#!/usr/bin/env bash

#
# Copyright (C) 2020, Maxim Lihachev, <envrm@yandex.ru>
#
# 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 3.
#
# 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, see <http://www.gnu.org/licenses/>.
#

: <<'MAN'

=head1 NAME

kubectl-http is a wrapper for I<`kubectl proxy'> command which shows links to resources.

=head1 USAGE

kubectl http [all|pods|services] [standard kubectl selectors]

=head1 OPTIONS

  -h   --help         = show this help
  -hl  --hyperlinks   = use terminal emulator's hyperlinks feature

Basic selectors:

  all                       pods and services
  po   pod      pods        pods
  svc  service  services    services

=head1 BUGS

If you find a bug, please report it at B<L<https://code.envrm.info/src/scripts-kubernetes>>.

=head1 AUTHORS

envrm B<L<https://code.envrm.info>>.

=cut
MAN

rstc="\033[00m"
blue="\033[1;36m"
green="\033[1;32m"
magenta="\033[1;35m"
red="\033[1;31m"
yellow="\033[1;33m"

USE_HYPERLINKS=false

# Default resource's type to query
TYPE=svc

# Default kubectl's proxy endpoint
PROXY_URL="http://127.0.0.1:8001"

shortname() {
	local name_length=${2:-30}

	host=${1/:*}
	port=${1/*:}

	if [ "${#1}" -gt "$name_length" ]; then
		echo "$(head -c "$name_length" <<<"$host")~:$port"
	else
		echo "$1"
	fi
}

# Print horizontal rule
hr() {
	echo -e -n "$magenta"
	printf "%${COLS}s" | sed 's/ /─/g'
	echo -e "$rstc"
}

usage() {
	sed -E -n '/^.*MAN/,/^MAN$/{//!p;}; /^MAN$/q' "$0" | sed -E 's/=head. |[LIBC]<|\b>*//g; /=cut/d'

	exit "${1:-0}"
}

footer() {
	>&2 echo
	>&2 hr
	>&2 echo -e " ${magenta}The index page with the links to resources: ${blue}${PROXY_URL}/index"
	>&2 hr
	>&2 echo
}

# Remove temporary directory
cleanup() {
	rm -rf "$WWW_DIRECTORY"
}

kubectl_get() {
	local resource=${1:-svc}

	shift

	[ $# -eq 0 ] && local filter="-A"

	case "$resource" in
		all) { kubectl_get pods "$@"; kubectl_get svc "$@"; };;
		svc)  eval kubectl get svc "$@" "$filter" --no-headers=true \
			-o=custom-columns=NAME:.metadata.selfLink,PORTS:.spec.ports[*].port;;
		pods) eval kubectl get pod "$@" "$filter" --no-headers=true \
			-o=custom-columns=NAME:.metadata.selfLink,PORTS:.spec.containers[*].ports[*].containerPort;;
	esac | grep -v '<none>' | sed -E 's/[[:space:]]+/,/g'
}

die() {
	>&2 echo -e "${red}ERROR: ${*}${rstc}"

	exit 1
}

# Clean up temporary files on exit
trap cleanup EXIT SIGINT SIGHUP SIGQUIT

KUBECTL_ARGS=()

while [[ $# -gt 0 ]]; do
	key="$1"

	case $key in
		-h|--help)            usage 0;;
		-hl|--hyperlinks)     USE_HYPERLINKS=true; shift;;
		all)                  TYPE=all; shift;;
		po|pod|pods)          TYPE=pods; shift;;
		svc|service|services) TYPE=svc; shift;;
		*)                    KUBECTL_ARGS+=("$1");  shift;;
	esac
done

set -- "${KUBECTL_ARGS[@]}"

# Temporary directory for index.html file
WWW_DIRECTORY=$(mktemp -d --tmpdir=/tmp KUBE_PROXY.XXXXXXXX)

COLS=$(tput cols)

declare -a SERVICES
declare -A URLS

mapfile -t SERVICES <<<"$(kubectl_get "$TYPE" "$@")"

[ "${#SERVICES}" -eq 0 ] && die "No resource found"

for service in "${SERVICES[@]}"; do
	svc_url=${service//,*/}
	ports=${service#*,}

	IFS=','
	for port in $ports; do
		id="$(cut -d '/' -f 5,6,7 <<<"$svc_url"):${port}"
		URLS["$id"]="${PROXY_URL}${svc_url}:${port}/proxy"
	done
done

mapfile -d '' SORTED_URLS < <(printf '%s\0' "${!URLS[@]}" | sort -z)

echo

MAX_VAL_LENGTH=$(printf '%s\n' "${URLS[@]}"  \
	| awk '{ print length }' \
	| sort -n -r \
	| head -n 1)

MAX_KEY_LENGTH=$(printf '%s\n' "${!URLS[@]}" \
	| sed -E 's/\/[^\/]+$//' \
	| awk '{ print length }' \
	| sort -n -r \
	| head -n 1)

# ~ ' - ' + ':' + 5-digit of port + spaces
MAX_NAME_LENGTH=$(( COLS - MAX_KEY_LENGTH - MAX_VAL_LENGTH - 15 ))

for key in "${SORTED_URLS[@]}"; do
	printf '<li><a href="%s">%s</a></li>\n' "${URLS[$key]}" "$key" >> "${WWW_DIRECTORY}/index.html"
	IFS='/' read -r ns rs name <<<"$key"

	if [ "$USE_HYPERLINKS" == "true" ]; then
		# Address under hyperlink
		echo -e -n "- \e]8;;${URLS[$key]}\e\\\\"
		echo -e -n "${magenta}${ns}${rstc}/"                                    # namespace
		echo -e -n "${yellow}${rs}${rstc}/"                                     # resource's type
		echo -e    "${green}${name}${rstc}\e]8;;\e\\"                           # resource's name
	else
		# - namespace/service http://127.0.0.1:8001/api/.../service:port/proxy
		echo -e -n " - ${magenta}${ns}${rstc}/"                                 # namespace
		echo -e -n "${yellow}${rs}${rstc}/"                                     # resource's type

		if [ "$MAX_NAME_LENGTH" -gt 10 ]; then
			echo -e -n "${green}$(shortname "$name" "$MAX_NAME_LENGTH") "   # short resource's name
		else
			echo -e -n "${green}${name}\n - "                               # resource's name on the its own line
		fi

		echo -e    "${blue}${URLS[$key]}${rstc}"                                # API URL
	fi
done | column -t

footer

>&2 kubectl proxy --www="$WWW_DIRECTORY" --www-prefix=/index