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

usage(){
	cat <<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 -b or --bare, clone bare repositories (for a server) instead of working directories.
	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.

	NOTE: This script requires GNU versions of grep and sed. If you are on a Mac, you will need to
	install GNU versions (via Homebrew, MacPorts, etc.) and make sure they are first in your path,
	or modify the script to use the GNU versions if they're named differently.

EXAMPLE
	${0##*/} /standardebooks.org/ebooks
EOF
	exit
}

# functions used by the script
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 "$1 is required but not installed.${suggestion}";
	}
}

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

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

require "git"

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

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

# process each of the parameters one at a time, shifting each time to get the next one
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
			;;
		-b|--bare)
			bare="--mirror"
			shift 1
			;;
		*)
			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

# update any existing repositories
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 it's not a repository directory, skip it
	git -C "${item}" rev-parse > /dev/null 2>&1 || continue

	# this works whether the repository is bare or a working directory
	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

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

# get all of the repository names from the GitHub API, one "page" at a time
url="https://api.github.com/orgs/standardebooks/repos?per_page=100"
repoUrls=""

while true; do
	# get a "page" worth of repository URL's
	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

	# parse the response to get the current page's URL's
	currentRepoUrls=$(printf "%s" "${response}" | awk 'BEGIN { FS="\""; RS="," }; { if ($2 == "clone_url") {print $4} }')
	# add them to the full list in repoUrls
	repoUrls=$(printf "%s\n%s" "${repoUrls}" "${currentRepoUrls}")
	# set the variable to get the next "page"
	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

# skip the non-ebook repositories by removing their names from the list
repoUrls=$(printf "%s" "${repoUrls}" | grep -v -e "/tools.git\$" -e "/web.git\$" -e "/manual.git\$" -e "/standard-blackletter.git\$" -e "/sublime-text-se-plugin.git\$" | awk 'NF')

# process the list, reading one repository at a time
printf "%s\n" "${repoUrls}" | while IFS= read -r repoUrl; do
	# make sure it's not an empty string
	[ -n "${repoUrl}" ] || continue

	# strip everything prior to the last segment of the name
	repoName="${repoUrl##*/}"
	if [ "${bare}" = "" ]; then
		repoName="${repoName%.git}"
	fi

	# if the repo already exists, skip it (handled in the update above)
	[ -d "${repoName}" ] && continue

	# if the repository name has been truncated due to GitHub's name length limits,
	# but a local clone with the full name exists, don't attempt to clone it again
	repoNameLength=$(printf "%s" "${repoName%.git}" | 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

	# clone the repository, creating either a bare or working directory based on the option
	if [ "${verbosity}" -lt 2 ]; then
		git clone -q ${bare} "${repoUrl}"
	else
		git clone -v ${bare} "${repoUrl}"
	fi

	# if a directory with the repository name doesn't exist, the clone did not complete successfully
	if ! [ -d "${repoName}" ]; then
		printf "Failed to clone %s.\n" "${repoName}." 1>&2
	elif [ "${verbosity}" -gt 0 ]; then
		printf "Done.\n"
	fi

	# if the repository doesn't have a metadata file, skip to the next repository
	metadata=$(git -C "${repoName}" show HEAD:src/epub/content.opf > /dev/null 2>&1) || continue

	# get the last segment of the dc:identifier from the metadata
	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 [ "${bare}" = "" ]; then
		properName="${properName%.git}"
	fi

	# if for some reason the repository name isn't the same as the identifier (they are identical
	# 99% of the time), rename the directory to be the identifier name; not sure why this is done, either
	if [ "${repoName}" != "${properName}" ]; then
		if [ -d "${properName}" ]; then
			if [ "${verbosity}" -gt 0 ]; then
				printf "Not moving %s to %s: directory exists\n" "${repoName}" "${properName}"
			fi
		else
			if [ "${verbosity}" -gt 0 ]; then
				printf "Moving %s to %s\n" "${repoName}" "${properName}"
			fi
			mv "${repoName}" "${properName}"
		fi
	fi
done