// widgets.rs — Shared TUI helpers and reusable components

use ratatui::{
    layout::{Margin, Rect},
    style::{Color, Modifier, Style},
    text::Line,
    widgets::{Block, Borders, Paragraph, Scrollbar, ScrollbarOrientation, ScrollbarState, Wrap},
    Frame,
    crossterm::event::KeyCode,
};
use crate::agent::context::{ContextSection, ConversationEntry};

/// UI-only tree node for the section tree display.
/// Built from ContextSection data; not used for budgeting.
#[derive(Debug, Clone)]
pub struct SectionView {
    pub name: String,
    pub tokens: usize,
    pub content: String,
    pub children: Vec<SectionView>,
    /// Extra status text shown after the token count.
    pub status: String,
}

/// Build a SectionView tree from a ContextSection.
/// Each entry becomes a child with label + expandable content.
pub fn section_to_view(section: &ContextSection) -> SectionView {
    let children: Vec<SectionView> = section.entries().iter().map(|ce| {
        let content = match &ce.entry {
            ConversationEntry::Log(_) => String::new(),
            ConversationEntry::Thinking(text) => text.clone(),
            _ => ce.entry.message().content_text().to_string(),
        };
        SectionView {
            name: ce.entry.label(),
            tokens: ce.tokens(),
            content,
            children: Vec::new(),
            status: String::new(),
        }
    }).collect();
    SectionView {
        name: section.name.clone(),
        tokens: section.tokens(),
        content: String::new(),
        children,
        status: String::new(),
    }
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

/// Standard pane block — cyan border, right-aligned title.
pub fn pane_block(title: &str) -> Block<'_> {
    Block::default()
        .title_top(Line::from(format!(" {} ", title)).right_aligned())
        .borders(Borders::ALL)
        .border_style(Style::default().fg(Color::Cyan))
}

/// Focused pane block — brighter border to indicate focus.
pub fn pane_block_focused(title: &str, focused: bool) -> Block<'_> {
    let color = if focused { Color::White } else { Color::Cyan };
    Block::default()
        .title_top(Line::from(format!(" {} ", title)).right_aligned())
        .borders(Borders::ALL)
        .border_style(Style::default().fg(color))
}

/// Format a duration in seconds as a compact human-readable string.
pub fn format_age(secs: f64) -> String {
    if secs < 60.0 { format!("{:.0}s", secs) }
    else if secs < 3600.0 { format!("{:.0}m", secs / 60.0) }
    else if secs < 86400.0 { format!("{:.1}h", secs / 3600.0) }
    else { format!("{:.0}d", secs / 86400.0) }
}

/// Format a unix epoch timestamp as age from now.
pub fn format_ts_age(ts: i64) -> String {
    let now = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .unwrap_or_default()
        .as_secs() as i64;
    format_age((now - ts).max(0) as f64)
}

/// Key legend for SectionTree panes.
pub fn tree_legend() -> Line<'static> {
    Line::styled(
        " ↑↓:nav  →/Enter:expand  ←:collapse  e:expand all  c:collapse all  PgUp/Dn  Home/End ",
        Style::default().fg(Color::DarkGray),
    )
}

/// Render a paragraph with a vertical scrollbar.
pub fn render_scrollable(
    frame: &mut Frame,
    area: Rect,
    lines: Vec<Line<'_>>,
    block: Block<'_>,
    scroll: u16,
) {
    let content_len = lines.len();
    let para = Paragraph::new(lines)
        .block(block)
        .wrap(Wrap { trim: false })
        .scroll((scroll, 0));
    frame.render_widget(para, area);

    let visible = area.height.saturating_sub(2) as usize;
    if content_len > visible {
        let mut sb_state = ScrollbarState::new(content_len)
            .position(scroll as usize);
        frame.render_stateful_widget(
            Scrollbar::new(ScrollbarOrientation::VerticalRight),
            area.inner(Margin { vertical: 1, horizontal: 0 }),
            &mut sb_state,
        );
    }
}

// ---------------------------------------------------------------------------
// SectionTree — expand/collapse tree renderer for ContextSection
// ---------------------------------------------------------------------------

pub struct SectionTree {
    pub selected: Option<usize>,
    pub expanded: std::collections::HashSet<usize>,
    pub scroll: u16,
}

impl SectionTree {
    pub fn new() -> Self {
        Self { selected: None, expanded: std::collections::HashSet::new(), scroll: 0 }
    }

    fn total_nodes(&self, sections: &[SectionView]) -> usize {
        fn count_all(s: &SectionView) -> usize {
            1 + s.children.iter().map(|c| count_all(c)).sum::<usize>()
        }
        sections.iter().map(|s| count_all(s)).sum()
    }

    pub fn item_count(&self, sections: &[SectionView]) -> usize {
        fn count(section: &SectionView, expanded: &std::collections::HashSet<usize>, idx: &mut usize) -> usize {
            let my_idx = *idx;
            *idx += 1;
            let mut total = 1;
            if expanded.contains(&my_idx) {
                for child in &section.children {
                    total += count(child, expanded, idx);
                }
            }
            total
        }
        let mut idx = 0;
        sections.iter().map(|s| count(s, &self.expanded, &mut idx)).sum()
    }

    pub fn handle_nav(&mut self, code: KeyCode, sections: &[SectionView], height: u16) {
        let item_count = self.item_count(sections);
        let page = height.saturating_sub(2) as usize;
        match code {
            KeyCode::Up => {
                self.selected = Some(self.selected.unwrap_or(0).saturating_sub(1));
            }
            KeyCode::Down => {
                let max = item_count.saturating_sub(1);
                self.selected = Some(self.selected.map_or(0, |s| (s + 1).min(max)));
            }
            KeyCode::PageUp => {
                let sel = self.selected.unwrap_or(0);
                self.selected = Some(sel.saturating_sub(page));
                self.scroll = self.scroll.saturating_sub(page as u16);
                return;
            }
            KeyCode::PageDown => {
                let max = item_count.saturating_sub(1);
                let sel = self.selected.map_or(0, |s| (s + page).min(max));
                self.selected = Some(sel);
                self.scroll += page as u16;
                return;
            }
            KeyCode::Home => {
                self.selected = Some(0);
            }
            KeyCode::End => {
                self.selected = Some(item_count.saturating_sub(1));
            }
            KeyCode::Right | KeyCode::Enter => {
                if let Some(sel) = self.selected {
                    self.expanded.insert(sel);
                }
            }
            KeyCode::Left => {
                if let Some(sel) = self.selected {
                    self.expanded.remove(&sel);
                }
            }
            KeyCode::Char('e') => {
                let total = self.total_nodes(sections);
                for i in 0..total {
                    self.expanded.insert(i);
                }
            }
            KeyCode::Char('c') => {
                self.expanded.clear();
            }
            _ => {}
        }
        self.scroll_to_selected(height);
    }

    fn scroll_to_selected(&mut self, height: u16) {
        if let Some(sel) = self.selected {
            let sel_line = sel as u16;
            let visible = height.saturating_sub(2);
            if sel_line < self.scroll {
                self.scroll = sel_line;
            } else if sel_line >= self.scroll + visible {
                self.scroll = sel_line.saturating_sub(visible.saturating_sub(1));
            }
        }
    }

    pub fn render_sections(&self, sections: &[SectionView], lines: &mut Vec<Line>) {
        let mut idx = 0;
        for section in sections {
            self.render_one(section, 0, lines, &mut idx);
        }
    }

    fn render_one(
        &self,
        section: &SectionView,
        depth: usize,
        lines: &mut Vec<Line>,
        idx: &mut usize,
    ) {
        let my_idx = *idx;
        let selected = self.selected == Some(my_idx);
        let expanded = self.expanded.contains(&my_idx);
        let has_children = !section.children.is_empty();
        let has_content = !section.content.is_empty();
        let expandable = has_children || has_content;

        let indent = "  ".repeat(depth + 1);
        let marker = if !expandable { " " } else if expanded { "▼" } else { "▶" };
        let name_col = format!("{}{} {}", indent, marker, section.name);
        let tokens_col = format!("{:>6} tokens", section.tokens);
        let label = if section.status.is_empty() {
            format!("{:40} {}", name_col, tokens_col)
        } else {
            format!("{:40} {:16} {}", name_col, tokens_col, section.status)
        };
        let style = if selected {
            Style::default().fg(Color::Yellow).add_modifier(Modifier::BOLD)
        } else {
            Style::default()
        };
        lines.push(Line::styled(label, style));
        *idx += 1;

        if expanded {
            if has_children {
                for child in &section.children {
                    self.render_one(child, depth + 1, lines, idx);
                }
            } else if has_content {
                let content_indent = format!("{}    │ ", "  ".repeat(depth + 1));
                let content_lines: Vec<&str> = section.content.lines().collect();
                let show = content_lines.len().min(50);
                for line in &content_lines[..show] {
                    lines.push(Line::styled(
                        format!("{}{}", content_indent, line),
                        Style::default().fg(Color::DarkGray),
                    ));
                }
                if content_lines.len() > 50 {
                    lines.push(Line::styled(
                        format!("{}... ({} more lines)", content_indent, content_lines.len() - 50),
                        Style::default().fg(Color::DarkGray),
                    ));
                }
            }
        }
    }
}