#!/bin/bash

# the goto command allows changing directory using directory aliases

# directory where goto files live
readonly __GOTO_ROOT_DIR=~/.goto
# goto configuration file that contains the directory mappings
readonly __GOTO_FILE=${__GOTO_ROOT_DIR}/goto.yaml
# path to yq executable used by goto
readonly __GOTO_YQ=/usr/local/bin/yq

__goto_exists() {
  [[ -f ${__GOTO_FILE} ]]
}

__goto_load_entries() {
  # load the directory mappings from the configuration file into the variable reference passed as parameter
  # $1: name of the result associative array to create

  local -n data_ref=$1
  data_ref=()

  if ! __goto_exists; then
    return
  fi

  local -a entries
  local entry key value

  mapfile entries < <(${__GOTO_YQ} 'explode(.) | to_entries[] | "\(.key) \(.value)"' ${__GOTO_FILE})

  for entry in "${entries[@]}"; do
    if [[ -z "${entry}" ]]; then
      continue
    fi

    IFS=' ' read key value <<< "${entry}"

    if [[ -z "${key}" ]] || [[ -z "${value}" ]]; then
      continue
    fi

    data_ref["${key}"]="${value}"
  done
}

__goto_load_keys() {
  # load the directory keys from the configuration file into the variable reference passed as parameter
  # $1: name of the result array to create

  local -n data_ref=$1
  data_ref=()

  if ! __goto_exists; then
    return
  fi

  mapfile data_ref < <(${__GOTO_YQ} 'keys[]' ${__GOTO_FILE})
}

__goto_comp_keys() {
  # loads and initializes directory aliases completions for the goto command

  local -a data
  __goto_load_keys data

  _comp_compgen -- -W '"${data[@]}"'
}

__goto_resolve_path() {
  # resolves a path to its canonical form
  # $1: path to resolve

  readlink -m "${1/#\~/${HOME}}"
}

__goto_prompt() {
  # prompt string for the terminal

  local -A data
  __goto_load_entries data

  local entry_key entry_value best_match="" best_key=""

  for entry_key in "${!data[@]}"; do
    entry_value=$(__goto_resolve_path "${data[${entry_key}]}")

    # select the closest ancestor of the current working directory
    if [[ "${PWD}" == "${entry_value}"?(/*) ]] && [[ ${#entry_value} -gt ${#best_match} ]]; then
      best_match="${entry_value}"
      best_key="${entry_key}"
    fi
  done

  if [[ -n "${best_key}" ]]; then
    local remaining="${PWD#${best_match}}"
    printf '%s' "#${best_key}${remaining}"
  else
    local w='\w'
    printf '%s' "${w@P}"
  fi
}

__goto_test() {
  # validates the goto configuration file
  # command: goto -t

  local -A data
  __goto_load_entries data

  local entry_key entry_value
  local -i ret_code=0

  for entry_key in "${!data[@]}"; do
    entry_value=$(__goto_resolve_path "${data[${entry_key}]}")

    if ! [[ -e "${entry_value}" ]]; then
      echo "Not found: ${entry_key} → ${entry_value}"
      ret_code=1
    elif ! [[ -d "${entry_value}" ]]; then
      echo "Not a directory: ${entry_key} → ${entry_value}"
      ret_code=1
    fi
  done

  if (( ret_code == 0 )); then
    echo 'Configuration ok'
  fi

  return ${ret_code}
}

__goto_edit() {
  # edits the goto configuration file
  # command: goto -e

  ${EDITOR:-nano} ${__GOTO_FILE}
}

__goto_list() {
  # displays the goto configuration file
  # command: goto -l

  local -A data
  __goto_load_entries data

  local -a sorted_keys
  mapfile -d '' sorted_keys < <(printf '%s\0' "${!data[@]}" | sort -z)

  local entry_key entry_value

  for entry_key in "${sorted_keys[@]}"; do
    entry_value=$(__goto_resolve_path "${data[${entry_key}]}")
    echo "${entry_key};${entry_value}"
  done | column -t -s ';'
}

__goto_add() {
  # adds or replaces an entry to the goto configuration file
  # command: goto -a <directory alias>[:<directory path>]
  # $1: directory alias and optional path

  local dir_alias dir_path

  IFS=':' read dir_alias dir_path <<< "$1"

  if [[ -n "${dir_path}" ]]; then
    dir_path="$(__goto_resolve_path "${dir_path}")"
  else
    dir_path="${PWD}"
  fi

  if __goto_exists; then
    dir_alias="${dir_alias}" dir_path="${dir_path}" ${__GOTO_YQ} -i '.[env(dir_alias)] |= env(dir_path)' ${__GOTO_FILE}
  else
    dir_alias="${dir_alias}" dir_path="${dir_path}"  ${__GOTO_YQ} '.[env(dir_alias)] = env(dir_path)' ${__GOTO_FILE}
  fi
}

__goto_remove() {
  # removes an entry from the goto configuration file
  # command: goto -r <directory alias>
  # $1: directory alias

  if ! __goto_exists; then
    return
  fi

  dir_alias="$1" ${__GOTO_YQ} -i 'del(.[env(dir_alias)])' ${__GOTO_FILE}
}

__goto_get() {
  # returns the path denoted by a directory alias
  # command: goto -g <directory alias>
  # $1: directory alias

  if ! __goto_exists; then
    echo "goto: $1: configuration file not found" >&2
    return 10
  fi

  local dir_path=$(dir_alias="$1" ${__GOTO_YQ} 'explode(.)[env(dir_alias)] // ""' ${__GOTO_FILE})

  if [[ -z "${dir_path}" ]]; then
    echo "goto: $1: no such entry" >&2
    return 11
  fi

  __goto_resolve_path "${dir_path}"
}

goto() {
  # the goto command

  local can_run_main=true
  local OPTIND OPT OPTARG

  while getopts ':a:r:g:elt' OPT; do
    case "${OPT}" in
      a)
        __goto_add "${OPTARG}"
        can_run_main=false
        ;;
      r)
        __goto_remove "${OPTARG}"
        can_run_main=false
        ;;
      g)
        __goto_get "${OPTARG}"
        return
        ;;
      e)
        __goto_edit
        return
        ;;
      l)
        __goto_list
        return
        ;;
      t)
        __goto_test
        return
        ;;
      :)
        echo "goto: missing argument for option '${OPTARG}'" >&2
        return 1
        ;;
      *)
        echo "goto: invalid option '${OPTARG}'" >&2
        return 1
        ;;
    esac
  done

  shift $((OPTIND-1))

  if (( $# > 1 )); then
    echo 'goto: too many arguments' >&2
    return 1
  fi

  if ! ${can_run_main}; then
    if (( $# > 0 )); then
      echo 'goto: too many arguments' >&2
      return 1
    fi

    return
  fi

  if (( $# == 0 )); then
    echo 'goto: not enough arguments' >&2
    return
  fi

  local dir_path
  dir_path=$(__goto_get "$1")
  local -i ret_code=$?

  if (( ret_code != 0 )); then
    return ${ret_code}
  fi

  cd ${dir_path}
}

. ${__GOTO_ROOT_DIR}/completion.bash