#!/usr/bin/env bash
set -euo pipefail
# POS: communication telegram — Send Telegram messages via Bot API (--send, test, config set)
# POS_FLAGS: --send

CONFIG_DIR="$HOME/.config/linux_post_install"
CONFIG_FILE="$CONFIG_DIR/telegram.env"
API="https://api.telegram.org"

usage() {
    cat <<EOF
Usage: pos communication telegram [command] [args]

Send Telegram messages via the Bot API.

Commands:
  --send "text"             Send a text message to the configured chat
  --send "text" --token <t> --chat-id <id>   Override token/chat for one send
  --send "text" --parse-mode <mode>   Format mode: plain (default), markdown, html
  test                      Send a test message using the current config
  config                    Show current config (token masked)
  config set KEY=VALUE      Set TELEGRAM_BOT_TOKEN or TELEGRAM_CHAT_ID

Config file: $CONFIG_FILE
Keys: TELEGRAM_BOT_TOKEN | TELEGRAM_CHAT_ID

Precedence: CLI flags > environment > config file.

Examples:
  pos communication telegram config set TELEGRAM_BOT_TOKEN=123456:ABC-DEF
  pos communication telegram config set TELEGRAM_CHAT_ID=987654321
  pos communication telegram --send "Backup finished"
  pos communication telegram --send "*Backup finished*" --parse-mode markdown
  pos communication telegram test
EOF
    exit 0
}

err() { echo "ERROR: $*" >&2; exit 1; }

load_config() {
    [ -f "$CONFIG_FILE" ] || return 0
    local k v
    while IFS='=' read -r k v; do
        [ -n "$k" ] || continue
        case "$k" in
            \#*) continue ;;
        esac
        v="${v%\"}"; v="${v#\"}"; v="${v%\'}"; v="${v#\'}"
        if [ -z "${!k:-}" ]; then
            export "$k"="$v"
        fi
    done < <(grep -E '^[A-Z_]+=' "$CONFIG_FILE" || true)
}

mask_token() {
    local t="$1"
    [ -z "$t" ] && { echo "(not set)"; return; }
    if [ "${#t}" -le 12 ]; then
        echo "${t:0:4}... (${#t} chars)"
    else
        echo "${t:0:6}...${t: -4} (${#t} chars)"
    fi
}

cmd_send() {
    local text="$1" parse_mode="${2:-}"
    [ -z "${TELEGRAM_BOT_TOKEN:-}" ] && err "No bot token — run 'pos communication telegram config set TELEGRAM_BOT_TOKEN=...'"
    [ -z "${TELEGRAM_CHAT_ID:-}" ] && err "No chat id — run 'pos communication telegram config set TELEGRAM_CHAT_ID=...'"
    local args=(--data-urlencode "chat_id=${TELEGRAM_CHAT_ID}" --data-urlencode "text=${text}")
    [ -n "$parse_mode" ] && args+=(--data-urlencode "parse_mode=${parse_mode}")
    curl -fsS -m 20 -X POST "$API/bot${TELEGRAM_BOT_TOKEN}/sendMessage" "${args[@]}" >/dev/null
    echo "[+] Message sent to chat ${TELEGRAM_CHAT_ID}"
}

cmd_config() {
    load_config
    echo "Config: $CONFIG_FILE"
    echo "  TELEGRAM_BOT_TOKEN = $(mask_token "${TELEGRAM_BOT_TOKEN:-}")"
    echo "  TELEGRAM_CHAT_ID   = ${TELEGRAM_CHAT_ID:-}"
}

cmd_config_set() {
    local kv="$1"
    local key="${kv%%=*}"
    local val="${kv#*=}"
    case "$key" in
        TELEGRAM_BOT_TOKEN|TELEGRAM_CHAT_ID) ;;
        *) err "Unknown key '$key' (allowed: TELEGRAM_BOT_TOKEN, TELEGRAM_CHAT_ID)" ;;
    esac
    [ -z "$val" ] && err "No value given (expected $key=...)"

    mkdir -p "$CONFIG_DIR"
    if [ -f "$CONFIG_FILE" ]; then
        if grep -q "^${key}=" "$CONFIG_FILE"; then
            sed -i "s|^${key}=.*|${key}=${val}|" "$CONFIG_FILE"
        else
            echo "${key}=${val}" >>"$CONFIG_FILE"
        fi
    else
        echo "${key}=${val}" >"$CONFIG_FILE"
    fi
    chmod 600 "$CONFIG_FILE"
    echo "[+] $key saved to $CONFIG_FILE"
}

cmd="${1:-}"

case "$cmd" in
    -h|--help) usage ;;
    --send)
        shift
        [ $# -ge 1 ] || usage
        text="$1"
        shift
        parse_mode=""
        while [ $# -gt 0 ]; do
            case "$1" in
                --token)   TELEGRAM_BOT_TOKEN="$2"; shift 2 ;;
                --chat-id) TELEGRAM_CHAT_ID="$2"; shift 2 ;;
                --parse-mode)
                    case "$2" in
                        plain|markdown|html) ;;
                        *) err "Unknown parse mode '$2' (allowed: plain, markdown, html)" ;;
                    esac
                    parse_mode="$2"; shift 2 ;;
                *) err "Unknown option '$1'" ;;
            esac
        done
        [ "$parse_mode" = "plain" ] && parse_mode=""
        load_config
        cmd_send "$text" "$parse_mode"
        ;;
    test)
        load_config
        cmd_send "Test message from pos $(date '+%Y-%m-%d %H:%M:%S')"
        ;;
    config)
        shift
        case "${1:-}" in
            set) shift; [ $# -eq 1 ] || usage; cmd_config_set "$1" ;;
            *) cmd_config ;;
        esac
        ;;
    *)
        echo "ERROR: Unknown telegram command '$cmd'"
        echo "Run 'pos communication telegram --help' for usage."
        exit 1
        ;;
esac