local M = {}

local output_viewer_pid = 0

local compile = function(file)
  return vim.fn.jobstart({ "compiledoc", file }, {
    on_exit = function(_, exit_code) if exit_code == 0 then print("Finished compiling.") end end,
    on_stderr = function(_, err, _) print(table.concat(err, "\n")) end,
    stderr_buffered = true
  })
end

local file_exists = function(name)
   local f=io.open(name,"r")
   if f~=nil then io.close(f) return true else return false end
end


M.open_document_preview = function()
  local filename = vim.api.nvim_buf_get_name(0)
  local compile_job = compile(filename)

  vim.api.nvim_create_augroup("compileDoc", {})

  vim.api.nvim_create_autocmd("BufWritePost", {
    group = "compileDoc",
    pattern = { "*.tex", "*.md", "*.puml" },
    callback = function() compile(filename) end
  })

  local output_file_extension
  local output_file_viewer

  if string.match(filename, "%.tex$") or string.match(filename, "%.md") then
    output_file_extension = ".pdf"
    output_file_viewer = "zathura"
  elseif string.match(filename, "%.puml$") then
    output_file_extension = ".png"
    output_file_viewer = "feh"
  end

  local output_filename = string.gsub(filename, "%..+$", output_file_extension)

  vim.fn.jobwait({compile_job})

  if not file_exists(output_filename) then
    local scan = require'plenary.scandir'
    local build_dir = scan.scan_dir({ '.', '..' }, { depth = 1, add_dirs = true, search_pattern = 'build' })
    local result = scan.scan_dir(build_dir[1], { depth = 3, search_pattern = ".*%.pdf" })

    output_filename = result[1]
  end

  output_viewer_pid = vim.fn.jobstart({ output_file_viewer, output_filename })
end

M.close_document_preview = function()
  vim.api.nvim_del_augroup_by_name("compileDoc")
  if (output_viewer_pid ~= 0) then
    vim.fn.jobstop(output_viewer_pid)
  end
end

return M