mod app;
mod domain;
mod infrastructure;
mod ui;

use std::io;
use std::path::PathBuf;
use std::sync::Arc;

use crossterm::event::{self, Event};
use crossterm::terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen};
use crossterm::ExecutableCommand;
use ratatui::backend::CrosstermBackend;
use ratatui::Terminal;
use tokio::sync::Mutex;

use crate::app::{App, SyncCommand, SyncStats};
use crate::domain::models::*;
use crate::infrastructure::api::ApiClient;
use crate::infrastructure::db::Db;
use crate::ui::{draw, AppView, NetworkStatus};

fn find_secret_file() -> Option<PathBuf> {
    if let Ok(path) = std::env::var("GOOGLE_CLIENT_SECRET_FILE") {
        let p = PathBuf::from(&path);
        if p.exists() {
            return Some(p);
        }
    }

    let config_path = dirs::config_dir()
        .unwrap_or_else(|| PathBuf::from("."))
        .join("task_app")
        .join("client_secret.json");
    if config_path.exists() {
        return Some(config_path);
    }

    let local_path = PathBuf::from("client_secret.json");
    if local_path.exists() {
        return Some(local_path);
    }

    None
}

fn main() -> io::Result<()> {
    let db_path = dirs::data_dir()
        .unwrap_or_else(|| PathBuf::from("."))
        .join("task_app")
        .join("tasks.db");

    std::fs::create_dir_all(db_path.parent().unwrap()).ok();

    let db = Arc::new(Db::new(db_path.to_str().unwrap()).expect("Failed to open database"));

    let secret_path = find_secret_file().unwrap_or_else(|| {
        eprintln!(
            "ERROR: Google client secret file not found.\n\
             Place client_secret.json in one of:\n\
             - Set GOOGLE_CLIENT_SECRET_FILE env var\n\
             - ~/.config/task_app/client_secret.json\n\
             - ./client_secret.json (current directory)"
        );
        std::process::exit(1);
    });

    enable_raw_mode()?;
    let mut stdout = io::stdout();
    stdout.execute(EnterAlternateScreen)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    let api_client = Arc::new(
        tokio::runtime::Runtime::new()
            .unwrap()
            .block_on(async {
                ApiClient::new(&secret_path)
                    .await
                    .expect("Failed to create ApiClient")
            }),
    );

    let network_status = Arc::new(Mutex::new(NetworkStatus::Online));
    let sync_stats = Arc::new(Mutex::new(SyncStats::default()));
    let (sync_tx, mut sync_rx) = tokio::sync::mpsc::channel::<SyncCommand>(32);

    let mut app = App::new(db.clone(), api_client.clone(), sync_tx.clone());

    let network_clone = network_status.clone();
    let stats_clone = sync_stats.clone();
    let db_clone = db.clone();
    let api_clone = api_client.clone();

    std::thread::spawn(move || {
        let rt = tokio::runtime::Runtime::new().unwrap();
        rt.block_on(async move {
            run_sync_engine(db_clone, api_clone, network_clone, stats_clone, &mut sync_rx).await;
        });
    });

    // Trigger initial sync if already authenticated
    if !app.needs_auth {
        let _ = sync_tx.try_send(SyncCommand::InitialSync);
    }

    while !app.should_quit {
        // Poll auth status (non-blocking)
        app.poll_auth();

        // Check if initial sync has loaded data into DB
        app.check_initial_load();

        terminal.draw(|frame| {
            let status = {
                let guard = network_status.blocking_lock();
                guard.clone()
            };
            app.network_status = status;

            {
                let guard = sync_stats.blocking_lock();
                app.sync_stats = guard.clone();
            }

            // Reload lists/tasks if sync engine changed data in background
            app.refresh_if_needed();

            let view = AppView {
                lists: &app.lists,
                tasks: &app.tasks,
                selected_list: app.selected_list,
                selected_task: app.selected_task,
                focus: app.focus.clone(),
                show_popup: app.show_popup.as_ref(),
                popup_input: &app.popup_input,
                popup_cursor: app.popup_cursor,
                popup_secondary: &app.popup_secondary,
                popup_secondary_cursor: app.popup_secondary_cursor,
                draft_date: app.draft_date,
                network_status: &app.network_status,
                task_list_scroll: app.task_list_scroll,
                detail_scroll: app.detail_scroll,
                auth_error: app.auth_error.as_deref(),
                sync_stats: &app.sync_stats,
            };
            draw(frame, view);
        })?;

        if event::poll(std::time::Duration::from_millis(100))? {
            if let Event::Key(key) = event::read()? {
                app.handle_key(key);
            }
        }
    }

    disable_raw_mode()?;
    io::stdout().execute(LeaveAlternateScreen)?;
    Ok(())
}

async fn run_sync_engine(
    db: Arc<Db>,
    api: Arc<ApiClient>,
    network_status: Arc<Mutex<NetworkStatus>>,
    sync_stats: Arc<Mutex<SyncStats>>,
    rx: &mut tokio::sync::mpsc::Receiver<SyncCommand>,
) {
    loop {
        match rx.recv().await {
            Some(SyncCommand::TriggerSync) => {
                push_sync(&db, &api, &network_status, &sync_stats).await;
            }
            Some(SyncCommand::FullSync) => {
                push_sync(&db, &api, &network_status, &sync_stats).await;
                pull_sync(&db, &api, &network_status, &sync_stats, true).await;
            }
            Some(SyncCommand::InitialSync) => {
                run_initial_sync(&db, &api, &network_status, &sync_stats).await;
            }
            Some(SyncCommand::Shutdown) | None => break,
        }
    }
}

async fn run_initial_sync(
    db: &Arc<Db>,
    api: &Arc<ApiClient>,
    network_status: &Arc<Mutex<NetworkStatus>>,
    sync_stats: &Arc<Mutex<SyncStats>>,
) {
    *network_status.lock().await = NetworkStatus::Syncing;

    let mut total_lists = 0usize;
    let mut total_tasks = 0usize;

    match api.fetch_lists().await {
        Ok(lists) => {
            total_lists = lists.len();
            for list in &lists {
                db.insert_list(list).ok();
            }
            for list in &lists {
                if let Ok(tasks) = api.fetch_tasks(&list.id).await {
                    total_tasks += tasks.len();
                    db.replace_all_tasks(&list.id, &tasks).ok();
                }
            }
            *network_status.lock().await = NetworkStatus::Online;
        }
        Err(_) => {
            *network_status.lock().await = NetworkStatus::Offline;
        }
    }

    let now = chrono::Local::now().naive_local();
    let mut stats = sync_stats.lock().await;
    stats.last_sync_time = Some(now);
    stats.last_pull_time = Some(now);
    stats.lists_changed = total_lists;
    stats.tasks_changed = total_tasks;
    stats.version += 1;
}

async fn push_sync(
    db: &Arc<Db>,
    api: &Arc<ApiClient>,
    network_status: &Arc<Mutex<NetworkStatus>>,
    sync_stats: &Arc<Mutex<SyncStats>>,
) {
    if !api.has_token() {
        *network_status.lock().await = NetworkStatus::Offline;
        return;
    }

    let items = db.drain_sync();
    let count = items.len();

    if count == 0 {
        *network_status.lock().await = NetworkStatus::Online;
        return;
    }

    *network_status.lock().await = NetworkStatus::Syncing;

    let mut all_ok = true;
    for item in &items {
        let result = match item.action {
            SyncAction::Create => {
                let task = serde_json::from_str::<Task>(&item.payload).unwrap_or_else(|_| Task {
                    id: item.task_id.clone(),
                    list_id: item.list_id.clone(),
                    title: String::new(),
                    notes: None,
                    status: TaskStatus::NeedsAction,
                    due: None,
                    position: 0,
                    created_at: None,
                    updated_at: None,
                });
                api.create_task(&item.list_id, &task).await
            }
            SyncAction::Update => {
                let task = serde_json::from_str::<Task>(&item.payload).unwrap_or_else(|_| Task {
                    id: item.task_id.clone(),
                    list_id: item.list_id.clone(),
                    title: String::new(),
                    notes: None,
                    status: TaskStatus::NeedsAction,
                    due: None,
                    position: 0,
                    created_at: None,
                    updated_at: None,
                });
                api.update_task(&item.list_id, &task).await
            }
            SyncAction::Delete => {
                api.delete_task(&item.list_id, &item.task_id).await
            }
            SyncAction::Reorder => {
                api.move_task(&item.list_id, &item.task_id, None, None).await
            }
        };

        if let Err(err) = result {
            eprintln!("[task_app] Sync failed (retry {}/{}): action={:?} task={} error={}",
                item.retries, MAX_SYNC_RETRIES, item.action, item.task_id, err);
            if item.retries < MAX_SYNC_RETRIES {
                let _ = db.push_sync_with_retry(
                    item.action.clone(),
                    &item.task_id,
                    &item.list_id,
                    &item.payload,
                    item.retries + 1,
                );
            } else {
                eprintln!("[task_app] Dropping sync item after {} failed attempts: action={:?} task={}",
                    MAX_SYNC_RETRIES, item.action, item.task_id);
            }
            all_ok = false;
        }
    }

    *network_status.lock().await = if all_ok {
        NetworkStatus::Online
    } else {
        let remaining = db.has_pending_sync();
        if remaining {
            NetworkStatus::Offline
        } else {
            NetworkStatus::Online
        }
    };

    let mut stats = sync_stats.lock().await;
    stats.last_sync_time = Some(chrono::Local::now().naive_local());
    stats.lists_changed = 0;
    stats.tasks_changed = count;
    stats.version += 1;
}

async fn pull_sync(
    db: &Arc<Db>,
    api: &Arc<ApiClient>,
    network_status: &Arc<Mutex<NetworkStatus>>,
    sync_stats: &Arc<Mutex<SyncStats>>,
    force_full: bool,
) {
    if !api.has_token() {
        *network_status.lock().await = NetworkStatus::Offline;
        return;
    }

    if db.has_pending_sync() {
        return;
    }

    *network_status.lock().await = NetworkStatus::Syncing;

    let mut total_lists = 0usize;
    let mut total_tasks = 0usize;

    let last_pull = {
        let stats = sync_stats.lock().await;
        stats.last_pull_time
    };

    let use_incremental = !force_full && last_pull.is_some();

    match api.fetch_lists().await {
        Ok(lists) => {
            total_lists = lists.len();
            for list in &lists {
                db.insert_list(list).ok();
            }
            for list in &lists {
                let result = if use_incremental {
                    api.fetch_tasks_since(&list.id, last_pull.as_ref().unwrap()).await
                } else {
                    api.fetch_tasks(&list.id).await
                };
                if let Ok(tasks) = result {
                    total_tasks += tasks.len();
                    if use_incremental {
                        for task in &tasks {
                            db.insert_task(task).ok();
                        }
                    } else {
                        db.replace_all_tasks(&list.id, &tasks).ok();
                    }
                }
            }
            *network_status.lock().await = NetworkStatus::Online;
        }
        Err(_) => {
            *network_status.lock().await = NetworkStatus::Offline;
        }
    }

    let now = chrono::Local::now().naive_local();
    let mut stats = sync_stats.lock().await;
    stats.last_sync_time = Some(now);
    stats.last_pull_time = Some(now);
    stats.lists_changed = total_lists;
    stats.tasks_changed = total_tasks;
    stats.version += 1;
}