chartml-chart-cartesian 4.0.0

use chartml_core::data::DataTable;
use chartml_core::element::{ChartElement, Dimensions};
use chartml_core::error::ChartError;
use chartml_core::plugin::{ChartConfig, ChartRenderer};
use chartml_core::spec::VisualizeSpec;

mod bar;
mod line;
mod area;
pub(crate) mod helpers;

pub use bar::{bar_animation_origin, render_bar};
pub use line::render_line;
pub use area::render_area;

pub struct CartesianRenderer;

impl CartesianRenderer {
    pub fn new() -> Self {
        Self
    }
}

impl Default for CartesianRenderer {
    fn default() -> Self {
        Self::new()
    }
}

impl ChartRenderer for CartesianRenderer {
    fn render(&self, data: &DataTable, config: &ChartConfig) -> Result<ChartElement, ChartError> {
        match config.visualize.chart_type.as_str() {
            "bar" => bar::render_bar(data, config),
            "line" => line::render_line(data, config),
            "area" => area::render_area(data, config),
            other => Err(ChartError::UnknownChartType(other.to_string())),
        }
    }

    fn default_dimensions(&self, _spec: &VisualizeSpec) -> Option<Dimensions> {
        Some(Dimensions::new(400.0))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use chartml_core::element::count_elements;
    use chartml_core::data::{Row, DataTable};
    use serde_json::json;

    fn make_bar_rows() -> Vec<Row> {
        vec![
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(100))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(200))].into_iter().collect(),
            [("month".to_string(), json!("Mar")), ("revenue".to_string(), json!(150))].into_iter().collect(),
        ]
    }

    fn make_bar_data() -> DataTable {
        DataTable::from_rows(&make_bar_rows()).unwrap()
    }

    fn make_bar_config() -> ChartConfig {
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            columns: month
            rows: revenue
        "#).unwrap();
        ChartConfig {
            visualize: viz,
            title: Some("Test Bar".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string(), "#4A7C59".to_string()],
            theme: chartml_core::theme::Theme::default(),
        }
    }

    fn make_line_config() -> ChartConfig {
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: line
            columns: month
            rows: revenue
        "#).unwrap();
        ChartConfig {
            visualize: viz,
            title: Some("Test Line".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string(), "#4A7C59".to_string()],
            theme: chartml_core::theme::Theme::default(),
        }
    }

    fn make_area_config() -> ChartConfig {
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: area
            columns: month
            rows: revenue
        "#).unwrap();
        ChartConfig {
            visualize: viz,
            title: Some("Test Area".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string(), "#4A7C59".to_string()],
            theme: chartml_core::theme::Theme::default(),
        }
    }

    // ----- Phase 4: theme typography wiring -----

    /// Verify that non-default Theme typography values flow through to the
    /// emitted `ChartElement::Text` nodes. Specifically: a custom label
    /// family, letter-spacing, and text-transform must appear on every
    /// `axis-label` / `tick-value` / `legend-label` text element, while
    /// defaults continue to produce the omitted-attribute legacy path.
    #[test]
    fn phase4_theme_typography_flows_to_axis_label_text() {
        use chartml_core::theme::{TextTransform, Theme};

        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.label_font_family = "serif".into();
        t.label_letter_spacing = 1.5;
        t.label_text_transform = TextTransform::Uppercase;
        t.label_font_weight = 600;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();

        // Walk the tree: for every axis-label text, assert the new fields
        // are set from the theme override.
        fn walk<'a>(el: &'a ChartElement, out: &mut Vec<&'a ChartElement>) {
            match el {
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    for c in children {
                        walk(c, out);
                    }
                }
                _ => out.push(el),
            }
        }
        let mut leaves = Vec::new();
        walk(&element, &mut leaves);

        let mut axis_label_count = 0usize;
        for leaf in &leaves {
            if let ChartElement::Text {
                class,
                font_family,
                letter_spacing,
                text_transform,
                font_weight,
                ..
            } = leaf
            {
                // Only inspect axis-label role (which reads the label_* group).
                let is_axis_label = class
                    .split_whitespace()
                    .any(|c| c == "axis-label");
                if !is_axis_label {
                    continue;
                }
                axis_label_count += 1;

                assert_eq!(
                    font_family.as_deref(),
                    Some("serif"),
                    "axis-label text must carry theme.label_font_family"
                );
                assert_eq!(
                    letter_spacing.as_deref(),
                    Some("1.5"),
                    "axis-label text must carry theme.label_letter_spacing"
                );
                assert_eq!(
                    text_transform.as_deref(),
                    Some("uppercase"),
                    "axis-label text must carry theme.label_text_transform"
                );
                assert_eq!(
                    font_weight.as_deref(),
                    Some("600"),
                    "axis-label text must carry theme.label_font_weight"
                );
            }
        }
        assert!(
            axis_label_count > 0,
            "bar chart should have at least one axis-label text"
        );
    }

    /// Verify the same properties propagate to `tick-value` (numeric) text
    /// elements, which read from the `numeric_*` group for family/size but
    /// inherit `label_*` for weight, letter-spacing, and text-transform.
    #[test]
    fn phase4_theme_typography_flows_to_tick_value_text() {
        use chartml_core::theme::{TextTransform, Theme};

        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.numeric_font_family = "monospace".into();
        t.label_letter_spacing = 0.75;
        t.label_text_transform = TextTransform::Lowercase;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();

        let mut found = false;
        fn visit<F: FnMut(&ChartElement)>(el: &ChartElement, f: &mut F) {
            f(el);
            match el {
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    for c in children {
                        visit(c, f);
                    }
                }
                _ => {}
            }
        }
        visit(&element, &mut |el| {
            if let ChartElement::Text {
                class,
                font_family,
                letter_spacing,
                text_transform,
                ..
            } = el
            {
                if class
                    .split_whitespace()
                    .any(|c| c == "tick-value")
                {
                    found = true;
                    assert_eq!(
                        font_family.as_deref(),
                        Some("monospace"),
                        "tick-value text must carry theme.numeric_font_family"
                    );
                    assert_eq!(
                        letter_spacing.as_deref(),
                        Some("0.75"),
                        "tick-value text must inherit theme.label_letter_spacing"
                    );
                    assert_eq!(
                        text_transform.as_deref(),
                        Some("lowercase"),
                        "tick-value text must inherit theme.label_text_transform"
                    );
                }
            }
        });
        assert!(found, "bar chart should emit at least one tick-value text");
    }

    #[test]
    fn bar_chart_renders() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_bar_config();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Bar render failed: {:?}", result.err());
        let element = result.unwrap();
        let rect_count = count_elements(&element, &|e| matches!(e, ChartElement::Rect { .. }));
        assert_eq!(rect_count, 3, "Should have 3 bars for 3 data points, got {}", rect_count);
    }

    #[test]
    fn bar_chart_has_svg_root() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_bar_config();
        let element = renderer.render(&data, &config).unwrap();
        assert!(matches!(element, ChartElement::Svg { .. }), "Root should be Svg");
    }

    #[test]
    fn bar_chart_has_no_title_in_svg() {
        // Title is rendered as HTML outside the SVG (matching JS chartml).
        // The SVG element tree must NOT contain a chart-title text element.
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_bar_config();
        let element = renderer.render(&data, &config).unwrap();
        let title_count = count_elements(&element, &|e| {
            matches!(e, ChartElement::Text { class, .. } if class == "chart-title")
        });
        assert_eq!(title_count, 0, "Title must not be in the SVG element tree");
    }

    #[test]
    fn bar_chart_has_axes() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_bar_config();
        let element = renderer.render(&data, &config).unwrap();
        let axis_line_count = count_elements(&element, &|e| {
            matches!(e, ChartElement::Line { class, .. } if class == "axis-line")
        });
        assert!(axis_line_count >= 1, "Should have axis lines, got {}", axis_line_count);
    }

    #[test]
    fn line_chart_renders() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_line_config();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Line render failed: {:?}", result.err());
        let element = result.unwrap();
        let path_count = count_elements(&element, &|e| matches!(e, ChartElement::Path { .. }));
        assert!(path_count >= 1, "Should have at least 1 path for the line, got {}", path_count);
    }

    #[test]
    fn line_chart_path_has_stroke() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_line_config();
        let element = renderer.render(&data, &config).unwrap();
        // Find the path and check it has a stroke
        fn find_path(el: &ChartElement) -> Option<&ChartElement> {
            match el {
                ChartElement::Path { .. } => Some(el),
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    children.iter().find_map(find_path)
                }
                _ => None,
            }
        }
        let path = find_path(&element).expect("Should find a path element");
        match path {
            ChartElement::Path { stroke, .. } => {
                assert!(stroke.is_some(), "Line path should have a stroke");
            }
            _ => unreachable!(),
        }
    }

    #[test]
    fn area_chart_renders() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_area_config();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Area render failed: {:?}", result.err());
        let element = result.unwrap();
        let path_count = count_elements(&element, &|e| matches!(e, ChartElement::Path { .. }));
        assert!(path_count >= 1, "Should have at least 1 path for the area, got {}", path_count);
    }

    #[test]
    fn area_chart_path_has_fill() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let config = make_area_config();
        let element = renderer.render(&data, &config).unwrap();
        fn find_path(el: &ChartElement) -> Option<&ChartElement> {
            match el {
                ChartElement::Path { .. } => Some(el),
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    children.iter().find_map(find_path)
                }
                _ => None,
            }
        }
        let path = find_path(&element).expect("Should find a path element");
        match path {
            ChartElement::Path { fill, .. } => {
                assert!(fill.is_some(), "Area path should have a fill");
            }
            _ => unreachable!(),
        }
    }

    #[test]
    fn unknown_type_errors() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config();
        config.visualize.chart_type = "unknown".to_string();
        let result = renderer.render(&data, &config);
        assert!(result.is_err(), "Unknown chart type should produce error");
        match result.unwrap_err() {
            ChartError::UnknownChartType(t) => assert_eq!(t, "unknown"),
            other => panic!("Expected UnknownChartType, got {:?}", other),
        }
    }

    #[test]
    fn bar_chart_no_title() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config();
        config.title = None;
        let element = renderer.render(&data, &config).unwrap();
        let title_count = count_elements(&element, &|e| {
            matches!(e, ChartElement::Text { class, .. } if class == "chart-title")
        });
        assert_eq!(title_count, 0, "Should have no title element when title is None");
    }

    #[test]
    fn default_dimensions_returns_some() {
        let renderer = CartesianRenderer::new();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            columns: x
            rows: y
        "#).unwrap();
        let dims = renderer.default_dimensions(&viz);
        assert!(dims.is_some());
        assert_eq!(dims.unwrap().height, 400.0);
    }

    #[test]
    fn bar_chart_adaptive_padding_2_bars() {
        // With n=2 bars and adaptive padding=0.2, each bar should be ~36.4% of inner_width.
        // inner_width = 800 - left_margin - right_margin ≈ 800 - 60 - 20 = 720
        // bandwidth = 0.8/2.2 * inner_width ≈ 0.3636 * inner_width ≈ 261px
        // Bar should NOT be close to 50% (which would indicate no padding).
        let rows: Vec<Row> = vec![
            [("region".to_string(), json!("US")), ("revenue".to_string(), json!(55000))].into_iter().collect(),
            [("region".to_string(), json!("EU")), ("revenue".to_string(), json!(40000))].into_iter().collect(),
        ];
        let data = DataTable::from_rows(&rows).unwrap();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            columns: region
            rows: revenue
        "#).unwrap();
        let config = ChartConfig {
            visualize: viz,
            title: Some("Regional Revenue".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string()],
            theme: chartml_core::theme::Theme::default(),
        };
        let renderer = CartesianRenderer::new();
        let element = renderer.render(&data, &config).unwrap();

        // Find all Rect elements (bars)
        let mut bar_widths = Vec::new();
        fn collect_bar_widths(el: &ChartElement, widths: &mut Vec<f64>) {
            match el {
                ChartElement::Rect { width, class, .. } if class.split_whitespace().any(|c| c == "bar") => {
                    widths.push(*width);
                }
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    for child in children { collect_bar_widths(child, widths); }
                }
                _ => {}
            }
        }
        collect_bar_widths(&element, &mut bar_widths);

        assert_eq!(bar_widths.len(), 2, "Should have 2 bars");
        let bar_width = bar_widths[0];
        println!("Bar width: {:.2}px", bar_width);

        // JS applies maxBarWidth = inner_width * 0.2 clamp.
        // With y_tick_labels pre-computation: for revenue values 100/200, the
        // tick label "200" ≈ 21px + 15px buffer = 36px left margin.
        // inner_width = 800 - 36 - 30 = 734px → maxBarWidth = 146.8px.
        // bandwidth for 2 bars, padding=0.2 = ~234px → clamped to ~146.8px.
        assert!(
            bar_width <= 150.0,
            "Bar width {:.1}px exceeds maxBarWidth clamp",
            bar_width
        );
        assert!(
            bar_width > 50.0,
            "Bar width {:.1}px is unreasonably narrow",
            bar_width
        );
    }

    #[test]
    fn stacked_bar_chart_renders() {
        let rows: Vec<Row> = vec![
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(100)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(50)), ("product".to_string(), json!("B"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(200)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(80)), ("product".to_string(), json!("B"))].into_iter().collect(),
        ];
        let data = DataTable::from_rows(&rows).unwrap();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            mode: stacked
            columns: month
            rows: revenue
            marks:
              color: product
        "#).unwrap();
        let config = ChartConfig {
            visualize: viz,
            title: Some("Stacked Bar".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string()],
            theme: chartml_core::theme::Theme::default(),
        };
        let renderer = CartesianRenderer::new();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Stacked bar render failed: {:?}", result.err());
        let element = result.unwrap();
        let rect_count = count_elements(&element, &|e| matches!(e, ChartElement::Rect { class, .. } if class.split_whitespace().any(|c| c == "bar")));
        assert_eq!(rect_count, 4, "Should have 4 bars (2 categories x 2 series), got {}", rect_count);
    }

    #[test]
    fn grouped_bar_chart_renders() {
        let rows: Vec<Row> = vec![
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(100)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(50)), ("product".to_string(), json!("B"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(200)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(80)), ("product".to_string(), json!("B"))].into_iter().collect(),
        ];
        let data = DataTable::from_rows(&rows).unwrap();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            mode: grouped
            columns: month
            rows: revenue
            marks:
              color: product
        "#).unwrap();
        let config = ChartConfig {
            visualize: viz,
            title: None,
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string()],
            theme: chartml_core::theme::Theme::default(),
        };
        let renderer = CartesianRenderer::new();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Grouped bar render failed: {:?}", result.err());
        let element = result.unwrap();
        let rect_count = count_elements(&element, &|e| matches!(e, ChartElement::Rect { class, .. } if class.split_whitespace().any(|c| c == "bar")));
        assert_eq!(rect_count, 4, "Should have 4 bars (2 categories x 2 series), got {}", rect_count);
    }

    #[test]
    fn multi_series_line_chart_renders() {
        let rows: Vec<Row> = vec![
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(100)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(50)), ("product".to_string(), json!("B"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(200)), ("product".to_string(), json!("A"))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(80)), ("product".to_string(), json!("B"))].into_iter().collect(),
        ];
        let data = DataTable::from_rows(&rows).unwrap();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: line
            columns: month
            rows: revenue
            marks:
              color: product
        "#).unwrap();
        let config = ChartConfig {
            visualize: viz,
            title: Some("Multi Line".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string(), "#D4A445".to_string()],
            theme: chartml_core::theme::Theme::default(),
        };
        let renderer = CartesianRenderer::new();
        let result = renderer.render(&data, &config);
        assert!(result.is_ok(), "Multi-series line render failed: {:?}", result.err());
        let element = result.unwrap();
        let path_count = count_elements(&element, &|e| matches!(e, ChartElement::Path { class, .. } if class.split_whitespace().any(|c| c == "chartml-line-path")));
        assert_eq!(path_count, 2, "Should have 2 line paths for 2 series, got {}", path_count);
    }

    #[test]
    fn empty_data_returns_error() {
        let renderer = CartesianRenderer::new();
        let data = DataTable::from_rows(&Vec::<Row>::new()).unwrap();
        let config = make_bar_config();
        let result = renderer.render(&data, &config);
        assert!(result.is_err(), "Empty data should produce an error");
    }

    #[test]
    fn x_axis_horizontal_few_labels() {
        use crate::helpers::{generate_x_axis, GridConfig};
        let labels = vec!["A".into(), "B".into(), "C".into()];
        let result = generate_x_axis(&crate::helpers::XAxisParams {
            labels: &labels, display_label_overrides: None,
            range: (0.0, 800.0), y_position: 350.0, available_width: 800.0,
            x_format: None, chart_height: None, grid: &GridConfig::default(), axis_label: None,
            theme: &chartml_core::theme::Theme::default(),
        });
        // Should be horizontal — no transforms on text elements
        let text_with_transform = result.elements.iter().filter(|e| {
            matches!(e, ChartElement::Text { transform: Some(_), .. })
        }).count();
        assert_eq!(text_with_transform, 0, "Horizontal strategy should have no transforms");
    }

    #[test]
    fn x_axis_rotated_many_labels() {
        use crate::helpers::{generate_x_axis, GridConfig};
        let labels: Vec<String> = (0..20).map(|i| format!("Category Number {}", i)).collect();
        let result = generate_x_axis(&crate::helpers::XAxisParams {
            labels: &labels, display_label_overrides: None,
            range: (0.0, 300.0), y_position: 350.0, available_width: 300.0,
            x_format: None, chart_height: None, grid: &GridConfig::default(), axis_label: None,
            theme: &chartml_core::theme::Theme::default(),
        });
        // Should be rotated — text elements have transforms
        let text_with_transform = result.elements.iter().filter(|e| {
            matches!(e, ChartElement::Text { transform: Some(_), .. })
        }).count();
        assert!(text_with_transform > 0, "Rotated strategy should have transforms");
    }

    #[test]
    fn x_axis_sampled_100_labels() {
        use crate::helpers::{generate_x_axis, GridConfig};
        let labels: Vec<String> = (0..100).map(|i| format!("Long Category Name {}", i)).collect();
        let result = generate_x_axis(&crate::helpers::XAxisParams {
            labels: &labels, display_label_overrides: None,
            range: (0.0, 400.0), y_position: 350.0, available_width: 400.0,
            x_format: None, chart_height: None, grid: &GridConfig::default(), axis_label: None,
            theme: &chartml_core::theme::Theme::default(),
        });
        // Should be sampled — fewer label texts than total categories
        let label_count = result.elements.iter().filter(|e| {
            matches!(e, ChartElement::Text { class, .. } if class.split_whitespace().any(|c| c == "tick-label"))
        }).count();
        assert!(label_count < 100, "Sampled should show fewer labels: got {}", label_count);
        assert!(label_count >= 3, "Should show at least a few labels");
    }

    #[test]
    fn line_chart_grid_dash_array() {
        let data = make_bar_data();
        // Use unquoted dashArray value (matching the examples_source.md spec)
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
type: line
columns: month
rows: revenue
style:
  grid:
    x: true
    y: true
    color: '#e0e0e0'
    opacity: 0.5
    dashArray: 4,4
  showDots: true
"#).unwrap();

        // Verify the grid spec parsed correctly
        let grid_spec = viz.style.as_ref().unwrap().grid.as_ref().unwrap();
        assert_eq!(grid_spec.dash_array, Some("4,4".to_string()), "GridSpec.dash_array should parse from YAML");
        assert_eq!(grid_spec.x, Some(true), "grid.x should be true");
        assert_eq!(grid_spec.y, Some(true), "grid.y should be true");

        let config = ChartConfig {
            visualize: viz,
            title: Some("Dashed Grid Test".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string()],
            theme: chartml_core::theme::Theme::default(),
        };

        // Verify GridConfig resolves correctly
        let grid_config = crate::helpers::GridConfig::from_config(&config);
        assert_eq!(grid_config.dash_array, Some("4,4".to_string()), "GridConfig.dash_array should be set");
        assert!(grid_config.show_x, "grid.show_x should be true");
        assert!(grid_config.show_y, "grid.show_y should be true");

        let renderer = CartesianRenderer::new();
        let element = renderer.render(&data, &config).unwrap();

        // Count grid lines and verify ALL have stroke_dasharray set
        let mut dashed_grid_count = 0;
        let mut total_grid_count = 0;
        fn check_grid(el: &ChartElement, dashed: &mut usize, total: &mut usize) {
            match el {
                ChartElement::Line { class, stroke_dasharray, .. } if class.contains("grid-line") => {
                    *total += 1;
                    if let Some(da) = stroke_dasharray {
                        if !da.is_empty() {
                            *dashed += 1;
                        }
                    }
                }
                ChartElement::Svg { children, .. } | ChartElement::Group { children, .. } => {
                    for child in children {
                        check_grid(child, dashed, total);
                    }
                }
                _ => {}
            }
        }
        check_grid(&element, &mut dashed_grid_count, &mut total_grid_count);

        assert!(total_grid_count > 0, "Should have grid lines, got {}", total_grid_count);
        assert_eq!(dashed_grid_count, total_grid_count,
            "All {} grid lines should have stroke_dasharray='4,4', but only {} do",
            total_grid_count, dashed_grid_count);
    }

    // ----- Phase 5: theme shape/stroke wiring -----

    /// Collect every `Path` stroke_width on elements whose class matches
    /// `series-line` (the series-weight role wired in Phase 5).
    fn collect_series_stroke_widths(el: &ChartElement, out: &mut Vec<f64>) {
        match el {
            ChartElement::Path { stroke_width: Some(w), class, .. }
                if class.split_whitespace().any(|c| c == "series-line") =>
            {
                out.push(*w);
            }
            ChartElement::Svg { children, .. }
            | ChartElement::Group { children, .. } => {
                for c in children {
                    collect_series_stroke_widths(c, out);
                }
            }
            _ => {}
        }
    }

    /// Collect every `Line` stroke_width bucketed by role
    /// (`axis-line`, `grid-line`, `tick`).
    fn collect_line_stroke_widths_by_class(
        el: &ChartElement,
        out: &mut std::collections::HashMap<String, Vec<f64>>,
    ) {
        match el {
            ChartElement::Line { stroke_width: Some(w), class, .. } => {
                for token in class.split_whitespace() {
                    if matches!(token, "axis-line" | "grid-line" | "tick") {
                        out.entry(token.to_string()).or_default().push(*w);
                    }
                }
            }
            ChartElement::Svg { children, .. }
            | ChartElement::Group { children, .. } => {
                for c in children {
                    collect_line_stroke_widths_by_class(c, out);
                }
            }
            _ => {}
        }
    }

    /// Collect all `(rx, ry)` pairs on `Rect` elements with a `bar` class.
    fn collect_bar_corner_radii(
        el: &ChartElement,
        out: &mut Vec<(Option<f64>, Option<f64>)>,
    ) {
        match el {
            ChartElement::Rect { rx, ry, class, .. }
                if class.split_whitespace().any(|c| c == "bar") =>
            {
                out.push((*rx, *ry));
            }
            ChartElement::Svg { children, .. }
            | ChartElement::Group { children, .. } => {
                for c in children {
                    collect_bar_corner_radii(c, out);
                }
            }
            _ => {}
        }
    }

    /// Collect every `Circle.r` on elements whose class contains `dot-marker`.
    fn collect_dot_radii(el: &ChartElement, out: &mut Vec<f64>) {
        match el {
            ChartElement::Circle { r, class, .. }
                if class.split_whitespace().any(|c| c == "dot-marker") =>
            {
                out.push(*r);
            }
            ChartElement::Svg { children, .. }
            | ChartElement::Group { children, .. } => {
                for c in children {
                    collect_dot_radii(c, out);
                }
            }
            _ => {}
        }
    }

    #[test]
    fn phase5_bar_corner_radius_omitted_by_default() {
        // Default theme MUST NOT emit rx/ry on bar rects (byte-identical contract).
        let renderer = CartesianRenderer::new();
        let element = renderer
            .render(&make_bar_data(), &make_bar_config())
            .expect("render");

        let mut radii = Vec::new();
        collect_bar_corner_radii(&element, &mut radii);
        assert!(!radii.is_empty(), "expected bar rects in default bar chart");
        for (rx, ry) in &radii {
            assert!(rx.is_none(), "default theme must leave Rect.rx == None");
            assert!(ry.is_none(), "default theme must leave Rect.ry == None");
        }
    }

    #[test]
    fn phase5_custom_bar_corner_radius_emits_rx_ry() {
        use chartml_core::theme::{BarCornerRadius, Theme};
        let renderer = CartesianRenderer::new();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.bar_corner_radius = BarCornerRadius::Uniform(8.0);
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut radii = Vec::new();
        collect_bar_corner_radii(&element, &mut radii);
        assert!(!radii.is_empty());
        for (rx, ry) in &radii {
            assert_eq!(*rx, Some(8.0), "rx must match theme.bar_corner_radius");
            assert_eq!(*ry, Some(8.0), "ry must match theme.bar_corner_radius");
        }
    }

    // ---- Phase follow-up: BarCornerRadius::Top top-only rounding ----

    fn collect_bar_elements<'a>(el: &'a ChartElement, out: &mut Vec<&'a ChartElement>) {
        match el {
            ChartElement::Rect { class, .. } | ChartElement::Path { class, .. }
                if class.split_whitespace().any(|c| c == "bar-rect") =>
            {
                out.push(el);
            }
            ChartElement::Svg { children, .. } | ChartElement::Group { children, .. } => {
                for c in children {
                    collect_bar_elements(c, out);
                }
            }
            _ => {}
        }
    }

    #[test]
    fn phase_followup_bar_top_rounding_zero_is_plain_rect() {
        use chartml_core::theme::{BarCornerRadius, Theme};
        let renderer = CartesianRenderer::new();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.bar_corner_radius = BarCornerRadius::Top(0.0);
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut bars = Vec::new();
        collect_bar_elements(&element, &mut bars);
        assert!(!bars.is_empty());
        for b in &bars {
            match b {
                ChartElement::Rect { rx, ry, .. } => {
                    assert!(rx.is_none(), "Top(0.0) must emit Rect with rx=None");
                    assert!(ry.is_none(), "Top(0.0) must emit Rect with ry=None");
                }
                other => panic!("Top(0.0) must emit Rect, got {:?}", other),
            }
        }
    }

    #[test]
    fn phase_followup_bar_top_rounding_vertical() {
        use chartml_core::theme::{BarCornerRadius, Theme};
        let renderer = CartesianRenderer::new();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.bar_corner_radius = BarCornerRadius::Top(8.0);
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut bars = Vec::new();
        collect_bar_elements(&element, &mut bars);
        assert!(!bars.is_empty(), "expected bar elements");
        for b in &bars {
            match b {
                ChartElement::Path { d, .. } => {
                    assert_eq!(
                        d.matches("A 8,8").count(),
                        2,
                        "vertical Top(8) must produce 2 arcs, got d={d}"
                    );
                }
                other => panic!("vertical Top(8) must emit Path, got {:?}", other),
            }
        }
    }

    #[test]
    fn phase_followup_bar_top_rounding_horizontal() {
        use chartml_core::theme::{BarCornerRadius, Theme};
        let renderer = CartesianRenderer::new();
        let mut config = make_bar_config();
        config.visualize.orientation = Some(chartml_core::spec::Orientation::Horizontal);
        let mut t = Theme::default();
        t.bar_corner_radius = BarCornerRadius::Top(8.0);
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut bars = Vec::new();
        collect_bar_elements(&element, &mut bars);
        assert!(!bars.is_empty(), "expected bar elements (horizontal)");
        for b in &bars {
            match b {
                ChartElement::Path { d, .. } => {
                    assert_eq!(
                        d.matches("A 8,8").count(),
                        2,
                        "horizontal Top(8) must produce 2 arcs, got d={d}"
                    );
                }
                other => panic!("horizontal Top(8) must emit Path, got {:?}", other),
            }
        }
    }

    #[test]
    fn phase_followup_bar_top_rounding_negative_vertical() {
        // Drive build_bar_element directly so the test doesn't depend on a
        // chart spec that emits negative values.
        use chartml_core::theme::{BarCornerRadius, Theme};
        use crate::bar::{build_bar_element, BarRectSpec};

        let mut theme = Theme::default();
        theme.bar_corner_radius = BarCornerRadius::Top(8.0);

        let pos = build_bar_element(
            BarRectSpec {
                x: 100.0, y: 50.0, width: 40.0, height: 200.0,
                is_horizontal: false, is_negative: false,
                fill: "#000".into(),
                class: "bar bar-rect".into(),
                data: None,
            },
            &theme,
        );
        let neg = build_bar_element(
            BarRectSpec {
                x: 100.0, y: 50.0, width: 40.0, height: 200.0,
                is_horizontal: false, is_negative: true,
                fill: "#000".into(),
                class: "bar bar-rect".into(),
                data: None,
            },
            &theme,
        );

        let pos_d = match &pos {
            ChartElement::Path { d, .. } => d.clone(),
            _ => panic!("pos must be Path"),
        };
        let neg_d = match &neg {
            ChartElement::Path { d, .. } => d.clone(),
            _ => panic!("neg must be Path"),
        };

        assert_eq!(pos_d.matches("A 8,8").count(), 2);
        assert_eq!(neg_d.matches("A 8,8").count(), 2);

        // Positive vertical: top rounding → path starts at (x, y+r) = (100, 58).
        assert!(
            pos_d.starts_with("M 100,58"),
            "pos vertical Top path should start at y+r=58, got {pos_d}"
        );
        // Negative vertical: bottom rounding → path starts at the (square)
        // top-left corner (100, 50).
        assert!(
            neg_d.starts_with("M 100,50"),
            "neg vertical Top path should start at (x, y)=(100, 50), got {neg_d}"
        );
        // Negative path must reference the bottom-edge-minus-r coordinate
        // y1-r = 50+200-8 = 242 where its arcs live.
        assert!(
            neg_d.contains(",242"),
            "neg vertical Top path should contain y1-r=242, got {neg_d}"
        );
    }

    #[test]
    fn phase5_custom_series_line_weight_flows_to_line_path() {
        use chartml_core::theme::Theme;
        let renderer = CartesianRenderer::new();
        let mut config = make_line_config();
        let mut t = Theme::default();
        t.series_line_weight = 4.0;
        config.theme = t;
        let element = renderer
            .render(&make_bar_data(), &config)
            .expect("render");

        let mut widths = Vec::new();
        collect_series_stroke_widths(&element, &mut widths);
        assert!(!widths.is_empty(), "expected at least one series-line path");
        for w in &widths {
            assert_eq!(*w, 4.0, "series-line stroke_width must read from theme");
        }
    }

    #[test]
    fn phase5_custom_series_line_weight_flows_to_area_outline() {
        use chartml_core::theme::Theme;
        let renderer = CartesianRenderer::new();
        let mut config = make_area_config();
        let mut t = Theme::default();
        t.series_line_weight = 3.5;
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut widths = Vec::new();
        collect_series_stroke_widths(&element, &mut widths);
        assert!(!widths.is_empty(), "expected area outline series-line path");
        for w in &widths {
            assert_eq!(*w, 3.5);
        }
    }

    #[test]
    fn phase5_custom_dot_radius_flows_to_line_markers() {
        use chartml_core::theme::Theme;
        let renderer = CartesianRenderer::new();
        let mut config = make_line_config();
        let mut t = Theme::default();
        t.dot_radius = 10.0;
        config.theme = t;
        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut radii = Vec::new();
        collect_dot_radii(&element, &mut radii);
        assert!(!radii.is_empty(), "expected dot-marker circles on line chart");
        for r in &radii {
            assert_eq!(*r, 10.0);
        }
    }

    #[test]
    fn phase5_custom_axis_and_grid_line_weights_flow_to_line_strokes() {
        use chartml_core::theme::Theme;
        let renderer = CartesianRenderer::new();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.axis_line_weight = 2.5;
        t.grid_line_weight = 0.5;
        config.theme = t;

        let element = renderer.render(&make_bar_data(), &config).expect("render");

        let mut by_class: std::collections::HashMap<String, Vec<f64>> =
            std::collections::HashMap::new();
        collect_line_stroke_widths_by_class(&element, &mut by_class);

        let axis = by_class.get("axis-line").cloned().unwrap_or_default();
        let ticks = by_class.get("tick").cloned().unwrap_or_default();
        let grid = by_class.get("grid-line").cloned().unwrap_or_default();

        assert!(!axis.is_empty(), "expected axis-line elements");
        assert!(!ticks.is_empty(), "expected tick elements");
        assert!(!grid.is_empty(), "expected grid-line elements");

        for w in &axis {
            assert_eq!(*w, 2.5, "axis-line stroke_width must read from theme.axis_line_weight");
        }
        for w in &ticks {
            assert_eq!(*w, 2.5, "tick stroke_width must read from theme.axis_line_weight");
        }
        for w in &grid {
            assert_eq!(*w, 0.5, "grid-line stroke_width must read from theme.grid_line_weight");
        }
    }

    #[test]
    fn x_axis_date_labels_reformatted() {
        use crate::helpers::{generate_x_axis, GridConfig};
        let labels: Vec<String> = vec![
            "2024-01-01".into(), "2024-01-02".into(), "2024-01-03".into()
        ];
        let result = generate_x_axis(&crate::helpers::XAxisParams {
            labels: &labels, display_label_overrides: None,
            range: (0.0, 800.0), y_position: 350.0, available_width: 800.0,
            x_format: None, chart_height: None, grid: &GridConfig::default(), axis_label: None,
            theme: &chartml_core::theme::Theme::default(),
        });
        // Labels should be reformatted as "Jan 01", "Jan 02", etc.
        let has_reformatted = result.elements.iter().any(|e| {
            matches!(e, ChartElement::Text { content, .. } if content.starts_with("Jan"))
        });
        assert!(has_reformatted, "Date labels should be reformatted");
    }

    // ----- Phase 6: theme.grid_style gating -----

    /// Walk an element tree and count grid-line-x (vertical) and grid-line-y
    /// (horizontal) gridlines emitted by the cartesian renderer.
    fn count_grid_lines(el: &ChartElement) -> (usize, usize) {
        let (mut vx, mut hy) = (0usize, 0usize);
        fn visit(el: &ChartElement, vx: &mut usize, hy: &mut usize) {
            match el {
                ChartElement::Line { class, .. } => {
                    let has_x = class.split_whitespace().any(|c| c == "grid-line-x");
                    let has_y = class.split_whitespace().any(|c| c == "grid-line-y");
                    if has_x {
                        *vx += 1;
                    }
                    if has_y {
                        *hy += 1;
                    }
                }
                ChartElement::Svg { children, .. }
                | ChartElement::Group { children, .. } => {
                    for c in children {
                        visit(c, vx, hy);
                    }
                }
                _ => {}
            }
        }
        visit(el, &mut vx, &mut hy);
        (vx, hy)
    }

    /// Build a bar-chart config with both horizontal and vertical gridlines
    /// enabled (show_y defaults to true; explicitly force show_x via spec).
    fn make_bar_config_both_grids() -> ChartConfig {
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            columns: month
            rows: revenue
            style:
              grid:
                x: true
                y: true
        "#).unwrap();
        ChartConfig {
            visualize: viz,
            title: Some("Test Bar GridStyle".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string()],
            theme: chartml_core::theme::Theme::default(),
        }
    }

    #[test]
    fn phase6_grid_style_both_default_emits_both_orientations() {
        use chartml_core::theme::{GridStyle, Theme};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config_both_grids();
        let mut t = Theme::default();
        t.grid_style = GridStyle::Both;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        let (vx, hy) = count_grid_lines(&element);
        assert!(vx > 0, "Both: expected vertical gridlines (grid-line-x)");
        assert!(hy > 0, "Both: expected horizontal gridlines (grid-line-y)");
    }

    #[test]
    fn phase6_grid_style_horizontal_only_skips_vertical() {
        use chartml_core::theme::{GridStyle, Theme};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config_both_grids();
        let mut t = Theme::default();
        t.grid_style = GridStyle::HorizontalOnly;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        let (vx, hy) = count_grid_lines(&element);
        assert_eq!(vx, 0, "HorizontalOnly: no grid-line-x expected, got {}", vx);
        assert!(hy > 0, "HorizontalOnly: expected grid-line-y lines");
    }

    #[test]
    fn phase6_grid_style_vertical_only_skips_horizontal() {
        use chartml_core::theme::{GridStyle, Theme};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config_both_grids();
        let mut t = Theme::default();
        t.grid_style = GridStyle::VerticalOnly;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        let (vx, hy) = count_grid_lines(&element);
        assert!(vx > 0, "VerticalOnly: expected grid-line-x lines");
        assert_eq!(hy, 0, "VerticalOnly: no grid-line-y expected, got {}", hy);
    }

    #[test]
    fn phase6_grid_style_none_skips_all_gridlines() {
        use chartml_core::theme::{GridStyle, Theme};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_bar_config_both_grids();
        let mut t = Theme::default();
        t.grid_style = GridStyle::None;
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        let (vx, hy) = count_grid_lines(&element);
        assert_eq!(vx, 0, "None: no grid-line-x expected, got {}", vx);
        assert_eq!(hy, 0, "None: no grid-line-y expected, got {}", hy);
    }

    // ----- Phase 7: zero-line wiring -----

    fn make_bar_data_crossing_zero() -> DataTable {
        let rows = vec![
            [("month".to_string(), json!("Jan")), ("revenue".to_string(), json!(-5))].into_iter().collect(),
            [("month".to_string(), json!("Feb")), ("revenue".to_string(), json!(0))].into_iter().collect(),
            [("month".to_string(), json!("Mar")), ("revenue".to_string(), json!(10))].into_iter().collect(),
        ];
        DataTable::from_rows(&rows).unwrap()
    }

    fn count_zero_lines(el: &ChartElement) -> usize {
        count_elements(el, &|e| {
            matches!(e, ChartElement::Line { class, .. } if class.split_whitespace().any(|c| c == "zero-line"))
        })
    }

    /// With the default theme (`zero_line: None`), no zero-line element must
    /// ever be emitted — even when the data range obviously crosses zero.
    #[test]
    fn phase7_default_theme_emits_no_zero_line() {
        let renderer = CartesianRenderer::new();
        let data = make_bar_data_crossing_zero();
        let config = make_bar_config();
        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(count_zero_lines(&element), 0, "default theme must not emit zero-line");
    }

    /// With a non-default `zero_line` spec AND data that strictly crosses zero,
    /// exactly one `zero-line` Line must be emitted with the spec'd color/width.
    #[test]
    fn phase7_bar_crossing_zero_emits_one_zero_line() {
        use chartml_core::theme::{Theme, ZeroLineSpec};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data_crossing_zero();
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.zero_line = Some(ZeroLineSpec { color: "#ff0000".into(), width: 1.5 });
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(count_zero_lines(&element), 1, "expected exactly one zero-line");

        // Verify the emitted element has the configured stroke + width.
        fn find_zero_line(el: &ChartElement) -> Option<(String, Option<f64>)> {
            match el {
                ChartElement::Line { class, stroke, stroke_width, .. }
                    if class.split_whitespace().any(|c| c == "zero-line") =>
                {
                    Some((stroke.clone(), *stroke_width))
                }
                ChartElement::Group { children, .. } | ChartElement::Svg { children, .. } => {
                    children.iter().find_map(find_zero_line)
                }
                _ => None,
            }
        }
        let (stroke, width) = find_zero_line(&element).expect("zero-line present");
        assert_eq!(stroke, "#ff0000");
        assert_eq!(width, Some(1.5));
    }

    /// Horizontal bar parity: crossing-zero data + non-default zero_line must
    /// emit exactly one zero-line, and for a horizontal bar chart (numeric axis
    /// is x) that line must run vertically — x1 == x2 and y1 != y2.
    #[test]
    fn phase7_horizontal_bar_crossing_zero_emits_one_zero_line() {
        use chartml_core::theme::{Theme, ZeroLineSpec};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data_crossing_zero();
        let viz: VisualizeSpec = serde_yaml::from_str(r#"
            type: bar
            orientation: horizontal
            columns: month
            rows: revenue
        "#).unwrap();
        let mut theme = Theme::default();
        theme.zero_line = Some(ZeroLineSpec { color: "#ff0000".into(), width: 1.5 });
        let config = ChartConfig {
            visualize: viz,
            title: Some("Test Horizontal Bar".to_string()),
            width: 800.0,
            height: 400.0,
            colors: vec!["#2E7D9A".to_string()],
            theme,
        };

        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(count_zero_lines(&element), 1, "expected exactly one zero-line");

        // Find the emitted zero-line Line and assert it runs vertically with
        // the spec'd stroke + width.
        struct ZeroLineGeom {
            x1: f64,
            y1: f64,
            x2: f64,
            y2: f64,
            stroke: String,
            stroke_width: Option<f64>,
        }
        fn find_zero_line_geom(el: &ChartElement) -> Option<ZeroLineGeom> {
            match el {
                ChartElement::Line { class, x1, y1, x2, y2, stroke, stroke_width, .. }
                    if class.split_whitespace().any(|c| c == "zero-line") =>
                {
                    Some(ZeroLineGeom {
                        x1: *x1,
                        y1: *y1,
                        x2: *x2,
                        y2: *y2,
                        stroke: stroke.clone(),
                        stroke_width: *stroke_width,
                    })
                }
                ChartElement::Group { children, .. } | ChartElement::Svg { children, .. } => {
                    children.iter().find_map(find_zero_line_geom)
                }
                _ => None,
            }
        }
        let ZeroLineGeom { x1, y1, x2, y2, stroke, stroke_width: width } =
            find_zero_line_geom(&element).expect("zero-line present");
        assert!(
            (x1 - x2).abs() < f64::EPSILON,
            "horizontal-bar zero-line must be vertical: x1={x1} x2={x2}",
        );
        assert!(
            (y1 - y2).abs() > f64::EPSILON,
            "horizontal-bar zero-line must have non-zero height: y1={y1} y2={y2}",
        );
        assert_eq!(stroke, "#ff0000");
        assert_eq!(width, Some(1.5));
    }

    /// With a non-default `zero_line` spec BUT data entirely positive (so the
    /// domain floor is 0 and doesn't strictly cross zero), no zero-line is emitted.
    #[test]
    fn phase7_bar_all_positive_emits_no_zero_line() {
        use chartml_core::theme::{Theme, ZeroLineSpec};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data(); // values: 100, 200, 150 — all positive
        let mut config = make_bar_config();
        let mut t = Theme::default();
        t.zero_line = Some(ZeroLineSpec { color: "#ff0000".into(), width: 1.5 });
        config.theme = t;

        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(
            count_zero_lines(&element),
            0,
            "all-positive data must not emit a zero-line",
        );
    }

    /// Line chart parity: crossing-zero data + non-default zero_line emits one line.
    #[test]
    fn phase7_line_crossing_zero_emits_one_zero_line() {
        use chartml_core::theme::{Theme, ZeroLineSpec};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data_crossing_zero();
        let mut config = make_line_config();
        let mut t = Theme::default();
        t.zero_line = Some(ZeroLineSpec { color: "#00ff00".into(), width: 2.0 });
        config.theme = t;
        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(count_zero_lines(&element), 1);
    }

    // ----- Phase 8: dot_halo wiring -----

    fn count_halos(el: &ChartElement) -> usize {
        count_elements(el, &|e| matches!(e, ChartElement::Path { class, .. } if class == "dot-halo"))
    }

    fn count_dot_markers(el: &ChartElement) -> usize {
        count_elements(el, &|e| matches!(e, ChartElement::Circle { class, .. } if class.contains("dot-marker")))
    }

    #[test]
    fn phase8_line_default_theme_emits_no_halo() {
        let renderer = CartesianRenderer::new();
        let element = renderer.render(&make_bar_data(), &make_line_config()).unwrap();
        assert_eq!(count_halos(&element), 0, "default theme line chart must emit zero halos");
    }

    #[test]
    fn phase8_line_halo_matches_dot_count_and_ordering() {
        use chartml_core::theme::Theme;
        let renderer = CartesianRenderer::new();
        let data = make_bar_data();
        let mut config = make_line_config();
        let mut t = Theme::default();
        t.dot_halo_color = Some("#ffffff".to_string());
        t.dot_halo_width = 1.5;
        config.theme = t;
        let element = renderer.render(&data, &config).unwrap();

        let dot_n = count_dot_markers(&element);
        let halo_n = count_halos(&element);
        assert!(dot_n > 0, "line chart should produce at least one dot-marker");
        assert_eq!(halo_n, dot_n, "one halo per dot-marker required");

        // Halo must precede its dot: in the lines group, walk children and
        // assert every dot-halo Path is immediately followed by a Circle.
        fn walk_lines_group(el: &ChartElement) -> Option<&Vec<ChartElement>> {
            match el {
                ChartElement::Group { class, children, .. } if class == "lines" => Some(children),
                ChartElement::Svg { children, .. } | ChartElement::Group { children, .. } => {
                    children.iter().find_map(walk_lines_group)
                }
                _ => None,
            }
        }
        let lines = walk_lines_group(&element).expect("lines group");
        let mut pair = 0;
        let mut iter = lines.iter().peekable();
        while let Some(el) = iter.next() {
            if let ChartElement::Path { class, .. } = el {
                if class == "dot-halo" {
                    match iter.peek() {
                        Some(ChartElement::Circle { class: cc, .. }) => {
                            assert!(cc.contains("dot-marker"));
                            pair += 1;
                        }
                        other => panic!("halo not followed by dot: {:?}", other.map(|_| "other")),
                    }
                }
            }
        }
        assert_eq!(pair, dot_n);

        // Verify stroke / stroke-width on first halo.
        fn first_halo(el: &ChartElement) -> Option<(String, f64)> {
            match el {
                ChartElement::Path { class, stroke, stroke_width, .. } if class == "dot-halo" => {
                    Some((stroke.clone().unwrap_or_default(), stroke_width.unwrap_or(-1.0)))
                }
                ChartElement::Svg { children, .. } | ChartElement::Group { children, .. } => {
                    children.iter().find_map(first_halo)
                }
                _ => None,
            }
        }
        let (stroke, width) = first_halo(&element).unwrap();
        assert_eq!(stroke, "#ffffff");
        assert!((width - 1.5).abs() < 1e-9);
    }

    /// Area chart parity: crossing-zero data + non-default zero_line emits one line.
    #[test]
    fn phase7_area_crossing_zero_emits_one_zero_line() {
        use chartml_core::theme::{Theme, ZeroLineSpec};
        let renderer = CartesianRenderer::new();
        let data = make_bar_data_crossing_zero();
        let mut config = make_area_config();
        let mut t = Theme::default();
        t.zero_line = Some(ZeroLineSpec { color: "#0000ff".into(), width: 1.0 });
        config.theme = t;
        let element = renderer.render(&data, &config).unwrap();
        assert_eq!(count_zero_lines(&element), 1);
    }
}