import type { TangledLocation } from './forge-tangled.js'

export interface PageFetchResponse {
  text(): Promise<string>
}

export type PageFetch = (url: string) => Promise<PageFetchResponse>

const PULL_URI = /at:\/\/did:[^/"'<\s]+\/sh\.tangled\.repo\.pull\/[^/"'<\s]+/
const pullPage = (location: TangledLocation, number: number): string =>
  `https://${location.host}/${location.owner}/${location.repo}/pulls/${number}`

/** Resolve an appview number only when the page itself names the pull record. Tangled returns its
 * 404 page with HTTP 200, so the body proof, rather than the response status, is authoritative. */
export async function pullAtNumber(
  fetchPage: PageFetch,
  location: TangledLocation,
  number: number,
): Promise<string | undefined> {
  const body = await (await fetchPage(pullPage(location, number))).text()
  return PULL_URI.exec(body)?.[0]
}

/** Find a newly opened pull in the appview's newest-first list, verifying every candidate page.
 * The cap is deliberately small: a fresh pull is normally the first row, and exhausting the cap is
 * logged rather than silently turning an incomplete search into an assertion. */
export async function numberForPull(
  fetchPage: PageFetch,
  location: TangledLocation,
  uri: string,
  options: { limit?: number; log?: (message: string) => void } = {},
): Promise<string | undefined> {
  const listUrl = `https://${location.host}/${location.owner}/${location.repo}/pulls`
  const body = await (await fetchPage(listUrl)).text()
  const numbers: number[] = []
  const seen = new Set<number>()
  const href = /\/pulls\/([1-9][0-9]*)/g
  for (const match of body.matchAll(href)) {
    const number = Number(match[1])
    if (!seen.has(number)) {
      seen.add(number)
      numbers.push(number)
    }
  }
  const limit = options.limit ?? 5
  for (const number of numbers.slice(0, limit)) {
    if ((await pullAtNumber(fetchPage, location, number)) === uri) return pullPage(location, number)
  }
  if (numbers.length > limit) {
    options.log?.(`tangled page-link search for ${uri} exhausted its ${limit}-candidate budget`)
  }
  return undefined
}