New `archtec_playerdata` API v2 proposal

[Niklp09]

This is a proposal for the archtec_playerdata API v2.

Some basic notes:

• Every key has a fixed type
• Allowed types are number, string, boolean, table
• Tables can only contain values of these ^ types
• The data gets stored per player in modstorage (as json)

Public functions

• Register new key (v1 has a static struct table)

  archtec_playerdata.register_key("nodes_dug", "number", 0)
  -- keyname (str); type (str) ; default value (depends on type)
  -- Returns `nil`

• Get the default value of a key

  archtec_playerdata.get_default("key")
  -- key (str)
  -- Returns the default value of `key` or `nil`

• Get the value of a key

  archtec_playerdata.get("Playername", "key")
  -- playername (str); key (str)
  -- Returns value of `key` or the default value of `key` (or `nil` when for example the key doesn't exist)

• Set a key to value

  archtec_playerdata.set("Playername", "key", true)
  -- playername (str); key (str); value (depends on set type)
  -- Returns `true` on success or `false` on failure

• Mod a key by value

  archtec_playerdata.mod("Playername", "key", 1)
  -- playername (str); key (str); value (number)
  -- Returns `true` on success or `false` on failure

• Get all key-value pairs of a player

  archtec_playerdata.get_all("Playername")
  -- playername (str)
  -- Returns a `table` with all values (or defaults if not changed) or `nil` for unknown players

• Migrate data of a key on server start

  archtec_playerdata.register_upgrade({
  name = "archtec:fix_nodes_dug_count",
  key = "nodes_dug",
  func = function(name,  value)
      -- Return new value
      return value + 1
      -- OR migrate via global API to new key name
      archtec_playerdata.set(name, "new_key", value)
  end
  })
  -- inside table: id (str); key (str); func (function)
  -- Returns `nil`
  -- `func` gets called in a loop over all players; returning `nil` doesn't modify the value
  -- `name` gets stored in the database when the upgrade is done (to not run the upgrade again)

Cc: @debagos @blaboing

[Niklp09]

Some interesting benchmark results:

BATCH 1: test results with 100000 iterations per function:
minetest.serialize():    TIME: 2192.18ms (2192179us)   MIN: 17us   MAX: 1.07ms (1069us)   AVG: 21.92us
minetest.deserialize():    TIME: 1001.25ms (1001245us)   MIN: 6us   MAX: 1.24ms (1244us)   AVG: 10.01us
minetest.write_json():    TIME: 2333.47ms (2333472us)   MIN: 22us   MAX: 85us   AVG: 23.33us
minetest.parse_json():    TIME: 2344.72ms (2344722us)   MIN: 22us   MAX: 701us   AVG: 23.45us
4 benchmarks done
BATCH 2: test results with 100000 iterations per function:
minetest.serialize():    TIME: 2041.88ms (2041876us)   MIN: 15us   MAX: 652us   AVG: 20.42us
minetest.deserialize():    TIME: 998.06ms (998062us)   MIN: 6us   MAX: 750us   AVG: 9.98us
minetest.write_json():    TIME: 2339.71ms (2339714us)   MIN: 22us   MAX: 77us   AVG: 23.4us
minetest.parse_json():    TIME: 2330.71ms (2330707us)   MIN: 22us   MAX: 681us   AVG: 23.31us
4 benchmarks done
BATCH 3: test results with 100000 iterations per function:
minetest.serialize():    TIME: 2053.68ms (2053679us)   MIN: 15us   MAX: 683us   AVG: 20.54us
minetest.deserialize():    TIME: 999.78ms (999783us)   MIN: 6us   MAX: 983us   AVG: 10us
minetest.write_json():    TIME: 2322.41ms (2322412us)   MIN: 22us   MAX: 77us   AVG: 23.22us
minetest.parse_json():    TIME: 2323.4ms (2323396us)   MIN: 22us   MAX: 694us   AVG: 23.23us
4 benchmarks done