use crate::{
    bus::Client,
    controller::Operation,
    model::{ConfigurationSummary, Settings, Status, SubscriptionSummary},
};
use anyhow::{Result, ensure};
use crossterm::{
    event::{self, Event, KeyCode, KeyModifiers},
    execute,
    terminal::{self, EnterAlternateScreen, LeaveAlternateScreen},
};
use ratatui::{
    Terminal,
    backend::CrosstermBackend,
    layout::{Constraint, Layout},
    style::{Color, Modifier, Style},
    widgets::{Block, Borders, Cell, Paragraph, Row, Table, TableState, Tabs},
};
use std::{
    io::{self, IsTerminal},
    time::Duration,
};

type Screen = Terminal<CrosstermBackend<io::Stdout>>;
struct Restore;
impl Drop for Restore {
    fn drop(&mut self) {
        let _ = terminal::disable_raw_mode();
        let _ = execute!(io::stdout(), LeaveAlternateScreen);
    }
}

struct Ui {
    tab: usize,
    row: usize,
    viewed: Option<String>,
    filter: String,
    editing_filter: bool,
    chooser: bool,
    chooser_query: String,
    chooser_row: usize,
    console: bool,
    details: bool,
    help: bool,
    first_g: bool,
    status: Status,
    subscriptions: Vec<SubscriptionSummary>,
    entries: Vec<ConfigurationSummary>,
    settings: Settings,
    message: String,
    logs: Vec<String>,
}

impl Ui {
    async fn refresh(&mut self, client: &Client) -> Result<()> {
        self.status = client.read("Status").await?;
        self.subscriptions = client.read("Subscriptions").await?;
        if !self
            .subscriptions
            .iter()
            .any(|s| Some(&s.name) == self.viewed.as_ref())
        {
            self.viewed = self.subscriptions.first().map(|s| s.name.clone());
        }
        self.entries = client.configurations(self.viewed.as_deref()).await?;
        self.settings = client.read("Settings").await?;
        self.logs = client.read("Logs").await?;
        self.row = self.row.min(
            if self.tab == 1 {
                self.subscriptions.len()
            } else {
                self.visible().len()
            }
            .saturating_sub(1),
        );
        Ok(())
    }
    fn visible(&self) -> Vec<&ConfigurationSummary> {
        let query = self.filter.to_lowercase();
        self.entries
            .iter()
            .filter(|e| {
                e.name.to_lowercase().contains(&query)
                    || e.host
                        .as_deref()
                        .unwrap_or("")
                        .to_lowercase()
                        .contains(&query)
            })
            .collect()
    }
    fn choices(&self) -> Vec<&SubscriptionSummary> {
        self.subscriptions
            .iter()
            .filter(|s| fuzzy(&self.chooser_query, &s.name))
            .collect()
    }
    fn selected_row(&self) -> Option<&ConfigurationSummary> {
        self.visible().get(self.row).copied()
    }
}

pub async fn run(client: Client) -> Result<()> {
    ensure!(
        io::stdin().is_terminal() && io::stdout().is_terminal(),
        "The TUI needs a terminal; use status --json for scripts"
    );
    let status = client.read("Status").await?;
    let mut ui = Ui {
        tab: 0,
        row: 0,
        viewed: None,
        filter: String::new(),
        editing_filter: false,
        chooser: false,
        chooser_query: String::new(),
        chooser_row: 0,
        console: false,
        details: false,
        help: false,
        first_g: false,
        status,
        subscriptions: vec![],
        entries: vec![],
        settings: Settings::default(),
        message: String::new(),
        logs: vec![],
    };
    ui.refresh(&client).await?;
    terminal::enable_raw_mode()?;
    execute!(io::stdout(), EnterAlternateScreen)?;
    let _restore = Restore;
    let mut screen = Terminal::new(CrosstermBackend::new(io::stdout()))?;
    let mut last_refresh = std::time::Instant::now();
    loop {
        draw(&mut screen, &ui)?;
        if !event::poll(Duration::from_millis(200))? {
            if last_refresh.elapsed() >= Duration::from_secs(2) {
                if let Err(error) = ui.refresh(&client).await {
                    ui.message = error.to_string();
                }
                last_refresh = std::time::Instant::now();
            }
            continue;
        }
        let Event::Key(key) = event::read()? else {
            continue;
        };
        if key.kind == event::KeyEventKind::Release {
            continue;
        }
        if key.code == KeyCode::Char('c') && key.modifiers.contains(KeyModifiers::CONTROL) {
            break;
        }
        if ui.chooser {
            match key.code {
                KeyCode::Esc => ui.chooser = false,
                KeyCode::Enter => {
                    if let Some(name) = ui.choices().get(ui.chooser_row).map(|s| s.name.clone()) {
                        ui.viewed = Some(name);
                        ui.filter.clear();
                        ui.row = 0;
                    }
                    ui.chooser = false;
                    ui.refresh(&client).await?;
                }
                KeyCode::Down => {
                    ui.chooser_row = (ui.chooser_row + 1).min(ui.choices().len().saturating_sub(1))
                }
                KeyCode::Up => ui.chooser_row = ui.chooser_row.saturating_sub(1),
                KeyCode::Char('n' | 'j') if key.modifiers.contains(KeyModifiers::CONTROL) => {
                    ui.chooser_row = (ui.chooser_row + 1).min(ui.choices().len().saturating_sub(1))
                }
                KeyCode::Char('p' | 'k') if key.modifiers.contains(KeyModifiers::CONTROL) => {
                    ui.chooser_row = ui.chooser_row.saturating_sub(1)
                }
                KeyCode::Backspace => {
                    ui.chooser_query.pop();
                    ui.chooser_row = 0;
                }
                KeyCode::Char(c) => {
                    ui.chooser_query.push(c);
                    ui.chooser_row = 0;
                }
                _ => {}
            }
            continue;
        }
        if ui.editing_filter {
            match key.code {
                KeyCode::Esc => {
                    ui.filter.clear();
                    ui.editing_filter = false;
                }
                KeyCode::Enter => ui.editing_filter = false,
                KeyCode::Backspace => {
                    ui.filter.pop();
                }
                KeyCode::Char(c) => ui.filter.push(c),
                _ => {}
            }
            ui.row = 0;
            continue;
        }
        if ui.details || ui.help {
            if matches!(key.code, KeyCode::Esc | KeyCode::Enter | KeyCode::Char('q')) {
                ui.details = false;
                ui.help = false;
            }
            continue;
        }
        let mut operation = None;
        match key.code {
            KeyCode::Char('q') => break,
            KeyCode::Esc => {
                ui.tab = 0;
                ui.filter.clear();
            }
            KeyCode::Char('h') | KeyCode::Left => {
                ui.tab = (ui.tab + 2) % 3;
                ui.row = 0;
            }
            KeyCode::Char('l') | KeyCode::Right => {
                ui.tab = (ui.tab + 1) % 3;
                ui.row = 0;
            }
            KeyCode::Char('j') | KeyCode::Down => ui.row = ui.row.saturating_add(1),
            KeyCode::Char('k') | KeyCode::Up => ui.row = ui.row.saturating_sub(1),
            KeyCode::Char('g') if ui.first_g => {
                ui.row = 0;
                ui.first_g = false;
            }
            KeyCode::Char('g') => {
                ui.first_g = true;
                continue;
            }
            KeyCode::Char('G') => {
                ui.row = if ui.tab == 1 {
                    ui.subscriptions.len()
                } else {
                    ui.visible().len()
                }
                .saturating_sub(1)
            }
            KeyCode::Char('/') if ui.tab == 0 => {
                ui.editing_filter = true;
            }
            KeyCode::Char('s') => {
                ui.chooser = true;
                ui.chooser_query.clear();
                ui.chooser_row = 0;
            }
            KeyCode::Char('J' | 'K') => {
                if !ui.subscriptions.is_empty() {
                    let index = ui
                        .subscriptions
                        .iter()
                        .position(|s| Some(&s.name) == ui.viewed.as_ref())
                        .unwrap_or(0);
                    let next = if key.code == KeyCode::Char('J') {
                        (index + 1) % ui.subscriptions.len()
                    } else {
                        (index + ui.subscriptions.len() - 1) % ui.subscriptions.len()
                    };
                    ui.viewed = Some(ui.subscriptions[next].name.clone());
                    ui.filter.clear();
                    ui.row = 0;
                    ui.refresh(&client).await?;
                }
            }
            KeyCode::Char('c') => ui.console = !ui.console,
            KeyCode::Char('?') => ui.help = true,
            KeyCode::Char('d') if ui.tab == 0 => ui.details = true,
            KeyCode::Char(' ') => {
                operation = Some(if ui.status.requested_enabled {
                    Operation::Disable
                } else {
                    Operation::Enable
                })
            }
            KeyCode::Char('x') if ui.tab == 0 => operation = Some(Operation::Unset),
            KeyCode::Char('u') => {
                operation = Some(Operation::Refresh {
                    name: if ui.tab == 1 {
                        ui.subscriptions.get(ui.row).map(|s| s.name.clone())
                    } else {
                        ui.viewed.clone()
                    },
                })
            }
            KeyCode::Enter if ui.tab == 0 => {
                if let Some(entry) = ui.selected_row() {
                    operation = Some(Operation::Select {
                        id: entry.id.clone(),
                    });
                }
            }
            KeyCode::Enter if ui.tab == 1 => {
                if let Some(s) = ui.subscriptions.get(ui.row) {
                    ui.viewed = Some(s.name.clone());
                    ui.filter.clear();
                    ui.row = 0;
                    ui.tab = 0;
                    ui.refresh(&client).await?;
                }
            }
            KeyCode::Char('a') if ui.tab == 1 => {
                match form(
                    &mut screen,
                    "Add subscription",
                    &["Name", "URL"],
                    &[String::new(), String::new()],
                )? {
                    Some(values) => {
                        operation = Some(Operation::AddSubscription {
                            name: values[0].clone(),
                            url: values[1].clone(),
                        })
                    }
                    None => {}
                }
            }
            KeyCode::Char('e') if ui.tab == 1 => {
                if let Some(s) = ui.subscriptions.get(ui.row) {
                    if let Some(values) = form(
                        &mut screen,
                        "Edit subscription URL",
                        &["URL"],
                        &[String::new()],
                    )? {
                        operation = Some(Operation::EditSubscription {
                            name: s.name.clone(),
                            url: values[0].clone(),
                        });
                    }
                }
            }
            KeyCode::Char('x') if ui.tab == 1 => {
                if let Some(s) = ui.subscriptions.get(ui.row) {
                    if let Some(values) = form(
                        &mut screen,
                        "Type delete to remove this subscription",
                        &["Confirmation"],
                        &[String::new()],
                    )? {
                        if values[0] == "delete" {
                            operation = Some(Operation::DeleteSubscription {
                                name: s.name.clone(),
                            });
                        }
                    }
                }
            }
            KeyCode::Char('e') | KeyCode::Enter if ui.tab == 2 => {
                let current = [
                    &ui.settings.ping_url,
                    &ui.settings.speed_url,
                    &ui.settings.maximum_download_mib.to_string(),
                    &ui.settings.maximum_duration_seconds.to_string(),
                ]
                .map(|v| v.to_string());
                if let Some(values) = form(
                    &mut screen,
                    "Settings",
                    &[
                        "HTTPS Ping URL",
                        "Speed URL",
                        "Maximum MiB",
                        "Maximum seconds",
                    ],
                    &current,
                )? {
                    let parsed = (values[2].parse::<u64>(), values[3].parse::<u64>());
                    match parsed {
                        (Ok(bytes), Ok(seconds)) => {
                            operation = Some(Operation::SaveSettings {
                                settings: Settings {
                                    ping_url: values[0].clone(),
                                    speed_url: values[1].clone(),
                                    maximum_download_mib: bytes,
                                    maximum_duration_seconds: seconds,
                                },
                            })
                        }
                        _ => ui.message = "Limits must be positive integers".into(),
                    }
                }
            }
            KeyCode::Char('e') => {
                suspend(&mut screen)?;
                let result = crate::editor::open(&ui.logs);
                resume(&mut screen)?;
                if let Err(error) = result {
                    ui.message = error.to_string();
                }
            }
            KeyCode::Char('t' | 'b') if ui.tab == 0 => {
                if let Some(entry) = ui.selected_row() {
                    let id = entry.id.clone();
                    suspend(&mut screen)?;
                    let result = async {
                        let _agent = crate::authentication::TerminalAgent::start(true)?;
                        client
                            .diagnostic(Some(&id), key.code == KeyCode::Char('b'), true)
                            .await
                    }
                    .await;
                    resume(&mut screen)?;
                    ui.message = match result {
                        Ok(value) => value,
                        Err(error) => error.to_string(),
                    };
                }
            }
            _ => {}
        }
        ui.first_g = false;
        if let Some(operation) = operation {
            suspend(&mut screen)?;
            let result = async {
                let _agent = crate::authentication::TerminalAgent::start(true)?;
                client.change(operation, true).await
            }
            .await;
            resume(&mut screen)?;
            ui.message = match result {
                Ok(()) => "Applied".into(),
                Err(error) => error.to_string(),
            };
            ui.refresh(&client).await?;
        }
        ui.row = ui.row.min(
            if ui.tab == 1 {
                ui.subscriptions.len()
            } else {
                ui.visible().len()
            }
            .saturating_sub(1),
        );
    }
    Ok(())
}

fn suspend(screen: &mut Screen) -> Result<()> {
    terminal::disable_raw_mode()?;
    execute!(screen.backend_mut(), LeaveAlternateScreen)?;
    Ok(())
}
fn resume(screen: &mut Screen) -> Result<()> {
    terminal::enable_raw_mode()?;
    execute!(screen.backend_mut(), EnterAlternateScreen)?;
    screen.clear()?;
    Ok(())
}

fn form(
    screen: &mut Screen,
    title: &str,
    labels: &[&str],
    initial: &[String],
) -> Result<Option<Vec<String>>> {
    let mut values = initial.to_vec();
    let mut field = 0;
    let mut discarding = false;
    loop {
        screen.draw(|frame| {
            let text = labels
                .iter()
                .enumerate()
                .map(|(i, label)| {
                    let value = if *label == "URL" {
                        "*".repeat(values[i].chars().count())
                    } else {
                        values[i].clone()
                    };
                    format!("{} {label}: {value}", if field == i { ">" } else { " " })
                })
                .collect::<Vec<_>>()
                .join("\n\n");
            let help = if discarding {
                "Discard edits? y confirms, any other key resumes"
            } else {
                "Tab moves fields. Enter saves from the last field. Esc cancels."
            };
            frame.render_widget(
                Paragraph::new(format!("{text}\n\n{help}"))
                    .block(Block::default().borders(Borders::ALL).title(title)),
                frame.area(),
            );
        })?;
        let Event::Key(key) = event::read()? else {
            continue;
        };
        if discarding {
            if key.code == KeyCode::Char('y') {
                return Ok(None);
            }
            discarding = false;
            continue;
        }
        match key.code {
            KeyCode::Esc => {
                if values == initial {
                    return Ok(None);
                }
                discarding = true;
            }
            KeyCode::Tab => field = (field + 1) % values.len(),
            KeyCode::BackTab => field = (field + values.len() - 1) % values.len(),
            KeyCode::Enter if field + 1 == values.len() => return Ok(Some(values)),
            KeyCode::Enter => field += 1,
            KeyCode::Backspace => {
                values[field].pop();
            }
            KeyCode::Char(c) if !key.modifiers.contains(KeyModifiers::CONTROL) => {
                if values[field].len() < 16384 {
                    values[field].push(c);
                }
            }
            _ => {}
        }
    }
}

fn draw(screen: &mut Screen, ui: &Ui) -> Result<()> {
    screen.draw(|frame| {
        let layout = Layout::vertical([Constraint::Length(1), Constraint::Length(2), Constraint::Min(4), Constraint::Length(if ui.console { 6 } else { 0 }), Constraint::Length(2)]).split(frame.area());
        frame.render_widget(Tabs::new(["Connections", "Subscriptions", "Settings"]).select(ui.tab).highlight_style(Style::default().fg(Color::Cyan).add_modifier(Modifier::BOLD)), layout[0]);
        let actions = match ui.tab {
            0 => format!("{} [s]  Update [u]  Details [d]  Ping [t]  Speed [b]  {}", ui.viewed.as_deref().unwrap_or("No subscription"), if ui.filter.is_empty() && !ui.editing_filter { String::new() } else { format!("/ {}", ui.filter) }),
            1 => "Add [a]  Edit [e]  Update [u]  Delete [x]  Open [Enter]".into(),
            _ => "Edit settings [e]".into(),
        };
        frame.render_widget(Paragraph::new(actions), layout[1]);
        if ui.help {
            frame.render_widget(Paragraph::new("h/l: screens   j/k: rows   gg/G: first/last\nEnter: select/open   Space: enable/disable   x: unset/delete\ns: subscription chooser   J/K: cycle subscriptions   /: filter\nd: details   t: Ping   b: Speed   c: console   e: logs/editor\n?: help   Esc: back/clear   q: quit\nSelection and viewed subscription are separate.\nClosing this interface leaves the service running."), layout[2]);
        } else if ui.details {
            let text = ui.selected_row().map(|e| format!("{}\nID: {}\nHost: {}\nPort: {}\nStatus: {}\n{}", e.name, e.id, e.host.as_deref().unwrap_or("unavailable"), e.port.map(|p| p.to_string()).unwrap_or_default(), e.status, e.explanation.as_deref().unwrap_or("Trojan / TCP / TLS"))).unwrap_or_else(|| "No configuration highlighted".into());
            frame.render_widget(Paragraph::new(text), layout[2]);
        } else if ui.chooser {
            let choices = ui.choices();
            let rows = choices.iter().map(|s| Row::new([s.name.as_str()]));
            let mut state = TableState::default().with_selected(Some(ui.chooser_row));
            frame.render_stateful_widget(Table::new(rows, [Constraint::Percentage(100)]).block(Block::default().borders(Borders::ALL).title(format!("Choose subscription / {}", ui.chooser_query))).row_highlight_style(Style::default().bg(Color::DarkGray)), layout[2], &mut state);
        } else if ui.tab == 0 {
            let rows = ui.visible().into_iter().map(|entry| Row::new([
                Cell::from(if entry.selected { "*" } else { " " }),
                Cell::from(format!("{}{}", if entry.status == "supported" { String::new() } else { format!("[{}] ", entry.status) }, entry.name)),
                Cell::from(entry.host.clone().unwrap_or_default()), Cell::from(entry.ping_ms.map(|v| format!("{v} ms")).unwrap_or_else(|| "?".into())), Cell::from(entry.speed_bytes_per_second.map(|v| format!("{:.1} MiB/s", v / 1048576.0)).unwrap_or_else(|| "?".into())),
            ]));
            let mut state = TableState::default().with_selected(Some(ui.row));
            frame.render_stateful_widget(Table::new(rows, [Constraint::Length(1), Constraint::Percentage(40), Constraint::Percentage(35), Constraint::Length(9), Constraint::Length(9)]).header(Row::new(["", "Name", "Host", "Delay", "Speed"])).row_highlight_style(Style::default().bg(Color::DarkGray)), layout[2], &mut state);
        } else if ui.tab == 1 {
            let mut state = TableState::default().with_selected(Some(ui.row));
            frame.render_stateful_widget(Table::new(ui.subscriptions.iter().map(|s| Row::new([s.name.as_str()])), [Constraint::Percentage(100)]).row_highlight_style(Style::default().bg(Color::DarkGray)), layout[2], &mut state);
        } else {
            frame.render_widget(Paragraph::new(format!("HTTPS Ping URL: {}\nSpeed URL: {}\nMaximum download MiB: {}\nMaximum duration seconds: {}", ui.settings.ping_url, ui.settings.speed_url, ui.settings.maximum_download_mib, ui.settings.maximum_duration_seconds)), layout[2]);
        }
        if ui.console { frame.render_widget(Paragraph::new(ui.logs.iter().rev().take(5).cloned().collect::<Vec<_>>().join("\n")).block(Block::default().borders(Borders::TOP)), layout[3]); }
        frame.render_widget(Paragraph::new(format!("{} | Routing: {} | Health: {} | Selected: {}\n{}", if ui.status.requested_enabled { "Enabled" } else { "Disabled" }, ui.status.routing, ui.status.health, ui.status.selected_configuration.as_deref().unwrap_or("unset"), ui.message)), layout[4]);
    })?;
    Ok(())
}

fn fuzzy(query: &str, value: &str) -> bool {
    let value = value.to_lowercase();
    let mut chars = value.chars();
    query
        .to_lowercase()
        .chars()
        .all(|wanted| chars.by_ref().any(|c| c == wanted))
}