local lpeg = lpeg

local namespace_lookup: {string: string} = {
  pdf = "http://iso.org/pdf/ssn",
  pdf2 = "http://iso.org/pdf2/ssn",
  mathml = "http://www.w3.org/1998/Math/MathML",
  latex = "https://www.latex-project.org/ns/dflt",
  ['latex-book'] = "https://www.latex-project.org/ns/book",
  user = "data:something-custom",
}

local anonymous_namespace = namespace_lookup.pdf

local unmapped_namespaces = {
  [namespace_lookup.pdf] = true,
  [namespace_lookup.pdf2] = true,
  [namespace_lookup.mathml] = true,
}

local delim = lpeg.P',' * lpeg.P' '^0
local comment = lpeg.P'%' * (1-lpeg.P'\n')^0 * lpeg.P'\n'
local word = lpeg.R('az', 'AZ', '09', '--')^1
local line = lpeg.Ct(lpeg.Cg(word, 'name') * delim * lpeg.Cg(word, 'mapped') * delim * lpeg.Cg(word/namespace_lookup, 'ns') * delim * (lpeg.Cg(word, 'class') * delim)^-1) * (lpeg.P'\n' + comment)
local document = lpeg.Ct((comment + line)^0) * (lpeg.P(-1) + lpeg.Cp())

local record ParsedEntry
  name: string
  mapped: string
  ns: string
  class: string
end
local function parse_ns_file(file_tag: string): {ParsedEntry}
  local filename = assert(kpse.find_file(string.format('tagpdf-ns-%s.def', file_tag)), 'file not found')
  local f = assert(io.open(filename, 'r'))
  local text = f:read'a'
  assert(f:close())
  local result, err_offset = document:match(text)
  if err_offset then
    print('!!! ERROR', filename, err_offset)
  end
  return result as {ParsedEntry}
end

local parsed = {}
for _, ns in ipairs{'pdf', 'pdf2', 'mathml', 'latex-book'} do
  parsed[namespace_lookup[ns]] = parse_ns_file(ns)
end
-- parsed[namespace_lookup.latex] = parse_ns_file('latex', namespace_lookup.latex, namespace_lookup)
parsed[namespace_lookup.latex] = parse_ns_file('latex-lab')

local role_maps: {string | boolean: {string: string | {string}}} = {}
for k, v in pairs(parsed) do
  if not unmapped_namespaces[k] then
    local ns_role_map: {string: string | {string}} = {}
    role_maps[k] = ns_role_map
    for _, entry in ipairs(v) do
      local mapped_ns = entry.ns
      if mapped_ns == anonymous_namespace then
        ns_role_map[entry.name] = entry.mapped
      else
        ns_role_map[entry.name] = {entry.mapped, mapped_ns}
      end
    end
  end
end

local function add_mapping(source_tag: string, source_ns: string | boolean, target_tag: string, target_ns: string | boolean)
  local ns_role_map = role_maps[source_ns]
  if not ns_role_map then
    ns_role_map = {}
    role_maps[source_ns] = ns_role_map
  end
  if target_ns is string and target_ns ~= anonymous_namespace then
    ns_role_map[source_tag] = {target_tag, target_ns}
  else
    ns_role_map[source_tag] = target_tag
  end
end

local default_namespaces = {}
for _, ns in ipairs{'mathml', 'latex-book', 'latex', 'pdf', 'pdf2'} do
  local resolved = namespace_lookup[ns]
  for _, tag in ipairs(parsed[resolved]) do
    default_namespaces[tag.name] = resolved
  end
end

return {
  namespace_lookup = namespace_lookup,
  role_maps = role_maps,
  add_mapping = add_mapping,
  default_namespaces = default_namespaces,
}