/**
 * Stat sheet template engine — parses *.sheet.svg files and extracts
 * <text> elements containing ${key} template patterns.
 *
 * The SVG element is parsed once via DOMParser. The caller (StatsView)
 * reactively updates the text nodes whenever the stats store changes.
 */

/** Regex matching ${key} template patterns (captures the key name). */
const TEMPLATE_RE = /\$\{(\w+)\}/g;

/** A single template binding in a <text> element. */
export interface TextTemplate {
  el: SVGTextElement;
  template: string;
  keys: string[];
}

/** The result of parsing a stat sheet SVG string. */
export interface ParsedSheet {
  svgElement: SVGSVGElement;
  templates: TextTemplate[];
}

/**
 * Parse an SVG string into a live DOM element and extract all text
 * elements that contain ${key} template patterns.
 */
export function parseSheet(svgString: string): ParsedSheet {
  const parser = new DOMParser();
  const doc = parser.parseFromString(svgString, "image/svg+xml");
  const svgElement = doc.documentElement as unknown as SVGSVGElement;

  if (!svgElement || svgElement.tagName !== "svg") {
    return {
      svgElement: document.createElementNS(
        "http://www.w3.org/2000/svg",
        "svg",
      ) as SVGSVGElement,
      templates: [],
    };
  }

  const templates: TextTemplate[] = [];
  const textEls = svgElement.querySelectorAll("text");

  for (const el of textEls) {
    const content = el.textContent;
    if (!content) continue;

    TEMPLATE_RE.lastIndex = 0;
    const keys: string[] = [];
    let m: RegExpExecArray | null;
    while ((m = TEMPLATE_RE.exec(content)) !== null) {
      keys.push(m[1]);
    }

    if (keys.length > 0) {
      templates.push({ el: el as SVGTextElement, template: content, keys });
    }
  }

  return { svgElement, templates };
}