import { ARTICLES, PAGES, RELEASES, TAGS } from '../constants/collections'
import { createDiagnostics } from '../diagnostics'
import type { Diagnostics } from '../diagnostics/types'
import { createContentReader } from './reader'
import type { ArticleEntry, Content, PageEntry, ReleaseEntry, TagEntry } from './types'

interface CollectionReader<T> {
  list(): Promise<string[]>
  read(id: string): Promise<T | null>
}

function reason(error: unknown): string {
  const [first, ...rest] = (error instanceof Error ? error.message : String(error)).split('\n')
  return first.endsWith(':') && rest.length ? rest.join('; ') : first
}

async function readAll<T>(
  reader: CollectionReader<T>,
  collection: string,
  problems: Diagnostics,
): Promise<Map<string, T>> {
  const entries = new Map<string, T>()
  await Promise.all(
    (await reader.list()).map(async (id) => {
      try {
        const entry = await reader.read(id)
        if (entry) entries.set(id, entry)
      } catch (error) {
        problems.error(collection, id, reason(error))
      }
    }),
  )
  return entries
}

export async function loadContent(): Promise<Content> {
  const { collections } = createContentReader()
  const problems = createDiagnostics()
  const [articles, pages, tags, releases] = await Promise.all([
    readAll<ArticleEntry>(collections.articles, ARTICLES, problems),
    readAll<PageEntry>(collections.pages, PAGES, problems),
    readAll<TagEntry>(collections.tags, TAGS, problems),
    readAll<ReleaseEntry>(collections.releases, RELEASES, problems),
  ])
  return { articles, pages, tags, releases, diagnostics: problems.list }
}