feat: use swipe to complete items

frontend/src/lib/mvp-utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { dateKey, habitWeek, isHabitComplete, isTaskView, numericHabitInputValue } from './mvp-utils'
+import { dateKey, habitWeek, isHabitComplete, isTaskView, numericHabitInputValue, shouldToggleHabitSwipe } from './mvp-utils'
 
 describe('MVP view utilities', () => {
   it('formats a local date as YYYY-MM-DD', () => {
@@ -28,4 +28,11 @@ describe('MVP view utilities', () => {
     expect(numericHabitInputValue('')).toBeNull()
     expect(numericHabitInputValue(4)).toBe(4)
   })
+
+  it('toggles a habit only for a deliberate horizontal swipe', () => {
+    expect(shouldToggleHabitSwipe(78, 8)).toBe(true)
+    expect(shouldToggleHabitSwipe(-78, 8)).toBe(false)
+    expect(shouldToggleHabitSwipe(30, 2)).toBe(false)
+    expect(shouldToggleHabitSwipe(80, 35)).toBe(false)
+  })
 })

frontend/src/lib/mvp-utils.ts

@@ -34,3 +34,7 @@ export function numericHabitInputValue(input: number | string | undefined) {
   const value = Number(input)
   return Number.isFinite(value) && value >= 0 ? value : null
 }
+
+export function shouldToggleHabitSwipe(deltaX: number, deltaY: number) {
+  return deltaX >= 64 && Math.abs(deltaY) <= 24 && deltaX > Math.abs(deltaY) * 1.5
+}