import { CommandContext, Filter } from "https://deno.land/x/grammy@v1.30.0/mod.ts";
import { BotConfig } from "../../cfg/bot.ts"
import { Ctx } from "../ctx.ts";
import { LangManager } from "../lang/export.ts";

const CAPTCHA_FAILS_LIMIT = 3
const TIMEOUT_AFTER_FAIL_MINS = 5

export interface CaptchaSessionData {
  message_id: number,
  tries_failed: number,
  generated_at: number,
  // Captcha can be changed from a simple matematical ones
  // to a more complicated images or even science-related questions
  solution:     string, 
}

const randInt = (min: number, max: number): number =>
  Math.floor(Math.random() * (max - min) + min)

class Captcha {
  // ! READ ONLY ! Initialized by the constructor
  public _generated_at = Date.now()
  // ! READ ONLY ! Initialized by the constructor
  public _solution: number
  // ! READ ONLY ! Initialized by the constructor
  public _text: string

  constructor() {
    const number1 = randInt(-100, 100)
    const number2 = randInt(-100, 100)
    this._solution = number1 + number2
    this._text = `Captcha: ${number1}+${number2}=?`
  }
}
// User captcha response sanitizer/parser/validator
const isSolutionCorrect = (expectSolution: string, solution: string): boolean => {
  solution = solution.replace(' ','').replace('\t','') // Sanitizing
  return parseInt(solution, 10) == parseInt(expectSolution, 10) ? true : false
}

const initUserCaptcha = async (ctx: CommandContext<Ctx>) => {
  if (ctx.chat.type != "private" ||
    ctx.session.captcha_data) return

  if (ctx.session.chat_participant) {
    if (!ctx.msg?.from) return
    ctx.reply(LangManager.getLang(ctx.msg.from.language_code)
      .replies.captcha.already_in_chat)
  }

  const captcha = new Captcha()
  const msg = await ctx.reply(captcha._text)

  ctx.session.captcha_data = {
    message_id: msg.message_id,
    tries_failed: 0,
    generated_at: captcha._generated_at,
    solution: captcha._solution.toString(),
  }
}

const captchaPassed = async (botCfg: BotConfig, ctx: Filter<Ctx, "message:text">) => {
  if (ctx.session.captcha_data) {
    ctx.api.deleteMessage(
      ctx.chatId, ctx.session.captcha_data.message_id
    ).catch()
  }
  ctx.session.captcha_data = undefined
  ctx.session.captcha_solved = true
  const now = Math.floor(Date.now() / 1000);
  const linkExpireTimestamp = now + (12 * 60 * 60);
  const link = await ctx.api.createChatInviteLink(botCfg.chat_id, {
    member_limit: 1,
    expire_date: linkExpireTimestamp,
  })
  ctx.reply(LangManager.getLang(ctx.msg.from.language_code)
    .replies.captcha.passed(link.invite_link))
  ctx.session.captcha_data = undefined
}

// returns true if captcha is response to a captcha; else -- returns false
const handleNewMessage = async (botCfg: BotConfig, ctx: Filter<Ctx, "message:text">): Promise<boolean> => {
 if (ctx.message.chat.type != "private" || !ctx.session.captcha_data) return false
  if (isSolutionCorrect(ctx.session.captcha_data.solution, ctx.message.text)) {
    await captchaPassed(botCfg, ctx)
  } else {
    ctx.session.captcha_data.tries_failed++
    ctx.api.deleteMessage(ctx.chatId, ctx.msg.message_id).catch()
    if (ctx.session.captcha_data.tries_failed > CAPTCHA_FAILS_LIMIT) {
      ctx.reply(LangManager.getLang(ctx.msg.from.language_code)
        .replies.captcha.failed(TIMEOUT_AFTER_FAIL_MINS))
      ctx.api.deleteMessage(ctx.chatId, ctx.session.captcha_data.message_id).catch()
    } 
  }
  return true
}

const handleUserJoinChat = async (botCfg: BotConfig, ctx: Filter<Ctx, ":new_chat_members">) => {
  ctx.session.chat_participant = true
  const inviteLink = ctx.session.invite_link
  if (!inviteLink) return
  await ctx.api.revokeChatInviteLink(botCfg.chat_id, inviteLink)
}


export { handleNewMessage, handleUserJoinChat, initUserCaptcha }