import { slugify } from './utils';

/**
 * Pure content helpers — no DB, no `server-only`, so they are directly unit-testable.
 * The same heading algorithm backs both the table of contents and the rendered body,
 * which keeps TOC anchors in sync with the headings they point at.
 */

export type Heading = { id: string; text: string; level: number };

const HEADING_RE = /^(#{2,3})\s+(.+?)\s*#*\s*$/;

/** Words-per-minute used for the reading-time estimate. */
const WPM = 200;

export function readingMinutes(body: string): number {
  const words = body.trim().split(/\s+/).filter(Boolean).length;
  return Math.max(1, Math.round(words / WPM));
}

export function headingId(text: string): string {
  return slugify(text) || 'section';
}

/** Extract h2/h3 headings for a table of contents; ids are de-duplicated in document order. */
export function extractHeadings(body: string): Heading[] {
  const out: Heading[] = [];
  const seen = new Map<string, number>();
  for (const raw of body.split('\n')) {
    const m = HEADING_RE.exec(raw.trim());
    if (!m) continue;
    const level = m[1].length;
    const text = m[2].trim();
    const base = headingId(text);
    const n = seen.get(base) ?? 0;
    seen.set(base, n + 1);
    out.push({ id: n === 0 ? base : `${base}-${n}`, text, level });
  }
  return out;
}

export function isPublished(status: unknown): boolean {
  return status === 'published';
}

/** Keep only published items (a draft must never leak onto a public list). */
export function filterPublished<T extends { status: string }>(items: T[]): T[] {
  return items.filter((item) => isPublished(item.status));
}

/** Derive a plain-text excerpt from a markdown body when none is supplied. */
export function excerptFromBody(body: string, max = 180): string {
  const text = body
    .replace(/```[\s\S]*?```/g, ' ')
    .replace(/!\[[^\]]*\]\([^)]*\)/g, ' ')
    .replace(/\[([^\]]+)\]\([^)]*\)/g, '$1')
    .replace(/[#>*_`]/g, '')
    .replace(/\s+/g, ' ')
    .trim();
  return text.length > max ? `${text.slice(0, max).trimEnd()}…` : text;
}