#!/bin/bash

# cyche-source <name> <url> <ref-pattern>
#
# Check a git source for new updates.  A local cache repository is cloned if
# <name> doesn't exist.  If updates are found, we attempt to checkout the newest
# version according to <ref-pattern> (see <pattern> from git-for-each-ref(1)).
#
# The new (or current, if no update occurred) object hash is printed to stdout.
# This may be a commit hash.  However, if <ref-pattern> matches an annotated tag,
# then the hash names the tag object.  The caller should cache this hash value
# upon successful deployment.
#
# If the file tree is updated, this file exits non-zero.

gethash() {
    git for-each-ref \
        --count=1 \
        --format='%(objectname)' \
        --sort='-creatordate' \
        "$1" # pattern
}

cd '/services'

if ! [ -d "$1" ]; then
    git clone "$2" "$1" >&2
    touch "$1/.git/previous_hash"
    touch "$1/.git/previous_slug"
fi

cd "$1"

git remote set-url origin "$2" >&2 # pick up url changes
git fetch --all --prune >&2

prev=$(cat '.git/previous_hash')
next=$(gethash "$3")

if [ -z "$next" ]; then
    # no matching refs
    next="$prev"
fi

echo "$next"

if [ "$prev" != "$next" ]; then
    # update file tree
    git submodule deinit --all --force >/dev/null 2>&1
    git reset . >/dev/null 2>&1
    git checkout . >/dev/null 2>&1
    git clean -xffd >/dev/null 2>&1

    git checkout "$next" >/dev/null 2>&1
    git submodule update --init --recursive >/dev/null 2>&1

    exit 1
fi

exit 0