feat: alert evaluation logic (target/atl/drop) with dedup

tests/alerts/evaluate.test.ts

@@ -0,0 +1,112 @@
+import { describe, it, expect } from 'vitest'
+import { evaluateAlert, type SnapshotInput } from '@/lib/alerts/evaluate'
+
+function snap(price: number, daysAgo: number): SnapshotInput {
+  const d = new Date()
+  d.setDate(d.getDate() - daysAgo)
+  return { price, scrapedAt: d }
+}
+
+describe('evaluateAlert', () => {
+  describe('target_price', () => {
+    it('triggers when current price <= threshold', () => {
+      const r = evaluateAlert({
+        alert: { type: 'target_price', config: { threshold: 100 }, lastTriggeredAt: null },
+        currentPrice: 99,
+        history: [],
+      })
+      expect(r.triggered).toBe(true)
+    })
+
+    it('does not trigger when price > threshold', () => {
+      const r = evaluateAlert({
+        alert: { type: 'target_price', config: { threshold: 100 }, lastTriggeredAt: null },
+        currentPrice: 101,
+        history: [],
+      })
+      expect(r.triggered).toBe(false)
+    })
+  })
+
+  describe('all_time_low', () => {
+    it('triggers when current is below all previous successful prices', () => {
+      const r = evaluateAlert({
+        alert: { type: 'all_time_low', config: {}, lastTriggeredAt: null },
+        currentPrice: 50,
+        history: [snap(60, 1), snap(70, 5), snap(80, 10)],
+      })
+      expect(r.triggered).toBe(true)
+      expect(r.context.prevMin).toBe(60)
+    })
+
+    it('does not trigger when current equals previous min', () => {
+      const r = evaluateAlert({
+        alert: { type: 'all_time_low', config: {}, lastTriggeredAt: null },
+        currentPrice: 60,
+        history: [snap(60, 1)],
+      })
+      expect(r.triggered).toBe(false)
+    })
+
+    it('does not trigger with no history (first scrape)', () => {
+      const r = evaluateAlert({
+        alert: { type: 'all_time_low', config: {}, lastTriggeredAt: null },
+        currentPrice: 50,
+        history: [],
+      })
+      expect(r.triggered).toBe(false)
+    })
+  })
+
+  describe('percent_drop', () => {
+    it('triggers when price drops >= percent vs lookback avg', () => {
+      const r = evaluateAlert({
+        alert: { type: 'percent_drop', config: { lookback_days: 7, percent: 10 }, lastTriggeredAt: null },
+        currentPrice: 80,
+        history: [snap(100, 1), snap(100, 3), snap(100, 6), snap(50, 30)],
+      })
+      expect(r.triggered).toBe(true)
+      expect(r.context.percent).toBeGreaterThanOrEqual(10)
+    })
+
+    it('does not trigger when drop is smaller than threshold', () => {
+      const r = evaluateAlert({
+        alert: { type: 'percent_drop', config: { lookback_days: 7, percent: 10 }, lastTriggeredAt: null },
+        currentPrice: 95,
+        history: [snap(100, 1), snap(100, 3)],
+      })
+      expect(r.triggered).toBe(false)
+    })
+
+    it('does not trigger with no history in lookback window', () => {
+      const r = evaluateAlert({
+        alert: { type: 'percent_drop', config: { lookback_days: 7, percent: 10 }, lastTriggeredAt: null },
+        currentPrice: 50,
+        history: [snap(100, 30)],
+      })
+      expect(r.triggered).toBe(false)
+    })
+  })
+
+  describe('dedup', () => {
+    it('does not trigger if last triggered within 24h', () => {
+      const recent = new Date(Date.now() - 1000 * 60 * 60 * 12)
+      const r = evaluateAlert({
+        alert: { type: 'target_price', config: { threshold: 100 }, lastTriggeredAt: recent },
+        currentPrice: 50,
+        history: [],
+      })
+      expect(r.triggered).toBe(false)
+    })
+
+    it('triggers if last triggered > 24h ago', () => {
+      const old = new Date(Date.now() - 1000 * 60 * 60 * 25)
+      const r = evaluateAlert({
+        alert: { type: 'target_price', config: { threshold: 100 }, lastTriggeredAt: old },
+        currentPrice: 50,
+        history: [],
+      })
+      expect(r.triggered).toBe(true)
+    })
+  })
+})