use ratatui::{
    layout::{Constraint, Direction, Layout, Rect},
    style::{Color, Modifier, Style},
    text::{Line, Span},
    widgets::{Block, Borders, Cell, Clear, Paragraph, Row, Table, TableState},
    Frame,
};

use crate::app::{
    App, Focus, ModalKind, GLOBAL_CHECKSUM, GLOBAL_COUNT, GLOBAL_HUT_ID, GLOBAL_HUT_TYPE,
    GLOBAL_LOT_STATUS, GLOBAL_PATH, GLOBAL_TARE, ROW_COUNT, ROW_MAT_ID, ROW_QUANTITY, ROW_UOM,
};

const GLOBAL_LABELS: &[&str] = &[
    "Hut ID",
    "Checksum",
    "Tare",
    "Lot Status",
    "Path",
    "Hut Type",
];

const ROW_LABELS: &[&str] = &["Material ID", "Quantity", "UOM"];

// ── colour palette ────────────────────────────────────────────────────────────

const C_FOCUSED: Color = Color::Cyan;
const C_UNFOCUSED: Color = Color::DarkGray;
const C_ACCENT: Color = Color::Yellow;
const C_ROW_SEL: Color = Color::Blue;
const C_BORDER: Color = Color::Gray;
const C_HEADER: Color = Color::White;

fn focused_style(is_focused: bool) -> Style {
    if is_focused {
        Style::default().fg(C_FOCUSED).add_modifier(Modifier::BOLD)
    } else {
        Style::default().fg(C_UNFOCUSED)
    }
}

fn focused_block<'a>(title: &'a str, is_focused: bool) -> Block<'a> {
    Block::default()
        .title(title)
        .borders(Borders::ALL)
        .border_style(if is_focused {
            Style::default().fg(C_FOCUSED)
        } else {
            Style::default().fg(C_BORDER)
        })
}

// ── main draw ────────────────────────────────────────────────────────────────

pub fn draw(f: &mut Frame, app: &App) {
    let area = f.area();

    // Overall vertical split: globals | lots | help bar
    let chunks = Layout::default()
        .direction(Direction::Vertical)
        .constraints([
            Constraint::Length(10), // global fields
            Constraint::Min(6),     // lot rows
            Constraint::Length(3),  // help bar
        ])
        .split(area);

    draw_globals(f, app, chunks[0]);
    draw_lots(f, app, chunks[1]);
    draw_help(f, chunks[2]);

    if let Some(modal) = &app.modal {
        draw_modal(f, modal, area);
    }
}

// ── globals panel ─────────────────────────────────────────────────────────────

fn draw_globals(f: &mut Frame, app: &App, area: Rect) {
    let outer = Block::default()
        .title(" Global Settings ")
        .borders(Borders::ALL)
        .border_style(Style::default().fg(C_ACCENT));
    let inner = outer.inner(area);
    f.render_widget(outer, area);

    // Two rows of three fields each
    let rows = Layout::default()
        .direction(Direction::Vertical)
        .constraints([
            Constraint::Length(3),
            Constraint::Length(3),
            Constraint::Length(3),
        ])
        .split(inner);

    // Row 0: Hut ID | Checksum | Tare
    let row0 = Layout::default()
        .direction(Direction::Horizontal)
        .constraints([
            Constraint::Ratio(2, 5),
            Constraint::Ratio(1, 5),
            Constraint::Ratio(2, 5),
        ])
        .split(rows[0]);

    // Row 1: Lot Status | Path | Hut Type
    let row1 = Layout::default()
        .direction(Direction::Horizontal)
        .constraints([
            Constraint::Ratio(1, 3),
            Constraint::Ratio(1, 3),
            Constraint::Ratio(1, 3),
        ])
        .split(rows[1]);

    let field_areas = [
        row0[0], // GLOBAL_HUT_ID
        row0[1], // GLOBAL_CHECKSUM
        row0[2], // GLOBAL_TARE
        row1[0], // GLOBAL_LOT_STATUS
        row1[1], // GLOBAL_PATH
        row1[2], // GLOBAL_HUT_TYPE
    ];

    for i in 0..GLOBAL_COUNT {
        let is_focused = app.focus == Focus::GlobalField(i);
        let label = GLOBAL_LABELS[i];
        let value: String = if i == GLOBAL_CHECKSUM {
            let checked = app.global[i] == "true";
            format!("[{}] (Space)", if checked { "x" } else { " " })
        } else if i == GLOBAL_LOT_STATUS {
            format!("{} (←/→)", app.global[i])
        } else {
            app.global[i].clone()
        };

        let display = if is_focused {
            format!("{} █", value)
        } else {
            value
        };

        let p = Paragraph::new(display)
            .block(focused_block(label, is_focused))
            .style(focused_style(is_focused));
        f.render_widget(p, field_areas[i]);
    }
}

// ── lots table ────────────────────────────────────────────────────────────────

fn draw_lots(f: &mut Frame, app: &App, area: Rect) {
    let outer = Block::default()
        .title(" Lot Rows  (+) Add   (-) Remove ")
        .borders(Borders::ALL)
        .border_style(Style::default().fg(C_ACCENT));
    let inner = outer.inner(area);
    f.render_widget(outer, area);

    if app.lots.is_empty() {
        let hint = Paragraph::new("No lots yet — press + to add one")
            .style(Style::default().fg(C_UNFOCUSED));
        f.render_widget(hint, inner);
        return;
    }

    // Column widths
    let col_constraints = [
        Constraint::Length(4),  // #
        Constraint::Min(18),    // Material ID
        Constraint::Length(12), // Quantity
        Constraint::Length(8),  // UOM
    ];

    let header_cells = ["#", "Material ID", "Quantity", "UOM"]
        .iter()
        .map(|h| Cell::from(*h).style(Style::default().fg(C_HEADER).add_modifier(Modifier::BOLD)));
    let header = Row::new(header_cells).height(1).bottom_margin(0);

    let rows: Vec<Row> = app
        .lots
        .iter()
        .enumerate()
        .map(|(row_idx, entry)| {
            let cells: Vec<Cell> = (0..ROW_COUNT + 1)
                .map(|col| {
                    if col == 0 {
                        // row number
                        Cell::from(format!("{:>2}", row_idx + 1))
                            .style(Style::default().fg(C_UNFOCUSED))
                    } else {
                        let field_idx = col - 1;
                        let is_focused = app.focus == Focus::LotField(row_idx, field_idx);
                        let text = if is_focused {
                            format!("{} █", entry.fields[field_idx])
                        } else {
                            entry.fields[field_idx].clone()
                        };
                        Cell::from(text).style(focused_style(is_focused))
                    }
                })
                .collect();

            let row_selected =
                matches!(&app.focus, Focus::LotRow(r) | Focus::LotField(r, _) if *r == row_idx);
            let row_style = if row_selected {
                Style::default().bg(Color::Rgb(20, 30, 50))
            } else {
                Style::default()
            };
            Row::new(cells).style(row_style).height(1)
        })
        .collect();

    let table = Table::new(rows, col_constraints)
        .header(header)
        .block(Block::default())
        .row_highlight_style(Style::default().bg(C_ROW_SEL));

    let mut state = TableState::default();
    f.render_stateful_widget(table, inner, &mut state);
}

// ── help bar ──────────────────────────────────────────────────────────────────

fn draw_help(f: &mut Frame, area: Rect) {
    let spans = vec![
        Span::styled(" Tab ", Style::default().fg(Color::Black).bg(C_ACCENT)),
        Span::raw(" Next field  "),
        Span::styled(" + ", Style::default().fg(Color::Black).bg(Color::Green)),
        Span::raw(" Add lot  "),
        Span::styled(" - ", Style::default().fg(Color::Black).bg(Color::Red)),
        Span::raw(" Remove lot  "),
        Span::styled(" c ", Style::default().fg(Color::Black).bg(Color::Cyan)),
        Span::raw(" Output CSV  "),
        Span::styled(" q ", Style::default().fg(Color::Black).bg(Color::Magenta)),
        Span::raw(" Quit  "),
    ];

    let help = Paragraph::new(Line::from(spans)).block(
        Block::default()
            .borders(Borders::ALL)
            .border_style(Style::default().fg(C_BORDER)),
    );
    f.render_widget(help, area);
}

// ── modal overlay ─────────────────────────────────────────────────────────────

fn draw_modal(f: &mut Frame, kind: &ModalKind, area: Rect) {
    let (title, body) = match kind {
        ModalKind::ConfirmClose => (
            " Output CSV and Close ",
            "Output generated CSV to stdout and exit?\n\n  [y] Yes    [n] Cancel",
        ),
        ModalKind::ConfirmQuit => (
            " Quit Without Output ",
            "Quit without outputting anything?\n\n  [y] Yes    [n] Cancel",
        ),
    };

    let popup_width = 50u16;
    let popup_height = 7u16;
    let x = area.x + area.width.saturating_sub(popup_width) / 2;
    let y = area.y + area.height.saturating_sub(popup_height) / 2;
    let popup_area = Rect::new(
        x,
        y,
        popup_width.min(area.width),
        popup_height.min(area.height),
    );

    f.render_widget(Clear, popup_area);

    let color = match kind {
        ModalKind::ConfirmClose => Color::Cyan,
        ModalKind::ConfirmQuit => Color::Magenta,
    };

    let p = Paragraph::new(body)
        .block(
            Block::default()
                .title(title)
                .borders(Borders::ALL)
                .border_style(Style::default().fg(color).add_modifier(Modifier::BOLD)),
        )
        .style(Style::default().fg(C_HEADER));
    f.render_widget(p, popup_area);
}