local function file_exists(file_path)
  local file = io.open(file_path, "rb")
  if file then file:close() end
  return file ~= nil
end

local remote_prefix_patterns = {'ssh://', 'http[s]?://', '%w+@'}

local function transform_url(remote)
  for _, pattern in pairs(remote_prefix_patterns) do
    local regex_pattern = string.format('^%s(.*)', pattern)
    if remote:match(regex_pattern) then
      local _url = remote:match(regex_pattern, 1)
      _url = _url:gsub('(:)(%a+)', '/%2')
      _url = _url:gsub('.git$', '')

      if not _url:match('^http[s]?://') then
        return string.format('%s%s', 'https://', _url)
      end

      return _url
    end
  end
end

-- TODO: add more providers
-- TODO: add feature to specify provider
local provider_mapping = {
  ['github'] = '%s/blob/%s/%s#L%i',
  ['bitbucket'] = '%s/src/%s/%s#lines-%i',
  ['forgejo'] = '%s/src/commit/%s/%s#L%i',
}

local function get_provider_template(remote)
  local transformed_url = transform_url(remote)

  if not transformed_url then return end

  for domain, template_string in pairs(provider_mapping) do
    if transformed_url:match(domain) then
      return transformed_url, template_string
    end
  end
end

local function source_open()
  local git_conf_path = '.git/config'

  -- TODO: determine based on recursively traversing upwards in path
  if not file_exists(git_conf_path) then return end

  local _remote_output = io.popen('git remote get-url origin', 'r')

  -- TODO: test with other refs
  local _commit_output = io.popen('git show --pretty=%H HEAD', 'r')

  if _remote_output == nil or _commit_output == nil then return end

  local line_number = unpack(vim.api.nvim_win_get_cursor(0))
  local filepath = vim.api.nvim_buf_get_name(0)
  local relative_filepath = vim.fn.fnamemodify(filepath, ':.')

  local remote = _remote_output:read()
  local branch = _commit_output:read()

  local transformed_url, template_string = get_provider_template(remote)

  for _, variable in pairs({ filepath, transformed_url, template_string }) do
    if variable == nil then
      return
    end
  end

  local template_args = { transformed_url, branch, relative_filepath, line_number }
  local url = template_string:format(unpack(template_args))

  os.execute(('xdg-open %s'):format(url))
end

local function setup(opts)
  vim.api.nvim_create_user_command('SourceOpen', source_open, {})
end

return { setup = setup }