#!/usr/bin/env bash
# This script was written to display the weather conditions on the command line using the darksky.net api

# strict mode
set -Eeuo pipefail
IFS=$'\n\t'

# debug mode
#set -o verbose

readonly script_name=${0##*/}

readonly ip_api_host="ipinfo.io"
readonly ip_api_protocol="http"

readonly ip_auth_token_file=${script_name}"_ip.token"
readonly ip_auth_token=`cat ~/bin/${ip_auth_token_file}`

readonly ip_api_uri=${ip_api_protocol}"://"${ip_api_host}

# Dark Sky api host
readonly ds_api_host="api.darksky.net"
readonly ds_api_protocol="https"

# api auth token file
readonly ds_auth_token_file=${script_name}"_ds.token"

# Dark Sky api auth token (get your own here --> https://darksky.net/dev/register)
readonly ds_auth_token=`cat ~/bin/${ds_auth_token_file}`

readonly ds_api_uri=${ds_api_protocol}"://"${ds_api_host}"/forecast/"${ds_auth_token}

readonly tool_name="Weather"
readonly logname="${USER}"

# function to catch error messages
# ${1} = error message
# ${2} = exit code
function __throw_error() {

    # validate arguments
    if [ ${#} -eq 2 ]; then
        local message=${1}
        local exit_code=${2}

        # log specific error message to syslog and write to STDERR
        logger -s -p user.err -t ${script_name}"["${logname}"]" -- ${message}

        exit ${exit_code}
    else
        # log generic error message to syslog and write to STDERR
        logger -s -p user.err -t ${tool_name}"["${logname}"]" -- "an unknown error occured"
        exit 255
    fi
}

# validate api connectivity
# ${1} = api host
# ${2} = api protocol
function __validate_api_connectivity() {
    if [ ${#} -eq 2 ]; then
        # test tcp connectivity on specified host and port
        ( >/dev/tcp/${1}/${2} ) >/dev/null 2>&1
        return ${?}
    else
        return 1
    fi
}

function __get_location() {
    # query location api for gps coordinates
    local coordinates=$( curl -sH "Authorization: Bearer "${ip_auth_token} ${ip_api_uri}/loc )
    echo ${coordinates}
}

function __get_city() {
    # query location api for gps coordinates
    local city=$( curl -sH "Authorization: Bearer "${ip_auth_token} ${ip_api_uri}/city )
    echo ${city}
}

function __get_region {
    # query location api for gps coordinates
    local region=$( curl -sH "Authorization: Bearer "${ip_auth_token} ${ip_api_uri}/region )
    echo ${region}
}

function __get_summary() {
    # query api for current summary
    local current_summary=$( curl -s "${ds_api_uri}/${coordinates}" | jq -r '.currently.summary' )
    echo ${current_summary}
}

function __get_temperature() {
    # query api for current temperature
    local current_temperature=$( curl -s "${ds_api_uri}/${coordinates}" | jq -r '.currently.temperature' | awk '{print int($1+0.5)}' )
    echo ${current_temperature}
}

# ${1} = dependency
function __check_dependency() {
    if [ ${#} -eq 1 ]; then
        local dependency=${1}
        local exit_code=${null:-}
        type ${dependency} &>/dev/null; exit_code=${?}

        if [ ${exit_code} -ne 0 ]; then
            return 255
        fi
    else
        return 1
    fi
}

####################
### main program ###
####################

# validate dependencies
readonly -a dependencies=( 'awk' 'jq' 'logger' )
declare -i dependency=0

while [ "${dependency}" -lt "${#dependencies[@]}" ]; do
    __check_dependency ${dependencies[${dependency}]} || __throw_error ${dependencies[${dependency}]}" required" ${?}
    (( ++dependency ))
done

unset dependency

# make sure we're using least bash 4 for proper support of associative arrays
[ $( echo ${BASH_VERSION} | grep -o '^[0-9]' ) -ge 4 ] || __throw_error "Please upgrade to at least bash version 4" ${?}

# make sure we have both api tokens
[ -s ${ds_auth_token} ] && __throw_error "Dark Sky token file not found" ${?}
[ -s ${ip_auth_token} ] && __throw_error "Ipinfo token file not found" ${?}

# make sure we can reach both apis
__validate_api_connectivity ${ds_api_host} ${ds_api_protocol} || __throw_error "Unable to establish tcp connection to "${ds_api_host} ${?}
__validate_api_connectivity ${ip_api_host} ${ip_api_protocol} || __throw_error "Unable to establish tcp connection to "${ip_api_host} ${?}

# get current geolocation coordinates
coordinates=$( __get_location ) || __throw_error "Unable to get geolocation" ${?}

# get current city
city=$( __get_city ) || __throw_error "Unable to get city" ${?}

# get current region
region=$( __get_region ) || __throw_error "Unable to get region" ${?}

# get the current temperature
current_temperature=$( __get_temperature ) || __throw_error "Unable to get temperature" ${?}

# get the current temperature
current_summary=$( __get_summary ) || __throw_error "Unable to get summary" ${?}

echo "It is currently "${current_temperature}"° and "${current_summary}" in "${city}", "${region}