zesdex/src/view/chat.rs

#![allow(clippy::cast_possible_truncation, clippy::cast_sign_loss, clippy::cast_precision_loss, clippy::cast_possible_wrap)]
//! Chat transcript panel rendering — tight inline log style.
//!
//! Flow: `draw_chat` turns `state.transcript_cache.messages` into a dense,
//! log-like transcript: each non-tool message gets a one-line
//! `{role} {time}  {content}` header with wrapped continuation lines
//! aligned under the content column; `Role::Tool` messages render as a
//! dim `↳`-prefixed sub-line attached to whatever came before, with no
//! header of their own. A streaming spinner line is appended when a turn
//! is in flight. The combined line list is sliced to the visible scroll
//! window before rendering.
//!
//! Design: no per-message card/border/badge — role identity comes from a
//! short colored label, and vertical space is reserved for a blank line
//! only when the speaker actually changes (Tool sub-lines never count as
//! a speaker change), keeping more history on screen at once.

use ratatui::layout::Rect;
use ratatui::style::{Color, Style, Modifier};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Borders, Paragraph, Wrap};
use ratatui::Frame;
use super::theme::Theme;
use crate::dto::chat::message::Role;

/// Column width reserved for the `{role} {time}  ` header prefix; wrapped
/// continuation lines and Tool sub-lines indent to this width so content
/// stays aligned under the first line's content column.
const PREFIX_WIDTH: usize = 12;

/// Break a flat run of styled spans into `Line`s at embedded `\n` boundaries.
fn split_spans_into_lines(spans: Vec<Span<'_>>) -> Vec<Line<'_>> {
    let mut lines = Vec::new();
    let mut current_spans = Vec::new();

    for span in spans {
        let text = span.content.as_ref();
        let mut parts = text.split('\n').peekable();
        while let Some(part) = parts.next() {
            if !part.is_empty() {
                current_spans.push(Span::styled(part.to_string(), span.style));
            }
            if parts.peek().is_some() {
                lines.push(Line::from(std::mem::take(&mut current_spans)));
            }
        }
    }
    if !current_spans.is_empty() {
        lines.push(Line::from(current_spans));
    }
    if lines.is_empty() {
        lines.push(Line::from(vec![]));
    }
    lines
}

fn role_accent_color(role: &Role) -> Color {
    match role {
        Role::User => Theme::ROLE_USER,
        Role::Assistant => Theme::ROLE_ASSISTANT,
        Role::System => Theme::ROLE_SYSTEM,
        Role::Tool => Theme::ROLE_TOOL,
    }
}

/// Short lowercase label for the `{role} {time}` header column. Callers pad
/// it to a fixed width themselves (not padded here so tests can assert the
/// raw label).
fn format_role_label(role: &Role) -> &'static str {
    match role {
        Role::User => "you",
        Role::Assistant => "ai",
        Role::System => "sys",
        Role::Tool => "tool",
    }
}

fn format_timestamp(ts: i64) -> String {
    if ts <= 0 { return String::new(); }
    let secs = ts / 1000;
    let mins = (secs / 60) % 60;
    let hrs = (secs / 3600) % 24;
    format!("{hrs:02}:{mins:02}")
}

/// Whether a blank separator line should be inserted before rendering a
/// message from `role`, given the last non-Tool role that was rendered.
///
/// Why: `Role::Tool` messages render as an attached sub-line (see
/// `draw_chat`) and must never be passed as `prev_role` — a Tool message
/// never triggers a separator, and it never causes one to be inserted
/// before the next real turn either.
fn needs_speaker_separator(prev_role: Option<&Role>, role: &Role) -> bool {
    matches!(prev_role, Some(p) if p != role)
}

/// Render the scrollable chat transcript panel in tight inline-log style.
#[allow(clippy::too_many_lines)]
pub fn draw_chat(frame: &mut Frame, area: Rect, state: &crate::app::state::rest::AppStateRest) {
    let messages = &state.transcript_cache.messages;
    let scroll_offset = state.scroll.offset;
    let max_visible = (area.height as usize).saturating_sub(3);
    // Wrap width for content: total width minus the header/indent prefix
    // and minus the panel's left+right border columns.
    let content_width = area.width.saturating_sub(PREFIX_WIDTH as u16 + 2);

    let mut display_lines: Vec<Line> = Vec::new();
    let mut prev_role: Option<Role> = None;

    let title = if messages.is_empty() {
        String::from(" Chat ")
    } else {
        format!(" Chat  [{} msgs]", messages.len())
    };

    for msg in messages {
        let is_last = std::ptr::eq(msg, messages.last().unwrap());

        // Tool messages render as a dim sub-line attached to whatever came
        // before — no header, no speaker-change bookkeeping.
        if msg.role == Role::Tool {
            let content = if msg.content.trim().is_empty() {
                "(tool execution)".to_string()
            } else {
                msg.content.clone()
            };
            display_lines.push(Line::from(vec![
                Span::raw(" ".repeat(PREFIX_WIDTH)),
                Span::styled("↳ ", Style::default().fg(Theme::TEXT_DIM)),
                Span::styled(content, Style::default().fg(Theme::TEXT_DIM).add_modifier(Modifier::ITALIC)),
            ]));
            continue;
        }

        if needs_speaker_separator(prev_role.as_ref(), &msg.role) {
            display_lines.push(Line::from(Span::raw("")));
        }
        prev_role = Some(msg.role.clone());

        let accent = role_accent_color(&msg.role);
        let label = format_role_label(&msg.role);
        let ts_str = format_timestamp(msg.timestamp);
        let header_prefix = vec![
            Span::styled(format!("{label:<4} "), Style::default().fg(accent).add_modifier(Modifier::BOLD)),
            Span::styled(format!("{ts_str:<5}  "), Style::default().fg(Theme::TEXT_DIM)),
        ];

        let content_str = if msg.content.trim().is_empty() {
            if is_last && state.turn_in_flight() {
                "(streaming...)".to_string()
            } else {
                "(tool execution)".to_string()
            }
        } else {
            msg.content.clone()
        };

        let content_spans = super::markdown::render_markdown(&content_str, content_width);
        let content_lines = split_spans_into_lines(content_spans);
        let mut lines_iter = content_lines.into_iter();

        if let Some(first) = lines_iter.next() {
            let mut spans = header_prefix;
            spans.extend(first.spans);
            display_lines.push(Line::from(spans));
        } else {
            display_lines.push(Line::from(header_prefix));
        }

        for line in lines_iter {
            let mut spans = vec![Span::raw(" ".repeat(PREFIX_WIDTH))];
            spans.extend(line.spans);
            display_lines.push(Line::from(spans));
        }
    }

    // ── Streaming indicator ──────────────────────────────────────────────
    if state.turn_in_flight() {
        let spinner_frames = ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"];
        let frame_idx = (state.misc.tick_count as usize / 2) % spinner_frames.len();
        let spinner = spinner_frames[frame_idx];

        if needs_speaker_separator(prev_role.as_ref(), &Role::Assistant) {
            display_lines.push(Line::from(Span::raw("")));
        }
        display_lines.push(Line::from(vec![
            Span::styled(
                format!("{:<4} ", format_role_label(&Role::Assistant)),
                Style::default().fg(Theme::ROLE_ASSISTANT).add_modifier(Modifier::BOLD),
            ),
            Span::styled(format!("{spinner}  "), Style::default().fg(Theme::TEXT_DIM)),
            Span::styled("generating...", Style::default().fg(Theme::TEXT_MUTED).add_modifier(Modifier::ITALIC)),
        ]));
    }

    // ── Scrolling ────────────────────────────────────────────────────────
    let block = Block::default()
        .borders(Borders::ALL)
        .border_style(Style::default().fg(Theme::BORDER))
        .title(Span::styled(title, Style::default().fg(Theme::TEXT_MUTED)));

    let total = display_lines.len();
    let max_offset = total.saturating_sub(max_visible);
    let offset = scroll_offset.min(max_offset);

    let end_idx = total.saturating_sub(offset);
    let start_idx = end_idx.saturating_sub(max_visible);
    let visible: Vec<Line> = if start_idx < end_idx && start_idx < total {
        display_lines[start_idx..end_idx].to_vec()
    } else {
        display_lines[total.saturating_sub(max_visible)..total].to_vec()
    };

    let scroll_pct = if total > max_visible {
        ((offset as f64 / max_offset as f64) * 100.0) as u8
    } else {
        0
    };

    let block = if scroll_pct > 0 {
        let scroll_title = format!(" Chat  [{} msgs]  ── {}% ↑ ", messages.len(), scroll_pct);
        Block::default()
            .borders(Borders::ALL)
            .border_style(Style::default().fg(Theme::BORDER))
            .title(Span::styled(scroll_title, Style::default().fg(Theme::TEXT_MUTED)))
    } else {
        block
    };

    let paragraph = Paragraph::new(visible)
        .block(block)
        .style(Style::default().bg(Theme::BG))
        .wrap(Wrap { trim: false });

    frame.render_widget(paragraph, area);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn no_separator_when_no_previous_message() {
        assert!(!needs_speaker_separator(None, &Role::User));
    }

    #[test]
    fn no_separator_when_same_speaker_repeats() {
        assert!(!needs_speaker_separator(Some(&Role::Assistant), &Role::Assistant));
    }

    #[test]
    fn separator_when_speaker_changes() {
        assert!(needs_speaker_separator(Some(&Role::User), &Role::Assistant));
    }

    #[test]
    fn role_labels_are_lowercase_and_fit_prefix_width() {
        assert_eq!(format_role_label(&Role::User), "you");
        assert_eq!(format_role_label(&Role::Assistant), "ai");
        assert_eq!(format_role_label(&Role::System), "sys");
        assert_eq!(format_role_label(&Role::Tool), "tool");
        for role in [Role::User, Role::Assistant, Role::System, Role::Tool] {
            assert!(format_role_label(&role).len() <= 4);
        }
    }
}