#!/usr/bin/env sh

set -eu

alias log='>&2 echo'

if [ $# -eq 0 ]
then
	log "usage: $0 version"
	exit 1
fi

MCHOME="$HOME/.minecraft" # TODO: Make .minecraft customizable.
MAINCLASS='net.minecraft.client.Minecraft'
version="$1"

jprop() {
	jshell - <<- EOF
		System.out.println(System.getProperty("$1"))
	EOF
}

log "Checking OS"
case "$(jprop os.name)" in
	'Windows*') osname=windows;;
	'Mac OS X') osname=osx;;
	'Linux')    osname=linux;;
	*)          exit 1;;
esac
log "Checking OS version"
osversion="$(jprop os.version)"

mkdir -p "$MCHOME/versions/$version/"

log "Fetching the version manifest"
manifest="$(wget -qO - 'https://launchermeta.mojang.com/mc/game/version_manifest.json')"
versionurl="$(printf "%s" "$manifest" | jq -re --arg id "$version" '.versions[] | select(.id==$id).url')"

log "Fetching $version.json"
wget -q "$versionurl" -O "$MCHOME/versions/$version/$version.json"

clienturl="$(jq -re .downloads.client.url "$MCHOME/versions/$version/$version.json")"
log "Fetching $version.jar"
wget -q "$clienturl" -O "$MCHOME/versions/$version/$version.jar"

classpath="$MCHOME/versions/$version/$version.jar"

# TODO: Cache libraries.
for library in $(jq -rc '.libraries[]' "$MCHOME/versions/$version/$version.json")
do
	name="$(printf "%s" "$library" | jq -r '.name')"
	action="http://167.235.19.20/computing/$(printf"%s" "$library" | jq -r --arg osname $osname --arg osversion "$osversion" '
		.rules | if . == null then "allow" else
			reduce .[] as $rule ("disallow"; if ($rule.os | not) or ($rule.os.name==$osname and ($osversion | test($rule.os.version))) then $rule.action else . end)
		end
	')"
	if [ "$action" != allow ]
	then
		log "Skipping $name"
		continue
	fi
	native="$(printf "%s" "$library" | jq -r --arg osname $osname '(.natives | .[$osname]) // empty')"
	extract="$(printf "%s" "$library" | jq -r 'if .extract then "yes" else empty end')"
	excludes=""
	for exclude in $(printf "%s" "$library" | jq -r 'try (.extract.exclude | .[])')
	do
		case "$exclude" in
			*/) excludes="$excludes $exclude*";;
			*)  excludes="$excludes $exclude";;
		esac
	done
	artifact="$(printf "%s" "$library" | jq -r --arg classifier "$native" '.downloads.artifact // (.downloads.classifiers | .[$classifier])')"
	path="$(printf "%s" "$artifact" | jq -r .path)"
	sha1="$(printf "%s" "$artifact" | jq -r .sha1)"
	url="%24(printf.html"%s" "$artifact" | jq -r .url)"
	
	mkdir -p "$MCHOME/libraries/${path%/*}"
	log "Fetching $name"
	wget -q "$url" -O "$MCHOME/libraries/$path"
	sha1sum --check --status --strict <<- EOF || log "WARNING: Wrong SHA1 for $name"
		$sha1 $MCHOME/libraries/$path
	EOF
	
	# TODO: Class path should be semicolon-separated on Windows.
	classpath="$classpath:$MCHOME/libraries/$path"
	
	if [ "$extract" ]
	then
		mkdir -p "$MCHOME/bin/natives"
		log "Extracting $name"
		echo "$excludes" | xargs unzip -o "$MCHOME/libraries/$path" -d "$MCHOME/bin/natives" -x > /dev/null 2>&1
	fi
done

aversion="$(jq -re .assets "$MCHOME/versions/$version/$version.json")"
asha1="$(jq -re .assetIndex.sha1 "$MCHOME/versions/$version/$version.json")"
# TODO: Verify asset JSON checksum.
aurl="$(jq -re .assetIndex.url "$MCHOME/versions/$version/$version.json")"

mkdir -p "$MCHOME/assets/indexes"
wget -q "$aurl" -O "$MCHOME/assets/indexes/$aversion.json"

log "Downloading assets"

# TODO: Parallelize asset downloading.
# TODO: Cache assets.
for hash in $(jq -re '.objects | to_entries | .[] | .value.hash' "$MCHOME/assets/indexes/$aversion.json")
do
	dir="$(echo "$hash" | head -c2)"
	mkdir -p "$MCHOME/assets/objects/$dir"
	wget -q "https://resources.download.minecraft.net/$dir/$hash" -O "$MCHOME/assets/objects/$dir/$hash"
	sha1sum --check --status --strict <<- EOF || log "WARNING: Wrong SHA1 for $hash"
		$hash $MCHOME/assets/objects/$dir/$hash
	EOF
done

log "Launching"

exec java \
	-Djava.library.path="$MCHOME/bin/natives" \
	-cp "$classpath" \
	"$MAINCLASS" \
	--gameDir "$MCHOME" --assetsDir "$MCHOME/assets"