/**
 * Cook recipe feedback and search signals (YunYouJun/cook#100 follow-up).
 *
 * - `report`: a user flags a recipe (dead video, wrong ingredients, ...).
 *   Signing in is optional; anonymous reports are keyed by a random device id.
 * - `signal`: anonymous, aggregated search signals (a selection with no
 *   results, or which result was opened at which rank) used to tune filtering.
 * - `export`: maintainers pull everything for the recipe-data-review skill.
 *   Only over the HTTP trigger with the COOK_FEEDBACK_EXPORT_TOKEN header.
 *
 * All collections are ADMINONLY; browsers only reach them through this
 * function. Raw device ids and uids are hashed before they are stored as a
 * reporter key; the uid itself is kept only on reports from signed-in users so
 * maintainers can follow up.
 */

const { Buffer } = require('node:buffer')
const crypto = require('node:crypto')
const process = require('node:process')

const FEEDBACK = 'cook_recipe_feedback'
const SIGNALS = 'cook_search_signals'
const QUOTA = 'cook_feedback_quota'

const KINDS = new Set(['video', 'stuff', 'info', 'other'])
const MODES = new Set(['loose', 'strict', 'survival'])
const SIGNAL_TYPES = new Set(['empty', 'open'])
const DAILY_QUOTA = 200
const MAX_NOTE = 200
const MAX_NAME = 100
const MAX_STUFF = 12
const MAX_WORD = 20
const DEVICE_ID_RE = /^[\w-]{16,64}$/
const EXPORT_PAGE = 1000
const ANON_UIDS = new Set(['', 'anon'])

let app

function getApp() {
  if (!app) {
    // Loaded lazily so tests can inject a fake app without the SDK installed.
    const tcb = require('@cloudbase/node-sdk')
    app = tcb.init({ env: tcb.SYMBOL_CURRENT_ENV })
  }
  return app
}

function callerUid() {
  try {
    const info = getApp().auth().getUserInfo()
    const uid = info && info.uid ? String(info.uid) : ''
    return ANON_UIDS.has(uid) || (info && info.isAnonymous === true) ? '' : uid
  }
  catch {
    return ''
  }
}

function fail(code) {
  return { ok: false, code }
}

function hash(text) {
  return crypto.createHash('sha256').update(text).digest('hex').slice(0, 32)
}

/** Calendar day in China, which is when the quota resets. */
function today(now) {
  return new Date(now + 8 * 3600 * 1000).toISOString().slice(0, 10)
}

function isWord(value, max = MAX_WORD) {
  return typeof value === 'string' && value.trim().length > 0 && value.length <= max
}

function isIndex(value, max) {
  return Number.isInteger(value) && value >= 0 && value <= max
}

/** Who is calling: the account when signed in, otherwise the device. */
function readReporter(event) {
  const uid = callerUid()
  if (uid)
    return { key: hash(`uid:${uid}`), uid }
  if (typeof event.deviceId === 'string' && DEVICE_ID_RE.test(event.deviceId))
    return { key: hash(`device:${event.deviceId}`), uid: '' }
  return null
}

/** Count one call against the reporter's daily quota. */
async function takeQuota(reporter, now) {
  const db = getApp().database()
  const id = hash(`${reporter.key}|${today(now)}`)
  const doc = db.collection(QUOTA).doc(id)
  const result = await doc.update({ count: db.command.inc(1) })
  if (!result || !result.updated) {
    await doc.set({ count: 1, day: today(now) })
    return true
  }
  const current = await doc.get()
  const count = current && current.data && current.data[0] ? current.data[0].count : 0
  return count <= DAILY_QUOTA
}

async function report(event, reporter, now) {
  const { recipeId, recipeName, kind } = event
  const note = typeof event.note === 'string' ? event.note.trim().slice(0, MAX_NOTE) : ''
  if (!isIndex(recipeId, 1e6) || !isWord(recipeName, MAX_NAME) || !KINDS.has(kind))
    return fail('INVALID_REPORT')
  if (!await takeQuota(reporter, now))
    return fail('RATE_LIMITED')

  // One report per reporter, recipe and kind per day; repeats just update the note.
  const day = today(now)
  const id = hash(`${reporter.key}|${recipeId}|${kind}|${day}`)
  await getApp().database().collection(FEEDBACK).doc(id).set({
    recipeId,
    recipeName: recipeName.trim(),
    kind,
    note,
    reporter: reporter.key,
    uid: reporter.uid,
    day,
    createdAt: now,
  })
  return { ok: true }
}

function readSelection(event) {
  const stuff = Array.isArray(event.stuff) ? event.stuff : null
  if (!stuff || !stuff.length || stuff.length > MAX_STUFF || !stuff.every(item => isWord(item)))
    return null
  const tool = event.tool ?? ''
  const mode = event.mode ?? 'loose'
  if ((tool && !isWord(tool)) || !MODES.has(mode))
    return null
  return { stuff: [...new Set(stuff.map(item => item.trim()))].sort(), tool, mode }
}

async function signal(event, reporter, now) {
  const selection = readSelection(event)
  if (!selection || !SIGNAL_TYPES.has(event.type))
    return fail('INVALID_SIGNAL')
  const open = event.type === 'open'
  if (open && (!isIndex(event.recipeId, 1e6) || !isIndex(event.rank, 999)))
    return fail('INVALID_SIGNAL')
  if (!await takeQuota(reporter, now))
    return fail('RATE_LIMITED')

  const db = getApp().database()
  const recipeId = open ? event.recipeId : -1
  const rank = open ? event.rank : 0
  const id = hash([event.type, selection.stuff.join('、'), selection.tool, selection.mode, recipeId].join('|'))
  const doc = db.collection(SIGNALS).doc(id)
  const day = today(now)
  const result = await doc.update({ count: db.command.inc(1), rankSum: db.command.inc(rank), lastDay: day })
  if (!result || !result.updated)
    await doc.set({ type: event.type, ...selection, recipeId, count: 1, rankSum: rank, firstDay: day, lastDay: day })
  return { ok: true }
}

function sameToken(given, expected) {
  if (typeof given !== 'string' || !expected)
    return false
  const a = Buffer.from(given)
  const b = Buffer.from(expected)
  return a.length === b.length && crypto.timingSafeEqual(a, b)
}

async function readAll(name, where) {
  const db = getApp().database()
  const rows = []
  for (let skip = 0; ; skip += EXPORT_PAGE) {
    const query = where ? db.collection(name).where(where) : db.collection(name)
    const result = await query.skip(skip).limit(EXPORT_PAGE).get()
    const page = (result && result.data) || []
    rows.push(...page.map(({ _id, _openid, uid, ...rest }) => ({ ...rest, signedIn: Boolean(uid) })))
    if (page.length < EXPORT_PAGE)
      return rows
  }
}

async function exportAll(since) {
  const db = getApp().database()
  const after = Number.isFinite(since) && since > 0 ? since : 0
  return {
    ok: true,
    feedback: await readAll(FEEDBACK, after ? { createdAt: db.command.gt(after) } : null),
    signals: await readAll(SIGNALS, null),
  }
}

/** Requests through the HTTP trigger: only the token-protected export. */
async function handleHttp(event) {
  const headers = event.headers || {}
  if (!sameToken(headers['x-cook-token'], process.env.COOK_FEEDBACK_EXPORT_TOKEN || ''))
    return { statusCode: 401, body: JSON.stringify(fail('UNAUTHORIZED')) }
  const params = event.queryStringParameters || {}
  const body = await exportAll(Number(params.since))
  return { statusCode: 200, headers: { 'content-type': 'application/json' }, body: JSON.stringify(body) }
}

async function main(event = {}) {
  try {
    if (event.httpMethod)
      return await handleHttp(event)

    const reporter = readReporter(event)
    if (!reporter)
      return fail('REPORTER_REQUIRED')
    const now = Date.now()
    switch (event.action) {
      case 'report':
        return await report(event, reporter, now)
      case 'signal':
        return await signal(event, reporter, now)
      default:
        return fail('UNKNOWN_ACTION')
    }
  }
  catch (error) {
    console.error('[cook-feedback]', event.action || event.httpMethod, error && error.message)
    return fail('INTERNAL_ERROR')
  }
}

exports.main = main
exports._internal = {
  DAILY_QUOTA,
  FEEDBACK,
  QUOTA,
  SIGNALS,
  setAppForTest(nextApp) {
    app = nextApp
  },
}