//! Calendar view - upcoming releases.

use ratatui::{
    Frame,
    layout::{Constraint, Layout, Rect},
    style::{Modifier, Style},
    text::{Line, Span},
    widgets::Paragraph,
};

use crate::data::CalendarEntry;
use crate::theme;
use crate::ui::pane::Pane;

struct CalendarCell {
    day: u8,
    dim: bool,
    is_today: bool,
    events: Vec<CalendarEntry>,
}

pub fn render_calendar(frame: &mut Frame, area: Rect, calendar: &[CalendarEntry]) {
    let meta = "upcoming releases · May 2026";

    let footer = Line::from(vec![
        Span::styled("[h/l]", Style::default().fg(theme::GRAY)),
        Span::styled(" month · ", Style::default().fg(theme::FG2)),
        Span::styled("[Enter]", Style::default().fg(theme::GRAY)),
        Span::styled(" details", Style::default().fg(theme::FG2)),
        Span::raw("  "),
        Span::styled(
            format!("{} upcoming", calendar.len()),
            Style::default().fg(theme::GRAY),
        ),
    ]);

    let pane = Pane::new("Calendar")
        .meta(meta)
        .focused(true)
        .footer(footer);

    let block = pane.build_block();
    let inner = block.inner(area);
    frame.render_widget(block, area);

    // Build calendar grid for May 2026
    let today_day = 8u8; // May 8, 2026
    let year = 2026u16;
    let month = 5u8;

    // May 2026 starts on Friday (day_of_week = 5)
    let start_dow = 5u8;
    let days_in_month = 31u8;
    let days_in_prev = 30u8; // April has 30 days

    let mut cells: Vec<CalendarCell> = Vec::new();

    // Previous month days
    for i in 0..start_dow {
        cells.push(CalendarCell {
            day: days_in_prev - start_dow + i + 1,
            dim: true,
            is_today: false,
            events: Vec::new(),
        });
    }

    // Current month days
    for d in 1..=days_in_month {
        let events: Vec<CalendarEntry> = calendar
            .iter()
            .filter(|e| {
                if let Some(day_str) = e.date.split('-').nth(2) {
                    if let Ok(day) = day_str.parse::<u8>() {
                        let month_match = e.date.contains(&format!("{:04}-{:02}", year, month));
                        return month_match && day == d;
                    }
                }
                false
            })
            .cloned()
            .collect();

        cells.push(CalendarCell {
            day: d,
            dim: false,
            is_today: d == today_day,
            events,
        });
    }

    // Next month days to fill 6 weeks (42 cells)
    let mut next_day = 1u8;
    while cells.len() < 42 {
        cells.push(CalendarCell {
            day: next_day,
            dim: true,
            is_today: false,
            events: Vec::new(),
        });
        next_day += 1;
    }

    // Layout: header + day-of-week + 6 rows of days
    let chunks = Layout::vertical([
        Constraint::Length(1), // Month header
        Constraint::Length(1), // Day of week labels
        Constraint::Fill(1),   // Calendar grid
    ])
    .split(inner);

    // Month header: "◀ May 2026 ▶"
    let header = Line::from(vec![
        Span::styled("◀ ", Style::default().fg(theme::GRAY)),
        Span::styled(
            "May 2026",
            Style::default()
                .fg(theme::YELLOW)
                .add_modifier(Modifier::BOLD),
        ),
        Span::styled(" ▶", Style::default().fg(theme::GRAY)),
    ]);
    frame.render_widget(
        Paragraph::new(header).alignment(ratatui::layout::Alignment::Center),
        chunks[0],
    );

    // Day of week labels
    let dow_labels = ["sun", "mon", "tue", "wed", "thu", "fri", "sat"];
    let cell_width = chunks[2].width / 7;
    let dow_spans: Vec<Span> = dow_labels
        .iter()
        .map(|&d| {
            let pad = cell_width.saturating_sub(3) as usize;
            Span::styled(
                format!("{}{}", d, " ".repeat(pad)),
                Style::default().fg(theme::GRAY),
            )
        })
        .collect();
    frame.render_widget(Paragraph::new(Line::from(dow_spans)), chunks[1]);

    // Calendar grid - 6 rows x 7 cols
    let row_height = chunks[2].height / 6;
    let grid_rows = Layout::vertical(vec![Constraint::Length(row_height); 6]).split(chunks[2]);

    for (row_idx, row_area) in grid_rows.iter().enumerate() {
        let col_areas = Layout::horizontal(vec![Constraint::Ratio(1, 7); 7]).split(*row_area);

        for (col_idx, col_area) in col_areas.iter().enumerate() {
            let cell_idx = row_idx * 7 + col_idx;
            if cell_idx < cells.len() {
                render_calendar_cell(frame, *col_area, &cells[cell_idx]);
            }
        }
    }
}

fn render_calendar_cell(frame: &mut Frame, area: Rect, cell: &CalendarCell) {
    if area.height == 0 || area.width == 0 {
        return;
    }

    let day_style = if cell.dim {
        Style::default().fg(theme::BG4)
    } else if cell.is_today {
        Style::default().fg(theme::FG1)
    } else {
        Style::default().fg(theme::FG2)
    };

    let mut lines: Vec<Line> = Vec::new();

    // First line: day number with optional today marker
    let day_line = if cell.is_today {
        Line::from(vec![
            Span::styled(format!("{}", cell.day), day_style),
            Span::styled(" ●", Style::default().fg(theme::ORANGE)),
        ])
    } else {
        Line::from(Span::styled(format!("{}", cell.day), day_style))
    };
    lines.push(day_line);

    // Event lines
    let max_events = (area.height.saturating_sub(1)) as usize;
    for event in cell.events.iter().take(max_events) {
        let event_style = match event.status.as_str() {
            "announced" => Style::default().fg(theme::YELLOW),
            "monitored" => Style::default().fg(theme::GREEN),
            _ => Style::default().fg(theme::FG2),
        };

        let mut display = event.artist.clone();
        let max_len = area.width.saturating_sub(1) as usize;
        if display.len() > max_len {
            display.truncate(max_len.saturating_sub(1));
            display.push('…');
        }

        lines.push(Line::from(Span::styled(display, event_style)));
    }

    let para = Paragraph::new(lines);
    frame.render_widget(para, area);
}