/**
 * scripts/generate-docs/lib/search-index.ts
 *
 * Builds `.documentation/js/search-index.js` from the outline of every rendered
 * page. `ss docs` opens the site over `file://`, where `fetch()` of a JSON file
 * is refused — so the index ships as a script that sets `window.SS_DOCS_INDEX`.
 *
 * Entry shape (short keys keep the file small):
 *   { s: slug, a: 'd' | 't' (discover / tech), t: {fr,en} title, g: {fr,en} group | null,
 *     x: {fr,en} intro excerpt, h: [[anchorId, titleFr, titleEn, textFr, textEn], …] }
 */
import { localise, type Localised } from './i18n-types';
import type { LocalisedString } from './markdown-parser';
import type { PageOutline } from './page-outline';
import type { PagePlacement } from './sidebar-builder';
import type { Skill } from './skill-parser';

export interface SearchPageInput {
  slug: string;
  title: LocalisedString;
  placement?: PagePlacement;
  outline: PageOutline;
}

type SectionTuple = [string, string, string, string, string];

interface SearchEntry {
  s: string;
  a: 'd' | 't';
  t: Localised;
  g: Localised | null;
  x: Localised;
  h: SectionTuple[];
}

const SECTION_TEXT_MAX = 400;
const INTRO_TEXT_MAX = 220;
const SKILL_TEXT_MAX = 220;

function clip(text: string, max: number): string {
  if (text.length <= max) return text;
  const cut = text.slice(0, max);
  const space = cut.lastIndexOf(' ');
  return (space > max * 0.6 ? cut.slice(0, space) : cut) + '…';
}

function clipBoth(value: Localised, max: number): Localised {
  return { fr: clip(value.fr, max), en: clip(value.en, max) };
}

/** The skill catalogue page lists every skill as an anchored row (`#skill-<slug>`). */
export const SKILL_CATALOGUE_PAGE = 'commands';

function toEntry(page: SearchPageInput, skills: Skill[]): SearchEntry {
  const h: SectionTuple[] = page.outline.sections.map((sec) => [
    sec.id,
    sec.title.fr,
    sec.title.en,
    clip(sec.text.fr, SECTION_TEXT_MAX),
    clip(sec.text.en, SECTION_TEXT_MAX),
  ]);
  if (page.slug === SKILL_CATALOGUE_PAGE) {
    for (const skill of skills) {
      const text = clip(skill.description ?? '', SKILL_TEXT_MAX);
      h.push([`skill-${skill.slug}`, `/${skill.slug}`, `/${skill.slug}`, text, text]);
    }
  }
  return {
    s: page.slug,
    a: page.placement?.audience === 'discover' ? 'd' : 't',
    t: localise(page.placement?.label ?? page.title),
    g: page.placement?.group ? localise(page.placement.group) : null,
    x: clipBoth(page.outline.intro, INTRO_TEXT_MAX),
    h,
  };
}

/** One page per line, so a content change shows up as a readable git diff. */
export function buildSearchIndex(pages: SearchPageInput[], skills: Skill[], version: string): string {
  const entries = pages.map((p) => JSON.stringify(toEntry(p, skills)));
  return (
    '/* AUTO-GENERATED by scripts/generate-docs — do not edit. Rebuild with `npm run build:docs`. */\n' +
    `window.SS_DOCS_INDEX = {"version":${JSON.stringify(version)},"pages":[\n` +
    entries.join(',\n') +
    '\n]};\n'
  );
}

/**
 * Throws when a search result would point to an anchor missing from its page —
 * the failure mode of the previous hand-written index (21 dead anchors out of 22).
 */
export function assertIndexAnchors(pages: SearchPageInput[], skills: Skill[], htmlBySlug: Map<string, string>): void {
  const dead: string[] = [];
  for (const page of pages) {
    const html = htmlBySlug.get(page.slug) ?? '';
    for (const [id] of toEntry(page, skills).h) {
      if (!html.includes(` id="${id}"`)) dead.push(`${page.slug}.html#${id}`);
    }
  }
  if (dead.length) {
    throw new Error(`search index points to anchors missing from their page:\n  - ${dead.join('\n  - ')}`);
  }
}