feat: reimplement datatype.bigInt (#791)

Co-authored-by: ST-DDT <[email protected]>

1 files changed, 49 insertions, 10 deletions

diff --git a/src/modules/datatype/index.ts b/src/modules/datatype/index.ts
index df2cac87..c8b9718f 100644
--- a/src/modules/datatype/index.ts
+++ b/src/modules/datatype/index.ts
@@ -261,20 +261,59 @@ export class Datatype {
   /**
    * Returns a [BigInt](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#bigint_type) number.
    *
-   * @param value When provided, this method simply converts it to `BigInt` type.
+   * @param options Maximum value or options object.
+   * @param options.min Lower bound for generated bigint. Defaults to `0n`.
+   * @param options.max Upper bound for generated bigint. Defaults to `min + 999999999999999n`.
+   *
+   * @throws When options define `max < min`.
    *
    * @example
-   * faker.datatype.bigInt() // 8507209999914928n
-   * faker.datatype.bigInt('156') // 156n
-   * faker.datatype.bigInt(30) // 30n
-   * faker.datatype.bigInt(3000n) // 3000n
-   * faker.datatype.bigInt(true) // 1n
+   * faker.datatype.bigInt() // 55422n
+   * faker.datatype.bigInt(100n) // 52n
+   * faker.datatype.bigInt({ min: 1000000n }) // 431433n
+   * faker.datatype.bigInt({ max: 100n }) // 42n
+   * faker.datatype.bigInt({ min: 10n, max: 100n }) // 36n
    */
-  bigInt(value?: string | number | bigint | boolean): bigint {
-    if (value === undefined) {
-      value = Math.floor(this.number() * 99999999999) + 10000000000;
+  bigInt(
+    options?:
+      | bigint
+      | boolean
+      | number
+      | string
+      | {
+          min?: bigint | boolean | number | string;
+          max?: bigint | boolean | number | string;
+        }
+  ): bigint {
+    let min: bigint;
+    let max: bigint;
+
+    if (typeof options === 'object') {
+      min = BigInt(options.min ?? 0);
+      max = BigInt(options.max ?? min + BigInt(999999999999999));
+    } else {
+      min = BigInt(0);
+      max = BigInt(options ?? 999999999999999);
     }
 
-    return BigInt(value);
+    if (max === min) {
+      return min;
+    }
+
+    if (max < min) {
+      throw new FakerError(`Max ${max} should be larger then min ${min}.`);
+    }
+
+    const delta = max - min;
+
+    const offset =
+      BigInt(
+        this.faker.random.numeric(delta.toString(10).length, {
+          allowLeadingZeros: true,
+        })
+      ) %
+      (delta + BigInt(1));
+
+    return min + offset;
   }
 }