import { expect, test } from 'vitest'
import { clampPan, clampZoom, coverScale, sourceRect } from '../components/cropMath'

test('coverScale scales the shorter side to fill the viewport', () => {
  expect(coverScale(1000, 2000, 200)).toBeCloseTo(0.2)
  expect(coverScale(2000, 1000, 200)).toBeCloseTo(0.2)
})

test('clampZoom keeps zoom within [1, 4]', () => {
  expect(clampZoom(0.5)).toBe(1)
  expect(clampZoom(10)).toBe(4)
  expect(clampZoom(2)).toBe(2)
})

test('clampPan keeps a square image centered at zoom 1 (no room to pan)', () => {
  const clamped = clampPan({ x: 50, y: 50 }, 400, 400, 200, 1)
  expect(clamped).toEqual({ x: 0, y: 0 })
})

test('clampPan allows panning up to the overflow at higher zoom', () => {
  // 400x400 image, viewport 200, zoom 2 -> scale = 0.5*2 = 1, scaledSize 400, overflow (400-200)/2=100
  const clamped = clampPan({ x: 1000, y: -1000 }, 400, 400, 200, 2)
  expect(clamped).toEqual({ x: 100, y: -100 })
})

test('clampPan never lets the image show empty space (overflow stays >= 0)', () => {
  const clamped = clampPan({ x: 5, y: 5 }, 300, 900, 240, 1)
  // shorter side (300) covers the viewport exactly at zoom 1, so no pan room on x
  expect(clamped.x).toBe(0)
  // long side has plenty of room
  expect(Math.abs(clamped.y)).toBeLessThanOrEqual(5)
})

test('sourceRect at zoom 1 with no offset centers the full covering square', () => {
  const rect = sourceRect(400, 400, 200, 1, { x: 0, y: 0 })
  expect(rect.sx).toBeCloseTo(0)
  expect(rect.sy).toBeCloseTo(0)
  expect(rect.sw).toBeCloseTo(400)
  expect(rect.sh).toBeCloseTo(400)
})

test('sourceRect shrinks the source square as zoom increases', () => {
  const rect = sourceRect(400, 400, 200, 2, { x: 0, y: 0 })
  expect(rect.sw).toBeCloseTo(200)
  expect(rect.sh).toBeCloseTo(200)
  expect(rect.sx).toBeCloseTo(100)
  expect(rect.sy).toBeCloseTo(100)
})

test('sourceRect shifts opposite the pan offset', () => {
  const zoomed = sourceRect(400, 400, 200, 2, { x: 50, y: 0 })
  // positive offset.x pans the image right on screen -> source window moves left
  expect(zoomed.sx).toBeLessThan(100)
})