Conversion Rate Optimization for SaaS: A/B Testing, Psychology, and Data

// A/B test calculator
export const calculateABTest = createServerFn({ method: "POST" }).handler(
  async ({ data }: { data: {
    controlVisitors: number
    controlConversions: number
    variantVisitors: number
    variantConversions: number
  }}) => {
    const controlRate = data.controlConversions / data.controlVisitors
    const variantRate = data.variantConversions / data.variantVisitors

    // Calculate statistical significance (chi-squared)
    const improvement = ((variantRate - controlRate) / controlRate) * 100

    // Sample size needed for 80% power at 95% significance
    const baseline = controlRate
    const minimumDetectableEffect = 0.1 // 10% relative improvement
    const zAlpha = 1.96 // 95% confidence
    const zBeta = 0.84 // 80% power
    const sampleSize =
      ((zAlpha + zBeta) ** 2 * 2 * baseline * (1 - baseline)) /
      (minimumDetectableEffect ** 2)

    return {
      controlRate,
      variantRate,
      improvement,
      sampleSizeNeeded: Math.ceil(sampleSize),
      currentSampleSize: data.controlVisitors + data.variantVisitors,
      sufficientData: (data.controlVisitors + data.variantVisitors) >= sampleSize,
    }
  }
)

// A/B test: headline variants
const headlineVariants = {
  control: {
    headline: "Build Your SaaS Faster",
    subheadline: "A production-ready starter with auth, billing, and more.",
    cta: "Get Started",
  },
  variantA: {
    headline: "Ship Your SaaS in Days, Not Months",
    subheadline: "Pre-built auth, billing, marketing, and multi-language support.",
    cta: "Start Building Free →",
  },
  variantB: {
    headline: "The SaaS Starter That Saves You 200 Hours",
    subheadline: "Everything you need to launch — without rebuilding the boring parts.",
    cta: "See What's Included",
  },
}

// Dynamic pricing based on A/B test assignment
export const getPricingVariant = createServerFn({ method: "GET" }).handler(
  async ({}, { context }) => {
    const variants = [
      { id: "control", starter: 29, pro: 79, enterprise: 199 },
      { id: "lower_prices", starter: 19, pro: 59, enterprise: 149 },
      { id: "higher_prices", starter: 39, pro: 99, enterprise: 249 },
      { id: "different_tiers", starter: 29, growth: 69, scale: 149 },
    ]

    const index = Math.abs(hashString(context.user.id ?? "anon")) % variants.length
    const variant = variants[index]

    // Track assignment
    await context.env.DB.prepare(`
      INSERT INTO ab_assignments
        (user_id, test_name, variant, assigned_at)
      VALUES (?, 'pricing_page', ?, ?)
    `).bind(context.user.id ?? "anon", variant.id, Date.now()).run()

    return variant
  }
)

const trialEmailSequence = [
  { day: 0, type: "welcome", subject: "Welcome! Here's your first step" },
  { day: 1, type: "activation", subject: "Set up your project in 2 minutes" },
  { day: 3, type: "tip", subject: "Most users love this feature" },
  { day: 5, type: "case_study", subject: "How [customer] saved 20 hours/week" },
  { day: 7, type: "mid_trial", subject: "Halfway through your trial" },
  { day: 10, type: "offer", subject: "Convert now and save 20% on annual" },
  { day: 12, type: "urgent", subject: "Your trial ends in 2 days" },
  { day: 14, type: "expired", subject: "Your trial has ended" },
]

// Database schema for experiments
export const experiments = sqliteTable("experiments", {
  id: text("id").primaryKey(),
  name: text("name").notNull(),
  slug: text("slug").notNull().unique(),
  status: text("status", {
    enum: ["draft", "running", "paused", "concluded"],
  }).notNull().default("draft"),
  controlVariant: text("control_variant").notNull(),
  variants: text("variants").notNull(), // JSON array
  hypothesis: text("hypothesis"),
  targetMetric: text("target_metric").notNull(),
  minimumSampleSize: integer("minimum_sample_size"),
  startedAt: integer("started_at", { mode: "timestamp" }),
  concludedAt: integer("concluded_at", { mode: "timestamp" }),
  winnerVariant: text("winner_variant"),
})

// Track event for experiment
export const trackExperimentEvent = createServerFn({ method: "POST" }).handler(
  async ({ data, context }: { data: {
    experimentId: string
    variant: string
    event: string
    value?: number
  }}) => {
    await context.env.DB.prepare(`
      INSERT INTO experiment_events
        (id, experiment_id, variant, event, value, user_id, created_at)
      VALUES (?, ?, ?, ?, ?, ?, ?)
    `).bind(
      crypto.randomUUID(),
      data.experimentId,
      data.variant,
      data.event,
      data.value ?? null,
      context.user.id ?? null,
      Date.now()
    ).run()
  }
)