import Handlebars from 'handlebars';

/** One numbered clause of a dynamic article, with optional nested bullets. */
export interface RenderedClause {
  text: string;
  bullets: string[];
}

/** A dynamic article ready for the Handlebars template. */
export interface RenderedArticle {
  number: number;
  title: string;
  /** Set (instead of clauses) when the body is a single plain paragraph. */
  paragraph?: string;
  clauses: RenderedClause[];
}

/**
 * Parse a template article body into clauses. Format: one clause per line;
 * lines prefixed with "- " become bullets nested under the preceding clause.
 * A body that reduces to a single clause without bullets renders as a plain
 * paragraph rather than a numbered list of one.
 */
export function parseArticleBody(body: string): Pick<RenderedArticle, 'paragraph' | 'clauses'> {
  const lines = (body ?? '')
    .split('\n')
    .map((line) => line.trim())
    .filter((line) => line.length > 0);

  const clauses: RenderedClause[] = [];
  for (const line of lines) {
    if (line.startsWith('- ')) {
      const bullet = line.slice(2).trim();
      if (clauses.length === 0) {
        clauses.push({ text: bullet, bullets: [] });
      } else {
        clauses[clauses.length - 1].bullets.push(bullet);
      }
    } else {
      clauses.push({ text: line, bullets: [] });
    }
  }

  if (clauses.length === 1 && clauses[0].bullets.length === 0) {
    return { paragraph: clauses[0].text, clauses: [] };
  }
  return { clauses };
}

/**
 * Interpolate Handlebars placeholders ({{client.companyName}}, {{contractDate}},
 * …) inside admin-authored template text against the contract view model.
 * Malformed placeholders must never break document generation — fall back to
 * the raw text.
 */
export function interpolateTemplateText(text: string, context: unknown): string {
  if (!text || !text.includes('{{')) return text ?? '';
  try {
    return Handlebars.compile(text)(context);
  } catch {
    return text;
  }
}