#!/usr/bin/env bash

set -o pipefail

IFS= read -rd '' USAGE <<EOF

Zettel helper script.

Usage:

    zet create|c TITLE...   : Create a new zettel
    zet edit|e QUERY...     : Search for a zettel and edit it
    zet help|h              : Show this help screen
    zet id QUERY...         : Search for a zettel and display its ID
    zet print|p QUERY...    : Search for a zettel and print it
    zet push                : Push changes
    zet search|s QUERY...   : Print IDs and titles of zettels matching QUERY
    zet view|v QUERY...     : Search for a zettel and view it

EOF

set -o errexit

COMMAND="${1:-}"
shift 1

SELECTED_ZET=''
ZET_DIR=${ZET_DIR:-.}
ZET_LIST=()

cmd_create() {
  create_zettel "${1^}"
}

cmd_edit() {
  parse_zet_list < <(search_zettel "$@")
  select_zet
  edit_zet "$SELECTED_ZET"
}

cmd_id() {
  parse_zet_list < <(search_zettel "$@")
  select_zet

  echo "$SELECTED_ZET"
}

cmd_links() {
  QUERY="$1"

  generate_links "$(cmd_search "$QUERY")"
}

cmd_push() {
  git push
}

cmd_search() {
  parse_zet_list < <(search_zettel "$@")
  printf "%s\n" "${ZET_LIST[@]}"
}

cmd_view() {
  parse_zet_list < <(search_zettel "$@")
  select_zet
  view_zettel "$SELECTED_ZET"
}

commit_zettel() {
  ZID="$1"
  MESSAGE="$2"

  if [[ -z "$MESSAGE" ]]; then
    get_title "$ZID"
  fi

  git add "$ZID"
  git commit -m "$MESSAGE"
}

create_zettel() {
  TITLE="$1"
  ZID=$(new_zid)

  mkdir -p "$ZID"
  echo "= $TITLE" > "$ZID/index.adoc"
  edit_file "$ZID/index.adoc"
  on_save "$ZID"
}

delete_zettel() {
  [[ -d "$ZID" ]] && rm -fr "$ZID"
  commit_zettel "$ZID"
}

edit_file() {
  "$EDITOR" "$1"
}

edit_zet() {
  edit_file "$1/index.adoc"
  on_save "$1"
}

generate_links() {
  echo "$1" | while IFS= read -r line; do
    id="${line%% *}"
    title="${line#* }"
    echo "* link:../${id}/index.adoc[${title}]"
  done
}

get_latest_zettel() {
  find . -maxdepth 1 -type d -name '[0-9]*' -printf '%f\n' | sort -r | head -n 1
}

get_title() {
  get_title_from_file "$1/index.adoc"
}

get_title_from_file() {
  head -n 1 "$1" | sed -e 's/^[#=] //'
}

main() {
  if [[ -z "$COMMAND" ]]; then
    show_usage
    exit 1
  fi

  case "$COMMAND" in
    create | c)
      cmd_create "$@"
      ;;

    edit | e)
      cmd_edit "$@"
      ;;

    help | h)
      show_usage
      ;;

    id)
      cmd_id "$@"
      ;;

    links | l)
      cmd_links "$@"
      ;;

    push)
      cmd_push
      ;;

    search | s)
      cmd_search "$@"
      ;;

    view | v)
      cmd_view "$@"
      ;;

    *)
      echo "ERROR: $COMMAND"
      show_usage
      exit 1
      ;;
  esac
}

new_zid() {
  EXISTING_ZETTELS=$(find . -maxdepth 1 -type d -regex './[0-9]+' | wc -l)

  echo $((EXISTING_ZETTELS + 1))
}

on_save() {
  ZID="$1"

  if [[ -s "$ZID/index.adoc" ]]; then
    TITLE=$(get_title "$ZID")
    commit_zettel "$ZID" "$TITLE"
  else
    echo "Deleting empty zettel: $ZID"
    delete_zettel "$ZID"
  fi
}

parse_zet_list() {
  ZET_LIST=()

  while IFS= read -r ZID; do
    TITLE=$(get_title "$ZID")
    ZET_LIST+=("$ZID $TITLE")
  done
}

search_zettel() {
  if [[ "$*" == "latest" ]] || [[ "$*" == "l" ]]; then
    get_latest_zettel
    return
  fi

  QUERY="$*"

  git grep -i --name-only -P "\b$QUERY\b" | grep -o -E '[0-9]+' | sort -un
}

select_zet() {
  if [[ "${#ZET_LIST[@]}" == 0 ]]; then
    echo "No zettels to select"
    exit 1
  fi

  if [[ "${#ZET_LIST[@]}" == 1 ]]; then
    SELECTED_ZET=$(awk '{ print $1 }' <<<"${ZET_LIST[0]}")
    return
  fi

  selector

  if [[ -z "$SELECTED_ZET" ]]; then
    echo "No zet selected"
    exit 1
  fi
}

selector() {
  ITEM=$(printf "%s\n" "${ZET_LIST[@]}" | fzf --prompt="Select a zet: ")

  SELECTED_ZET=$(awk '{ print $1 }' <<< "$ITEM")
}

show_usage() {
  echo "$USAGE"
}

view_zettel() {
  cat "$1/index.adoc"
}

(cd "$ZET_DIR" && main "$@")