#!/usr/bin/env bash
# Hand a Railway environment over to an exe.dev VM.
# From https://exe.dev/deploy/migrate-railway
#
#   handover my-app.exe.xyz          copy config, variables, and data (Railway keeps running)
#   handover my-app.exe.xyz --move   stop the app on Railway, copy the data again, and start it on the VM
#
# Run it on your computer, in a directory linked with `railway link` to the
# project and environment to move. It reads from Railway with your Railway
# CLI login; nothing here writes to Railway, except --move, which removes
# the running deployment of each app service (railway down) after you say yes.
# Everything goes straight to the VM over SSH.
set -euo pipefail

vm=${1:?usage: handover my-app.exe.xyz [--move]}
mode=${2:-}
kit=https://exe.dev/deploy/migrate-railway

command -v railway >/dev/null || { echo "handover: install the Railway CLI first: https://docs.railway.com/cli" >&2; exit 1; }
railway status --json >/dev/null || { echo "handover: run 'railway link' here first, and pick the environment to move" >&2; exit 1; }
ssh -n "$vm" true || { echo "handover: can't reach $vm over SSH" >&2; exit 1; }

# Railway's description of the environment, and the kit's importer on the VM.
tmp=$(mktemp -d)
trap 'rm -rf "$tmp"' EXIT
railway status --json > "$tmp/status.json"
railway environment config --json > "$tmp/environment.json"
tar -C "$tmp" -cf - status.json environment.json |
  ssh "$vm" "umask 077 && mkdir -p railway/variables railway/data && tar -x -C railway &&
    { test -x railway/import || curl -fsSL $kit/import -o railway/import && chmod +x railway/import; }"
plan=$(ssh -n "$vm" railway/import plan)

col() { cut -f"$1" <<<"$line"; }
each() {  # KIND: the plan's lines of that kind, one at a time, in $line
  grep "^$1"$'\t' <<<"$plan" || true
}
save() {  # FILE: stdin to ~/railway/data/FILE on the VM, complete or not at all
  ssh "$vm" "umask 077 && cat > 'railway/data/$1.part' && mv 'railway/data/$1.part' 'railway/data/$1'"
}
stopped=
stop() {  # SERVICE: remove its running deployment on Railway (--move only)
  [ "$mode" = --move ] || return 0
  grep -qxF "$1" <<<"$stopped" && return 0
  railway down --service "$1" --yes </dev/null
  stopped+="$1"$'\n'
}

if [ "$mode" = --move ]; then
  echo "This stops these services on Railway, so nothing changes their data while it moves:"
  each stop | cut -f2 | sed 's/^/  /'
  read -r -p "Type yes to go on: " ok </dev/tty
  [ "$ok" = yes ] || exit 1
elif [ -n "$mode" ]; then
  echo "handover: unknown option $mode" >&2; exit 1
fi

while IFS= read -r line <&3; do
  echo "variables: $(col 2)"
  railway variable list --service "$(col 2)" --json </dev/null |
    ssh "$vm" "umask 077 && cat > 'railway/variables/$(col 2).json'"
done 3< <(each vars)

# A volume can only be read while its service runs: copy it, then stop the service.
while IFS= read -r line <&3; do
  echo "volume: $(col 2) ($(col 3))"
  railway ssh --service "$(col 2)" </dev/null -- "tar -C '$(col 3)' --numeric-owner -cf - ." | save "$(col 2).tar"
  stop "$(col 2)"
done 3< <(each volume)

while IFS= read -r line <&3; do stop "$(col 2)"; done 3< <(each stop)
[ -z "$stopped" ] || sleep 15

while IFS= read -r line <&3; do
  echo "database: $(col 2) (pg_dump)"
  railway ssh --service "$(col 2)" </dev/null -- 'pg_dump --format=custom --no-owner --no-privileges -h localhost -U "${PGUSER:-postgres}" "${PGDATABASE:-railway}"' |
    save "$(col 2).pgdump"
done 3< <(each postgres)

while IFS= read -r line <&3; do
  echo "database: $(col 2) (redis-cli --rdb)"
  railway ssh --service "$(col 2)" </dev/null -- 'redis-cli -a "$REDIS_PASSWORD" --no-auth-warning --rdb /tmp/handover.rdb >/dev/null 2>&1 && cat /tmp/handover.rdb && rm -f /tmp/handover.rdb' |
    save "$(col 2).rdb"
done 3< <(each redis)

while IFS= read -r line <&3; do echo "not copied: $(col 2) ($(col 3))"; done 3< <(each skip)

if [ "$mode" = --move ]; then
  ssh -t "$vm" railway/move
  exit
fi
ssh -n "$vm" 'date -u +%FT%TZ > railway/handed-over'

echo
echo "Handed over. Now push the code Railway runs, from each repository's checkout:"
each push | awk -F'\t' '!seen[$3]++' | while IFS= read -r line; do
  echo
  echo "  # $(col 4 | sed 's/^$/the code you deploy with railway up/') (for $(grep "^push"$'\t'".*"$'\t'"$(col 3)"$'\t' <<<"$plan" | cut -f2 | paste -sd, -))"
  echo "  ssh $vm git init -q --bare git/$(col 3).git"
  echo "  git remote add exe $vm:git/$(col 3).git"
  echo "  git push exe $(col 5)"
done