post-checkout

#!/bin/sh

# --- Command line
previous_head="$1"
new_head="$2"
branch_checkout="$3"

# --- Constants
separator="/"
master_branch="master"

# --- Functions
database_exists () {
  name=${1:0:63}
  return  `psql -U postgres -lqtA | cut -d\| -f1 | grep -qFx "$name"`
}

kill_connections() {
  psql -U postgres -c "SELECT pg_terminate_backend(pg_stat_activity.pid) FROM pg_stat_activity WHERE pg_stat_activity.datname = '$database_name' AND pid <> pg_backend_pid();" > /dev/null
}

duplicate_database_to() {
  name=${1:0:63}
  echo "Creating $name from $database_name"
  createdb -T $database_name $name
}

drop_database() {
  name=${1:0:63}
  echo "Deleting existing $name"
  dropdb -U postgres "$name"
}

rename_database() {
  old_name=${1:0:63}
  new_name=${2:0:63}
  # echo "Renaming $old_name to $new_name"
  psql -U postgres -c "SET standard_conforming_strings=on;" -q -b
  psql -U postgres -c "ALTER DATABASE \"$old_name\" RENAME TO \"$new_name\";" -q -e
  psql -U postgres -c "SET standard_conforming_strings=off;" -q -b
}

alias branch_name='git name-rev --name-only'

# --- Variables
previous_branch=`branch_name $previous_head`
new_branch=`git branch | grep -e "^*" | cut -d' ' -f 2`
database_name="db/beanstack_development"
old_database=$database_name$separator$previous_branch
new_database=$database_name$separator$new_branch
main_backup=$database_name$separator$master_branch
# --- Script

# --- Exit script if it is not a branch change
if [ $branch_checkout -eq 0 ]; then
  exit 0
fi

echo "Switching from $previous_branch to $new_branch"
echo "Killing existing connections to $database_name"
kill_connections

if ! database_exists $main_backup; then
  duplicate_database_to $main_backup
fi

if [ "$previous_branch" == "$new_branch" ]; then
  exit 0
fi

if [ "$previous_branch" != "$master_branch" ]; then
  if database_exists $old_database; then
    drop_database $old_database
  fi
  if database_exists $new_database; then
    rename_database $database_name $old_database
  else
    duplicate_database_to $old_database
  fi
fi

if [ "$previous_branch" != "$new_branch" ]; then
  if database_exists $new_database; then
    if database_exists $database_name; then
      drop_database $database_name
    fi
    rename_database $new_database $database_name
  fi
fi