use anyhow::Result;
use chrono::{DateTime, Utc};
use crossterm::{
    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode, KeyEventKind},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use ratatui::{
    backend::CrosstermBackend,
    layout::{Constraint, Direction, Layout},
    style::{Color, Modifier, Style},
    text::{Line, Span},
    widgets::{Block, Borders, List, ListItem, Paragraph},
    Frame, Terminal,
};
use std::{
    io::{self, Stdout},
    time::Duration,
};
use tokio::sync::mpsc;

use crate::client::AtProtoClient;

#[derive(Debug, Clone)]
pub struct Message {
    pub handle: String,
    pub content: String,
    pub timestamp: DateTime<Utc>,
    pub is_own: bool,
}

impl Message {
    pub fn new(handle: String, content: String, is_own: bool) -> Self {
        Self {
            handle,
            content,
            timestamp: Utc::now(),
            is_own,
        }
    }

    pub fn format_display(&self) -> String {
        let time_str = self.timestamp.format("%H:%M:%S").to_string();
        format!("[{}] {}: {}", time_str, self.handle, self.content)
    }
}

pub struct TuiApp {
    messages: Vec<Message>,
    input: String,
    scroll_offset: usize,
    status: String,
    message_count: usize,
    connected: bool,
    should_quit: bool,
}

impl TuiApp {
    pub fn new() -> Self {
        Self {
            messages: Vec::new(),
            input: String::new(),
            scroll_offset: 0,
            status: "Connecting...".to_string(),
            message_count: 0,
            connected: false,
            should_quit: false,
        }
    }

    pub fn add_message(&mut self, message: Message) {
        self.messages.push(message);
        self.message_count += 1;
        
        // Keep only last 1000 messages
        if self.messages.len() > 1000 {
            self.messages.remove(0);
        }
        
        // Auto-scroll to bottom unless user is scrolling up
        if self.scroll_offset == 0 {
            self.scroll_offset = 0; // Stay at bottom
        }
    }

    pub fn set_connection_status(&mut self, connected: bool) {
        self.connected = connected;
        self.status = if connected {
            format!("Connected • {} messages", self.message_count)
        } else {
            "Reconnecting...".to_string()
        };
    }

    pub fn handle_input(&mut self, key: KeyCode) -> Option<String> {
        match key {
            KeyCode::Enter => {
                if !self.input.is_empty() {
                    let message = self.input.clone();
                    self.input.clear();
                    return Some(message);
                }
            }
            KeyCode::Char(c) => {
                self.input.push(c);
            }
            KeyCode::Backspace => {
                self.input.pop();
            }
            KeyCode::Up => {
                if self.scroll_offset < self.messages.len().saturating_sub(1) {
                    self.scroll_offset += 1;
                }
            }
            KeyCode::Down => {
                if self.scroll_offset > 0 {
                    self.scroll_offset -= 1;
                }
            }
            KeyCode::PageUp => {
                self.scroll_offset = (self.scroll_offset + 10).min(self.messages.len().saturating_sub(1));
            }
            KeyCode::PageDown => {
                self.scroll_offset = self.scroll_offset.saturating_sub(10);
            }
            KeyCode::Esc => {
                self.should_quit = true;
            }
            _ => {}
        }
        None
    }

    pub fn should_quit(&self) -> bool {
        self.should_quit
    }

    pub fn draw(&self, frame: &mut Frame) {
        let vertical = Layout::default()
            .direction(Direction::Vertical)
            .constraints([
                Constraint::Min(0),       // Messages area
                Constraint::Length(3),    // Status area
                Constraint::Length(3),    // Input area
            ])
            .split(frame.size());

        // Render messages
        let visible_messages: Vec<ListItem> = self.messages
            .iter()
            .rev()
            .skip(self.scroll_offset)
            .take(vertical[0].height as usize - 2) // Account for borders
            .map(|msg| {
                let style = if msg.is_own {
                    Style::default().fg(Color::Green).add_modifier(Modifier::BOLD)
                } else {
                    Style::default().fg(Color::White)
                };
                
                ListItem::new(Line::from(Span::styled(msg.format_display(), style)))
            })
            .collect::<Vec<_>>()
            .into_iter()
            .rev()
            .collect();

        let messages_list = List::new(visible_messages)
            .block(Block::default().borders(Borders::ALL).title("Messages"));
        frame.render_widget(messages_list, vertical[0]);

        // Render status
        let status_style = if self.connected {
            Style::default().fg(Color::Green)
        } else {
            Style::default().fg(Color::Yellow)
        };
        
        let status_paragraph = Paragraph::new(self.status.clone())
            .style(status_style)
            .block(Block::default().borders(Borders::ALL).title("Status"));
        frame.render_widget(status_paragraph, vertical[1]);

        // Render input
        let input_paragraph = Paragraph::new(self.input.clone())
            .block(Block::default().borders(Borders::ALL).title("Input (Esc to quit)"));
        frame.render_widget(input_paragraph, vertical[2]);
    }
}

pub async fn run_tui(
    client: &AtProtoClient,
    mut message_rx: mpsc::UnboundedReceiver<Message>,
) -> Result<()> {
    // Setup terminal
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    let mut app = TuiApp::new();
    
    // Add welcome message
    app.add_message(Message::new(
        "system".to_string(),
        "Welcome to Think TUI! Connecting to jetstream...".to_string(),
        false,
    ));

    let result = run_tui_loop(&mut terminal, &mut app, client, &mut message_rx).await;

    // Restore terminal
    disable_raw_mode()?;
    execute!(
        terminal.backend_mut(),
        LeaveAlternateScreen,
        DisableMouseCapture
    )?;
    terminal.show_cursor()?;

    result
}

async fn run_tui_loop(
    terminal: &mut Terminal<CrosstermBackend<Stdout>>,
    app: &mut TuiApp,
    client: &AtProtoClient,
    message_rx: &mut mpsc::UnboundedReceiver<Message>,
) -> Result<()> {
    loop {
        // Draw the UI
        terminal.draw(|f| app.draw(f))?;

        // Handle events with a timeout so we can check for messages
        if event::poll(Duration::from_millis(100))? {
            if let Event::Key(key) = event::read()? {
                if key.kind == KeyEventKind::Press {
                    // Handle Ctrl+C
                    if matches!(key.code, KeyCode::Char('c')) && key.modifiers.contains(crossterm::event::KeyModifiers::CONTROL) {
                        break;
                    }

                    // Handle other input
                    if let Some(message) = app.handle_input(key.code) {
                        // Publish the message
                        match client.publish_blip(&message).await {
                            Ok(_) => {
                                // Add our own message to the display
                                app.add_message(Message::new(
                                    "you".to_string(),
                                    message,
                                    true,
                                ));
                            }
                            Err(e) => {
                                // Add error message
                                app.add_message(Message::new(
                                    "error".to_string(),
                                    format!("Failed to publish: {}", e),
                                    false,
                                ));
                            }
                        }
                    }
                }
            }
        }

        // Check for new messages from jetstream
        while let Ok(message) = message_rx.try_recv() {
            app.add_message(message);
            app.set_connection_status(true);
        }

        // Check if we should quit
        if app.should_quit() {
            break;
        }
    }

    Ok(())
}