#!/bin/sh

# AT Command Script Variables and Functions
TMP_DIR="/tmp"
DEVICE_FILE="/dev/smd7"
TIMEOUT=4  # Set a timeout for the response

start_listening() {
    cat "$DEVICE_FILE" > /tmp/device_readout &
    CAT_PID=$!
}

send_at_command() {
    echo "Enter AT command (or type 'exit' to quit): "
    read at_command
    if [ "$at_command" = "exit" ]; then
        return 1
    fi
    echo -e "${at_command}\r" > "$DEVICE_FILE"
}

wait_for_response() {
    local start_time=$(date +%s)
    local current_time
    local elapsed_time

    echo "Command sent, waiting for response..."
    while true; do
        if grep -qe "OK" -e "ERROR" /tmp/device_readout; then
            echo "Response received:"
            cat /tmp/device_readout
            return 0
        fi
        current_time=$(date +%s)
        elapsed_time=$((current_time - start_time))
        if [ "$elapsed_time" -ge "$TIMEOUT" ]; then
            echo "Error: Response timed out."
            return 1
        fi
        sleep 1
    done
}

cleanup() {
    kill "$CAT_PID"
    wait "$CAT_PID" 2>/dev/null
    rm -f /tmp/device_readout
}

    if [ -c "$DEVICE_FILE" ]; then
        while true; do
            start_listening
            send_at_command
            if [ $? -eq 1 ]; then
                cleanup
                break
            fi
            wait_for_response
            cleanup
        done
    else
        echo "Error: Device $DEVICE_FILE does not exist or is not a character special file."
    fi