use std::{
    borrow::Cow,
    cmp::min,
    collections::{HashMap, hash_map::DefaultHasher},
    hash::{Hash, Hasher},
    sync::{OnceLock, RwLock},
};

use crate::{
    i18n::t,
    ui::dashboard::{
        MonitorStatus, MonitorViewState,
        model::{BORDER_LINES_VIEW, DashboardViewState, GroupViewState},
    },
};
use once_cell::sync::Lazy;
use ratatui::{
    Frame,
    layout::{Alignment, Constraint, Direction, Layout, Rect},
    style::{Color, Modifier, Style},
    text::{Line, Span},
    widgets::{Block, Borders, Padding, Row, Table},
};

const STATUS_LINE_LENGTH: usize = 100;
const MAX_NAME_LENGTH: usize = 30;

static UP_SPAN: Lazy<Span<'static>> =
    Lazy::new(|| Span::styled("■", Style::default().fg(Color::Green)));

static DOWN_SPAN: Lazy<Span<'static>> =
    Lazy::new(|| Span::styled("■", Style::default().fg(Color::Red)));

static UNKNOWN_SPAN: Lazy<Span<'static>> =
    Lazy::new(|| Span::styled("■", Style::default().fg(Color::Yellow)));

static STATUS_LINE_CACHE: OnceLock<RwLock<HashMap<u64, Vec<&'static Span<'static>>>>> = OnceLock::new();

pub fn render_monitor_list(main_frame: &mut Frame, area: Rect, state: &mut DashboardViewState) {
    let available_height = area.height as usize;
    let max_scroll = state.get_total_lenght().saturating_sub(available_height);

    if state.scroll_state.get_position() > max_scroll {
        state.scroll_state = state.scroll_state.position(max_scroll);
    }

    let scroll_pos = state.scroll_state.get_position();
    let mut current_y = area.y as usize;
    let mut rendered_height = 0;
    let mut lines_skipped = 0;
    let half = state.get_total_lenght().saturating_div(2);

    for group in state.groups.iter() {
        let group_height = group.monitors.len() + BORDER_LINES_VIEW;

        if lines_skipped + group_height <= scroll_pos {
            lines_skipped += group_height;
            continue;
        }

        let visible_height = if lines_skipped < scroll_pos {
            group_height - (scroll_pos - lines_skipped)
        } else {
            group_height
        }
        .min(available_height - rendered_height);

        let group_area = Rect {
            x: area.x,
            y: current_y as u16,
            width: area.width,
            height: visible_height as u16,
        };

        render_group(main_frame, group_area, group, half > rendered_height);

        current_y += visible_height;
        rendered_height += visible_height;
        lines_skipped += group_height;
    }
}

fn render_group(frame: &mut Frame, area: Rect, group: &GroupViewState, is_first_half: bool) {
    let chunks = Layout::default()
        .direction(Direction::Vertical)
        .margin(0)
        .constraints([Constraint::Length(1), Constraint::Min(1)])
        .split(area);

    if chunks[0].height == 0 || chunks[1].height == 0 || group.monitors.is_empty() {
        return;
    }

    let group_title = Line::from(vec![
        Span::styled(format!("{} ", group.name), title_style()),
        Span::styled(
            format!("({})", group.monitors.len()),
            Style::default().fg(Color::Gray),
        ),
    ]);

    let title_block = Block::default()
        .borders(Borders::ALL)
        .border_style(Style::default().fg(Color::Blue))
        .title(group_title)
        .title_alignment(Alignment::Left);

    frame.render_widget(title_block, chunks[0]);

    if !group.monitors.is_empty() {
        render_monitor_table(frame, chunks[1], &group.monitors, is_first_half);
    }
}

fn render_monitor_table(
    frame: &mut Frame,
    area: Rect,
    monitors: &[MonitorViewState],
    is_first_half: bool,
) {
    let max_items = area.height as usize;
    let items_to_show = min(monitors.len(), max_items);
    let index = if is_first_half {
        monitors.len().saturating_sub(max_items.saturating_sub(2)) // 2 = Table header + botton
    } else {
        0
    };
    let monitors = &monitors[index..index + items_to_show.min(monitors.len() - index)];

    let header_cells = vec![
        "".to_string(),
        t("monitor"),
        t("Response"),
        t("uptime"),
        t("history"),
    ];

    let header = Row::new(header_cells).style(title_style()).height(1);

    let rows: Vec<Row> = monitors
        .iter()
        .take(items_to_show)
        .map(|monitor| create_monitor_item(monitor))
        .collect();

    let widths = vec![
        Constraint::Length(3),
        Constraint::Length(MAX_NAME_LENGTH as u16),
        Constraint::Length(10),
        Constraint::Length(10),
        Constraint::Length(STATUS_LINE_LENGTH as u16),
    ];

    let table = Table::new(rows, widths)
        .header(header)
        .block(
            Block::default()
                .borders(Borders::LEFT | Borders::RIGHT | Borders::BOTTOM)
                .border_style(Style::default().fg(Color::Blue))
                .padding(Padding::horizontal(2)),
        )
        .column_spacing(1)
        .style(Style::default());

    frame.render_widget(table, area);
}

pub fn get_status_color(status: &MonitorStatus) -> Color {
    match status {
        MonitorStatus::Up => Color::Green,
        MonitorStatus::Down => Color::Red,
        MonitorStatus::Unknown => Color::Yellow,
    }
}

pub fn get_status_emoji(status: &MonitorStatus) -> Cow<'static, str> {
    static UP_ICON: &str = "✅";
    static DOWN_ICON: &str = "❌";
    static UNKNOWN_ICON: &str = "❓";
    match status {
        MonitorStatus::Up => Cow::Borrowed(UP_ICON),
        MonitorStatus::Down => Cow::Borrowed(DOWN_ICON),
        MonitorStatus::Unknown => Cow::Borrowed(UNKNOWN_ICON),
    }
}

fn create_monitor_item(monitor: &MonitorViewState) -> Row<'_> {
    let status_icon = get_status_emoji(&monitor.status);
    let status_color = get_status_color(&monitor.status);

    let display_name: Cow<str> = if monitor.name.len() > MAX_NAME_LENGTH {
        Cow::Owned(format!(
            "{:.width$}...",
            monitor.name,
            width = MAX_NAME_LENGTH - 3
        ))
    } else {
        Cow::Borrowed(&monitor.name)
    };

    let response_text = format!("{:>7}ms", monitor.response_time);
    let uptime_text = format!("{:>7}%", monitor.uptime_24h);

    let status_line_spans = get_cached_status_line(&monitor.status_history);

    Row::new(vec![
        get_formated_line(format!("{} ", status_icon), status_color, Modifier::empty()),
        get_formated_line(display_name.to_string(), Color::White, Modifier::empty()),
        get_formated_line(response_text, Color::Cyan, Modifier::empty()),
        get_formated_line(uptime_text, Color::Magenta, Modifier::empty()),
        status_line_spans,
    ])
    .style(Style::default())
    .height(1)
}

fn get_formated_line(text: String, color: Color, modifier: Modifier) -> Line<'static> {
    Line::from(vec![Span::styled(
        text,
        Style::default().fg(color).add_modifier(modifier),
    )])
}

fn get_status_span(status: &MonitorStatus) -> &'static Span<'static> {
    match status {
        MonitorStatus::Up => &UP_SPAN,
        MonitorStatus::Down => &DOWN_SPAN,
        MonitorStatus::Unknown => &UNKNOWN_SPAN,
    }
}

fn title_style() -> Style {
    Style::default()
        .fg(Color::Yellow)
        .add_modifier(Modifier::BOLD)
}

fn calculate_history_hash(status_history: &[MonitorStatus]) -> u64 {
    let mut hasher = DefaultHasher::new();
    status_history
        .iter()
        .take(STATUS_LINE_LENGTH)
        .for_each(|status| {
            status.hash(&mut hasher);
        });
    hasher.finish()
}

fn get_cached_status_line(status_history: &[MonitorStatus]) -> Line<'static> {
    let hash = calculate_history_hash(status_history);
    let cache = STATUS_LINE_CACHE.get_or_init(|| RwLock::new(HashMap::new()));
    {
        let read = cache.read().unwrap();
        if let Some(spans) = read.get(&hash) {
            return Line::from(spans.iter().map(|&span| span.clone()).collect::<Vec<_>>());
        }
    }

    let spans: Vec<&'static Span<'static>> = status_history
        .iter()
        .rev()
        .take(STATUS_LINE_LENGTH)
        .map(|status| get_status_span(status))
        .collect();

    let mut write = cache.write().unwrap();
    if write.len() > 1000 {
        let keys_to_remove: Vec<_> = write.keys().take(250).copied().collect();

        for key in keys_to_remove {
            write.remove(&key);
        }
    }
    write.insert(hash, spans.clone());
    Line::from(spans.iter().map(|&span| span.clone()).collect::<Vec<_>>())
}