feat(tui): add markdown table parsing and rendering

Implemented full markdown table support:
- Parse tables with headers, rows, and alignment.
- Render tables as a grid when width permits, falling back to a stacked layout for narrow widths.
- Added helper structs (`ParsedTable`, `TableAlignment`) and functions for splitting rows, parsing alignments, column width constraints, cell alignment, and wrapping.
- Integrated table rendering into `render_markdown_lines`.
- Added unit tests for grid rendering and narrow fallback behavior.

crates/owlen-tui/src/chat_app.rs

@@ -8630,6 +8630,57 @@ fn render_markdown_lines(
     base_style: Style,
 ) -> Vec<Line<'static>> {
     let width = available_width.max(1);
+    let lines: Vec<&str> = if markdown.is_empty() {
+        Vec::new()
+    } else {
+        markdown.lines().collect()
+    };
+
+    if lines.is_empty() {
+        return render_markdown_text_block(markdown, indent, width, base_style);
+    }
+
+    let mut output: Vec<Line<'static>> = Vec::new();
+    let mut buffer: Vec<&str> = Vec::new();
+    let mut index = 0usize;
+
+    while index < lines.len() {
+        if let Some((table, next_index)) = parse_markdown_table(&lines, index) {
+            if !buffer.is_empty() {
+                let block = buffer.join("\n");
+                output.extend(render_markdown_text_block(
+                    &block, indent, width, base_style,
+                ));
+                buffer.clear();
+            }
+            output.extend(render_markdown_table(&table, indent, width, base_style));
+            index = next_index;
+        } else {
+            buffer.push(lines[index]);
+            index += 1;
+        }
+    }
+
+    if !buffer.is_empty() {
+        let block = buffer.join("\n");
+        output.extend(render_markdown_text_block(
+            &block, indent, width, base_style,
+        ));
+    }
+
+    if output.is_empty() {
+        output.extend(render_markdown_text_block("", indent, width, base_style));
+    }
+
+    output
+}
+
+fn render_markdown_text_block(
+    markdown: &str,
+    indent: &str,
+    width: usize,
+    base_style: Style,
+) -> Vec<Line<'static>> {
     let mut text = from_str(markdown);
     let mut output: Vec<Line<'static>> = Vec::new();
 
@@ -8652,15 +8703,682 @@ fn render_markdown_lines(
     }
 
     if output.is_empty() {
+        output.push(blank_line(indent, base_style));
+    }
+
+    output
+}
+
+#[derive(Debug)]
+struct ParsedTable {
+    headers: Vec<String>,
+    rows: Vec<Vec<String>>,
+    alignments: Vec<TableAlignment>,
+}
+
+#[derive(Clone, Copy, Debug)]
+enum TableAlignment {
+    Left,
+    Center,
+    Right,
+}
+
+fn parse_markdown_table(lines: &[&str], start: usize) -> Option<(ParsedTable, usize)> {
+    if start + 1 >= lines.len() {
+        return None;
+    }
+
+    let header_line = lines[start].trim();
+    let alignment_line = lines[start + 1].trim();
+
+    if header_line.is_empty() || !header_line.contains('|') {
+        return None;
+    }
+
+    let headers = split_table_row(header_line);
+    if headers.is_empty() {
+        return None;
+    }
+
+    let alignments = parse_alignment_row(alignment_line, headers.len())?;
+    let mut rows = Vec::new();
+    let mut index = start + 2;
+
+    while index < lines.len() {
+        let raw = lines[index];
+        let trimmed = raw.trim();
+
+        if trimmed.is_empty() || !trimmed.contains('|') {
+            break;
+        }
+
+        if trimmed
+            .chars()
+            .all(|ch| matches!(ch, '-' | ':' | '|' | ' '))
+        {
+            break;
+        }
+
+        let mut cells = split_table_row(trimmed);
+        if cells.iter().all(|cell| cell.is_empty()) {
+            break;
+        }
+
+        if cells.len() < headers.len() {
+            cells.resize(headers.len(), String::new());
+        } else if cells.len() > headers.len() {
+            cells.truncate(headers.len());
+        }
+
+        rows.push(cells);
+        index += 1;
+    }
+
+    Some((
+        ParsedTable {
+            headers,
+            rows,
+            alignments,
+        },
+        index,
+    ))
+}
+
+fn split_table_row(line: &str) -> Vec<String> {
+    let trimmed = line.trim();
+    if trimmed.is_empty() {
+        return vec![String::new()];
+    }
+
+    let mut chars = trimmed.chars().peekable();
+    // Discard a single leading pipe if present.
+    if matches!(chars.peek(), Some('|')) {
+        chars.next();
+    }
+
+    let mut cells = Vec::new();
+    let mut current = String::new();
+    let mut escape = false;
+
+    for ch in chars {
+        if escape {
+            current.push(ch);
+            escape = false;
+            continue;
+        }
+        match ch {
+            '\\' => {
+                escape = true;
+            }
+            '|' => {
+                cells.push(current.trim().to_string());
+                current.clear();
+            }
+            _ => current.push(ch),
+        }
+    }
+
+    if escape {
+        current.push('\\');
+    }
+
+    if !trimmed.ends_with('|') || !current.trim().is_empty() {
+        cells.push(current.trim().to_string());
+    }
+
+    if cells.is_empty() {
+        cells.push(String::new());
+    }
+
+    cells
+}
+
+fn parse_alignment_row(line: &str, expected_columns: usize) -> Option<Vec<TableAlignment>> {
+    let trimmed = line.trim();
+    if trimmed.is_empty() || !trimmed.contains('-') {
+        return None;
+    }
+
+    let raw_cells = split_table_row(trimmed);
+    if raw_cells.len() != expected_columns {
+        return None;
+    }
+
+    let mut alignments = Vec::with_capacity(expected_columns);
+    for cell in raw_cells {
+        let cell_trimmed = cell.trim();
+        if cell_trimmed.is_empty() {
+            alignments.push(TableAlignment::Left);
+            continue;
+        }
+
+        if !cell_trimmed.chars().all(|ch| matches!(ch, '-' | ':' | ' ')) {
+            return None;
+        }
+
+        if !cell_trimmed.contains('-') {
+            return None;
+        }
+
+        let left = cell_trimmed.starts_with(':');
+        let right = cell_trimmed.ends_with(':');
+        let alignment = match (left, right) {
+            (true, true) => TableAlignment::Center,
+            (false, true) => TableAlignment::Right,
+            _ => TableAlignment::Left,
+        };
+        alignments.push(alignment);
+    }
+
+    Some(alignments)
+}
+
+fn render_markdown_table(
+    table: &ParsedTable,
+    indent: &str,
+    available_width: usize,
+    base_style: Style,
+) -> Vec<Line<'static>> {
+    const MIN_CELL_WIDTH: usize = 3;
+
+    if table.headers.is_empty() {
+        return render_markdown_text_block("", indent, available_width.max(1), base_style);
+    }
+
+    let indent_width = UnicodeWidthStr::width(indent);
+    let padding_cost = 1 + table.headers.len() * 3;
+    let available_content = available_width.saturating_sub(indent_width + padding_cost);
+
+    if available_content < table.headers.len().saturating_mul(MIN_CELL_WIDTH) {
+        return render_markdown_table_stacked(table, indent, available_width, base_style);
+    }
+
+    let mut desired_widths = vec![MIN_CELL_WIDTH; table.headers.len()];
+    for (index, header) in table.headers.iter().enumerate() {
+        desired_widths[index] = desired_widths[index].max(cell_display_width(header));
+    }
+    for row in &table.rows {
+        for (index, cell) in row.iter().enumerate().take(desired_widths.len()) {
+            desired_widths[index] = desired_widths[index].max(cell_display_width(cell));
+        }
+    }
+
+    let constrained = constrain_column_widths(&desired_widths, available_content, MIN_CELL_WIDTH)
+        .unwrap_or_else(|| vec![MIN_CELL_WIDTH; table.headers.len()]);
+
+    if constrained.iter().sum::<usize>() > available_content {
+        return render_markdown_table_stacked(table, indent, available_width, base_style);
+    }
+
+    render_markdown_table_grid(table, indent, available_width, base_style, &constrained)
+}
+
+fn render_markdown_table_grid(
+    table: &ParsedTable,
+    indent: &str,
+    available_width: usize,
+    base_style: Style,
+    column_widths: &[usize],
+) -> Vec<Line<'static>> {
+    let mut output = Vec::new();
+    output.extend(render_table_summary_lines(
+        table,
+        indent,
+        available_width,
+        base_style,
+    ));
+    output.push(blank_line(indent, base_style));
+
+    output.push(build_table_border_line(
+        '┌',
+        '┬',
+        '┐',
+        column_widths,
+        indent,
+        base_style,
+    ));
+
+    let header_styles = vec![base_style.add_modifier(Modifier::BOLD); table.headers.len()];
+    output.extend(render_table_row_lines(
+        &table.headers,
+        column_widths,
+        &table.alignments,
+        indent,
+        base_style,
+        &header_styles,
+    ));
+
+    if table.rows.is_empty() {
+        output.push(build_table_border_line(
+            '└',
+            '┴',
+            '┘',
+            column_widths,
+            indent,
+            base_style,
+        ));
+        return output;
+    }
+
+    output.push(build_table_border_line(
+        '├',
+        '┼',
+        '┤',
+        column_widths,
+        indent,
+        base_style,
+    ));
+
+    let body_styles = vec![base_style; table.headers.len()];
+    for (index, row) in table.rows.iter().enumerate() {
+        output.extend(render_table_row_lines(
+            row,
+            column_widths,
+            &table.alignments,
+            indent,
+            base_style,
+            &body_styles,
+        ));
+
+        if index == table.rows.len() - 1 {
+            output.push(build_table_border_line(
+                '└',
+                '┴',
+                '┘',
+                column_widths,
+                indent,
+                base_style,
+            ));
+        } else {
+            output.push(build_table_border_line(
+                '├',
+                '┼',
+                '┤',
+                column_widths,
+                indent,
+                base_style,
+            ));
+        }
+    }
+
+    output
+}
+
+fn render_markdown_table_stacked(
+    table: &ParsedTable,
+    indent: &str,
+    available_width: usize,
+    base_style: Style,
+) -> Vec<Line<'static>> {
+    let mut output = Vec::new();
+    output.extend(render_table_summary_lines(
+        table,
+        indent,
+        available_width,
+        base_style,
+    ));
+
+    if table.rows.is_empty() {
+        output.push(blank_line(indent, base_style));
+        let mut spans = Vec::new();
+        if !indent.is_empty() {
+            spans.push(Span::styled(indent.to_string(), base_style));
+        }
+        spans.push(Span::styled(
+            "(No rows)",
+            base_style.add_modifier(Modifier::ITALIC),
+        ));
+        output.push(Line::from(spans));
+        return output;
+    }
+
+    output.push(blank_line(indent, base_style));
+
+    let indent_width = UnicodeWidthStr::width(indent);
+    let available = available_width.saturating_sub(indent_width).max(1);
+    let header_style = base_style.add_modifier(Modifier::BOLD);
+
+    for (row_index, row) in table.rows.iter().enumerate() {
+        if row_index > 0 {
+            output.push(blank_line(indent, base_style));
+        }
+
+        for (column_index, header) in table.headers.iter().enumerate() {
+            let value = row.get(column_index).map(String::as_str).unwrap_or("");
+            let bullet_prefix = if column_index == 0 {
+                format!("• {}: ", header)
+            } else {
+                format!("  {}: ", header)
+            };
+            let prefix_width = UnicodeWidthStr::width(bullet_prefix.as_str());
+            let value_width = available.saturating_sub(prefix_width);
+
+            if value_width == 0 {
+                let mut spans = Vec::new();
+                if !indent.is_empty() {
+                    spans.push(Span::styled(indent.to_string(), base_style));
+                }
+                spans.push(Span::styled(bullet_prefix.clone(), header_style));
+                output.push(Line::from(spans));
+
+                let wrapped_values = wrap_table_cell(value, available.max(1));
+                for wrapped in wrapped_values {
+                    let mut continuation = Vec::new();
+                    if !indent.is_empty() {
+                        continuation.push(Span::styled(indent.to_string(), base_style));
+                    }
+                    continuation.push(Span::styled(" ".repeat(prefix_width), header_style));
+                    continuation.push(Span::styled(wrapped, base_style));
+                    output.push(Line::from(continuation));
+                }
+                continue;
+            }
+
+            let wrapped_values = wrap_table_cell(value, value_width.max(1));
+            for (line_index, wrapped) in wrapped_values.into_iter().enumerate() {
+                let mut spans = Vec::new();
+                if !indent.is_empty() {
+                    spans.push(Span::styled(indent.to_string(), base_style));
+                }
+                if line_index == 0 {
+                    spans.push(Span::styled(bullet_prefix.clone(), header_style));
+                } else {
+                    spans.push(Span::styled(" ".repeat(prefix_width), header_style));
+                }
+                spans.push(Span::styled(wrapped, base_style));
+                output.push(Line::from(spans));
+            }
+        }
+    }
+
+    output
+}
+
+fn render_table_summary_lines(
+    table: &ParsedTable,
+    indent: &str,
+    available_width: usize,
+    base_style: Style,
+) -> Vec<Line<'static>> {
+    let mut output = Vec::new();
+    let indent_width = UnicodeWidthStr::width(indent);
+    let summary_width = available_width.saturating_sub(indent_width).max(1);
+
+    let column_list = if table.headers.is_empty() {
+        String::from("No columns")
+    } else {
+        table.headers.join(", ")
+    };
+
+    let row_count = table.rows.len();
+    let prefix = if row_count == 0 {
+        "Table:".to_string()
+    } else if row_count == 1 {
+        "Table (1 row):".to_string()
+    } else {
+        format!("Table ({} rows):", row_count)
+    };
+
+    let prefix_width = UnicodeWidthStr::width(prefix.as_str());
+    if summary_width <= prefix_width + 1 {
+        let mut combined = prefix.clone();
+        if !column_list.is_empty() {
+            combined.push(' ');
+            combined.push_str(&column_list);
+        }
+        let wrapped = {
+            let mut result = wrap_unicode(combined.as_str(), summary_width);
+            if result.is_empty() {
+                result.push(String::new());
+            }
+            result
+        };
+        for (index, text) in wrapped.into_iter().enumerate() {
+            let mut spans = Vec::new();
+            if !indent.is_empty() {
+                spans.push(Span::styled(indent.to_string(), base_style));
+            }
+            let style = if index == 0 {
+                base_style.add_modifier(Modifier::BOLD)
+            } else {
+                base_style
+            };
+            spans.push(Span::styled(text, style));
+            output.push(Line::from(spans));
+        }
+        return output;
+    }
+
+    let rest_width = summary_width.saturating_sub(prefix_width + 1).max(1);
+    let mut rest_lines = if column_list.is_empty() {
+        vec![String::new()]
+    } else {
+        let mut wrapped = wrap_unicode(column_list.as_str(), rest_width);
+        if wrapped.is_empty() {
+            wrapped.push(String::new());
+        }
+        wrapped
+    };
+
+    for (index, text) in rest_lines.drain(..).enumerate() {
+        let mut spans = Vec::new();
+        if !indent.is_empty() {
+            spans.push(Span::styled(indent.to_string(), base_style));
+        }
+        if index == 0 {
+            spans.push(Span::styled(
+                format!("{prefix} "),
+                base_style.add_modifier(Modifier::BOLD),
+            ));
+            spans.push(Span::styled(text, base_style));
+        } else {
+            spans.push(Span::styled(" ".repeat(prefix_width + 1), base_style));
+            spans.push(Span::styled(text, base_style));
+        }
+        output.push(Line::from(spans));
+    }
+
+    output
+}
+
+fn build_table_border_line(
+    left: char,
+    mid: char,
+    right: char,
+    column_widths: &[usize],
+    indent: &str,
+    base_style: Style,
+) -> Line<'static> {
+    let mut line = String::new();
+    line.push(left);
+    for (index, width) in column_widths.iter().enumerate() {
+        line.push_str(&"─".repeat(width + 2));
+        if index == column_widths.len() - 1 {
+            line.push(right);
+        } else {
+            line.push(mid);
+        }
+    }
+
+    let mut spans = Vec::new();
+    if !indent.is_empty() {
+        spans.push(Span::styled(indent.to_string(), base_style));
+    }
+    spans.push(Span::styled(line, base_style));
+    Line::from(spans)
+}
+
+fn render_table_row_lines(
+    cells: &[String],
+    column_widths: &[usize],
+    alignments: &[TableAlignment],
+    indent: &str,
+    border_style: Style,
+    cell_styles: &[Style],
+) -> Vec<Line<'static>> {
+    let column_count = column_widths.len();
+    let mut column_lines: Vec<Vec<String>> = Vec::with_capacity(column_count);
+
+    for (index, width) in column_widths.iter().enumerate() {
+        let cell = cells.get(index).map(String::as_str).unwrap_or("");
+        column_lines.push(wrap_table_cell(cell, (*width).max(1)));
+    }
+
+    let max_height = column_lines
+        .iter()
+        .map(|lines| lines.len())
+        .max()
+        .unwrap_or(1);
+
+    let mut output = Vec::with_capacity(max_height);
+    for line_index in 0..max_height {
+        let mut spans = Vec::new();
+        if !indent.is_empty() {
+            spans.push(Span::styled(indent.to_string(), border_style));
+        }
+        spans.push(Span::styled("│".to_string(), border_style));
+
+        for (column_index, width) in column_widths.iter().enumerate() {
+            let content = column_lines
+                .get(column_index)
+                .and_then(|lines| lines.get(line_index))
+                .map(|s| s.as_str())
+                .unwrap_or("");
+            let alignment = alignments
+                .get(column_index)
+                .copied()
+                .unwrap_or(TableAlignment::Left);
+            let aligned = align_cell_line(alignment, content, *width);
+            let cell_style = cell_styles
+                .get(column_index)
+                .copied()
+                .unwrap_or(border_style);
+
+            spans.push(Span::styled(" ".to_string(), border_style));
+            spans.push(Span::styled(aligned, cell_style));
+            spans.push(Span::styled(" ".to_string(), border_style));
+            spans.push(Span::styled("│".to_string(), border_style));
+        }
+
+        output.push(Line::from(spans));
+    }
+
+    output
+}
+
+fn align_cell_line(alignment: TableAlignment, content: &str, width: usize) -> String {
+    let display_width = UnicodeWidthStr::width(content);
+    if display_width >= width {
+        return content.to_string();
+    }
+
+    let padding = width - display_width;
+    match alignment {
+        TableAlignment::Left => format!("{content}{}", " ".repeat(padding)),
+        TableAlignment::Right => format!("{}{}", " ".repeat(padding), content),
+        TableAlignment::Center => {
+            let left = padding / 2;
+            let right = padding - left;
+            format!("{}{}{}", " ".repeat(left), content, " ".repeat(right))
+        }
+    }
+}
+
+fn wrap_table_cell(content: &str, width: usize) -> Vec<String> {
+    if width == 0 {
+        return vec![String::new()];
+    }
+
+    let mut lines = Vec::new();
+    for segment in content.split('\n') {
+        let trimmed = segment.trim_end();
+        if trimmed.is_empty() {
+            lines.push(String::new());
+            continue;
+        }
+
+        let options = Options::new(width)
+            .word_separator(WordSeparator::UnicodeBreakProperties)
+            .break_words(true);
+        let wrapped = wrap(trimmed, options);
+
+        if wrapped.is_empty() {
+            lines.push(String::new());
+        } else {
+            lines.extend(wrapped.into_iter().map(|line| line.into_owned()));
+        }
+    }
+
+    if lines.is_empty() {
+        lines.push(String::new());
+    }
+
+    lines
+}
+
+fn constrain_column_widths(
+    desired: &[usize],
+    available: usize,
+    min_width: usize,
+) -> Option<Vec<usize>> {
+    if desired.is_empty() {
+        return Some(Vec::new());
+    }
+    if available < min_width.saturating_mul(desired.len()) {
+        return None;
+    }
+
+    let mut widths: Vec<usize> = desired
+        .iter()
+        .map(|value| (*value).max(min_width))
+        .collect();
+    let mut total: usize = widths.iter().sum();
+
+    if total <= available {
+        return Some(widths);
+    }
+
+    while total > available {
+        let mut changed = false;
+        for value in &mut widths {
+            if total <= available {
+                break;
+            }
+            if *value > min_width {
+                *value -= 1;
+                total -= 1;
+                changed = true;
+            }
+        }
+
+        if !changed {
+            break;
+        }
+    }
+
+    if total > available {
+        None
+    } else {
+        Some(widths)
+    }
+}
+
+fn cell_display_width(value: &str) -> usize {
+    value
+        .split('\n')
+        .map(|segment| UnicodeWidthStr::width(segment.trim_end()))
+        .max()
+        .unwrap_or(0)
+        .max(1)
+}
+
+fn blank_line(indent: &str, base_style: Style) -> Line<'static> {
     let mut spans = Vec::new();
     if !indent.is_empty() {
         spans.push(Span::styled(indent.to_string(), base_style));
     }
     spans.push(Span::styled(String::new(), base_style));
-        output.push(Line::from(spans));
+    Line::from(spans)
-    }
-
-    output
 }
 
 fn wrap_markdown_spans(
@@ -9112,7 +9830,63 @@ pub(crate) fn wrap_unicode(text: &str, width: usize) -> Vec<String> {
 
 #[cfg(test)]
 mod tests {
-    use super::wrap_unicode;
+    use super::{render_markdown_lines, wrap_unicode};
+    use ratatui::style::Style;
+    use ratatui::text::Line;
+
+    fn lines_to_strings(lines: &[Line<'_>]) -> Vec<String> {
+        lines
+            .iter()
+            .map(|line| {
+                line.spans
+                    .iter()
+                    .map(|span| span.content.as_ref())
+                    .collect::<String>()
+            })
+            .collect()
+    }
+
+    #[test]
+    fn render_markdown_table_draws_grid_when_width_allows() {
+        let lines = render_markdown_lines(
+            "| Name | Role |\n| --- | --- |\n| Alice | Developer |\n",
+            "",
+            60,
+            Style::default(),
+        );
+        let rendered = lines_to_strings(&lines);
+        assert!(
+            rendered.iter().any(|line| line.contains("Table (1 row):")),
+            "summary line should mention row count"
+        );
+        assert!(
+            rendered.iter().any(|line| line.contains('┌')),
+            "grid border should be present when width permits"
+        );
+        assert!(
+            rendered.iter().any(|line| line.contains("Alice")),
+            "table rows should include cell content"
+        );
+    }
+
+    #[test]
+    fn render_markdown_table_falls_back_when_narrow() {
+        let lines = render_markdown_lines(
+            "| Name | Role |\n| --- | --- |\n| Alice | Developer |\n",
+            "",
+            12,
+            Style::default(),
+        );
+        let rendered = lines_to_strings(&lines);
+        assert!(
+            rendered.iter().any(|line| line.contains("Name:")),
+            "stacked fallback should label headers inline"
+        );
+        assert!(
+            rendered.iter().all(|line| !line.contains('┌')),
+            "narrow layout should avoid grid borders"
+        );
+    }
 
     #[test]
     fn wrap_unicode_respects_cjk_display_width() {