import type { H3Event } from 'h3'

interface LookupValue {
  value: string | null
}

// title, date and author_or_director are lookups through the `books` link
export interface ReviewRow {
  id: number
  books: LookupValue[]
  title: LookupValue[]
  date: LookupValue[]
  author_or_director: LookupValue[]
  review: string | null
  medium: SelectOption | null
}

interface SelectOption {
  id: number
  value: string
}

interface Field {
  name: string
  select_options?: SelectOption[]
  link_row_table_id?: number
}

const FIELD_CACHE_MS = 10 * 60_000

let reviewFields: { fields: Field[], fetchedAt: number } | null = null

async function fields(event: H3Event): Promise<Field[]> {
  if (!reviewFields || Date.now() - reviewFields.fetchedAt > FIELD_CACHE_MS) {
    reviewFields = { fields: await listFields<Field>(event, diaryTable(event, 'reviews')), fetchedAt: Date.now() }
  }
  return reviewFields.fields
}

function toMedium(value: string | undefined): Medium | null {
  return MEDIUM_KEYS.find(medium => MEDIUMS[medium].label === value) ?? null
}

export function lookupValues(values: LookupValue[] | null | undefined): string[] {
  return (values ?? []).map(({ value }) => value?.trim()).filter((value): value is string => !!value)
}

export function toReview(row: ReviewRow): Review {
  return {
    id: row.id,
    date: lookupValues(row.date)[0] ?? '',
    title: lookupValues(row.title).join(' / ') || lookupValues(row.books).join(' / '),
    author: lookupValues(row.author_or_director).join(', ') || null,
    text: (row.review ?? '').replace(/&nbsp;/g, ' ').trim(),
    medium: toMedium(row.medium?.value)
  }
}

export async function mediumOptionId(event: H3Event, medium: Medium): Promise<number> {
  const options = (await fields(event)).find(field => field.name === 'medium')?.select_options ?? []
  const id = options.find(option => toMedium(option.value) === medium)?.id
  if (!id) {
    throw createError({ statusCode: 500, statusMessage: `The medium field has no "${MEDIUMS[medium].label}" option` })
  }
  return id
}

/** The books table, taken from the reviews table's `books` link field. */
export async function booksTableId(event: H3Event): Promise<string> {
  const id = (await fields(event)).find(field => field.name === 'books')?.link_row_table_id
  if (!id) {
    throw createError({ statusCode: 500, statusMessage: 'The reviews table has no "books" link field' })
  }
  return String(id)
}