#!/bin/sh
# Run slosh the way you want it while you are *working on* slosh: build a
# new binary, and pick it up without losing your screen.
#
#   contrib/slosh-dev                start (or reattach to) the dev session
#   contrib/slosh-dev restart        from inside it: come back on the new build
#   SESSION=work contrib/slosh-dev   a different session name
#
# A running session keeps the binary it started with -- `reload` re-reads the
# config, it cannot re-read the code -- so a new build needs a new server. The
# only thing worth saving across that is the layout, and slosh can write its
# own: `dump-layout` is the inverse of `--layout`.
#
# So this is a loop. It attaches; when the session ends *because you asked it
# to restart*, it rebuilds nothing, waits for nothing, and comes straight back
# with the layout you had -- same tabs, same splits, same proportions, same
# directories, same tab and pane focused. What it cannot bring back is what
# was running inside a program: a shell comes back as a shell, in the right
# directory, with an empty history.
set -e

here=$(cd "$(dirname "$0")" && pwd)
bin="$here/../build/slosh"
SESSION=${SESSION:-dev}
state="${XDG_RUNTIME_DIR:-/tmp}/slosh-dev-$SESSION"
layout="$state/session.layout"
flag="$state/restart"
mkdir -p "$state"

# `restart` runs *inside* the session, so it cannot do the restarting: the
# moment the session ends, so does the shell it was typed in. It leaves the
# layout and a note, and the loop below -- which is outside -- picks both up.
if [ "$1" = "restart" ]; then
  [ -n "$SLOSH" ] || { echo "slosh-dev restart: run this inside the session"; exit 1; }
  "$bin" -s "$SESSION" cmd '{"cmd":"dump-layout"}' \
    | sed -n 's/.*"kdl":"\(.*\)"}/\1/p' \
    | sed -e 's/\\n/\n/g' -e 's/\\"/"/g' -e 's/\\\\/\\/g' > "$layout"
  [ -s "$layout" ] || { echo "slosh-dev restart: could not dump the layout"; exit 1; }
  : > "$flag"
  "$bin" -s "$SESSION" cmd '{"cmd":"quit"}' >/dev/null
  exit 0
fi

# Anything else is the loop.
while :; do
  if [ -s "$layout" ]; then
    "$bin" -s "$SESSION" --layout "$layout" -- "${SHELL:-/bin/sh}" || true
  else
    "$bin" -s "$SESSION" -- "${SHELL:-/bin/sh}" || true
  fi

  # Detached, quit, or the last pane closed: all of those are you leaving. Only
  # the flag means "put it back".
  [ -f "$flag" ] || break
  rm -f "$flag"
  printf '\033[2J\033[H'
  echo "restarting $SESSION on $(cd "$here/.." && git rev-parse --short HEAD 2>/dev/null || echo 'the new build')..."
  sleep 0.2
done