INPUT_FILES = (function(prog)
  print("[INFO] bavbavhaus.net: collecting input files")
  local insert = table.insert
  local input_files = {}
  local pfile = io.popen(prog)
  for filename in pfile:lines() do
    insert(input_files, filename)
  end
  pfile:close()
  return input_files
end)("ls -t *.md")

OUTPUT_FILES = (function(pattern)
  print("[INFO] bavbavhaus.net: collecting output files")
  local split_extension = pandoc.path.split_extension
  local insert = table.insert
  local output_files = {}
  for _,filename in ipairs(INPUT_FILES) do
    local basename = split_extension(filename)
    insert(output_files, (pattern):format(basename))
  end
  return output_files
end)("public_html/%s.html")

PAGES = (function()
  print("[INFO] bavbavhaus.net: reading pages")
  local pages = pandoc.MetaList({})
  function pages:get(input_file)
    return self:find_if(function(page)
      return page["meta"]["input_file"] == input_file
    end)
  end
  local read = pandoc.read
  local ropts = pandoc.ReaderOptions({})
  for _,input_file in ipairs(INPUT_FILES) do
    print("[INFO] bavbavhaus.net: reading page: " .. input_file)
    local f = io.open(input_file)
    if not f then goto continue end
    pages:insert(read(f:read("a"), "markdown", ropts))
    f:close()
    ::continue::
  end
  return pages
end)()

do
  print("[INFO] bavbavhaus.net: updating pages metadata")
  for i,page in ipairs(PAGES) do
    local input_file = INPUT_FILES[i]
    local output_file = OUTPUT_FILES[i]
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["input_file"] = input_file
        meta["output_file"] = output_file
        meta["url"] = input_file
        meta["title"] = meta["title"] or input_file
        return meta
      end,
    })
  end
end

do
  print("[INFO] bavbavhaus.net: processing citations")
  local csl = "pandoc/csl/chicago-fullnote-sl"
  local citeproc = pandoc.utils.citeproc
  for i,page in ipairs(PAGES) do
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["csl"] = csl
        return meta
      end,
      Pandoc = function(doc)
        return citeproc(doc)
      end
    })
  end
end

BACKLINKS, FORELINKS = (function(pages)
  print("[INFO] bavbavhaus.net: scanning pages for internal links")
  local MetaList = pandoc.MetaList
  local MetaMap = pandoc.MetaMap
  local backlinks = MetaMap({})
  local forelinks = MetaMap({})
  for i,page in ipairs(pages) do
    local input_file = page["meta"]["input_file"]
    page:walk({
      Link = function(link)
        if not PAGES:get(link.target) then return end
        if input_file == link.target then return end
        if not backlinks[link.target] then
          backlinks[link.target] = MetaList({})
        end
        if not forelinks[input_file] then
          forelinks[input_file] = MetaList({})
        end
        if not backlinks[link.target]:includes(input_file) then
          backlinks[link.target]:insert(input_file)
        end
        if not forelinks[input_file]:includes(link.target) then
          forelinks[input_file]:insert(link.target)
        end
      end
    })
  end
  return backlinks, forelinks
end)(PAGES)

do
  print("[INFO] bavbavhaus.net: updating index page")
  local index = "README.md"
  FORELINKS[index] = pandoc.MetaList({})
  for i,page in ipairs(PAGES) do
    if PAGES[i]["meta"]["input_file"] == index then goto continue end
    FORELINKS[index]:insert(page["meta"]["input_file"])
    ::continue::
  end
end

do
  print("[INFO] bavbavhaus.net: updating link targets")
  local split_extension = pandoc.path.split_extension
  function update_target(target)
    return ("%s.html#start"):format(split_extension(target))
  end
  local Link = pandoc.Link
  for i,page in ipairs(PAGES) do
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["url"] = update_target(meta["url"])
        return meta
      end,
      Link = function(link)
        if not PAGES:get(link.target) then return end
        link.target = update_target(link.target)
        return Link(link.content, link.target)
      end
    })
  end
end

SITEMAP = (function()
  print("[INFO] bavbavhaus.net: generating sitemap")
  local sitemap = pandoc.MetaList({})
  local Link = pandoc.Link
  for _,page in ipairs(PAGES) do
    local meta = page["meta"]
    sitemap:insert(Link(meta["title"], meta["url"]))
  end
  return sitemap
end)()

do
  print("[INFO] bavbavhaus.net: updating sitemap metadata")
  for i,page in ipairs(PAGES) do
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["sitemap"] = SITEMAP
        return meta
      end
    })
  end
end

do
  print("[INFO] bavbavhaus.net: updating backlinks metadata")
  local compile = pandoc.template.compile
  local partial_template = (function(filepath)
    local f = io.open(filepath)
    if not f then return end
    local template = f:read("a")
    f:close()
    return compile(template)
  end)("pandoc/templates/bavbavhaus.net.partial.html5")
  local MetaList = pandoc.MetaList
  local RawBlock = pandoc.RawBlock
  local write = pandoc.write
  local WriterOptions = pandoc.WriterOptions
  for i,page in ipairs(PAGES) do
    local input_file = page["meta"]["input_file"]
    if not BACKLINKS[input_file] then goto continue end
    local backlinks = MetaList({})
    for _,backlink in ipairs(BACKLINKS[input_file]) do
      backlinks:insert(RawBlock("html5", write(
        PAGES:get(backlink),
        "html5",
        WriterOptions({
          identifier_prefix = "back/" .. backlink,
          table_of_contents = true,
          template = partial_template
        })
      )))
    end
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["backlinks"] = backlinks
        return meta
      end
    })
    ::continue::
  end
  print("[INFO] bavbavhaus.net: updating forelinks metadata")
  for i,page in ipairs(PAGES) do
    local input_file = page["meta"]["input_file"]
    if not FORELINKS[input_file] then goto continue end
    local forelinks = MetaList({})
    for _,forelink in ipairs(FORELINKS[input_file]) do
      forelinks:insert(RawBlock("html5", write(
        PAGES:get(forelink),
        "html5",
        WriterOptions({
          identifier_prefix = "fore/" .. forelink,
          table_of_contents = true,
          template = partial_template
        })
      )))
    end
    PAGES[i] = page:walk({
      Meta = function(meta)
        meta["forelinks"] = forelinks
        return meta
      end
    })
    ::continue::
  end
end

do
  print("[INFO] bavbavhaus.net: writing pages")
  local compile = pandoc.template.compile
  local WriterOptions = pandoc.WriterOptions
  local write = pandoc.write
  local wopts = WriterOptions({
      table_of_contents = true,
      template = (function(filepath)
        local f = io.open(filepath)
        if not f then return end
        local template = f:read("a")
        f:close()
        return compile(template)
      end)("pandoc/templates/bavbavhaus.net.html5")
  })
  for i,page in ipairs(PAGES) do
    local f = io.open(page["meta"]["output_file"], "w")
    f:write(write(page, "html", wopts)) 
    f:close()
  end
end