#!/bin/sh

die() {
	echo "$@" >&2
	exit 1
}

have_binary() {
	type "$1" > /dev/null 2> /dev/null
}

check_writable() {
	printf "" > "$1" && rm "$1"
}

try_download() {
	url="$1"
	output="$2"
	command="$3"
	util_name="$(set -- $command; echo "$1")"

	if ! have_binary "$util_name"; then
		return 1
	fi

	printf '==> Using %s to download "%s" to "%s"\n' "$util_name" "$url" "$output"
	if eval "$command"; then
		echo "==> Download complete!"
		return
	else
		echo "error: couldn't download with $util_name ($?)"
		return 1
	fi
}

download() {
	dl_url="$1"
	dl_output="$2"

	test "$#" -eq "2" || die "download requires exactly two arguments, was given $@"

	if ! check_writable "$dl_output"; then
		die "download error: cannot write to $dl_output"
	fi

	try_download "$dl_url" "$dl_output" "wget '$dl_url' -O '$dl_output'" && return
	try_download "$dl_url" "$dl_output" "curl --silent --fail --output '$dl_output' '$dl_url'" && return
	try_download "$dl_url" "$dl_output" "fetch '$dl_url' -o '$dl_output'" && return
	try_download "$dl_url" "$dl_output" "http '$dl_url' > '$dl_output'" && return
	try_download "$dl_url" "$dl_output" "ftp -o '$dl_output' '$dl_url'" && return

	die "Unable to download $dl_url. exiting."
}

unarchive() {
	ua_archivetype="$1"
	ua_infile="$2"
	ua_outfile="$3"
	ua_distname="$4"
	ua_binpostfix=""
	ua_os=$(uname -o)

	if [ "$ua_os" = "Msys" ] || [ "$ua_os" = "Cygwin" ] ; then
	    ua_binpostfix=".exe"
	fi
	ua_outfile="$ua_outfile$ua_binpostfix"

	if ! check_writable "$ua_outfile"; then
		die "unarchive error: cannot write to $ua_outfile"
	fi

	case "$ua_archivetype" in
		tar.gz)
			if have_binary tar; then
				echo "==> using 'tar' to extract binary from archive"
				< "$ua_infile" tar -Ozxf - "$ua_distname/$ua_distname$ua_binpostfix" > "$ua_outfile" \
					|| die "tar has failed"
			else
				die "no binary on system for extracting tar files"
			fi
			;;
		zip)
			if have_binary unzip; then
				echo "==> using 'unzip' to extract binary from archive"
				unzip -p "$ua_infile" "$ua_distname/$ua_distname$ua_binpostfix" > "$ua_outfile" \
					|| die "unzip has failed"
			else
				die "no installed method for extracting .zip archives"
			fi
			;;
		*)
			die "unrecognized archive type '$ua_archivetype'"
	esac

	chmod +x "$ua_outfile" || die "chmod has failed"
}

get_go_vars() {
	if [ ! -z "$GOOS" ] && [ ! -z "$GOARCH" ]; then
		printf "%s-%s" "$GOOS" "$GOARCH"
	elif have_binary go; then
		printf "%s-%s" "$(go env GOOS)" "$(go env GOARCH)"
	else
		die "no way of determining system GOOS and GOARCH\nPlease manually set GOOS and GOARCH then retry."
	fi
}

mkurl() {
	m_root="$1"
	m_name="$2"
	m_vers="$3"
	m_archive="$4"
	m_govars=$(get_go_vars) || die "could not get go env vars"

	echo "https://ipfs.io$m_root/$m_name/$m_vers/${m_name}_${m_vers}_$m_govars.$m_archive"
}

distroot="$1"
distname="$2"
outpath="$3"
version="$4"

if [ -z "$distroot" ] || [ -z "$distname" ] || [ -z "$outpath" ] || [ -z "$version" ]; then
	die "usage: dist_get <distroot> <distname> <outpath> <version>"
fi

case $version in
	v*)
		# correct input
		;;
	*)
		echo "invalid version '$version'" >&2
		die "versions must begin with 'v', for example: v0.4.0"
		;;
esac

# TODO: don't depend on the go tool being installed to detect this
goenv=$(get_go_vars) || die "could not get go env vars"

case $goenv in
	linux-*)
		archive="tar.gz"
		;;
	darwin-*)
		archive="tar.gz"
		;;
	windows-*)
		archive="zip"
		;;
	freebsd-*)
		archive="tar.gz"
		;;
	openbsd-*)
		archive="tar.gz"
		;;
	*)
		echo "unrecognized system environment: $goenv" >&2
		die "currently only linux, darwin, windows and freebsd are supported by this script"
esac


mkdir -p bin/tmp

url=$(mkurl "$distroot" "$distname" "$version" "$archive")
tmpfi="bin/tmp/$distname.$archive"

download "$url" "$tmpfi"
if [ $? -ne 0 ]; then
	die "failed to download $url to $tmpfi"
fi

unarchive "$archive" "$tmpfi" "$outpath" "$distname"
if [ $? -ne 0 ]; then
	die "failed to extract archive $tmpfi"
fi