#!/usr/bin/env bash
# This script cleans up local Git branches which have been merged into
# the main branch.  I use it to clean up the branch view in GitUp
# (my Git GUI of choice), so I'm not distracted by lots of old branches.
#
# It's based on the commands from this Stack Overflow post:
# https://stackoverflow.com/a/6127884/1558022

set -o errexit
set -o nounset

GIT_ROOT=$(git rev-parse --absolute-git-dir)

if [[ -f "$GIT_ROOT/refs/remotes/origin/HEAD" ]]
then
  PRIMARY_BRANCH=$(cat "$GIT_ROOT/refs/remotes/origin/HEAD" \
    | tr '/' ' ' \
    | awk '{print $5}')
elif [[ -f "$GIT_ROOT/refs/remotes/origin/live" ]]
then
  PRIMARY_BRANCH="live"
else
  PRIMARY_BRANCH="main"
fi

CURRENT_BRANCH=$(git branch --show-current)

if [[ "$PRIMARY_BRANCH" = "$CURRENT_BRANCH" ]]
then
  print_info "-> Current branch is $CURRENT_BRANCH, which is primary"
else
  print_info "-> Primary branch is $PRIMARY_BRANCH"
  print_info "-> Current branch is $CURRENT_BRANCH"
fi

for branch in $(git branch --merged "$PRIMARY_BRANCH" | grep -v '*')
do
  if [[ "$branch" == "$PRIMARY_BRANCH" ]]
  then
    continue
  fi

  if [[ "$branch" == "$CURRENT_BRANCH" ]]
  then
    continue
  fi

  git branch --delete "$branch"
done

# For Tailscale repos, the above check doesn't work. Branches get rebased
# or squashed before being merged into main, so the branch never shows up
# as merged -- it's a different commit in main and the branch.
#
# Instead, look for alexc/ branches that are more than a fortnight old and
# don't exist in the origin. These are branches I've either abandoned or
# merged into main.
PREFIXES=("alexc/" "danni/" "icio/" "kradalby/" "mpminardi/" "mprovost/" "zofrex/")
DAYS_AGO=14
THRESHOLD_DATE=$(date -v-"${DAYS_AGO}"d +%s)

for PREFIX in "${PREFIXES[@]}"; do
  git for-each-ref --format='%(refname:short)' refs/heads/"$PREFIX"* | while read -r branch; do
    # If the branch still exists on GitHub, ignore it -- this is likely
    # an active branch with an open PR.
    if git rev-parse --verify --quiet "origin/$branch" &>/dev/null; then
      continue
    fi

    # When did I last commit to this branch?
    commit_timestamp=$(git log -1 --format="%at" "$branch")
    if (( commit_timestamp > THRESHOLD_DATE )); then
      continue
    fi
  
    git branch --delete --force "$branch"
  done
done