Add core code and tests

README.md

@@ -1,23 +1,9 @@
-# prismarine-template
-[![NPM version](https://img.shields.io/npm/v/prismarine-template.svg)](http://npmjs.com/package/prismarine-template)
-[![Build Status](https://github.com/PrismarineJS/prismarine-template/workflows/CI/badge.svg)](https://github.com/PrismarineJS/prismarine-template/actions?query=workflow%3A%22CI%22)
+# prismarine-rng
+[![NPM version](https://img.shields.io/npm/v/prismarine-rng.svg)](http://npmjs.com/package/prismarine-rng)
+[![Build Status](https://github.com/PrismarineJS/prismarine-rng/workflows/CI/badge.svg)](https://github.com/PrismarineJS/prismarine-rng/actions?query=workflow%3A%22CI%22)
 [![Discord](https://img.shields.io/badge/chat-on%20discord-brightgreen.svg)](https://discord.gg/GsEFRM8)
 [![Gitter](https://img.shields.io/badge/chat-on%20gitter-brightgreen.svg)](https://gitter.im/PrismarineJS/general)
 [![Irc](https://img.shields.io/badge/chat-on%20irc-brightgreen.svg)](https://irc.gitter.im/)
-[![Try it on gitpod](https://img.shields.io/badge/try-on%20gitpod-brightgreen.svg)](https://gitpod.io/#https://github.com/PrismarineJS/prismarine-template)
+[![Try it on gitpod](https://img.shields.io/badge/try-on%20gitpod-brightgreen.svg)](https://gitpod.io/#https://github.com/PrismarineJS/prismarine-rng)
 
-A template repository to make it easy to create new prismarine repo
-
-## Usage
-
-```js
-const template = require('prismarine-template')
-
-template.helloWorld()
-```
-
-## API
-
-### helloWorld()
-
-Prints hello world
+Collection of utilities to work with minecraft RNG.

index.js

@@ -1,9 +1,6 @@
-if (typeof process !== 'undefined' && parseInt(process.versions.node.split('.')[0]) < 14) {
-  console.error('Your node version is currently', process.versions.node)
-  console.error('Please update it to a version >= 14.x.x from https://nodejs.org/')
-  process.exit(1)
-}
-
-module.exports.helloWorld = function () {
-  console.log('Hello world !')
+module.exports = {
+  LCG: require('./lib/LCG'),
+  Random: require('./lib/Random'),
+  crackPlayerSeed: require('./lib/PlayerSeedCracker'),
+  enchantments: require('./lib/enchantments')
 }

lib/LCG.js

@@ -0,0 +1,45 @@
+class LCG {
+  static JAVA = new LCG(0x5DEECE66Dn, 0xBn, 1n << 48n)
+
+  constructor (multiplier, addend, modulus) {
+    this.multiplier = multiplier
+    this.addend = addend
+    this.modulus = modulus
+    if ((this.modulus & -this.modulus) !== this.modulus) throw new Error('Modulus is not a power of 2')
+    this.mod = modulus - 1n
+  }
+
+  nextSeed (seed) {
+    return (seed * this.multiplier + this.addend) & this.mod
+  }
+
+  combine (steps) {
+    let multiplier = 1n
+    let addend = 0n
+
+    let intermediateMultiplier = this.multiplier
+    let intermediateAddend = this.addend
+
+    const longSteps = BigInt(steps) & this.mod
+    for (let k = longSteps; k !== 0n; k >>= 1n) {
+      if ((k & 1n) !== 0n) {
+        multiplier = BigInt.asIntN(64, multiplier * intermediateMultiplier)
+        addend = BigInt.asIntN(64, intermediateMultiplier * addend + intermediateAddend)
+      }
+
+      intermediateAddend = BigInt.asIntN(64, (intermediateMultiplier + 1n) * intermediateAddend)
+      intermediateMultiplier = BigInt.asIntN(64, intermediateMultiplier * intermediateMultiplier)
+    }
+
+    multiplier = multiplier & this.mod
+    addend = addend & this.mod
+
+    return new LCG(multiplier, addend, this.modulus)
+  }
+
+  invert () {
+    return this.combine(-1)
+  }
+}
+
+module.exports = LCG

lib/Random.js

@@ -0,0 +1,49 @@
+const LCG = require('./LCG')
+
+class Rand {
+  constructor (seed, lcg = LCG.JAVA) {
+    this.seed = seed ^ LCG.JAVA.multiplier
+    this.lcg = lcg
+  }
+
+  next (bits) {
+    this.seed = this.lcg.nextSeed(this.seed)
+    return this.seed >> (48n - BigInt(bits))
+  }
+
+  advance (lcg) {
+    this.seed = lcg.nextSeed(this.seed)
+  }
+
+  skip (skip) {
+    this.advance(this.lcg.combine(skip))
+  }
+
+  nextInt (bound) {
+    if (!bound) return Number(BigInt.asIntN(32, this.next(32)))
+
+    if (bound <= 0) {
+      throw new Error('bound must be positive')
+    }
+
+    bound = Math.floor(bound)
+
+    if ((bound & -bound) === bound) {
+      return Number(BigInt.asIntN(32, (BigInt(bound) * this.next(31)) >> 31n))
+    }
+
+    let bits, value
+    do {
+      bits = Number(BigInt.asIntN(32, this.next(31)))
+      value = bits % bound
+    } while (bits - value + (bound - 1) < 0)
+
+    return value
+  }
+
+  nextFloat () {
+    return Number(BigInt.asIntN(32, this.next(24))) / (1 << 24)
+  }
+}
+
+module.exports = Rand

lib/enchantments.js

@@ -0,0 +1,173 @@
+const LCG = require('./LCG')
+const Random = require('./Random')
+
+module.exports = (mcData) => {
+  const tiers = [
+    { name: 'wood', level: 0, uses: 59, speed: 2, damage: 0, enchantmentValue: 15 },
+    { name: 'stone', level: 1, uses: 131, speed: 4, damage: 1, enchantmentValue: 5 },
+    { name: 'iron', level: 2, uses: 250, speed: 6, damage: 2, enchantmentValue: 14 },
+    { name: 'diamond', level: 3, uses: 1561, speed: 8, damage: 3, enchantmentValue: 10 },
+    { name: 'gold', level: 0, uses: 32, speed: 12, damage: 0, enchantmentValue: 22 },
+    { name: 'netherite', level: 4, uses: 2031, speed: 9, damage: 4, enchantmentValue: 15 }
+  ]
+
+  function getTier (item) {
+    return tiers.find(tier => item.name.includes(tier.name))
+  }
+
+  function selectEnchantment (rand, item, level, bypassTreasureOnly) {
+    const tier = getTier(item)
+    const enchantmentValue = tier ? tier.enchantmentValue : 0
+    if (enchantmentValue <= 0) {
+      return []
+    }
+
+    const list = []
+
+    level += 1 + rand.nextInt(enchantmentValue / 4 + 1) + rand.nextInt(enchantmentValue / 4 + 1)
+    const var7 = (rand.nextFloat() + rand.nextFloat() - 1.0) * 0.15
+    level = Math.min(Math.max(Math.round(level + level * var7), 1), 2147483647)
+
+    let availableEnchants = getAvailableEnchantmentResults(level, item, bypassTreasureOnly)
+
+    if (availableEnchants.length > 0) {
+      list.push(getRandomEnchant(rand, availableEnchants))
+      while (rand.nextInt(50) <= level) {
+        availableEnchants = filterCompatibleEnchantments(availableEnchants, list[list.length - 1])
+        if (availableEnchants.length === 0) break
+        list.push(getRandomEnchant(rand, availableEnchants))
+        level /= 2
+      }
+    }
+    return list
+  }
+
+  function getRandomEnchant (rand, enchants) {
+    const totalWeight = enchants.reduce((acc, x) => acc + x.enchant.weight, 0)
+    let val = rand.nextInt(totalWeight)
+    for (const e of enchants) {
+      val -= e.enchant.weight
+      if (val < 0) return e
+    }
+    return null
+  }
+
+  function filterCompatibleEnchantments (enchants, last) {
+    return enchants.filter(e => e.enchant !== last.enchant && last.enchant.exclude.indexOf(e.enchant.name) === -1)
+  }
+
+  function canEnchant (enchant, item) {
+    // TODO: test category
+    return enchant.category === 'weapon' || enchant.category === 'breakable'
+  }
+
+  function getAvailableEnchantmentResults (cost, item, bypassTreasureOnly) {
+    const list = []
+    for (const enchant of mcData.enchantmentsArray) {
+      if (enchant.treasureOnly && !bypassTreasureOnly) continue
+      if (!enchant.discoverable) continue
+      if (!canEnchant(enchant, item) && item.id !== mcData.itemsByName.book.id) continue
+
+      for (let level = enchant.maxLevel; level > 0; level--) {
+        const minCost = enchant.minCost.a * level + enchant.minCost.b
+        const maxCost = enchant.maxCost.a * level + enchant.maxCost.b
+        if (cost >= minCost && cost <= maxCost) {
+          list.push({ enchant, level })
+          break
+        }
+      }
+    }
+
+    return list
+  }
+
+  function isAir (world, pos) {
+    const b = world.getBlock(pos)
+    return !b || b.type === mcData.blocksByName.air.id // TODO cave air, etc..
+  }
+
+  function enchantPower (world, pos) {
+    const b = world.getBlock(pos)
+    return b && b.type === mcData.blocksByName.bookshelf.id ? 1 : 0
+  }
+
+  function findEnchantment (playerSeed, item, power, matching) {
+    let nThrows = 0
+    const playerRand = new Random(playerSeed ^ LCG.JAVA.multiplier)
+    for (let i = 0; i < 1000000; i++) {
+      const xpseed = playerRand.nextInt()
+      const xprand = new Random(BigInt(xpseed))
+      for (let slot = 0; slot < 3; slot++) {
+        const cost = getEnchantmentCost(xprand, slot, power, item)
+        const list = getEnchantmentList(xpseed, item, slot, cost)
+        if (matching(list)) {
+          return {
+            found: list,
+            slot,
+            xpseed,
+            nThrows
+          }
+        }
+      }
+      // Throw an item
+      playerRand.nextFloat()
+      playerRand.nextFloat()
+      playerRand.nextFloat()
+      nThrows++
+    }
+    return null
+  }
+
+  function getEnchantmentList (xpseed, item, slot, level) {
+    const rand = new Random(BigInt(xpseed) + BigInt(slot))
+    const list = selectEnchantment(rand, item, level, false)
+
+    if (item.id === mcData.itemsByName.book.id && list.length > 0) {
+      list.splice(rand.nextInt(list.length), 1)
+    }
+
+    return list
+  }
+
+  function getEnchantmentCost (rand, slot, power, item) {
+    const tier = getTier(item)
+    let enchantmentValue = tier ? tier.enchantmentValue : 0
+    if (enchantmentValue <= 0) {
+      return []
+    }
+
+    if (enchantmentValue > 15) enchantmentValue = 15
+
+    const var6 = rand.nextInt(8) + 1 + (power >> 1) + rand.nextInt(power + 1)
+    if (slot === 0) {
+      return Math.max(Math.floor(var6 / 3), 1)
+    }
+    return slot === 1 ? Math.floor(var6 * 2 / 3 + 1) : Math.max(var6, power * 2)
+  }
+
+  function getEnchantmentPower (pos, world) {
+    let power = 0
+    for (let dz = -1; dz <= 1; dz++) {
+      for (let dx = -1; dx <= 1; dx++) {
+        if ((dz !== 0 || dx !== 0) && isAir(world, pos.offset(dx, 0, dz)) && isAir(world, pos.offset(dx, 1, dz))) {
+          power += enchantPower(world, pos.offset(2 * dx, 0, 2 * dz))
+          power += enchantPower(world, pos.offset(2 * dx, 1, 2 * dz))
+          if (dx !== 0 && dz !== 0) {
+            power += enchantPower(world, pos.offset(2 * dx, 0, dz))
+            power += enchantPower(world, pos.offset(2 * dx, 1, dz))
+            power += enchantPower(world, pos.offset(dx, 0, 2 * dz))
+            power += enchantPower(world, pos.offset(dx, 1, 2 * dz))
+          }
+        }
+      }
+    }
+    return power
+  }
+
+  return {
+    findEnchantment,
+    getEnchantmentList,
+    getEnchantmentCost,
+    getEnchantmentPower
+  }
+}

package.json

@@ -1,7 +1,7 @@
 {
-  "name": "prismarine-template",
+  "name": "prismarine-rng",
   "version": "1.0.0",
-  "description": "A template repository to make it easy to create new prismarine repo",
+  "description": "Collection of utilities to work with minecraft RNG.",
   "main": "index.js",
   "scripts": {
     "test": "jest --verbose",
@@ -11,21 +11,30 @@
   },
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/PrismarineJS/prismarine-template.git"
+    "url": "git+https://github.com/PrismarineJS/prismarine-rng.git"
   },
   "keywords": [
     "prismarine",
-    "template"
+    "rng",
+    "seed",
+    "java",
+    "random"
   ],
-  "author": "Romain Beaumont",
+  "author": "Karang",
   "license": "MIT",
   "bugs": {
-    "url": "https://github.com/PrismarineJS/prismarine-template/issues"
+    "url": "https://github.com/PrismarineJS/prismarine-rng/issues"
   },
-  "homepage": "https://github.com/PrismarineJS/prismarine-template#readme",
+  "standard": {
+    "parser": "babel-eslint"
+  },
+  "homepage": "https://github.com/PrismarineJS/prismarine-rng#readme",
   "devDependencies": {
+    "minecraft-data": "^2.73.1",
+    "prismarine-item": "^1.5.0",
+    "babel-eslint": "^10.1.0",
     "jest": "^26.1.0",
-    "prismarine-template": "file:.",
-    "standard": "^16.0.1"
+    "prismarine-rng": "file:.",
+    "standard": "^16.0.3"
   }
 }