#!/usr/bin/env bash
###############################################################################
# ebook.nb-plugin
#
# Ebook authoring with `nb`.
#
# Based on:
#   https://pandoc.org/epub.html
#
# Install with:
#   nb plugin install https://github.com/xwmx/nb/blob/master/plugins/ebook.nb-plugin
#
# https://github.com/xwmx/nb
###############################################################################

# Add the new subcommand name with `_subcommands add <name>`.
_subcommands add "ebook"

# Define help and usage text with `_subcommands describe <subcommand> <usage>`.
_subcommands describe "ebook" <<HEREDOC
Usage:
  nb ebook init [<name>] [--force]
  nb ebook publish

Subcommands:
  ebook init     Initialize the current notebook or notebook <name> with
                 placeholder files for authoring an ebook, creating the
                 notebook if it does not yet exist.
  ebook publish  Generate a .epub file using the current notebook contents.

Description:
  Ebook authoring with \`nb\`.

  \`nb ebook init\` populates an existing or new notebook with initial
  placeholder files for creating an ebook. Edit the title page and
  chapters using normal \`nb\` commands, then use \`nb ebook publish\`
  to generate an epub file.

  Chapters are expected to be markdown files with sequential numeric
  filename prefixes for ordering:

    01-example.md
    02-sample.md
    03-demo.md

  Create new chapters with \`nb add\`:

    nb add --filename "04-chapter4.md"

  title.txt contains the book metadata in a YAML block. For more information
  about the fields for this file, visit:

    https://pandoc.org/MANUAL.html#epub-metadata

  stylesheet.css contains base styling for the generated ebook. It can be used
  as it is and can also be edited using \`nb edit\`.

  As with all \`nb\` notebooks, changes are recorded automatically in git,
  providing automatic version control for all ebook content, source, and
  metadata files.

  Generated epub files are saved in the notebook and can be previewed in the
  terminal with \`nb show\`. Export a generated epub file with \`nb export\`:

    nb export 12 .

More info:
  https://pandoc.org/epub.html
HEREDOC

__get_sub_files() {
  local _chapter_filenames=($(_list_files "${_folder_path}"))
  local _files=()
  local _folder_path="${1:-}"

  local __filename=
  for   __filename in "${_chapter_filenames[@]:-}"
  do
    if [[ -d "${_folder_path}/${__filename}" ]]
    then
      _files+=($(
        __get_sub_files "${_folder_path}/${__filename}"
      ))
    else
      _files+=("${_folder_path}/${__filename}")
    fi
  done

  printf "%s\\n" "${_files[@]:-}"
}

# Define the subcommand as a function, named with a leading underscore.
_ebook() {
  local _force=0
  local _name=
  local _notebook_path=
  local _prompt=0
  local _subcommand=

  local __arg=
  for   __arg in "${@}"
  do
    case "${__arg}" in
      --force)
        _force=1
        ;;
      *)
        if [[ -z "${_subcommand:-}" ]]
        then
          _subcommand="${__arg}"
        else
          _name="${__arg}"
        fi
        ;;
    esac
  done


  [[ -z "${_subcommand:-}" ]] && _help "ebook" 1>&2 && exit 1

  case "${_subcommand:-}" in
    a|add|c|create|init|n|new)

      if [[ -z "${_name:-}" ]]
      then
        _prompt=1
        cat <<HEREDOC
Adding the following files to the current notebook:
  title.txt
  stylesheet.css
  01-chapter1.md
HEREDOC

        _notebook_path="$(_notebooks current --path)"
      elif _notebook_path="$(_notebooks show "${_name}" --path 2>/dev/null)"
      then
        _prompt=1
        cat <<HEREDOC
Adding the following files to ${_name}:
  title.txt
  stylesheet.css
  01-chapter1.md
HEREDOC
      fi

      if ((_prompt)) && ! ((_force))
      then
        while true
        do
          local __yn=
          IFS='' read -r -e -d $'\n' -p "Proceed?  [y/N] " __yn
          case ${__yn} in
            [Yy]*)
              break
              ;;
            *)
              printf "Exiting...\\n"
              exit 0
              ;;
          esac
        done
      fi

      if [[ -n "${_name:-}" ]] && [[ -z "${_notebook_path:-}" ]]
      then
        _notebooks add "${_name}"
        _notebook_path="$(_notebooks show "${_name}" --path)"
      fi

      cat <<HEREDOC | NB_NOTEBOOK_PATH="${_notebook_path}" _add "title.txt"       &&
---
title: Placeholder Title
author: Placeholder Name
rights:  Creative Commons Non-Commercial Share Alike 3.0
language: en-US
---
HEREDOC
      cat <<HEREDOC | NB_NOTEBOOK_PATH="${_notebook_path}" _add "stylesheet.css"  &&
/* This defines styles and classes used in the book */
body { margin: 5%; text-align: justify; font-size: medium; }
code { font-family: monospace; }
h1 { text-align: left; }
h2 { text-align: left; }
h3 { text-align: left; }
h4 { text-align: left; }
h5 { text-align: left; }
h6 { text-align: left; }
/* For title, author, and date on the cover page */
h1.title { }
p.author { }
p.date { }
nav#toc ol,
nav#landmarks ol { padding: 0; margin-left: 1em; }
nav#toc ol li,
nav#landmarks ol li { list-style-type: none; margin: 0; padding: 0; }
a.footnote-ref { vertical-align: super; }
em, em em em, em em em em em { font-style: italic;}
em em, em em em em { font-style: normal; }
code{ white-space: pre-wrap; }
span.smallcaps{ font-variant: small-caps; }
span.underline{ text-decoration: underline; }
q { quotes: "“" "”" "‘" "’"; }
div.column{ display: inline-block; vertical-align: top; width: 50%; }
div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;}
@media screen { /* Workaround for iBooks issue; see #6242 */
  .sourceCode {
    overflow: visible !important;
    white-space: pre-wrap !important;
  }
}
HEREDOC
      NB_NOTEBOOK_PATH="${_notebook_path}" _add \
        "01-chapter1.md" --content "# Chapter One" &&
          printf "Ebook initialized: %s\\n" "$(basename "${_notebook_path}")"
      ;;
    p|publish|g|generate|b|build)
      if ! hash pandoc 2>/dev/null
      then
        printf "Install Pandoc to generate an ebook: https://pandoc.org/\\n" 1>&2
        exit 1
      fi

      local _pandoc_arguments=()

      local _notebook_path=
      _notebook_path="$(_notebooks current --path)"

      local _notebook_name=
      _notebook_name="$(_notebooks current --name)"

      local _stylesheet_path="${_notebook_path}/stylesheet.css"

      if [[ -f "${_stylesheet:-}" ]]
      then
        _pandoc_arguments+=("--css" "${_stylesheet_path}")
      fi

      local _title_page_path="${_notebook_path}/title.txt"

      if [[ -f "${_title_page_path}" ]]
      then
        _pandoc_arguments+=("${_title_page_path}")
      else
        printf "title.txt required.\\n"
        exit 1
      fi

      local _chapter_filenames=($(
        _list '^[0-9]{1,}-' --sort --filenames --no-id --no-indicator | sort -n
      ))

      if [[ -z "${_chapter_filenames[*]:-}" ]]
      then
        printf "No chapters found.\\n" 1>&2
        exit 1
      fi

      local __filename=
      for   __filename in "${_chapter_filenames[@]:-}"
      do
        if [[ -d "${_notebook_path}/${__filename}" ]]
        then
          _pandoc_arguments+=($(
            __get_sub_files "${_notebook_path}/${__filename}"
          ))
        else
          _pandoc_arguments+=("${_notebook_path}/${__filename}")
        fi
      done

      local _output_filename=
      _output_filename="$(
        _notebooks current --filename "${_notebook_name}.epub"
      )"

      local _output_path="${_notebook_path}/${_output_filename}"

      pandoc -o "${_output_path}" "${_pandoc_arguments[@]}"       &&
        _index add "${_output_filename}"                          &&
          _git checkpoint "[nb] Added: %s" "${_output_filename}"  &&
            printf "Added: %s\\n" "$(_show "${_output_filename}" --info-line)"
      ;;
    *)
      _help "ebook" 1>&2 && exit 1
      ;;
  esac
}