You are refactoring a single JavaScript (D3) chart function. Goal: enforce a clear block structure, centralized style control, strict config-driven behavior, and production-ready code.

I. Assumptions
• Input: one JS function using D3.
• Preserve any `/* REQUIREMENTS_BEGIN … REQUIREMENTS_END */` block exactly at the top.

II. Mandatory Block Skeleton (use comments)
0 Metadata & Requirements
1 Config Parsing & Validation
2 Style & Helper Definitions
3 SVG Root Init (no viewBox, width/height from config || 800×600)
4 Layout & Dimensions
5 Data Preprocessing
6 Scales
7 Defs (gradients, patterns, filters)
8 Components (axes, grid, legend — NO titles)
9 Main Marks (bars, lines, etc.)
10 Enhancements & Interaction
11 Cleanup & Return

III. Style Rules (all in Block 2)
• const fillStyle = {token: color|gradient|pattern};
• fillStyle.typography = {labelTextSize, dataTextSize, axisTickTextSize, …};
• Later blocks must reference these tokens only.
• Implement estimateTextWidth() with detached in-memory SVG.

IV. Content Restrictions
• Do not render titles/subtitles.
• Delete optional effects that are off by default.
• No per-datum try/catch or value checks before scale usage.

V. Class Naming (add class attr on creation)
value | label | text | icon | image | mark | axis | other

VI. Naming Conventions
config, chartDataArray, svgRoot, mainChartGroup, barElements, xAxisGroup, xScale, yScale, colorScale, chartMargins, containerWidth/Height, innerWidth/Height.

VII. Commenting
Block headers only; minimal inline comments (focus on “why”).

VIII. Metadata JSON Template (inside REQUIREMENTS block; keep exact keys, fill enumerations with one value — use "none" if not applicable)
```json
{
  "chart_type": "Grouped Circular Bar Chart",
  "chart_name": "grouped_circular_bar_chart_01",
  "is_composite": false,
  "required_fields": ["x", "y", "group"],
  "hierarchy": ["group"],
  "required_fields_type": [["categorical"], ["numerical"], ["categorical"]],
  "required_fields_range": [[2,20],[0,"inf"],[2,5]],
  "required_fields_icons": ["group"],
  "required_other_icons": [],
  "required_fields_colors": ["group"],
  "required_other_colors": ["primary"],
  "min_height": 400,
  "min_width": 400,
  "background": "no",
  "elementAlignment": "none",            // left | center | right | top | bottom
  "xAxis": "none",                        // visible | minimal | none
  "yAxis": "none",                        // visible | minimal | none
  "gridLineType": "none",                // subtle | prominent | none
  "legend": "none",                       // normal | compact | detailed | none
  "dataLabelPosition": "none",            // outside | inside | center_element | auto | none
  "artisticStyle": "clean",               // clean | hand_drawn | gradient_gloss | shadow
  "valueSortDirection": "none",           // ascending | descending | none
  "iconographyUsage": "none"              // none | categorical_markers_overlay_internal | categorical_markers_overlay_edge | element_replacement | background_contextual | adjacent_indicator
}
```