#!/bin/bash

# this is just a library
# you will need to provide the following in the implementation:
# 1. the api url with it's corresponding token as
#    api_url="api.telegram.org/bot[insert your api token]/"
#    pay attention to the trailing forward slash
# 2. the following files to read and write from
#    updates.txt
#    sentmsgs.txt
#    delmsgs.txt
# 3. (optional) a directory for the bot's files as
#    bot_tmpdir="/some/path/"
#    pay attention to the trailing forward slash
# IMPORTANT: this library is not asynchronous, only one message
#            is read at a time and is done so in order
# IMPORTANT: this library uses the getUpdates method with
#            tcp_keepalive,NOT webhooks

# attempts to grab the last update's update_id and prints it to stdout
calc_offset() {
  local current="$(bc -l <<< "$(tail -n 1 "${bot_tmpdir}updates.txt" | \
                   grep -om1 "\"update_id\":[0-9]\+" | \
                   grep -om1 "[0-9]\+") + 1" 2>/dev/null)"
  [ ! -z "${current}" ] && printf "%d" "${current}"
}

# captures output of calc_offset to use as offset and fetches a single update with that offset
# uses tcp_keepalive method for 300 seconds, but telegram only keeps the connection open for 60 seconds
# prints result of fetching update if not empty and formats it for better use with the other functions
getupd() {
  local offset="$(calc_offset)"
  local update="$(curl -sX GET --keepalive-time 300 "${api_url}getUpdates" -d "offset=${offset}" \
   -d "limit=1" -d "timeout=300")"
  update="$(sed 's/{"ok":true,"result":\[\]}\|^{"ok":false.*\|^{"ok":true,"result":\[{\?//g;:a;N;$!ba;s/\n//g;s/}\]}$//g;' <<< "${update}")"
  [ ! -z "${update}" ] && printf "%s\n" "${update}" >> "${bot_tmpdir}updates.txt"
}

getmsg_id() {
  tail -n1 "${bot_tmpdir}${1}" | grep -om1\
  "\"message\":{\"message_id\":[0-9]\+\|^\"message_id\":[0-9]\+" | grep -om1 "[0-9]\+"
}

getusr_id() {
  tail -n1 "${bot_tmpdir}${1}" | grep -om1\
   "\"from\":{\"id\":[0-9]\+" | grep -om1 "[0-9]\+"
}

getchat_id() {
  tail -n1 "${bot_tmpdir}${1}" | grep -om1\
   "\"chat\":{\"id\":-\?[0-9]\+" | grep -om1 "\-\?[0-9]\+"
}

# makes decoding emojis possible, important for sending them too
utf-16-surrogate-pair-decode() {
  # shamelessly stolen from stackoverflow
  local out="$1"
  local remain=""
  local regexp='(.*)\\u[dD]([0-9a-fA-F]{3})\\u[dD]([0-9a-fA-F]{3})(.*)'
  while [[ "${out}" =~ $regexp ]] ; do
   # match 2 \udxxx hex values, calculate new U, then split and replace
   local W1="$(( ( 0xd${BASH_REMATCH[2]} & 0x3ff) <<10 ))"
   local W2="$(( 0xd${BASH_REMATCH[3]} & 0x3ff ))"
   U="$(( ( W1 | W2 ) + 0x10000 ))"
   remain="$(printf '\\U%8.8x' "${U}")${BASH_REMATCH[4]}${remain}"
   out="${BASH_REMATCH[1]}"
  done
  echo -e "${out}${remain}"
}

gettext() {
  local text="$(tail -n 1 "${bot_tmpdir}${1}" | grep -om1\
   '{\?\("text"\|"caption"\):"\(\\"\|[^"]*\)*"\(,\|}\)' | grep -v "^{" | tail -n1)"
  grep "^\"text\"" <<< "${text}" >/dev/null && utf-16-surrogate-pair-decode "${text:8:-2}"\
  || {
    grep "^\"caption\"" <<< "${text}" >/dev/null && utf-16-surrogate-pair-decode "${text:11:-2}"
  }
}

getusr_name(){
  local user_name="$(tail -n 1 "${bot_tmpdir}${1}" | grep -om1\
   '"first_name":"\(\\"\|[^"]*\)*",\("username"\|"language_code"\)' | head -n1)"
  grep "\"username\"$" <<< "${user_name}" >/dev/null && utf-16-surrogate-pair-decode "${user_name:14:-12}"\
  || {
    grep "\"language_code\"$" <<< "${user_name}" >/dev/null && utf-16-surrogate-pair-decode "${user_name:14:-17}"
  }
}

getusrname(){
  local username="$(tail -n 1 "${bot_tmpdir}${1}" | grep -om1\
   '"username":"\(\\"\|[^"]*\)*"\(,"language_code"\|},"chat"\)' | head -n1)"
  grep "\"language_code\"$" <<< "${username}" >/dev/null && utf-16-surrogate-pair-decode "${username:12:-17}"\
  || {
    grep "},\"chat\"$" <<< "${username}" >/dev/null && utf-16-surrogate-pair-decode "${username:12:-9}"
  }
}

getchat_title(){
  local chat_title="$(tail -n 1 "${bot_tmpdir}${1}" | grep -om1\
   '"title":"\(\\"\|[^"]*\)*","type":"group"' | head -n1)"
  [ ! -z "${chat_title}" ] && utf-16-surrogate-pair-decode "${chat_title:9:-16}"\
  || getusr_name "${1}"
}

getcbk_data() {
  local callbacks="$(tail -n 1 "${bot_tmpdir}${1}"\
   | grep "\"callback_query\"" | grep -om1 '"data":"\(\\"\|[^"]*\)*"}')"
   [ ! -z "${callbacks}" ] && utf-16-surrogate-pair-decode "${callbacks:8:-2}"
}

# $1 is name of a bash array with the number of columns in every row such as ( 1 1 3 ) for a 3 row keyboard in which the first and second row have 1 column, and the third has 3
# $2 is name of a bash array with as many text entries as there are columns, they are added left to right, up to down, to the rows/columns configuration passed as first arg
# $3 is name of a bash array with as many data entries as there are columns, they are added left to right, up to down, to the rows/columns configuration passed as first arg
mkinline_kbd(){
  local -n rows="${1}"
  local -n text="${2}"
  local -n data="${3}"
  local kbd="{\"inline_keyboard\":[]}"
  local unit="\"text\":\"\",\"callback_data\":\"\""
  local rowformat="[]"
  local colformat="{}"
  local rowfirstpass=1
  local colfirstpass=1

  for (( i=0; i<"${#rows[@]}"; i++ )); do
    [ "${rowfirstpass}" -eq 1 ] && {
      kbd="$(sed "s/]}$/${rowformat}]}/" <<< "${kbd}")"
      rowfirstpass=0
    } || kbd="$(sed "s/]}$/,${rowformat}]}/" <<< "${kbd}")"
    for (( j=0; j<"${rows[${i}]}"; j++)); do
      [ "${colfirstpass}" -eq 1 ] && {
        kbd="$(sed "s/]]}$/${colformat}]]}/" <<< "${kbd}")"
        colfirstpass=0
      } || kbd="$(sed "s/]]}$/,${colformat}]]}/" <<< "${kbd}")"
      kbd="$(sed "s/}]]}$/${unit}}]]}/" <<< "${kbd}")"
    done
    colfirstpass=1
  done

  for i in "${text[@]}"; do
    kbd="$(sed "s/\"text\":\"\"/\"text\":\"${i}\"/" <<< "${kbd}")"
  done

  for i in "${data[@]}"; do
    kbd="$(sed "s/\"callback_data\":\"\"/\"callback_data\":\"${i}\"/" <<< "${kbd}")"
  done
  sed "s/ /+/g;:a;N;$!ba;s/\n/%0A/g" <<< "${kbd}"
}

# $1 is target chat_id
# $2 is text
# $3 is inline keyboard (optional)
sendmsg() {
  local sentmsg
  [ -z "${3}" ] && sentmsg="$(curl -sX GET "${api_url}sendMessage" -d "chat_id=${1}" \
   -d "text=${2}")" \
   || sentmsg="$(curl -sX GET "${api_url}sendMessage" -d "chat_id=${1}" \
   -d "text=${2}" \
   -d "reply_markup=${3}")"
  sentmsg="$(sed 's/^{"ok":false.*\|^{"ok":true,"result":{\|}$//g' <<< "${sentmsg}")"
   [ ! -z "${sentmsg}" ] && printf "%s\n" "${sentmsg}" >> "${bot_tmpdir}sentmsgs.txt"
}

# $1 is target chat_id
# $2 is target msg_id
# $3 is text
# $4 is inline keyboard (optional)
replymsg() {
  local sentmsg
  [ -z "${4}" ] &&\
   sentmsg="$(curl -sX GET "${api_url}sendMessage" -d "chat_id=${1}" -d "reply_to_message_id=${2}"\
    -d "text=${3}")" ||
   sentmsg="$(curl -sX GET "${api_url}sendMessage" -d "chat_id=${1}" -d "reply_to_message_id=${2}"\
    -d "text=${3}" -d "reply_markup=${4}")"
  sentmsg="$(sed 's/^{"ok":false.*\|^{"ok":true,"result":{\|}$//g' <<< "${sentmsg}")"
  [ ! -z "${sentmsg}" ] && printf "%s\n" "${sentmsg}" >> "${bot_tmpdir}sentmsgs.txt"
}

# $1 is target chat_id
# $2 is target msg_id
# $3 is text
# $4 is inline keyboard (optional)
editmsg() {
  local editmsg
  [ -z "${4}" ] && editmsg="$(curl -sX GET "${api_url}editMessageText" -d "chat_id=${1}" -d "message_id=${2}" \
   -d "text=${3}")" || editmsg="$(curl -sX GET "${api_url}editMessageText" -d "chat_id=${1}" -d "message_id=${2}" \
   -d "text=${3}" -d "reply_markup=${4}")"
  editmsg="$(sed 's/^{"ok":false.*\|^{"ok":true,"result":{\|}$//g' <<< "${editmsg}")"
  [ ! -z "${editmsg}" ] && printf "%s\n" "${editmsg}" >> "${bot_tmpdir}sentmsgs.txt"
}

# $1 is target chat_id
# $2 is target msg_id
delmsg() {
  local delmsg
  delmsg="$(curl -sX GET "${api_url}deleteMessage" -d "chat_id=${1}"\
  -d "message_id=${2}")"
  [ ! -z "${delmsg}" ] && printf "deleted message %s from chat %s\n" "${2}" "${1}" >> "${bot_tmpdir}delmsgs.txt"
}

# $1 is the name of a bash associative array to be filled with the message contents
getmsg_content(){
  local -n _REF="${1}"
  _REF[user_id]="$(getusr_id "${2}")"
  _REF[user_name]="$(getusr_name "${2}")"
  _REF[username]="$(getusrname "${2}")"
  _REF[chat_id]="$(getchat_id "${2}")"
  _REF[chat_title]="$(getchat_title "${2}")"
  _REF[msg_id]="$(getmsg_id "${2}")"
  _REF[text]="$(gettext "${2}")"
  _REF[callback]="$(getcbk_data "${2}")"
}