// Typed client for the anonymous GET routes of the Journal API. It wraps an
// injected fetcher, so the Nuxt composable decides the base URL and headers
// and `node --test` can drive it with a stub. It never calls a write route.

import type {
  JournalAuthor,
  JournalCategory,
  JournalItem,
  JournalPage,
  JournalPost,
  JournalPostDetail,
  JournalTag,
} from './types.ts'

/** The Journal API's per_page ceiling. */
export const JOURNAL_MAX_PER_PAGE = 30

/** The Journal API's per_page default. */
export const JOURNAL_DEFAULT_PER_PAGE = 9

/** Issues one GET for `path` (e.g. "/posts") with `query`, resolving the parsed JSON. */
export type JournalFetcher = (path: string, query?: Record<string, string | number>) => Promise<unknown>

export interface PostListOptions {
  page?: number
  perPage?: number
  /** "<column> <asc|desc>", passed through verbatim. */
  sort?: string
  /** Category slug or id; the API includes nested children. */
  category?: string
  tag?: string
  search?: string
}

export interface AuthorPostListOptions {
  page?: number
  perPage?: number
  sort?: string
}

/** Clamps a per_page value to 1..30 like the API does; non-numeric gives the default 9. */
export function clampPerPage(value: unknown): number {
  const n = typeof value === 'number' ? value : typeof value === 'string' && value.trim() !== '' ? Number(value) : NaN
  if (!Number.isFinite(n)) return JOURNAL_DEFAULT_PER_PAGE
  const i = Math.trunc(n)
  if (i < 1) return 1
  if (i > JOURNAL_MAX_PER_PAGE) return JOURNAL_MAX_PER_PAGE
  return i
}

/** Query for GET /posts: per_page always clamped, other keys only when set. */
export function buildPostListQuery(opts: PostListOptions = {}): Record<string, string | number> {
  const q: Record<string, string | number> = { per_page: clampPerPage(opts.perPage) }
  if (opts.page !== undefined && Number.isInteger(opts.page) && opts.page > 0) q.page = opts.page
  if (opts.sort) q.sort = opts.sort
  if (opts.category) q.category = opts.category
  if (opts.tag) q.tag = opts.tag
  if (opts.search) q.search = opts.search
  return q
}

/** Encodes each "/"-separated segment of a slug (post slugs may contain "/"). */
export function encodeSlugPath(slug: string): string {
  return String(slug)
    .split('/')
    .map((part) => encodeURIComponent(part))
    .join('/')
}

/** Depth-first flattening of the categories tree, parents before children. */
export function flattenCategories(tree: readonly JournalCategory[] | null | undefined): JournalCategory[] {
  const out: JournalCategory[] = []
  const walk = (nodes: readonly JournalCategory[] | null | undefined): void => {
    for (const node of nodes ?? []) {
      out.push(node)
      walk(node.children)
    }
  }
  walk(tree)
  return out
}

/** True for a fetch error that carries HTTP status 404 (ofetch, h3 or plain). */
export function isNotFound(err: unknown): boolean {
  if (!err || typeof err !== 'object') return false
  const e = err as { status?: unknown; statusCode?: unknown; response?: { status?: unknown } }
  return e.status === 404 || e.statusCode === 404 || e.response?.status === 404
}

export interface JournalClient {
  getPost(slug: string): Promise<JournalPostDetail | null>
  listPosts(opts?: PostListOptions): Promise<JournalPage<JournalPost>>
  listCategories(): Promise<JournalCategory[]>
  findCategory(slug: string): Promise<JournalCategory | null>
  listTags(): Promise<JournalTag[]>
  getAuthor(slug: string): Promise<JournalAuthor | null>
  listAuthorPosts(slug: string, opts?: AuthorPostListOptions): Promise<JournalPage<JournalPost> | null>
}

export function createJournalClient(fetcher: JournalFetcher): JournalClient {
  const orNull = async <T>(p: Promise<T>): Promise<T | null> => {
    try {
      return await p
    } catch (err) {
      if (isNotFound(err)) return null
      throw err
    }
  }

  const listCategories = async (): Promise<JournalCategory[]> => {
    // include_empty=1 always (D-24): an empty category still has a page.
    const res = (await fetcher('/categories', { include_empty: 1 })) as JournalItem<JournalCategory[]>
    return Array.isArray(res?.data) ? res.data : []
  }

  return {
    async getPost(slug) {
      const res = (await orNull(fetcher(`/posts/${encodeSlugPath(slug)}`))) as JournalItem<JournalPostDetail> | null
      return res?.data ?? null
    },

    async listPosts(opts = {}) {
      return (await fetcher('/posts', buildPostListQuery(opts))) as JournalPage<JournalPost>
    },

    listCategories,

    async findCategory(slug) {
      const rows = flattenCategories(await listCategories())
      return rows.find((c) => c.slug === slug) ?? null
    },

    async listTags() {
      const res = (await fetcher('/tags')) as JournalItem<JournalTag[]>
      return Array.isArray(res?.data) ? res.data : []
    },

    async getAuthor(slug) {
      const res = (await orNull(fetcher(`/authors/${encodeURIComponent(slug)}`))) as JournalItem<JournalAuthor> | null
      return res?.data ?? null
    },

    async listAuthorPosts(slug, opts = {}) {
      const q: Record<string, string | number> = { per_page: clampPerPage(opts.perPage) }
      if (opts.page !== undefined && Number.isInteger(opts.page) && opts.page > 0) q.page = opts.page
      if (opts.sort) q.sort = opts.sort
      return (await orNull(fetcher(`/authors/${encodeURIComponent(slug)}/posts`, q))) as JournalPage<JournalPost> | null
    },
  }
}