get-peers.lua

local kwargs = {}
for i, k in ipairs(KEYS) do
  kwargs[k] = table.remove(ARGV, 1)
end

local pop_kwargs = function (name, required)
  local value = kwargs[name]
  if value == nil then
    if required then
      error(string.format("missing key %q", name))
    else
      redis.log(
        redis.LOG_NOTICE,
        string.format("get peers key %q was not provided", name))
      return nil
    end
  end
  redis.log(
    redis.LOG_NOTICE,
    string.format("get peers key %q has value %q", name, value))
  kwargs[name] = nil
  return value
end

local info_hash = pop_kwargs('info_hash', true)
local max_last_got_peers = pop_kwargs('max_last_got_peers', true)
local new_last_got_peers = pop_kwargs('new_last_got_peers', true)
local remote = pop_kwargs('remote', true)
local max_peers = pop_kwargs('max_peers', false)
local min_peer_score = pop_kwargs('min_peer_score', true)

for k in pairs(kwargs) do
  error({err='unexpected arg '..k})
end

if #ARGV ~= 0 then
  return {err=string.format("%d trailing args", #ARGV)}
end

local get_peers = function (key)
  redis.call('zremrangebyscore', key, '-inf', min_peer_score-1)
  if max_peers then
    return redis.call('zrandmember', key, max_peers)
  else
    return redis.call('zrange', key, 0, -1)
  end
end

local last_got_peers_key = "last_got_peers:" .. info_hash
local seeders_key = "seeders:" .. info_hash
local leechers_key = "leechers:" .. info_hash

local last_got_peers = redis.call('zscore', last_got_peers_key, remote)
if last_got_peers and last_got_peers > max_last_got_peers then
  max_peers = 0
end

local seeders = get_peers(seeders_key)
local leechers = get_peers(leechers_key)
if #seeders + #leechers > 0 then
  redis.call('zadd', last_got_peers_key, new_last_got_peers, remote)
end
local leecher_count = redis.call('zcount', leechers_key, min_peer_score, "+inf")
local seeder_count = redis.call('zcount', seeders_key, min_peer_score, "+inf")
return {
  seeders,
  seeder_count,
  leechers,
  leecher_count,
}