#!/usr/bin/env bash
set -euo pipefail

: "${DEPLOY_HOST:?Missing DEPLOY_HOST}"
: "${DEPLOY_USER:?Missing DEPLOY_USER}"
: "${DEPLOY_PATH:?Missing DEPLOY_PATH}"
: "${DEPLOY_SSH_KEY:?Configure the DEPLOY_SSH_KEY Actions secret}"
: "${DEPLOY_KNOWN_HOSTS:?Configure the DEPLOY_KNOWN_HOSTS Actions secret}"
: "${GITHUB_SHA:?Missing build commit}"
: "${GITHUB_RUN_NUMBER:?Missing run number}"
: "${GITHUB_RUN_ATTEMPT:?Missing run attempt}"
DEPLOY_PORT=${DEPLOY_PORT:-22}

# These values cross an SSH shell boundary. Reject shell syntax.
[[ $DEPLOY_HOST =~ ^[a-zA-Z0-9][a-zA-Z0-9.-]*$ ]]
[[ $DEPLOY_USER =~ ^[a-zA-Z0-9_][a-zA-Z0-9_-]*$ ]]
[[ $DEPLOY_PATH =~ ^/[a-zA-Z0-9_/-]+$ && $DEPLOY_PATH != / ]]
[[ $DEPLOY_PORT =~ ^[0-9]+$ && $GITHUB_SHA =~ ^[a-f0-9]{40}$ ]]
[[ $GITHUB_RUN_NUMBER =~ ^[0-9]+$ && $GITHUB_RUN_ATTEMPT =~ ^[0-9]+$ ]]
test -f _site/art/index.html
test -f _site/photo-publication.json

credentials=$(mktemp -d)
trap 'rm -rf "$credentials"' EXIT
chmod 700 "$credentials"
printf '%s\n' "$DEPLOY_SSH_KEY" > "$credentials/key"
printf '%s\n' "$DEPLOY_KNOWN_HOSTS" > "$credentials/known_hosts"
chmod 600 "$credentials/key" "$credentials/known_hosts"
target="$DEPLOY_USER@$DEPLOY_HOST"
release="$DEPLOY_PATH/releases/$GITHUB_RUN_NUMBER-$GITHUB_RUN_ATTEMPT-$GITHUB_SHA"
ssh_options=(-i "$credentials/key" -p "$DEPLOY_PORT" -o BatchMode=yes
    -o IdentitiesOnly=yes -o StrictHostKeyChecking=yes
    -o "UserKnownHostsFile=$credentials/known_hosts")
ssh "${ssh_options[@]}" "$target" "mkdir -p '$release'"
# Checksums and hard links avoid retransmitting existing photos on every build.
printf -v transport 'ssh -i %q -p %q -o BatchMode=yes -o IdentitiesOnly=yes -o StrictHostKeyChecking=yes -o UserKnownHostsFile=%q' \
    "$credentials/key" "$DEPLOY_PORT" "$credentials/known_hosts"
rsync -azc --delete --link-dest="$DEPLOY_PATH/current/" -e "$transport" _site/ "$target:$release/"
ssh "${ssh_options[@]}" "$target" "bash -s -- '$DEPLOY_PATH' '$release' '$GITHUB_RUN_NUMBER'" <<'REMOTE'
set -euo pipefail
destination=$1
release=$2
run=$3
exec 9>"$destination/deploy.lock"
flock 9
test -f "$release/art/index.html"
test -f "$release/photo-publication.json"
previous=0
if [ -f "$destination/current/deployment-run" ]; then
    previous=$(cat "$destination/current/deployment-run")
fi
if (( run < previous )); then
    echo "A newer workflow has already deployed; leaving the current site intact."
    exit 0
fi
printf '%s\n' "$run" > "$release/deployment-run"
chmod -R a+rX "$release"
temporary="$destination/.current-$run-$$"
ln -s "releases/$(basename "$release")" "$temporary"
mv -Tf "$temporary" "$destination/current"
echo "Deployed $release"
REMOTE