#!/bin/sh
# This is a git-annex external special remote program,
# which adds experimental ipfs support to git-annex.
#
# Install in PATH as git-annex-remote-ipfs
#
# Copyright 2015 Joey Hess; licenced under the GNU GPL version 3 or higher.

set -e

# use ipfs: as a prefix to indicate when an "url" is really stored in ipfs
isipfsurl () {
	echo "$1" | egrep -q "^ipfs:"
}

# convert an ipfs: url to an address that the ipfs client understands
urltoaddress () {
	echo "$1" | sed -e 's/^ipfs://'
}

addresstourl () {
	echo "ipfs:$1"
}

# Gets a VALUE response and stores it in $RET
getvalue () {
	read resp
	# Tricky POSIX shell code to split first word of the resp,
	# preserving all other whitespace
	case "${resp%% *}" in
		VALUE)
			RET="$(echo "$resp" | sed 's/^VALUE \?//')"
		;;
		*)
		RET=""
		;;
	esac
}

# Get a list of all known ipfs addresses for a key,
# storing it in a temp file.
getaddrs () {
        key="$1"
        tmp="$2"

        echo GETURLS "$key"
        getvalue
        while [ -n "$RET" ]; do
                if isipfsurl "$RET"; then
                        echo "$RET" >> "$tmp"
                fi
                getvalue
        done
}

# This has to come first, to get the protocol started.
echo VERSION 1

while read line; do
	set -- $line
	case "$1" in
		INITREMOTE)
			echo INITREMOTE-SUCCESS
		;;
		PREPARE)
			echo PREPARE-SUCCESS
		;;
		CLAIMURL)
			url="$2"
			if isipfsurl "$url"; then
				echo CLAIMURL-SUCCESS
			else
				echo CLAIMURL-FAILURE
			fi
		;;
		CHECKURL)
			url="$2"
			# TODO if size of file can be quickly determined
			# (without downloading it) return the size
			# instead of UNKNOWN
			echo CHECKURL-CONTENTS UNKNOWN "$(urltoaddress "$url")"
		;;
		TRANSFER)
			key="$3"
			file="$4"
			case "$2" in
				STORE)
					addr=$(ipfs add -q "$file" </dev/null) || true
					if [ -z "$addr" ]; then
						echo TRANSFER-FAILURE STORE "$key" "ipfs add failed"
					else
						echo "SETURIPRESENT" "$key" "$(addresstourl "$addr")"
						echo TRANSFER-SUCCESS STORE "$key"
					fi
				;;
				RETRIEVE)
					addrtmp=$(mktemp)
					getaddrs "$key" "$addrtmp"
					addr="$(urltoaddress "$(head "$addrtmp")")" || true
					rm -f "$addrtmp"
					if [ -z "$addr" ]; then
						echo TRANSFER-FAILURE RETRIEVE "$key" "no known ipfs address for this key"
					else
						if ! ipfs get --output="$file" "$addr" >&2 </dev/null; then
							echo TRANSFER-FAILURE RETRIEVE "$key" "failed downloading ipfs $addr"
						else
							echo TRANSFER-SUCCESS RETRIEVE "$key"
						fi
					fi
				;;
			esac
		;;
		CHECKPRESENT)
			key="$2"
			echo CHECKPRESENT-FAILURE "$key"
		;;
		REMOVE)
			key="$2"
			echo REMOVE-FAILURE "$key" "cannot remove content from ipfs (instead, run ipfs gc to clear your local ipfs cache)"
		;;
		*)
			echo UNSUPPORTED-REQUEST
		;;
	esac	
done
