use ratatui::{
    buffer::Buffer,
    layout::Rect,
    style::{Color, Modifier, Style},
    widgets::{Block, Borders, Widget},
};

use crate::model::Model;
use crate::ui::app::AppMode;
use crate::ui::cat_tree::{build_cat_tree, CatTreeEntry};
use crate::view::Axis;

fn axis_display(axis: Axis) -> (&'static str, Color) {
    match axis {
        Axis::Row => ("Row ↕", Color::Green),
        Axis::Column => ("Col ↔", Color::Blue),
        Axis::Page => ("Page ☰", Color::Magenta),
        Axis::None => ("None ∅", Color::DarkGray),
    }
}

pub struct CategoryPanel<'a> {
    pub model: &'a Model,
    pub mode: &'a AppMode,
    pub cursor: usize,
    pub expanded: &'a std::collections::HashSet<String>,
}

impl<'a> CategoryPanel<'a> {
    pub fn new(
        model: &'a Model,
        mode: &'a AppMode,
        cursor: usize,
        expanded: &'a std::collections::HashSet<String>,
    ) -> Self {
        Self {
            model,
            mode,
            cursor,
            expanded,
        }
    }
}

impl<'a> Widget for CategoryPanel<'a> {
    fn render(self, area: Rect, buf: &mut Buffer) {
        let is_item_add = matches!(self.mode, AppMode::ItemAdd { .. });
        let is_cat_add = matches!(self.mode, AppMode::CategoryAdd { .. });
        let is_active = matches!(self.mode, AppMode::CategoryPanel) || is_item_add || is_cat_add;

        let (border_color, title) = if is_active {
            (Color::Cyan, " Categories ")
        } else {
            (Color::DarkGray, " Categories ")
        };

        let block = Block::default()
            .borders(Borders::ALL)
            .border_style(Style::default().fg(border_color))
            .title(title);
        let inner = block.inner(area);
        block.render(area, buf);

        let view = self.model.active_view();
        let tree = build_cat_tree(self.model, self.expanded);

        if tree.is_empty() {
            buf.set_string(
                inner.x,
                inner.y,
                "(no categories — use :add-cat <name>)",
                Style::default().fg(Color::DarkGray),
            );
            return;
        }

        for (i, entry) in tree.iter().enumerate() {
            if i as u16 >= inner.height {
                break;
            }
            let y = inner.y + i as u16;
            let is_selected = i == self.cursor && is_active;

            let base_style = if is_selected {
                Style::default()
                    .fg(Color::Black)
                    .bg(Color::Cyan)
                    .add_modifier(Modifier::BOLD)
            } else {
                Style::default()
            };

            if is_selected {
                let fill = " ".repeat(inner.width as usize);
                buf.set_string(inner.x, y, &fill, base_style);
            }

            match entry {
                CatTreeEntry::Category {
                    name,
                    item_count,
                    expanded,
                } => {
                    let indicator = if *expanded { "▼" } else { "▶" };
                    let (axis_str, axis_color) = axis_display(view.axis_of(name));
                    let name_part = format!("{indicator} {name} ({item_count})");
                    let axis_part = format!(" [{axis_str}]");

                    buf.set_string(inner.x, y, &name_part, base_style);
                    if name_part.len() + axis_part.len() < inner.width as usize {
                        buf.set_string(
                            inner.x + name_part.len() as u16,
                            y,
                            &axis_part,
                            if is_selected {
                                base_style
                            } else {
                                Style::default().fg(axis_color)
                            },
                        );
                    }
                }
                CatTreeEntry::Item { item_name, .. } => {
                    let label = format!("  · {item_name}");
                    buf.set_string(inner.x, y, &label, base_style);
                }
            }
        }
    }
}