From 72e00a845d6e3f27f451cabc58334faffeb57f27 Mon Sep 17 00:00:00 2001
From: Ernest <soc221b.e@gmail.com>
Date: Fri, 3 Jan 2025 23:04:39 +0800
Subject: [PATCH] fix: bigint (#315)

---
 src/zod-bigint-faker.ts        | 38 +++++++++++++++---------------
 tests/zod-bigint-faker.test.ts | 43 ++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 19 deletions(-)

diff --git a/src/zod-bigint-faker.ts b/src/zod-bigint-faker.ts
index f4817ca..1b81853 100644
--- a/src/zod-bigint-faker.ts
+++ b/src/zod-bigint-faker.ts
@@ -6,7 +6,7 @@ export class ZodBigIntFaker extends ZodTypeFaker<z.ZodBigInt> {
   fake(): z.infer<z.ZodBigInt> {
     let min: undefined | bigint = undefined
     let max: undefined | bigint = undefined
-    let multipleOf: undefined | bigint = undefined
+    let multipleOf: bigint = 1n
     for (const check of this.schema._def.checks) {
       switch (check.kind) {
         case 'min':
@@ -16,31 +16,31 @@ export class ZodBigIntFaker extends ZodTypeFaker<z.ZodBigInt> {
           max = check.value - (check.inclusive ? 0n : 1n)
           break
         case 'multipleOf':
-          multipleOf = check.value
+          multipleOf = check.value < 0n ? -check.value : check.value
           break
         default:
           const _: never = check
       }
     }
-
-    // workaround: https://github.com/faker-js/faker/pull/3363
-    if (min === undefined && max !== undefined && max < 0n) {
-      min = max - (multipleOf === undefined ? 1_000n : multipleOf * 1_000n)
-    }
-
-    if (multipleOf !== undefined) {
-      if (min !== undefined && max !== undefined) {
-        return min + runFake(faker => faker.number.bigInt({ min: 0n, max: (max - min) / multipleOf })) * multipleOf
-      } else if (min !== undefined) {
-        return min + runFake(faker => faker.number.bigInt({ min: 0n })) * multipleOf
-      } else if (max !== undefined) {
-        return max - runFake(faker => faker.number.bigInt({ min: 0n })) * multipleOf
-      } else {
-        return runFake(faker => faker.number.bigInt({ min: 0n })) * multipleOf
-      }
+    const largeThanMultipleOf = multipleOf === undefined ? 1000n : multipleOf * 1000n
+    if (min !== undefined && max !== undefined) {
+    } else if (min !== undefined) {
+      max = min + largeThanMultipleOf
+    } else if (max !== undefined) {
+      min = max - largeThanMultipleOf
     } else {
-      return runFake(faker => faker.number.bigInt({ min, max }))
+      min = -largeThanMultipleOf
+      max = largeThanMultipleOf
     }
+    const data = min + runFake(faker => faker.number.bigInt({ min: 0n, max: (max - min) / multipleOf })) * multipleOf
+    const remaining = multipleOf - ((data < 0n ? -data : data) % multipleOf)
+    return data >= 0n
+      ? data + remaining > max
+        ? data - (multipleOf - remaining)
+        : data + remaining
+      : data - remaining < min
+        ? data + (multipleOf - remaining)
+        : data - remaining
   }
 
   static create(schema: z.ZodBigInt): ZodBigIntFaker {
diff --git a/tests/zod-bigint-faker.test.ts b/tests/zod-bigint-faker.test.ts
index 9072429..bec43f1 100644
--- a/tests/zod-bigint-faker.test.ts
+++ b/tests/zod-bigint-faker.test.ts
@@ -228,4 +228,47 @@ describe('edge case', () => {
     const data = faker.fake()
     expect(schema.safeParse(data).success).toBe(true)
   })
+
+  test('multiplyOf', () => {
+    for (let i = 0n; i < 2000n; i++) {
+      const schema = z
+        .bigint()
+        .multipleOf(37n)
+        .min(i)
+        .max(i + 37n)
+      const faker = zodBigIntFaker(schema)
+      const data = faker.fake()
+      expect(schema.safeParse(data).success).toBe(true)
+    }
+    for (let i = 0n; i > -2000n; i--) {
+      const schema = z
+        .bigint()
+        .multipleOf(37n)
+        .min(i - 37n)
+        .max(i)
+      const faker = zodBigIntFaker(schema)
+      const data = faker.fake()
+      expect(schema.safeParse(data).success).toBe(true)
+    }
+    for (let i = 0n; i < 2000n; i++) {
+      const schema = z
+        .bigint()
+        .multipleOf(-37n)
+        .min(i)
+        .max(i + 37n)
+      const faker = zodBigIntFaker(schema)
+      const data = faker.fake()
+      expect(schema.safeParse(data).success).toBe(true)
+    }
+    for (let i = 0n; i > -2000n; i--) {
+      const schema = z
+        .bigint()
+        .multipleOf(-37n)
+        .min(i - 37n)
+        .max(i)
+      const faker = zodBigIntFaker(schema)
+      const data = faker.fake()
+      expect(schema.safeParse(data).success).toBe(true)
+    }
+  })
 })