//! Overlay: usage statistics — detailed token usage, API call count, edit/
//! review/lesson activity counters, and session elapsed time.
use crate::view::sidebar::compute_usage_summary;
use crate::view::theme::Theme;
use ratatui::style::{Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Paragraph};
use ratatui::Frame;
use tracing::debug;

/// Render the Usage overlay.
#[tracing::instrument(skip_all)]
pub fn render(
    frame: &mut Frame,
    area: ratatui::layout::Rect,
    block: Block<'static>,
    state: &crate::state::AppStateRest,
) {
    let has_runtime = state.session_runtime.is_some();
    debug!("Rendering Usage overlay, has runtime: {has_runtime}");
    let block = block
        .title(Span::styled(
            " Usage ",
            Style::default()
                .fg(Theme::INFO)
                .add_modifier(Modifier::BOLD),
        ))
        .border_style(Style::default().fg(Theme::INFO));
    let runtime = state.session_runtime.as_ref();
    let now_ms = chrono::Utc::now().timestamp_millis();
    let summary = runtime.map(|r| compute_usage_summary(&r.usage, r.session_start, now_ms));
    let (edit_count, lesson_count, review_count, consec_empty) =
        runtime.map_or((0, 0, 0, 0), |r| {
            (
                r.edit_count,
                r.lessons.total,
                r.review_count,
                r.consecutive_empty_reviews,
            )
        });
    let mut lines = vec![
        Line::from(Span::styled(
            "  Token Usage",
            Style::default()
                .fg(Theme::INFO)
                .add_modifier(Modifier::BOLD),
        )),
        Line::from(Span::raw("")),
    ];
    if let Some(s) = &summary {
        lines.push(Line::from(Span::styled(
            format!("  Main agent:     {} tokens", s.main_tokens),
            Style::default().fg(Theme::TEXT),
        )));
        lines.push(Line::from(Span::styled(
            format!("  Self-learning:  {} tokens", s.self_learning_tokens),
            Style::default().fg(Theme::TEXT_MUTED),
        )));
        lines.push(Line::from(Span::styled(
            format!("  Total:          {} tokens", s.total_tokens),
            Style::default()
                .fg(Theme::TEXT)
                .add_modifier(Modifier::BOLD),
        )));
        lines.push(Line::from(Span::styled(
            format!("  API calls:      {}", s.api_calls),
            Style::default().fg(Theme::TEXT),
        )));
    } else {
        lines.push(Line::from(Span::styled(
            "  No active session.",
            Style::default().fg(Theme::TEXT_DIM),
        )));
    }
    lines.push(Line::from(Span::raw("")));
    lines.push(Line::from(Span::styled(
        "  Activity",
        Style::default()
            .fg(Theme::INFO)
            .add_modifier(Modifier::BOLD),
    )));
    lines.push(Line::from(Span::styled(
        format!("  Edits:          {edit_count}"),
        Style::default().fg(Theme::TEXT),
    )));
    lines.push(Line::from(Span::styled(
        format!("  Reviews:        {review_count}"),
        Style::default().fg(Theme::TEXT),
    )));
    lines.push(Line::from(Span::styled(
        format!("  Lessons:        {lesson_count}"),
        Style::default().fg(Theme::TEXT_MUTED),
    )));
    lines.push(Line::from(Span::styled(
        format!("  Empty reviews:  {consec_empty}"),
        Style::default().fg(if consec_empty > 3 {
            Theme::WARNING
        } else {
            Theme::TEXT_DIM
        }),
    )));
    if let Some(s) = &summary {
        lines.push(Line::from(Span::raw("")));
        lines.push(Line::from(Span::styled(
            format!(
                "  Session: {}h {}m {}s",
                s.elapsed_hours, s.elapsed_minutes, s.elapsed_seconds
            ),
            Style::default().fg(Theme::TEXT_DIM),
        )));
    }
    let paragraph = Paragraph::new(lines).block(block);
    frame.render_widget(paragraph, area);
}