//! Promo code management screen — list, create, delete codes.

use makeover_tui::makeover_layout::{Column, Priority, Width};
use makeover_tui::table::{self, Cell, Sizing, TableStyle};
use ratatui::Frame;
use ratatui::layout::{Constraint, Layout, Rect};
use ratatui::style::{Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Borders, Paragraph, TableState};

use super::App;
use crate::currency::Currency;
use crate::format;

/// The promo code columns. A code and what it takes off are the row; what it
/// applies to and how many times it has been used qualify it.
const CODE_COLUMNS: [Column<'static>; 4] = [
    Column {
        name: "Code",
        width: Width::Fill,
        priority: Priority::Essential,
        sortable: false,
        sorted: None,
    },
    Column {
        name: "Discount",
        width: Width::Fixed,
        priority: Priority::Essential,
        sortable: false,
        sorted: None,
    },
    Column {
        name: "Scope",
        width: Width::Fixed,
        priority: Priority::Secondary,
        sortable: false,
        sorted: None,
    },
    Column {
        name: "Uses",
        width: Width::Fixed,
        priority: Priority::Optional,
        sortable: false,
        sorted: None,
    },
];

/// The tracks the hand-written `Constraint`s carried.
const CODE_SIZING: Sizing<'static> = Sizing {
    lengths: &[("Code", 16), ("Discount", 12), ("Scope", 20), ("Uses", 10)],
    fallback: 10,
};

pub(crate) fn render(frame: &mut Frame, app: &App) {
    let area = frame.area();

    let title = Line::from(vec![
        Span::styled(
            " Makenot.work ",
            Style::default().add_modifier(Modifier::BOLD),
        ),
        Span::raw(" -- "),
        Span::styled("Promo Codes", Style::default().add_modifier(Modifier::BOLD)),
        Span::raw(" "),
    ]);

    let block = Block::default()
        .title(title)
        .borders(Borders::ALL)
        .border_style(Style::default().fg(app.theme.line_border));

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

    let chunks = Layout::vertical([
        Constraint::Length(1), // spacer
        Constraint::Length(1), // section header
        Constraint::Min(3),    // code list
        Constraint::Length(1), // status line
        Constraint::Length(1), // keybindings
    ])
    .split(inner);

    // Section header
    let count = app.promo_codes.len();
    let header = Paragraph::new(Line::from(vec![
        Span::raw("  "),
        Span::styled("Codes", Style::default().add_modifier(Modifier::BOLD)),
        if count == 0 {
            Span::raw("")
        } else {
            Span::raw(format!(" ({count})"))
        },
    ]));
    frame.render_widget(header, chunks[1]);

    // Code list
    if app.loading {
        let loading = Paragraph::new("  Loading...");
        frame.render_widget(loading, chunks[2]);
    } else if app.promo_codes.is_empty() {
        let empty = Paragraph::new("  No promo codes. Press [n] to create one.");
        frame.render_widget(empty, chunks[2]);
    } else {
        render_code_table(frame, app, chunks[2]);
    }

    // Status line
    if let Some(ref status) = app.promo_status {
        let style = if status.starts_with("Error") {
            Style::default().fg(app.theme.status_danger)
        } else {
            Style::default().fg(app.theme.status_success)
        };
        let status_line = Paragraph::new(Line::from(vec![
            Span::raw("  "),
            Span::styled(status.as_str(), style),
        ]));
        frame.render_widget(status_line, chunks[3]);
    }

    // Keybindings
    let editing = app.promo_editing_step.is_some();
    let mut key_spans = vec![Span::raw("  ")];

    if editing {
        key_spans.extend([
            Span::styled("[Enter]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" Confirm  "),
            Span::styled("[Esc]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" Cancel"),
        ]);
    } else {
        key_spans.extend([
            Span::styled("[j/k]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" Nav  "),
            Span::styled("[n]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" New  "),
        ]);
        if !app.promo_codes.is_empty() {
            key_spans.extend([
                Span::styled("[d]", Style::default().add_modifier(Modifier::BOLD)),
                Span::raw(" Delete  "),
            ]);
        }
        key_spans.extend([
            Span::styled("[r]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" Refresh  "),
            Span::styled("[Esc]", Style::default().add_modifier(Modifier::BOLD)),
            Span::raw(" Back"),
        ]);
    }

    let keys =
        Paragraph::new(Line::from(key_spans)).style(Style::default().fg(app.theme.content_muted));
    frame.render_widget(keys, chunks[4]);
}

fn render_code_table(frame: &mut Frame, app: &App, area: Rect) {
    let area = super::indent(area, 2);

    let rows: Vec<Vec<Cell>> = app
        .promo_codes
        .iter()
        .map(|code| {
            let discount = format_discount(
                code.discount_type.as_deref(),
                code.discount_value,
                app.currency(),
            );
            let scope = code
                .item_title
                .as_deref()
                .or(code.project_title.as_deref())
                .unwrap_or("All items");
            let uses = match code.max_uses {
                Some(max) => format!("{}/{}", code.use_count, max),
                None => code.use_count.to_string(),
            };

            vec![
                Cell::new("Code", code.code.as_str()),
                Cell::new("Discount", discount),
                Cell::new("Scope", scope),
                Cell::new("Uses", uses),
            ]
        })
        .collect();

    let style = TableStyle::from_theme(&app.theme);
    let table = table::table(&CODE_COLUMNS, &rows, &CODE_SIZING, &style, area.width);
    let mut state = TableState::default().with_selected(Some(app.selected_index));
    frame.render_stateful_widget(table, area, &mut state);
}

/// A promo discount: a percentage, or an amount off in the creator's own
/// currency. A fixed discount is denominated the same as the price it comes
/// off, so it takes the same currency rather than a bare dollar sign.
fn format_discount(dtype: Option<&str>, value: Option<i32>, currency: Currency) -> String {
    match (dtype, value) {
        (Some("percentage"), Some(v)) => format!("{v}% off"),
        (Some("fixed"), Some(v)) => format!("{} off", format::format_cents(i64::from(v), currency)),
        _ => "Free".to_string(),
    }
}