local M = {}
local function str_splice(string, start_idx, end_idx)
  local new_content = string:sub(1, start_idx - 1)
  if end_idx then
    return new_content .. string:sub(end_idx + 1)
  else
    return new_content
  end
end

local function str_rfind(string, idx, needle)
  for i = idx, 1, -1 do
    if string:sub(i, i - 1 + needle:len()) == needle then
      return i
    end
  end
end
local function get_to_line_end(string, idx)
  local newline = string:find('\n', idx, true)
  local to_end = newline and string:sub(idx, newline - 1) or string:sub(idx)
  return to_end, newline
end

M.decode_json = function(content)
  local ok, data = pcall(vim.json.decode, content, { luanil = { object = true } })
  while not ok do
    local char = data:match('invalid token at character (%d+)$')
    if char then
      local to_end, newline = get_to_line_end(content, char)
      if to_end:match('^//') then
        content = str_splice(content, char, newline)
        goto continue
      end
    end

    char = data:match('Expected object key string but found [^%s]+ at character (%d+)$')
    char = char or data:match('Expected value but found T_ARR_END at character (%d+)')
    if char then
      local comma_idx = str_rfind(content, char, ',')
      if comma_idx then
        content = str_splice(content, comma_idx, comma_idx)
        goto continue
      end
    end

    error(data)
    ::continue::
    ok, data = pcall(vim.json.decode, content, { luanil = { object = true } })
  end
  return data
end

return M