#' Add Google Scholar Metadata

#'

#' Add biobliographic metadata to pages in the format expected by Google

#' Scholar. Please reference the

#' [Google Scholar Inclusion](https://scholar.google.com/intl/en/scholar/inclusion.html#indexing)

#' page for the most up-to-date information and instructions. Note that this

#' function adds the `citation_` prefix to all of its arguments; the `title`

#' argument becomes the `citation_title` `<meta>` tag.

#'

#' @examples

#' meta_google_scholar(

#'   title = c(

#'     "The testis isoform of the phosphorylase kinase catalytic subunit (PhK-T)",

#'     "plays a critical role in regulation of glycogen mobilization in developing lung"

#'   ),

#'   author = c(

#'     "Liu, Li",

#'     "Rannels, Stephen R.",

#'     "Falconieri, Mary",

#'     "Phillips, Karen S.",

#'     "Wolpert, Ellen B.",

#'     "Weaver, Timothy E."

#'   ),

#'   publication_date = "1996/05/17",

#'   journal_title = "Journal of Biological Chemistry",

#'   volume = 271,

#'   issue = 20,

#'   firstpage = 11761,

#'   lastpage = 11766,

#'   pdf_url = "http://www.example.com/content/271/20/11761.full.pdf"

#' )

#'

#' @template describe-meta

#' @param title The title of the paper.

#'

#'   The title tag must contain the title of the paper. Don't use it for the

#'   title of the journal or a book in which the paper was published, or for the

#'   name of your repository. This tag is required for inclusion in Google

#'   Scholar.

#' @param author A vector of author names.

#'

#'   The `author` tag, must contain the authors (and only the actual authors) of

#'   the paper. Don't use it for the author of the website or for contributors

#'   other than authors, e.g., thesis advisors. Author names can be listed

#'   either as "Smith, John" or as "John Smith". Put each author name in a

#'   separate tag and omit all affiliations, degrees, certifications, etc., from

#'   this field. At least one author tag is required for inclusion in Google

#'   Scholar.

#' @param publication_date,online_date The date the paper was published in the

#'   journal (`publication_date`) or published online (`online_date`).

#'

#'   The `publication_date` tag must contain the date of publication, i.e., the

#'   date that would normally be cited in references to this paper from other

#'   papers. Don't use it for the date of entry into the repository - that

#'   should go into `online_date` instead. Provide full dates in the "2010/5/12"

#'   format if available; or a year alone otherwise. This tag is required for

#'   inclusion in Google Scholar.

#'

#' @param journal_title,conference_title,issn,isbn,volume,issue,firstpage,lastpage

#'   For journal and conference papers, provide the remaining bibliographic

#'   citation data in the following tags: `journal_title` or `conference_title`,

#'   `issn`, `isbn`, `volume`, `issue`, `firstpage`, and `lastpage.` These

#'   fields must contain sufficient information to identify a reference to this

#'   paper from another document, which is normally all of: (a) journal or

#'   conference name, (b) volume and issue numbers, if applicable, and (c) the

#'   number of the first page of the paper in the volume (or issue) in question.

#'

#' @param dissertation_institution,technical_report_institution,technical_report_number

#'   For theses, dissertations, and technical reports, provide the remaining

#'   bibliographic citation data in the following tags:

#'   `dissertation_institution`, `technical_report_institution` for the name of

#'   the institution and `technical_report_number` for the number of the

#'   technical report. As with journal and conference papers, you need to

#'   provide sufficient information to recognize a formal citation to this

#'   document from another article.

#'

#' @param pdf_url The `<meta>` tags normally apply only to the exact page on

#'   which they're provided. If this page shows only the abstract of the paper

#'   and you have the full text in a separate file, e.g., in the PDF format,

#'   please specify the locations of all full text versions using `pdf_url`. The

#'   content of the tag is the absolute URL of the PDF file; for security

#'   reasons, it must refer to a file in the same subdirectory as the HTML

#'   abstract.

#'

#' @template describe-meta-return

#'

#' @references <https://scholar.google.com/intl/en/scholar/inclusion.html#indexing>

#' @export

meta_google_scholar <- function(

  .meta = meta(),

  title,

  author,

  publication_date,

  online_date = NULL,

  journal_title = NULL,

  conference_title = NULL,

  volume = NULL,

  issue = NULL,

  firstpage = NULL,

  lastpage = NULL,

  pdf_url = NULL,

  issn = NULL,

  isbn = NULL,

  dissertation_institution = NULL,

  technical_report_institution = NULL,

  technical_report_number = NULL

) {

  )

  }

}

assert_valid_google_scholar_date <- function(x) {

  }

  }

}