#!/bin/sh
# Prepare the dev environment for a new checkout or worktree.
#
# Installed into the git hooks directory by script/setup.py. Deliberately tiny
# and self-contained: it stays valid on branches where the setup script does not
# exist, and simply does nothing there.

# $3 is 1 for a branch checkout, 0 for a file checkout.
[ "$3" = "1" ] || exit 0

top=$(git rev-parse --show-toplevel 2>/dev/null) || exit 0

# This also runs on ordinary branch switches, where there is nothing to do. Both
# layouts are checked because git for Windows runs hooks under its own bundled
# shell, where the environment lives in venv/Scripts rather than venv/bin.
[ -x "$top/venv/bin/python" ] && exit 0
[ -f "$top/venv/Scripts/python.exe" ] && exit 0

# Branches from before the setup script moved to Python carry only the shell
# entry point, so whichever one the checked out branch has is used.
py=
if [ -f "$top/script/setup.py" ]; then
  # The interpreter goes by different names across platforms, and on Windows
  # "python3" is often a stub that opens the app store instead of running
  # anything, so each candidate is tried before it is used. Doing nothing is the
  # right outcome when none of them work.
  for candidate in "python3" "python" "py -3"; do
    # Unquoted on purpose: the launcher candidate is a command plus a flag.
    if $candidate -c "" >/dev/null 2>&1; then
      py=$candidate
      break
    fi
  done
  [ -n "$py" ] || exit 0
elif ! [ -x "$top/script/setup" ]; then
  exit 0
fi

# Every worktree shares the hooks directory of the checkout it was created
# from, and the setup script run below is the one from whichever branch was just
# checked out. Older branches install their own pre-commit hook without checking
# for a worktree: that moves the shared hook aside as pre-commit.legacy and
# replaces it with one tied to this worktree's virtual environment, so commits
# break in every checkout. To rule that out, the hooks directory is copied
# before the setup script runs and put back exactly as it was afterwards,
# including removing any file the setup script added.
hooks=$(git rev-parse --path-format=absolute --git-path hooks 2>/dev/null) || exit 0
snap=$(mktemp -d "$hooks/.post-checkout.XXXXXX") || exit 0
cp -p "$hooks"/* "$snap"/ 2>/dev/null

# Clear VIRTUAL_ENV so a checkout made from a shell with an environment already
# activated still gets its own, rather than having the active one repointed at
# this working tree.
unset VIRTUAL_ENV
if [ -n "$py" ]; then
  # Unquoted on purpose, as above.
  $py "$top/script/setup.py"
else
  "$top/script/setup"
fi
status=$?

for f in "$hooks"/*; do
  [ -e "$snap/${f##*/}" ] || rm -f "$f"
done
# Files are moved rather than copied so a hook that is still running, such as
# this one, is swapped out atomically instead of being rewritten in place.
for f in "$snap"/*; do
  cmp -s "$f" "$hooks/${f##*/}" 2>/dev/null || mv -f "$f" "$hooks/${f##*/}"
done
rm -rf "$snap"
exit $status