#!/usr/bin/env bash
{
  # A note on updating bash scripts:
  #
  # Shells interpret a file as it executes. As a result, if you overwrite a script while it is
  # executing, the script will then continue execution within the new file. This quickly leads to
  # unpredictable behavior which could cause a painful update process (to say the least).
  #
  # However, we can instruct the shell to read the entirety of a file by placing its contents inside
  # of a code block and terminating the block with an exit keyword (in case the new file has any
  # additional lines).
  #
  # For more information, see:
  #   http://stackoverflow.com/a/2358491
  #   http://www.tldp.org/LDP/abs/html/special-chars.html#CODEBLOCKREF
  if impromptu_in_interactive_shell; then
    echo "Cannot update Impromptu within an interactive shell."
    echo "Please run \"impromptu update\"."
    return
  fi

  # Store original working directory.
  original_directory="$(pwd)"

  echo "Updating Impromptu..."
  echo "Impromptu directory: \"$IMPROMPTU_DIR\""

  # Check for git.
  if ! command -v "git" >/dev/null 2>&1; then
    echo "Error: Could not locate 'git' command."
    exit
  fi

  cd "$IMPROMPTU_DIR"

  # Find the git branch and check if we're in a repo.
  branch="$(git rev-parse --abbrev-ref HEAD 2>/dev/null)"
  if [[ -z "$branch" ]]; then
    echo "Error: Could not locate a git branch for \"$IMPROMPTU_DIR\"."
    exit
  fi

  # Check if we're on the master branch.
  if [[ "$branch" != "master" ]]; then
    printf "\nYour Impromptu directory is running branch \"$branch\", would you like to continue the update? (Y/n) "
    read answer
    if [[ "$answer" == n* ]]; then
      exit
    fi
  fi

  # Declare update variables and helper methods.
  update_tmp_directory="/tmp/impromptu-update"
  backup_tmp_directory="/tmp/impromptu-backup"
  updated_impromptu_version=

  clear_update_directory() {
    rm -rf "$update_tmp_directory"
  }

  catch_error() {
    if [[ "$?" -ne 0 ]]; then
      echo "$1"
      clear_update_directory
      exit
    fi
  }

  stop_server() {
    # Shut down the current impromptu server.
    source impromptu server shutdown

    # Give the server a second to shut down. If it's still running, kill it.
    # TODO: Wait for the server process to shut down instead of sleeping.
    sleep 1
    impromptu_ping_server
    if [[ "$?" -eq 0 ]]; then
      source impromptu kill
    fi
  }

  # Clear out tmp directories and stop the Impromptu server.
  clear_update_directory
  stop_server

  # Copy IMPROMPTU_DIR into a tmp directory (for updating).
  echo "Copying Impromptu into a temporary directory..."
  cp -RP "$IMPROMPTU_DIR" "$update_tmp_directory"

  # Update the tmp directory within a subshell.
  (
    # Reset the directory variables for the update.
    export IMPROMPTU_DIR="$update_tmp_directory"
    export IMPROMPTU_BIN=
    export IMPROMPTU_INTERNAL_BIN=

    cd "$IMPROMPTU_DIR"

    git pull
    catch_error "Error: Impromptu failed to pull the git repository. Please try again."

    npm update
    catch_error "Error: Impromptu failed to update npm. Please try again."

    # Test the prompt using the update directory.
    printf "\n\n\nPrinting test prompt...\n\n\n"
    cd "$original_directory"
    source impromptu print
    updated_impromptu_version=$(source impromptu version)

    # Shut down the update directory prompt server.
    stop_server

    printf "\n\nTake a look at your test prompt. Does everything look okay? (Y/n) "
    read answer
    if [[ "$answer" == n* ]]; then
      clear_update_directory
      echo "Update aborted."
      exit
    fi
  )

  # Copy IMPROMPTU_DIR into another tmp directory (for backup).
  echo "Creating a temporary backup..."
  rm -rf "$backup_tmp_directory"
  cp -RP "$IMPROMPTU_DIR" "$backup_tmp_directory"

  # Overwrite IMPROMPTU_DIR with updated tmp directory.
  echo "Updating local Impromptu directory..."
  rm -rf "$IMPROMPTU_DIR"
  cp -RP "$update_tmp_directory" "$IMPROMPTU_DIR"
  cd "$IMPROMPTU_DIR"

  # Globally install the same version of Impromptu.
  echo "Updating global Impromptu version..."
  update_global_impromptu="0"

  npm list -g impromptu | grep -q " \-> "
  if [[ "$?" -eq 0 ]]; then
    printf "\nThe global version of Impromptu is linked using npm."
    printf "\nWould you like to overwrite it? (Y/n) "
    read answer
    [[ "$answer" != n* ]]
    update_global_impromptu="$?";
  fi

  if [[ "$update_global_impromptu" -eq 0 ]]; then
    npm install -g "impromptu@$updated_impromptu_version"
  fi

  # Clean up!
  clear_update_directory
  printf "\nImpromptu was successfully updated!\n\n\n"
  exit
}