import { slugify } from './plans';

export { slugify } from './plans';

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

export type ContentBlock = {
  type: 'heading' | 'paragraph' | 'code' | 'list' | 'quote' | 'hr';
  level?: number;
  id?: string;
  text?: string;
  items?: string[];
  ordered?: boolean;
  lang?: string;
  code?: string;
};

/** Anchor id for a heading — a URL-safe slug. */
export function headingId(text: string): string {
  return slugify(text);
}

/** Rough reading time in minutes (≈200 words/min), ignoring fenced code. */
export function readingMinutes(body: string): number {
  const words = body
    .replace(/```[\s\S]*?```/g, ' ')
    .split(/\s+/)
    .filter(Boolean).length;
  return Math.max(1, Math.round(words / 200));
}

export function isPublished(item: { status: string }): boolean {
  return item.status === 'published';
}

export function filterPublished<T extends { status: string }>(items: T[]): T[] {
  return items.filter(isPublished);
}

function escapeHtml(value: string): string {
  return value.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
}

/** Allow only safe link targets; anything else becomes a no-op anchor. */
function sanitizeUrl(url: string): string {
  const trimmed = url.trim();
  if (/^(https?:|mailto:|\/|#)/i.test(trimmed)) return trimmed.replace(/"/g, '%22');
  return '#';
}

/**
 * Render a single markdown line's inline spans to (escaped) HTML: code, links, bold and italic.
 * Input is HTML-escaped first, so the result is safe to bind with `v-html`.
 */
export function renderInline(text: string): string {
  let out = escapeHtml(text);
  out = out.replace(/`([^`]+)`/g, '<code>$1</code>');
  out = out.replace(/\*\*([^*]+)\*\*/g, '<strong>$1</strong>');
  out = out.replace(/(^|[^*])\*([^*]+)\*/g, '$1<em>$2</em>');
  out = out.replace(/\[([^\]]+)\]\(([^)\s]+)\)/g, (_m, label: string, href: string) => `<a href="${sanitizeUrl(href)}">${label}</a>`);
  return out;
}

const KEYWORDS =
  'const|let|var|function|return|if|else|for|while|do|switch|case|break|continue|new|class|extends|interface|type|enum|import|from|export|default|await|async|try|catch|finally|throw|typeof|instanceof|in|of|as|is|null|undefined|true|false|this|super|void|yield|def|end|elif|then|fi|esac|echo|local|print|lambda|pass|raise|with|not|and|or|select|where|insert|update|delete|join|group|order|by|limit|pub|fn|impl|match|use|mod|struct|trait|package|func|go|defer';

const TOKEN_RE = new RegExp(
  `(\\/\\/[^\\n]*|\\/\\*[\\s\\S]*?\\*\\/)|("(?:\\\\.|[^"\\\\])*"|'(?:\\\\.|[^'\\\\])*'|\`(?:\\\\.|[^\`\\\\])*\`)|(\\b\\d+(?:\\.\\d+)?\\b)|(\\b(?:${KEYWORDS})\\b)`,
  'g',
);

/** Tiny language-agnostic highlighter over escaped code — comments, strings, numbers, keywords. */
export function highlightCode(code: string, _lang = ''): string {
  const escaped = escapeHtml(code);
  return escaped.replace(TOKEN_RE, (match, comment, str, num, keyword) => {
    if (comment) return `<span class="tok-com">${match}</span>`;
    if (str) return `<span class="tok-str">${match}</span>`;
    if (num) return `<span class="tok-num">${match}</span>`;
    if (keyword) return `<span class="tok-kw">${match}</span>`;
    return match;
  });
}

function uniqueHeadingId(used: Map<string, number>, text: string): string {
  const base = headingId(text) || 'section';
  const seen = used.get(base) ?? 0;
  used.set(base, seen + 1);
  return seen === 0 ? base : `${base}-${seen + 1}`;
}

const FENCE_RE = /^```(\w*)\s*$/;
const HEADING_RE = /^(#{1,6})\s+(.*)$/;
const HR_RE = /^(-{3,}|\*{3,}|_{3,})\s*$/;
const QUOTE_RE = /^>\s?/;
const UL_RE = /^[-*+]\s+/;
const OL_RE = /^\d+\.\s+/;

function startsBlock(line: string): boolean {
  return (
    FENCE_RE.test(line) ||
    HEADING_RE.test(line) ||
    HR_RE.test(line) ||
    QUOTE_RE.test(line) ||
    UL_RE.test(line) ||
    OL_RE.test(line)
  );
}

/**
 * Parse a markdown-lite body into renderable blocks. Supports fenced code (with an optional
 * language), ATX headings, ordered/unordered lists, blockquotes, horizontal rules and paragraphs.
 * Deliberately dependency-free — the content template ships no markdown package.
 */
export function renderBlocks(body: string): ContentBlock[] {
  const lines = body.replace(/\r\n/g, '\n').split('\n');
  const blocks: ContentBlock[] = [];
  const used = new Map<string, number>();
  let i = 0;

  while (i < lines.length) {
    const line = lines[i] ?? '';
    if (/^\s*$/.test(line)) {
      i++;
      continue;
    }

    const fence = line.match(FENCE_RE);
    if (fence) {
      const lang = fence[1] ?? '';
      i++;
      const buffer: string[] = [];
      while (i < lines.length && !/^```\s*$/.test(lines[i] ?? '')) {
        buffer.push(lines[i] ?? '');
        i++;
      }
      if (i < lines.length) i++;
      blocks.push({ type: 'code', lang, code: buffer.join('\n') });
      continue;
    }

    const heading = line.match(HEADING_RE);
    if (heading) {
      const text = (heading[2] ?? '').trim();
      blocks.push({ type: 'heading', level: (heading[1] ?? '').length, text, id: uniqueHeadingId(used, text) });
      i++;
      continue;
    }

    if (HR_RE.test(line)) {
      blocks.push({ type: 'hr' });
      i++;
      continue;
    }

    if (QUOTE_RE.test(line)) {
      const parts: string[] = [];
      while (i < lines.length && QUOTE_RE.test(lines[i] ?? '')) {
        parts.push((lines[i] ?? '').replace(QUOTE_RE, ''));
        i++;
      }
      blocks.push({ type: 'quote', text: parts.join(' ').trim() });
      continue;
    }

    if (UL_RE.test(line) || OL_RE.test(line)) {
      const ordered = OL_RE.test(line);
      const pattern = ordered ? OL_RE : UL_RE;
      const items: string[] = [];
      while (i < lines.length && pattern.test(lines[i] ?? '')) {
        items.push((lines[i] ?? '').replace(pattern, '').trim());
        i++;
      }
      blocks.push({ type: 'list', ordered, items });
      continue;
    }

    const buffer: string[] = [];
    while (i < lines.length) {
      const current = lines[i] ?? '';
      if (/^\s*$/.test(current) || startsBlock(current)) break;
      buffer.push(current.trim());
      i++;
    }
    blocks.push({ type: 'paragraph', text: buffer.join(' ') });
  }

  return blocks;
}

/** Table-of-contents entries (h2–h4) parsed from a body, reusing `renderBlocks` anchor ids. */
export function extractHeadings(body: string): TocEntry[] {
  return renderBlocks(body)
    .filter((b) => b.type === 'heading' && (b.level ?? 0) >= 2 && (b.level ?? 0) <= 4 && !!b.id)
    .map((b) => ({ id: b.id as string, text: b.text ?? '', level: b.level ?? 2 }));
}