#!/usr/bin/env bash
# vim: expandtab:ts=4:sw=4

: << =cut

=head1 NAME

http_response - Monitor HTTP response statistics

=head1 CONFIGURATION

The following environment variables are used:

=over

=item *

sites - The sites to check

=over

=item *

separated by spaces

=item *

can contain basic auth credentials

=item *

defaults to C<http://localhost/>

=back

=item *

max_time - Timeout for each site check in seconds

=over

=item *

defaults to C<5>

=back

=item *

short_label - Switch for shortening the label below the graph

=over

=item *

defaults to C<false>

=back

=item *

follow_redirect - Switch for following http redirects

=over

=item *

defaults to C<false>

=back

=back

=head2 CONFIGURATION EXAMPLE

 [http_response]
  env.sites http://example.com/ https://user:secret@example2.de
  env.max_time 20
  env.short_label true
  env.follow_redirect true

=head1 PREREQUISITES

This plugin needs at least bash version 4 to run.

Additionally the following programs must be present on your system:

=over

=item *

awk

=item *

curl

=item *

date

=item *

echo

=item *

mktemp

=back

=head1 SEE ALSO

This plugin unifies the functionalities of the following plugins into one
multigraph plugin:

=over

=item *

L<http_loadtime|https://gallery.munin-monitoring.org/plugins/munin/http_loadtime/>

=item *

L<http_responsecode|https://gallery.munin-monitoring.org/plugins/munin-contrib/http_responsecode/>

=back

In contrast to using these two plugins with the same configuration, this plugin
performs only one request per site and munin run to gather its statistics.

=head1 AUTHOR

Copyright (C) 2020-2021 Klaus Sperner

=head1 LICENSE

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; version 2 dated June,
1991.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

=head1 MAGIC MARKERS

 #%# family=manual

=cut

# shellcheck disable=SC1091
. "$MUNIN_LIBDIR/plugins/plugin.sh"

readonly uri_regex='^(https?://)([^:]*):(.*)@(.*)$'

strip_credentials_from_url() {
    if [[ "$1" =~ $uri_regex ]]; then
        echo "${BASH_REMATCH[1]}${BASH_REMATCH[4]}"
    else
        echo "$1"
    fi
}

extract_username_from_url() {
    if [[ "$1" =~ $uri_regex ]]; then
        echo "${BASH_REMATCH[2]}"
    else
        echo ""
    fi
}

extract_password_from_url() {
    if [[ "$1" =~ $uri_regex ]]; then
        echo "${BASH_REMATCH[3]}"
    else
        echo ""
    fi
}

compute_label() {
    if [[ "${short_label,,}" == "true" || "${short_label,,}" == "yes" ]]; then
        if [[ ${#1} -gt 33 ]]; then
            echo "${1:0:30}..."
        else
            echo "$1"
        fi
    else
        echo "$1"
    fi
}

check_programs_installed() {
    for program in "$@"; do
        if ! hash "$program" 2>/dev/null; then
            >&2 echo "The plugin http_response needs $program but it is not installed. Aborting."
            exit 1
        fi
    done
}

if [[ "${BASH_VERSINFO:-0}" -lt 4 ]]; then
    >&2 echo "The plugin http_response needs at least bash version 4. Aborting."
    exit 1
fi

check_programs_installed awk curl date echo mktemp

sites=${sites:-"http://localhost/"}
max_time=${max_time:-5}
short_label=${short_label:-"false"}
follow_redirect=${follow_redirect:-"false"}

if [[ ! "$max_time" =~ ^[0-9]+$ ]]; then
    >&2 echo "Invalid configuration: max_time $max_time must contain only digits. Aborting."
    exit 1
fi

if [[ "$1" == "config" ]]; then
    echo 'multigraph http_response_code'
    echo 'graph_args --base 1000 --lower-limit 0 --upper-limit 511'
    echo 'graph_title HTTP Response Codes'
    echo 'graph_vlabel Response Code'
    echo 'graph_category network'
    echo 'graph_info This graph shows HTTP response code statistics'
    echo 'graph_printf %3.0lf'
    for site in $sites; do
        site_without_credentials=$( strip_credentials_from_url "$site" )
        site_id="$( clean_fieldname "$site_without_credentials" )"
        echo "$site_id.label $( compute_label "$site_without_credentials" )"
        echo "$site_id.info HTTP response code statistics for $site_without_credentials"
        echo "$site_id.critical 99:399";
    done
    echo 'multigraph http_response_time'
    echo 'graph_args --base 1000 -l 0'
    echo 'graph_title HTTP Response Times'
    echo 'graph_vlabel Response Time in seconds'
    echo 'graph_category network'
    echo 'graph_info This graph shows HTTP response time statistics'
    for site in $sites; do
        site_without_credentials=$( strip_credentials_from_url "$site" )
        site_id="$( clean_fieldname "$site_without_credentials" )"
        echo "$site_id.label $( compute_label "$site_without_credentials" )"
        echo "$site_id.info HTTP response time statistics for $site_without_credentials"
    done
    exit 0
fi

declare -A response_codes
declare -A response_times

for site in $sites; do
    site_without_credentials=$( strip_credentials_from_url "$site" )
    username=$( extract_username_from_url "$site" )
    password=$( extract_password_from_url "$site" )

    configurable_arguments=()
    curl_config_file=""
    if [ -n "$username" ]; then
        if [ -z "$password" ]; then
            >&2 echo "Invalid configuration: username specified without password"
            exit 1
        fi
        curl_config_file=$(mktemp) || exit 1
        trap 'rm -f "$curl_config_file"' EXIT
        echo "user=${username}:${password}" >> "$curl_config_file"
        configurable_arguments+=(--config "$curl_config_file")
    fi

    if [[ "${follow_redirect,,}" == "true" || "${follow_redirect,,}" == "yes" ]]; then
        configurable_arguments+=(--location)
    fi

    site_id="$( clean_fieldname "$site_without_credentials" )"
    start=$(date +%s.%N)
    status_code=$( curl "${configurable_arguments[@]}" --write-out '%{http_code}' --max-time "$max_time" --silent --output /dev/null "$site_without_credentials" )
    return_code=$?
    load_time=$( echo "$start" "$(date +%s.%N)" | awk '{ print($2 - $1); }' )
    if [[ $return_code -ne 0 ]]; then
        load_time="U"
        status_code="U"
    fi
    response_codes+=(["$site_id"]="$status_code")
    response_times+=(["$site_id"]="$load_time")

    if [ -n "$curl_config_file" ]; then
        rm -f "$curl_config_file"
    fi
done

echo 'multigraph http_response_code'
for site_id in "${!response_codes[@]}"; do
    echo "${site_id}.value ${response_codes[${site_id}]}"
done

echo 'multigraph http_response_time'
for site_id in "${!response_times[@]}"; do
    echo "${site_id}.value ${response_times[${site_id}]}"
done