#!/usr/bin/env bash

GIT_DIR=$(git rev-parse --git-dir 2>/dev/null)

function show_contents {
  local file="${2/#~/$HOME}"
  if [ -f "$file" ]; then
    echo "$1 gitignore: $2" && cat "$file"
  else
    echo "There is no $1 .gitignore yet"
  fi
}

function cd_to_git_root {
  local error_level="$1"

  if ! git rev-parse --git-dir &>/dev/null; then
    if [ "$error_level" = '--warn' ]; then
      echo "Warning: Not currently in a Git repository" >&2
    elif [ "$error_level" = '--error' ]; then
      echo "Error: Not currently in a Git repository" >&2
      exit 1
    fi
  fi

  local result=
  if result=$(git rev-parse --show-toplevel 2>/dev/null); then
    cd "$result" || exit
  fi
}

function global_ignore() {
  if ! git config --global core.excludesFile 2>/dev/null; then
    if [ -f "$HOME/.gitignore" ]; then
      echo "$HOME/.gitignore"
    else
      echo "${XDG_CONFIG_HOME:-$HOME/.config}/git/ignore"
    fi
  fi
}

function show_global {
  show_contents Global "$(global_ignore)"
}

function add_global {
  local global_gitignore
  global_gitignore="$(global_ignore)"
  if [ -z "$global_gitignore" ]; then
    echo "Can't find global .gitignore."
    echo ""
    echo "Use 'git config --global --add core.excludesfile ~/.gitignore-global' to set the path to your global gitignore file to '~/.gitignore-global'."
    echo ""
  else
    add_patterns "$global_gitignore" "$@"
  fi
}

function show_local {
  cd_to_git_root --warn
  show_contents Local .gitignore
}

function add_local {
  cd_to_git_root --warn
  add_patterns .gitignore "$@"
}

function show_private {
  cd_to_git_root --error
  show_contents Private "${GIT_DIR}/info/exclude"
}

function add_private {
  cd_to_git_root --error
  test -d "${GIT_DIR}/info" || mkdir -p "${GIT_DIR}/info"
  add_patterns "${GIT_DIR}/info/exclude" "$@"
}

function add_patterns {
  echo "Adding pattern(s) to: $1"
  local file="${1/#~/$HOME}"
  dir_name=$(dirname "$file")
  if [ ! -d "$dir_name" ]; then
      mkdir -p "$dir_name"
  fi
  if [ -s "$file" ]; then
      # If the content of $file doesn't end with a newline, add one
      test "$(tail -c 1 "$file")" != "" && echo "" >> "$file"
  fi
  for pattern in "${@:2}"; do
    echo "... adding '$pattern'"
    (test -f "$file" && test "$pattern" && grep -q -F -x -- "$pattern" "$file") || echo "$pattern" >> "$file"
  done
}

if test $# -eq 0; then
   show_global
   echo "---------------------------------"
   show_local
   echo "---------------------------------"
   show_private
else
  case "$1" in
    -l|--local)
      test $# -gt 1 && add_local "${@:2}" && echo
      show_local
      ;;
    -g|--global)
      test $# -gt 1 && add_global "${@:2}" && echo
      show_global
      ;;
    -p|--private)
      test $# -gt 1 && add_private "${@:2}" && echo
      show_private
      ;;
    *)
      add_local "$@"
      ;;
  esac
fi