
            state.phase = ControllerPhase::Blocked;
            state.goal_status = GoalStatus::Blocked;
            state.set_stop_reason(
                "No actionable step remained and autonomous replan produced nothing.",
            );
            let reason = state
                .phase_notice()
                .unwrap_or_else(|| "Controller is blocked.".to_string());
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            let _ = event_tx.send(AppEvent::Session(SessionEntry {
                source: SessionSource::Warning,
                stream: SessionStream::Status,
                title: "Notice".to_string(),
                tag: Some(config.controller_id()),
                body: reason,
                run_id: repo::next_run_id(),
            }));
            continue;
        };

        let _ = event_tx.send(AppEvent::Session(SessionEntry {
            source: SessionSource::Executor,
            stream: SessionStream::Status,
            title: "Step".to_string(),
            tag: Some(step.id.clone()),
            body: format!("Executing {}", step.title),
            run_id: repo::next_run_id(),
        }));
        state.clear_stop_reason();
        state.clear_completion_summary();
        state.replan_required = false;
        state
            .blocked_steps
            .retain(|blocked_step| blocked_step != &step.id);
        plan.mark_active(&step.id);
        state.current_step_id = Some(step.id.clone());
        state.iteration += 1;
        refresh_usage_state(&mut state);
        toon::write_plan(&config.plan_file, &plan)?;
        toon::write_state(&config.state_file, &state)?;
        emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);

        let exec = executor::implement(&repo_root, &config, &state, &plan, &step, &event_tx)?;
        if goal_checker::needs_goal_clarification(&exec) {
            state.phase = ControllerPhase::Planning;
            state.set_stop_reason(format!(
                "Execution requested goal clarification while processing {}.",
                step.id
            ));
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            continue;
        }

        let verification = verifier::verify_step(&repo_root, &exec, &event_tx)?;
        if !verification.passed {
            plan.mark_blocked(&step.id);
            plan.append_step_note(&step.id, verification.summary.as_str());
            state.last_verification = Some(verification);
            state.blocked_steps.push(step.id.clone());
            state.replan_required = true;
            state.set_stop_reason(format!("Verification failed for {}.", step.id));
            toon::write_plan(&config.plan_file, &plan)?;
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            continue;
        }

        let cleanup = verifier::verify_cleanup(&config, &step, &exec)?;
        if !cleanup.passed {
            plan.mark_todo(&step.id);
            plan.append_step_note(&step.id, cleanup.summary.as_str());
            state.last_cleanup_summary = Some(cleanup);
            state.set_stop_reason(format!(
                "Cleanup requirements were not satisfied for {}.",
                step.id
            ));
            toon::write_plan(&config.plan_file, &plan)?;
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            continue;
        }

        let tests = verifier::run_tests(&repo_root, &exec, &event_tx)?;
        if !tests.passed {
            plan.mark_todo(&step.id);
            plan.append_step_note(&step.id, tests.summary.as_str());
            state.last_full_test_summary = Some(tests);
            state.set_stop_reason(format!("Tests failed for {}.", step.id));
            toon::write_plan(&config.plan_file, &plan)?;
            toon::write_state(&config.state_file, &state)?;
            emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
            continue;
        }

        plan.append_step_note(&step.id, completion_note(&exec));
        plan.mark_done(&step.id);
        state.complete_step(&step, verification, cleanup, tests);
        toon::write_plan(&config.plan_file, &plan)?;
        toon::write_state(&config.state_file, &state)?;
        emit_snapshot(&event_tx, &goal_md, &standards_md, &plan, &state);
    }

    Ok(())
}

fn refresh_usage_state(state: &mut crate::model::ControllerState) {
    let snapshot = crate::process::refresh_usage_snapshot(state);
    crate::process::persist_usage_snapshot(state, &snapshot);
}

fn process_planning_submission(
    repo_root: &std::path::Path,
    config: &TaskConfig,
    latest_user_input: &str,
    event_tx: &Sender<AppEvent>,
) -> Result<PlannerResponse> {
    let response = crate::planning::session::advance(
        repo_root,
        config,
        latest_user_input,
        event_tx,
    )?;
    if let Some(question) = response.question.clone() {
        let _ = event_tx.send(AppEvent::Session(SessionEntry {
            source: SessionSource::Planner,
            stream: SessionStream::Status,
            title: "Question".to_string(),
            tag: Some(config.controller_id()),
            body: question,
            run_id: repo::next_run_id(),
        }));
    }

    Ok(response)
}

fn emit_snapshot(
    event_tx: &Sender<AppEvent>,
    goal_md: &str,
    standards_md: &str,
    plan: &crate::model::Plan,
    state: &crate::model::ControllerState,
) {
    let _ = event_tx.send(AppEvent::Snapshot {
        goal_md: goal_md.to_string(),
        standards_md: standards_md.to_string(),
        plan: plan.clone(),
        state: state.clone(),
    });
}

fn resumable_step(
    plan: &crate::model::Plan,
    state: &crate::model::ControllerState,
) -> Option<crate::model::PlanStep> {
    let current_step_id = state.current_step_id.as_deref()?;
    plan.steps
        .iter()
        .find(|step| {
            step.id == current_step_id
                && matches!(
                    step.status,
                    StepStatus::Todo | StepStatus::Active | StepStatus::Blocked
                )
        })
        .cloned()
}

fn completion_note(exec: &crate::model::ExecutionResponse) -> String {
    let mut parts = Vec::new();

    let summary = exec.summary.trim();
    if !summary.is_empty() {
        parts.push(prompt::truncate_text(summary, 180));
    }

    let notes = exec
        .notes
        .iter()
        .map(|note| note.trim())
        .filter(|note| !note.is_empty())
        .map(|note| prompt::truncate_text(note, 120))
        .collect::<Vec<_>>();
    if !notes.is_empty() {
        parts.push(format!("Agent notes: {}", notes.join("; ")));
    }

    if parts.is_empty() {
        "Completed the step.".to_string()
    } else {
        prompt::truncate_text(&parts.join(" "), 240)
    }
}

fn build_completion_summary(plan: &crate::model::Plan) -> String {
    let completed_steps = plan
        .steps
        .iter()
        .filter(|step| step.status.is_done())
        .collect::<Vec<_>>();

    if completed_steps.is_empty() {
        return "Goal complete.".to_string();
    }

    let mut details = completed_steps
        .iter()
        .take(4)
        .map(|step| {
            let mut item = format!(
                "{}: {}",
                step.id,
                prompt::truncate_text(&step.title, 80)
            );
            if !step.notes.trim().is_empty() {
                item.push_str(" - ");
                item.push_str(&prompt::truncate_text(&step.notes, 120));
            }
            item
        })
        .collect::<Vec<_>>();
    let omitted = completed_steps.len().saturating_sub(details.len());
    if omitted > 0 {
        details.push(format!(
            "... and {} more completed step{}",
            omitted,
            if omitted == 1 { "" } else { "s" }
        ));
    }

    prompt::truncate_text(
        &format!(
            "Completed {} step{}: {}",
            completed_steps.len(),
            if completed_steps.len() == 1 { "" } else { "s" },
            details.join("; ")
        ),
        320,
    )
}

fn recover_stale_execution_state(
    config: &TaskConfig,
    plan: &mut crate::model::Plan,
    state: &mut crate::model::ControllerState,
    event_tx: &Sender<AppEvent>,
) -> Result<bool> {
    let current_step_id = state.current_step_id.clone();
    let has_stale_current_step = if let Some(current_step_id) = &current_step_id {
        !plan.steps.iter().any(|step| {
            step.id == *current_step_id
                && matches!(
                    step.status,
                    StepStatus::Todo | StepStatus::Active | StepStatus::Blocked
                )
        })
    } else {
        false
    };

    if !has_stale_current_step && state.current_step_id.is_some() {
        return Ok(false);
    }

    let active_steps = plan.active_step_ids();
    if !has_stale_current_step && active_steps.is_empty() {
        return Ok(false);
    }

    for step_id in &active_steps {
        plan.mark_todo(step_id);
        plan.append_step_note(
            step_id,
            "Controller recovered this step from stale active state and returned it to todo.",
        );
    }

    state.phase = ControllerPhase::Executing;
    state.goal_status = GoalStatus::InProgress;
    state.clear_stop_reason();
    state.replan_required = false;
    state.current_step_id = None;

    let reason = if has_stale_current_step && !active_steps.is_empty() {
        format!(
            "Recovered stale execution state for {}. Cleared current_step_id {}. Reset {} to todo.",
            config.controller_id(),
            current_step_id.unwrap_or_default(),
            active_steps.join(", ")
        )
    } else if has_stale_current_step {
        format!(
            "Recovered stale execution state for {}. Cleared current_step_id {}.",
            config.controller_id(),
            current_step_id.unwrap_or_default()
        )
    } else {
        format!(
            "Recovered stale active step state for {}. Reset {} to todo.",
            config.controller_id(),
            active_steps.join(", ")
        )
    };
    state.notes.push(reason.clone());
    toon::write_plan(&config.plan_file, plan)?;
    toon::write_state(&config.state_file, state)?;
    let _ = event_tx.send(AppEvent::Session(SessionEntry {
        source: SessionSource::Controller,
        stream: SessionStream::Status,
        title: "Notice".to_string(),
        tag: Some(config.controller_id()),
        body: reason,
        run_id: repo::next_run_id(),
    }));
    Ok(true)
}

#[cfg(test)]
mod tests {
    use std::sync::mpsc;

    use tempfile::tempdir;

    use super::*;
    use crate::model::{ControllerState, Plan, PlanStep, StepStatus};
    use crate::storage::toon;

    #[test]
    fn recovers_stale_active_step_without_current_step() {
        let temp = tempdir().expect("tempdir");
        let mut config = TaskConfig::default_for("stale-active");
        let root = temp.path().join(".agent/controllers/stale-active");
        config.goal_file = root.join("goal.md");
        config.plan_file = root.join("plan.toon");
        config.state_file = root.join("state.toon");
        config.standards_file = root.join("standards.md");

        let mut plan = Plan {
            version: 1,
            goal_summary: "goal".to_string(),
            steps: vec![PlanStep {
                id: "s1".to_string(),
                title: "Scope".to_string(),
                status: StepStatus::Active,
                attempts: 1,
                ..PlanStep::default()
            }],
        };
        let mut state = ControllerState {
            phase: ControllerPhase::Blocked,
            goal_status: GoalStatus::Blocked,
            ..ControllerState::default()
        };
        state
            .set_stop_reason("No actionable step remained and autonomous replan produced nothing.");

        toon::ensure_controller_files(&config).expect("ensure files");
        let (event_tx, event_rx) = mpsc::channel();

        let recovered = recover_stale_execution_state(&config, &mut plan, &mut state, &event_tx)
            .expect("recover");

        assert!(recovered);
        assert!(matches!(plan.steps[0].status, StepStatus::Todo));
        assert!(plan.steps[0].notes.contains("stale active state"));
        assert!(matches!(state.phase, ControllerPhase::Executing));
        assert!(matches!(state.goal_status, GoalStatus::InProgress));
        assert!(state.stop_reason.is_none());
        let event = event_rx.recv().expect("notice event");
        match event {
            AppEvent::Session(entry) => assert!(entry.body.contains("Reset s1 to todo")),
            other => panic!("unexpected event: {other:?}"),
        }
    }

    #[test]
    fn recovers_stale_current_step_reference() {
        let temp = tempdir().expect("tempdir");
        let mut config = TaskConfig::default_for("stale-current");
        let root = temp.path().join(".agent/controllers/stale-current");
        config.goal_file = root.join("goal.md");
        config.plan_file = root.join("plan.toon");
        config.state_file = root.join("state.toon");
        config.standards_file = root.join("standards.md");

        let mut plan = Plan {
            version: 1,
            goal_summary: "goal".to_string(),
            steps: vec![PlanStep {
                id: "s1".to_string(),
                title: "Scope".to_string(),
                status: StepStatus::Done,
                ..PlanStep::default()
            }],
        };
        let mut state = ControllerState {
            phase: ControllerPhase::Blocked,
            goal_status: GoalStatus::Blocked,
            current_step_id: Some("s1".to_string()),
            ..ControllerState::default()
        };

        toon::ensure_controller_files(&config).expect("ensure files");
        let (event_tx, event_rx) = mpsc::channel();

        let recovered = recover_stale_execution_state(&config, &mut plan, &mut state, &event_tx)
            .expect("recover");

        assert!(recovered);
        assert!(matches!(state.current_step_id, None));
        assert!(matches!(state.phase, ControllerPhase::Executing));
        assert!(matches!(state.goal_status, GoalStatus::InProgress));
        assert!(state.stop_reason.is_none());
        let event = event_rx.recv().expect("notice event");
        match event {
            AppEvent::Session(entry) => {
                assert!(entry.body.contains("Cleared current_step_id s1"));
            }
            other => panic!("unexpected event: {other:?}"),
        }
    }

    #[test]
    fn resumable_step_prefers_current_blocked_or_active_step() {
        let plan = Plan {
            version: 1,
            goal_summary: "goal".to_string(),
            steps: vec![
                PlanStep {
                    id: "s1".to_string(),
                    title: "Scope".to_string(),
                    status: StepStatus::Blocked,
                    ..PlanStep::default()
                },
                PlanStep {
                    id: "s2".to_string(),
                    title: "Other".to_string(),
                    status: StepStatus::Done,
                    ..PlanStep::default()
                },
            ],
        };
        let state = ControllerState {
            phase: ControllerPhase::Blocked,
            goal_status: GoalStatus::Blocked,
            current_step_id: Some("s1".to_string()),
            replan_required: true,
            ..ControllerState::default()
        };

        let resumed = resumable_step(&plan, &state).expect("expected resumable step");
        assert_eq!(resumed.id, "s1");
    }

    #[test]
    fn emit_snapshot_clones_current_plan_and_state() {
        let (event_tx, event_rx) = mpsc::channel();
        let plan = Plan {
            version: 1,
            goal_summary: "goal".to_string(),
            steps: vec![PlanStep {
                id: "s1".to_string(),
                title: "Scope".to_string(),
                status: StepStatus::Active,
                ..PlanStep::default()
            }],
        };
        let state = ControllerState {
            phase: ControllerPhase::Executing,
            current_step_id: Some("s1".to_string()),
            ..ControllerState::default()
        };

        emit_snapshot(&event_tx, "goal body", "standards body", &plan, &state);

        let event = event_rx.recv().expect("snapshot event");
        match event {
            AppEvent::Snapshot {
                goal_md,
                standards_md,
                plan,
                state,
            } => {
                assert_eq!(goal_md, "goal body");
                assert_eq!(standards_md, "standards body");
                assert!(matches!(plan.steps[0].status, StepStatus::Active));
                assert_eq!(state.current_step_id.as_deref(), Some("s1"));
            }
            other => panic!("unexpected event: {other:?}"),
        }
    }

    #[test]
    fn completion_note_uses_execution_summary_and_notes() {
        let note = completion_note(&crate::model::ExecutionResponse {
            summary: "Implemented the board note flow".to_string(),
            notes: vec![
                "Kept the change localized to completion handling".to_string(),
                "Verified the board still renders done steps".to_string(),
            ],
            ..crate::model::ExecutionResponse::default()
        });

        assert!(note.contains("Implemented the board note flow"));
        assert!(note.contains("Agent notes:"));
        assert!(note.contains("Kept the change localized"));
    }

    #[test]
    fn build_completion_summary_lists_done_steps() {
        let plan = Plan {
            version: 1,
            goal_summary: "goal".to_string(),
            steps: vec![
                PlanStep {
                    id: "s1".to_string(),
                    title: "First".to_string(),
                    notes: "Finished the first change.".to_string(),
                    status: StepStatus::Done,
                    ..PlanStep::default()
                },
                PlanStep {
                    id: "s2".to_string(),
                    title: "Second".to_string(),
                    notes: "Finished the second change.".to_string(),
                    status: StepStatus::Done,
                    ..PlanStep::default()
                },
            ],
        };

        let summary = build_completion_summary(&plan);
        assert!(summary.contains("Completed 2 steps"));
        assert!(summary.contains("s1: First"));
        assert!(summary.contains("s2: Second"));
    }
}