import { describe, expect, it } from 'vitest'
import { Rng, seedToRng } from '../src/renderer/game/core/rng'

describe('Rng', () => {
  it('is deterministic for same seed', () => {
    const a = new Rng(seedToRng('hello'))
    const b = new Rng(seedToRng('hello'))
    for (let i = 0; i < 100; i++) {
      expect(a.next()).toBe(b.next())
    }
  })

  it('differs for different seeds', () => {
    const a = new Rng(seedToRng('aaa'))
    const b = new Rng(seedToRng('bbb'))
    const seq = 20
    let diff = false
    for (let i = 0; i < seq; i++) {
      if (a.next() !== b.next()) diff = true
    }
    expect(diff).toBe(true)
  })

  it('produces values in [0, 1)', () => {
    const rng = new Rng(seedToRng('x'))
    for (let i = 0; i < 1000; i++) {
      const v = rng.next()
      expect(v).toBeGreaterThanOrEqual(0)
      expect(v).toBeLessThan(1)
    }
  })

  it('int works within bounds', () => {
    const rng = new Rng(seedToRng('y'))
    for (let i = 0; i < 500; i++) {
      const v = rng.int(0, 10)
      expect(v).toBeGreaterThanOrEqual(0)
      expect(v).toBeLessThanOrEqual(10)
      expect(Number.isInteger(v)).toBe(true)
    }
  })

  it('state roundtrip continues identically', () => {
    const a = new Rng(seedToRng('z'))
    const b = new Rng(seedToRng('z'))
    for (let i = 0; i < 10; i++) {
      a.next()
      b.next()
    }
    const snap = a.getState()
    const c = new Rng(snap)
    expect(c.next()).toBe(b.next())
    expect(c.next()).toBe(b.next())
  })
})