#!/bin/bash
set -e
set -o pipefail

usage(){
	fmt <<EOF
DESCRIPTION
	Syncs books from standardebooks.org GitHub org to specified folder.

USAGE
	${0##*/} [-v,-vv,--verbosity INTEGER] [-u,--update-only] [--token TOKEN] DIRECTORY

	With -v or --verbosity 1, display general progress updates.
	With -vv or --verbosity 2, display general progress updates and verbose git output.
	With --update-only, only sync existing repositories, do not download new repositories.
	With --token TOKEN, specify a GitHub access token to use for request. Useful for when you hit the rate limit.

	DIRECTORY should be where the repositories should go.

EXAMPLE
	${0##*/} /standardebooks.org/ebooks
EOF
	exit
}
die(){ printf "\033[0;7;31mError:\033[0m %s\n" "${1}" 1>&2; exit 1; }
require(){ command -v "$1" > /dev/null 2>&1 || { suggestion=""; if [ -n "$2" ]; then suggestion=" $2"; fi; die "$1 is not installed.${suggestion}"; } }

check_arg() {
	case "$2" in
		''|$1) die "$3" ;;
	esac
}
# End boilerplate

require "git" "Try: apt-get install git"

# Terminate on CTRL-C
trap ctrl_c INT
ctrl_c() {
	exit
}

if [[ $# -eq 0 ]]; then
	usage
fi

verbosity=0
updateOnly="false"
githubToken=""
target=""

while [ $# -gt 0 ]; do
	case "$1" in
		-h|--help)
			usage ;;
		-v)
			verbosity=1
			shift 1
			;;
		-vv)
			verbosity=2
			shift 1
			;;
		-u|--update-only)
			updateOnly="true"
			shift 1
			;;
		--verbosity)
			check_arg '*[!0-9]*' "$2" "Verbosity is not a positive integer."
			verbosity="$2"
			shift 2
			;;
		--token)
			check_arg '*[!0-9a-zA-Z]*' "$2" "Token is empty or contains illegal characters."
			githubToken="$2"
			shift 2
			;;
		*)
			break ;;
	esac
done

if [ $# -ne 1 ] || [ -z "$1" ]; then
	usage
fi

target="$1"

if ! [ -d "${target}" ]; then
	die "${target} is not a directory."
fi

if ! cd "${target}"; then
	die "Couldn’t cd into ${target}"
fi

if [ "${verbosity}" -gt 0 ]; then
	printf "Updating local repositories ... \n"
fi

for item in ./*; do
	[ -e "${item}" ] || break

	if [ "${verbosity}" -gt 0 ]; then
		printf "Updating %s ... " "${item}"
	fi

	if [ "${verbosity}" -lt 2 ]; then
		git -C "${item}" fetch -q
	else
		git -C "${item}" fetch -v
	fi

	if [ "${verbosity}" -gt 0 ]; then
		printf "Done.\n"
	fi
done

if [ "${updateOnly}" = "true" ]; then
	exit
fi

if [ "${verbosity}" -gt 0 ]; then
	printf "Cloning remote repositories ... \n"
	printf "Fetching repository urls ..."
fi

url="https://api.github.com/orgs/standardebooks/repos?per_page=100"
repoUrls=""

while true; do
	if [ -n "${githubToken}" ]; then
		response=$(curl -H "Authorization: token ${githubToken}" -si "${url}") ||
			die "Curl request failed."
	else
		response=$(curl -si "${url}") ||
			die "Curl request failed."
	fi

	if printf "%s" "${response}" | grep -q "^X-RateLimit-Remaining: 0$"; then
		limitReset=$(printf "%s" "${response}" | grep -oP "^X-RateLimit-Reset: \K[0-9]+$")
		printf "You have reached your daily allowance for unauthenticated GitHub API requests.\n\
			Either wait until %s or use an OAuth token.\n\
			You can create a new token at https://github.com/settings/tokens/new and \
			pass it to this script with the --token option.\n\
			The token does not need any permissions.\n" "$(date -d @"${limitReset}")" 1>&2
		exit
	fi


	currentRepoUrls=$(printf "%s" "${response}" | awk 'BEGIN { FS="\""; RS="," }; { if ($2 == "clone_url") {print $4} }')
	repoUrls=$(printf "%s\n%s" "${repoUrls}" "${currentRepoUrls}")
	url=$(printf "%s" "${response}" | grep -oP "<\Khttps://api.github.com/[^>]*(?=>; rel=\"next\",)") || break

	if [ "${verbosity}" -gt 0 ]; then
		printf "."
	fi
done

if [ "${verbosity}" -gt 0 ]; then
	printf " Done.\n"
fi

repoUrls=$(printf "%s" "${repoUrls}" | grep -v -e "/tools.git\$" -e "/web.git\$" -e "/manual.git\$" | awk 'NF')

printf "%s\n" "${repoUrls}" | while IFS= read -r repoUrl; do
	[ -n "${repoUrl}" ] || continue
	[ -d "${repoUrl##*/}" ] && continue

	repoName="${repoUrl##*/}"
	repoNameLength=$(printf "%s" "${repoName}" | wc -m)
	if [ "${repoNameLength}" -ge 100 ]; then
		if dirs=( "${repoName%%.git}"*/ ) && [[ -d ${dirs[0]} ]]; then
			continue
		fi
	fi

	if [ "${verbosity}" -gt 0 ]; then
		printf "Cloning %s ... \n" "${repoUrl}"
	fi

	if [ "${verbosity}" -lt 2 ]; then
		git clone -q --bare "${repoUrl}"
	else
		git clone -v --bare "${repoUrl}"
	fi

	if ! [ -d "${repoName}" ]; then
		printf "Failed to clone %s.\n" "${repoName}." 1>&2
	elif [ "${verbosity}" -gt 0 ]; then
		printf "Done.\n"
	fi

	properName="$(git -C "${repoName}" show HEAD:src/epub/content.opf |
		grep -oE "<dc:identifier id=\"uid\">url:https://standardebooks.org/ebooks/[^<]+<\/dc:identifier>" |
		sed -E "s/<[^>]+?>//g" |
		sed -E "s|url:https://standardebooks.org/ebooks/||g" |
		sed -E "s|/|_|g").git"

	if [ "${repoUrl##*/}" != "${properName}" ]; then
		if [ "${verbosity}" -gt 0 ]; then
			printf "Moving %s to %s\n" "${repoName}" "${properName}"
		fi
		mv "${repoName}" "${properName}"
	fi
done