// The HTML sitemap answers of the sitemap plugin (GET
// <backendBase>/_sitemap/api/v1/html?locale= and
// /_sitemap/api/v1/html/{group}?locale=&page=) reduced to the fields the
// layer renders, plus the checks of the layer's proxy route. Pure, so
// `node --test` drives it.

import type { SeoSitemapEntry, SeoSitemapGroup, SeoSitemapGroupPage, SeoSitemapOverview } from '../../app/utils/types.ts'

export const HTML_SITEMAP_LOCALE = /^[a-z]{2,3}(?:[-_][A-Za-z0-9]{2,8})*$/
export const HTML_SITEMAP_GROUP = /^[a-z0-9][a-z0-9-]{0,63}$/
/** Nesting deeper than this (a category tree) is cut off. */
const MAX_DEPTH = 8

const str = (v: unknown) => (typeof v === 'string' ? v : '')
const int = (v: unknown) => (typeof v === 'number' && Number.isInteger(v) && v >= 0 ? v : 0)

function entries(value: unknown, depth = 0): SeoSitemapEntry[] {
  if (!Array.isArray(value) || depth > MAX_DEPTH) return []
  const out: SeoSitemapEntry[] = []
  for (const e of value) {
    if (!e || typeof e !== 'object') continue
    const o = e as Record<string, unknown>
    const title = str(o.title)
    if (!title) continue
    const children = entries(o.children, depth + 1)
    out.push(children.length > 0 ? { title, url: str(o.url), children } : { title, url: str(o.url) })
  }
  return out
}

/** The overview with only its non-empty groups. */
export function htmlSitemapOverview(value: unknown): SeoSitemapOverview {
  const groups: SeoSitemapGroup[] = []
  const raw = value && typeof value === 'object' ? (value as { groups?: unknown }).groups : null
  for (const g of Array.isArray(raw) ? raw : []) {
    if (!g || typeof g !== 'object') continue
    const o = g as Record<string, unknown>
    const slug = str(o.slug)
    const list = entries(o.entries)
    if (!HTML_SITEMAP_GROUP.test(slug) || list.length === 0) continue
    groups.push({ key: str(o.key) || slug, slug, title: str(o.title) || slug, total: int(o.total) || list.length, entries: list, more: o.more === true })
  }
  return { groups }
}

/** One page of a group. */
export function htmlSitemapGroupPage(value: unknown, group: string): SeoSitemapGroupPage {
  const o = value && typeof value === 'object' ? (value as Record<string, unknown>) : {}
  const page = int(o.page) || 1
  return { group, title: str(o.title) || group, page, pages: Math.max(int(o.pages), page), entries: entries(o.entries) }
}

/** A page query value: 1 when absent, the number for 1 to 999999, else null. */
export function htmlSitemapPage(raw: unknown): number | null {
  if (raw === undefined || raw === null || raw === '') return 1
  if (typeof raw !== 'string' || !/^\d{1,6}$/.test(raw)) return null
  const n = Number(raw)
  return n >= 1 ? n : null
}