use std::process::Command;
use chrono::Utc;
use crossterm::event::{Event, KeyCode, KeyEvent, KeyModifiers};
use crate::state::{AppState, TimeItem};
use crate::config::Config;

pub enum Screen {
    Main,
    Help,
    ConfigHelp,
    NewEntry,
}

pub struct App {
    pub state: AppState,
    pub config: Config,
    pub current_screen: Screen,
    pub needs_redraw: bool,
    pub new_entry_buffer: String,
    pub new_entry_project: String,
    pub new_entry_cursor: usize,
    pub new_entry_mode: NewEntryMode,  // Task or Project
}

pub enum NewEntryMode {
    Task,
    Project,
}

impl App {
    pub fn new() -> anyhow::Result<Self> {
        Ok(Self {
            state: AppState::load()?,
            config: Config::load()?,
            current_screen: Screen::Main,
            needs_redraw: true,
            new_entry_buffer: String::new(),
            new_entry_project: String::new(),
            new_entry_cursor: 0,
            new_entry_mode: NewEntryMode::Task,
        })
    }

    pub fn handle_event(&mut self, event: Event) -> anyhow::Result<bool> {
        match self.current_screen {
            Screen::Main => self.handle_main_event(event),
            Screen::Help => self.handle_help_event(event),
            Screen::ConfigHelp => self.handle_config_help_event(event),
            Screen::NewEntry => self.handle_new_entry_event(event),
        }
    }

    fn handle_main_event(&mut self, event: Event) -> anyhow::Result<bool> {
        match event {
            Event::Key(KeyEvent {
                code,
                modifiers,
                ..
            }) => match (code, modifiers) {
                (KeyCode::Char('q'), _) => return Ok(true),
                (KeyCode::Char('j'), _) | (KeyCode::Down, _) => self.move_selection(1),
                (KeyCode::Char('k'), _) | (KeyCode::Up, _) => self.move_selection(-1),
                (KeyCode::Char('h'), _) | (KeyCode::Left, _) => self.change_pane(-1),
                (KeyCode::Char('l'), _) | (KeyCode::Right, _) => self.change_pane(1),
                (KeyCode::Char('n'), KeyModifiers::CONTROL) => self.change_pane(1),
                (KeyCode::Char('p'), KeyModifiers::CONTROL) => self.change_pane(-1),
                (KeyCode::Enter, _) => self.toggle_current_item()?,
                (KeyCode::Char('e'), KeyModifiers::CONTROL) => self.edit_config()?,
                (KeyCode::Char('?'), _) => self.current_screen = Screen::Help,
                (KeyCode::Char('c'), _) => self.edit_app_config()?,
                (KeyCode::Char('n'), _) => self.start_new_entry(),
                _ => {}
            },
            _ => {}
        }
        Ok(false)
    }

    fn handle_new_entry_event(&mut self, event: Event) -> anyhow::Result<bool> {
        match event {
            Event::Key(KeyEvent {
                code,
                modifiers,
                ..
            }) => {
                match (code, modifiers) {
                    (KeyCode::Esc, _) => {
                        self.current_screen = Screen::Main;
                        self.new_entry_buffer.clear();
                        self.new_entry_project.clear();
                        self.new_entry_mode = NewEntryMode::Task;
                    }
                    (KeyCode::Enter, _) => {
                        match self.new_entry_mode {
                            NewEntryMode::Task => {
                                if !self.new_entry_buffer.is_empty() {
                                    self.new_entry_mode = NewEntryMode::Project;
                                }
                            }
                            NewEntryMode::Project => {
                                if self.new_entry_project.is_empty() || self.config.is_valid_project(&self.new_entry_project) {
                                    // Create new time item
                                    let item = TimeItem {
                                        name: self.new_entry_buffer.clone(),
                                        tags: if self.new_entry_project.is_empty() {
                                            vec![]
                                        } else {
                                            vec![self.new_entry_project.clone()]
                                        },
                                        last_used: Some(Utc::now()),
                                    };
                                    // Add to current pane (or recurring if in recent)
                                    match self.state.current_pane {
                                        0 => self.state.permanent_items.push(item),  // Permanent Items
                                        1 => self.state.recurring_items.push(item),  // Recurring Items
                                        2 => self.state.recent_items.push(item),     // Ad-Hoc Items
                                        _ => unreachable!(),
                                    }
                                    self.state.save()?;
                                    
                                    // Clear and return to main screen
                                    self.current_screen = Screen::Main;
                                    self.new_entry_buffer.clear();
                                    self.new_entry_project.clear();
                                    self.new_entry_mode = NewEntryMode::Task;
                                }
                            }
                        }
                    }
                    (KeyCode::Backspace, _) => {
                        match self.new_entry_mode {
                            NewEntryMode::Task => {
                                if self.new_entry_cursor > 0 {
                                    self.new_entry_buffer.remove(self.new_entry_cursor - 1);
                                    self.new_entry_cursor -= 1;
                                }
                            }
                            NewEntryMode::Project => {
                                if self.new_entry_cursor > 0 {
                                    self.new_entry_project.remove(self.new_entry_cursor - 1);
                                    self.new_entry_cursor -= 1;
                                }
                            }
                        }
                    }
                    (KeyCode::Char(c), m) if m.is_empty() => {
                        match self.new_entry_mode {
                            NewEntryMode::Task => {
                                self.new_entry_buffer.insert(self.new_entry_cursor, c);
                                self.new_entry_cursor += 1;
                            }
                            NewEntryMode::Project => {
                                self.new_entry_project.insert(self.new_entry_cursor, c);
                                self.new_entry_cursor += 1;
                            }
                        }
                    }
                    _ => {}
                }
            }
            _ => {}
        }
        Ok(false)
    }

    fn handle_help_event(&mut self, event: Event) -> anyhow::Result<bool> {
        match event {
            Event::Key(KeyEvent { code, .. }) => match code {
                KeyCode::Char('c') => self.current_screen = Screen::ConfigHelp,
                KeyCode::Esc | KeyCode::Char('q') => self.current_screen = Screen::Main,
                _ => {}
            },
            _ => {}
        }
        Ok(false)
    }

    fn handle_config_help_event(&mut self, event: Event) -> anyhow::Result<bool> {
        match event {
            Event::Key(KeyEvent { code, .. }) => match code {
                KeyCode::Esc | KeyCode::Char('q') => self.current_screen = Screen::Help,
                _ => {}
            },
            _ => {}
        }
        Ok(false)
    }

    fn move_selection(&mut self, delta: i32) {
        let items_len = match self.state.current_pane {
            0 => self.state.permanent_items.len(),
            1 => self.state.recurring_items.len(),
            2 => self.state.recent_items.len(),
            _ => return,
        };

        if items_len == 0 {
            return;
        }

        let current = self.state.selected_indices[self.state.current_pane] as i32;
        let new_index = (current + delta).rem_euclid(items_len as i32) as usize;
        self.state.selected_indices[self.state.current_pane] = new_index;
    }

    fn change_pane(&mut self, delta: i32) {
        self.state.current_pane = ((self.state.current_pane as i32 + delta).rem_euclid(3)) as usize;
    }

    fn get_current_item(&self) -> Option<TimeItem> {
        let items = match self.state.current_pane {
            0 => &self.state.permanent_items,
            1 => &self.state.recurring_items,
            2 => &self.state.recent_items,
            _ => return None,
        };

        let index = self.state.selected_indices[self.state.current_pane];
        items.get(index).cloned()
    }

    fn toggle_current_item(&mut self) -> anyhow::Result<()> {
        if let Some(item) = self.get_current_item() {
            if self.state.active_timer.as_ref().map(|(active, _)| active.name == item.name).unwrap_or(false) {
                self.state.stop_timer()?;
            } else {
                self.state.start_timer(item)?;
            }
            self.state.save()?;
        }
        Ok(())
    }

    fn start_new_entry(&mut self) {
        self.current_screen = Screen::NewEntry;
        self.new_entry_buffer.clear();
        self.new_entry_project.clear();
        self.new_entry_cursor = 0;
        self.new_entry_mode = NewEntryMode::Task;
    }

    fn edit_app_config(&mut self) -> anyhow::Result<()> {
        use crossterm::{
            terminal::{disable_raw_mode, enable_raw_mode},
            execute,
            terminal::{LeaveAlternateScreen, EnterAlternateScreen},
        };
        use std::io::stdout;
        
        let editor = std::env::var("EDITOR").unwrap_or_else(|_| "vi".to_string());
        let config_path = Config::config_path()?;
        
        // Leave TUI mode
        disable_raw_mode()?;
        execute!(stdout(), LeaveAlternateScreen)?;

        // Run editor
        let status = Command::new(editor)
            .arg(&config_path)
            .status()?;

        if status.success() {
            // Reload entire application state
            self.config = Config::load()?;
            // Signal for complete reload
            self.current_screen = Screen::Main;
            self.needs_redraw = true;
        }

        // Return to TUI mode
        execute!(stdout(), EnterAlternateScreen)?;
        enable_raw_mode()?;
        
        Ok(())
    }

    fn edit_config(&mut self) -> anyhow::Result<()> {
        use crossterm::{
            terminal::{disable_raw_mode, enable_raw_mode},
            execute,
            terminal::{LeaveAlternateScreen, EnterAlternateScreen},
        };
        use std::io::stdout;
        
        let editor = std::env::var("EDITOR").unwrap_or_else(|_| "vi".to_string());
        let config_path = AppState::config_file()?;
        
        if !config_path.exists() {
            std::fs::write(&config_path, "# WAT Configuration\n# Add your permanent items here\n\npermanent_items:\n  - name: Daily Standup\n    tags: [daily, meeting]\n")?;
        }

        // Leave TUI mode
        disable_raw_mode()?;
        execute!(stdout(), LeaveAlternateScreen)?;

        // Run editor
        let status = Command::new(editor)
            .arg(&config_path)
            .status()?;

        if status.success() {
            // Reload entire application state
            self.state = AppState::load()?;
            // Signal for complete reload
            self.current_screen = Screen::Main;
            self.needs_redraw = true;
        }

        // Return to TUI mode
        execute!(stdout(), EnterAlternateScreen)?;
        enable_raw_mode()?;
        
        Ok(())
    }
}