import type { Paragraph, PhrasingContent, Root, RootContent } from "mdast";

// Display-only: preserve every inline node and character. Never rewrite source
// files, SQL, links, existing lists or short authored paragraphs.
export function readableParagraphs() {
  return (tree: Root) => {
    tree.children = tree.children.flatMap<RootContent>(node => {
      if (node.type !== "paragraph") return [node];
      const length = node.children.reduce((total, child) => total + ("value" in child ? String(child.value).length : 0), 0);
      if (length < 360) return [node];
      const paragraphs: Paragraph[] = [];
      let children: PhrasingContent[] = [];
      let size = 0;
      for (const child of node.children) {
        if (child.type !== "text") {
          children.push(child);
          if ("value" in child) size += String(child.value).length;
          continue;
        }
        // Boundaries must be outside inline code/emphasis/links. Decimal points
        // and identifiers cannot match because they have no following space.
        let start = 0;
        for (const match of child.value.matchAll(/;\s+|[.!?]\s+(?=[A-ZÀ-Ý])/g)) {
          const end = match.index! + match[0].length;
          if (size + end - start < 180) continue;
          children.push({ type: "text", value: child.value.slice(start, end) });
          paragraphs.push({ type: "paragraph", children });
          children = [];
          size = 0;
          start = end;
        }
        if (start < child.value.length) {
          children.push({ type: "text", value: child.value.slice(start) });
          size += child.value.length - start;
        }
      }
      if (children.length) paragraphs.push({ type: "paragraph", children });
      return paragraphs;
    });
  };
}