#let page(
  title: none,
  subtitle: none,
  description: none,
  author: none,
  date: none,
  collection: none,
  path: none,
  pdf: auto,
  preview: auto,
) = (
  title: title,
  subtitle: subtitle,
  description: description,
  author: author,
  date: date,
  collection: collection,
  path: path,
  pdf: pdf,
  preview: preview,
)

#let post(collection: "blog", ..args) = page(collection: collection, ..args)

#let authors(author) = {
  let entries = if author == none { () } else if type(author) == array { author } else { (author,) }
  entries.map(entry => if type(entry) == str {
    (name: entry, url: none)
  } else {
    (name: entry.name, url: entry.at("url", default: none))
  })
}

#let normalize-page(entry, defaults) = {
  let result = entry
  for (key, value) in defaults {
    if result.at(key, default: none) in (none, auto) {
      result.insert(key, value)
    }
  }
  result.by = authors(result.author)
  result.author = result.by.map(author => author.name)
  result
}

#let author-text(author) = context {
  for (i, entry) in authors(author).enumerate() {
    if i > 0 { [, ] }
    if entry.url == none {
      entry.name
    } else if target() == "html" {
      html.a(class: "author-link", href: entry.url, entry.name)
    } else {
      link(entry.url, entry.name)
    }
  }
}

#let format-date(date) = date.display("[month repr:long] [year]")

#let date-key(entry) = if entry.date == none { "" } else {
  entry.date.display("[year]-[month padding:zero]-[day padding:zero]")
}