Add basic booster pack generation

src/mlpccg/draft/booster.ts

@@ -0,0 +1,212 @@
+import { Card } from "../types";
+import { Pack, PackSchema, AlternateProvider } from "./types";
+import { getCards } from "../database";
+
+/*
+
+(This data was taken from the MLP:CCG wikia at mlpccg.fandom.com and confirmed
+ by people at the MLP:CCG Discord)
+
+Distribution rates for packs is usually 8 commons, 3 uncommons and 1 rare.
+
+No Fixed or Promo cards can be found in packs.
+
+UR distribution depends on set:
+	- PR has 1/13 chance of UR replacing a common
+	- CN->AD has 1/11 chance of UR replacing a common
+	- EO->FF has 1/3 chance of SR/UR replacing a common
+
+SR are twice as common as UR, so that's one more thing to keep in mind.
+
+Lastly, RR can replace another common in the ratio of ~1/2 every 6 boxes, depending
+on set. Specifically, this is the RR ratio for each set:
+	- EO->HM: 1/108
+	- MT->FF: 1/216
+
+*/
+
+// Returns the pack schema for a specific set
+async function setSchema(set: string): Promise<PackSchema> {
+  // Force set name to uppercase
+  set = set.toUpperCase();
+
+  // Return blank schemas for invalid sets
+  if (set == "RR" || set == "CS") {
+    return { slots: [] };
+  }
+
+  // Get cards for set
+  let cards = await getCards({ Sets: [set] });
+  let cardMap = spanByRarity(cards);
+
+  let rr: AlternateProvider[] = [];
+  let srur: AlternateProvider[] = [];
+
+  // Check for RR chances
+  /*
+  switch (set) {
+    case "EO":
+    case "HM":
+      rr = [
+        {
+          probability: 1.0 / 108.0,
+          provider: randomProvider([
+            //TODO
+          ])
+        }
+      ];
+      break;
+    case "MT":
+    case "HM":
+    case "SB":
+    case "FF":
+      rr = [
+        {
+          probability: 1.0 / 216.0,
+          provider: randomProvider([
+            //TODO
+          ])
+        }
+      ];
+      break;
+  }
+  */
+
+  // Check for SR/UR chances
+  switch (set) {
+    case "PR":
+      srur = [
+        {
+          probability: 1.0 / 13.0,
+          provider: randomProvider(cardMap["UR"])
+        }
+      ];
+      break;
+    case "CN":
+    case "CG":
+    case "AD":
+      srur = [
+        {
+          probability: 1.0 / 11.0,
+          provider: randomProvider(cardMap["UR"])
+        }
+      ];
+      break;
+    default:
+      srur = [
+        {
+          probability: (1.0 / 9.0) * 2.0,
+          provider: randomProvider(cardMap["SR"])
+        },
+        {
+          probability: 1.0 / 9.0,
+          provider: randomProvider(cardMap["UR"])
+        }
+      ];
+      break;
+  }
+
+  return {
+    slots: [
+      {
+        amount: 6,
+        provider: randomProvider(cardMap["C"]),
+        alternate: []
+      },
+      {
+        amount: 1,
+        provider: randomProvider(cardMap["C"]),
+        alternate: rr
+      },
+      {
+        amount: 1,
+        provider: randomProvider(cardMap["C"]),
+        alternate: srur
+      },
+      {
+        amount: 1,
+        provider: randomProvider(cardMap["R"]),
+        alternate: []
+      },
+      {
+        amount: 3,
+        provider: randomProvider(cardMap["U"]),
+        alternate: []
+      }
+    ]
+  };
+}
+
+export class PackBuilder {
+  schema: PackSchema;
+  constructor(schema: PackSchema) {
+    this.schema = schema;
+  }
+
+  buildPack(): Pack {
+    let pack = [];
+    for (const slot of this.schema.slots) {
+      let provider = slot.provider;
+
+      // Check for alternates by generating a random and checking cumulated
+      // probability. Ie. if one card would show 5% of the time, another would
+      // show up 10% of the time, the algorithm would do something like this:
+      //
+      // With Math.random() == 0.85:
+      //  ALTERNATE     NO ALTERNATE
+      // [0.00-0.05][0.06----0.15][0.16------------1.00]
+      //                                        ^ 0.85
+      //
+      // With Math.random() == 0.03:
+      //  ALTERNATE     NO ALTERNATE
+      // [0.00-0.05][0.06----0.15][0.16------------1.00]
+      //    ^ 0.03
+
+      const rnd = Math.random();
+      let currentProb = 0;
+      for (const alternate of slot.alternate) {
+        currentProb += alternate.probability;
+        // Alternate matched
+        if (currentProb > rnd) {
+          provider = alternate.provider;
+          break;
+        }
+      }
+      for (let i = 0; i < slot.amount; i++) {
+        const res = provider.next();
+        if (res.done) {
+          // No more cards to get from this, exit early
+          break;
+        }
+        pack.push(res.value);
+      }
+    }
+    return pack;
+  }
+
+  static async fromSet(set: string): Promise<PackBuilder> {
+    let schema = await setSchema(set);
+    let builder = new PackBuilder(schema);
+    return builder;
+  }
+}
+
+// Yields random cards from a chosen pool
+function* randomProvider(pool: Card[]) {
+  while (true) {
+    const idx = Math.floor(Math.random() * pool.length);
+    yield pool[idx];
+  }
+}
+
+// Divides a list of card to a map of rarities
+// ie. [ff14, ff16, ff17] => { "C" : ["ff14"], "U": ["ff17"], "R": ["ff16"] }
+function spanByRarity(pool: Card[]): Record<string, Card[]> {
+  return pool.reduce((map, current) => {
+    if (!(current.Rarity in map)) {
+      map[current.Rarity] = [];
+    }
+    map[current.Rarity] = current;
+    return map;
+  }, Object.create(null));
+}

src/mlpccg/draft/types.ts

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+import { Card } from "../types";
+
+export type Provider = Iterator<Card>;
+
+export type Pack = Card[];
+
+export interface PackSchema {
+  slots: PackSlot[];
+}
+
+export interface PackSlot {
+  amount: number;
+  provider: Provider;
+  alternate: AlternateProvider[];
+}
+
+export interface AlternateProvider {
+  probability: number;
+  provider: Provider;
+}