Subscriptions headline

import { CreditCardIcon, HourglassIcon, RepeatIcon, UsersIcon } from "lucide-react"

import { formatCurrency, formatNumber } from "@/lib/format"
import { StatCard } from "@/components/ui/stat-card"
import { StatCardGroup } from "@/components/ui/stat-card-group"

import { type SubscriptionStat } from "../data"

// One icon per headline, keyed by the stat rather than its position, so the row
// can be reordered without the icons following the wrong numbers.
const ICONS: Record<string, React.ReactNode> = {
  mrr: <CreditCardIcon />,
  live: <RepeatIcon />,
  trials: <HourglassIcon />,
  arpa: <UsersIcon />,
}

/** What the book is worth, how many are on it, and what an account is worth. */
export function SubscriptionStats({ stats }: { stats: SubscriptionStat[] }) {
  return (
    <StatCardGroup data-widget="widget-saas-subscriptions-subscription-stats" columns={4}>
      {stats.map((stat) => (
        <StatCard
          key={stat.key}
          label={stat.label}
          value={
            stat.format === "currency"
              ? formatCurrency(stat.value, "USD", { maximumFractionDigits: 0 })
              : formatNumber(stat.value, { maximumFractionDigits: 0 })
          }
          description={stat.description}
          icon={ICONS[stat.key]}
        />
      ))}
    </StatCardGroup>
  )
}

/**
 * What /subscriptions reads. The book is `db.subscriptions`, one per account,
 * joined to `db.customers` for the workspace behind it and `db.plans` for the
 * tier it sits on. Movements are read off the rows' own dates — a subscription
 * that started inside the window is new, one that cancelled inside it is churn
 * — so opening plus new minus churn closes on the book exactly. Nothing here
 * reads a clock: every window ends at REFERENCE_DATE.
 */
import { getInitials } from "@/lib/format"
import {
  db,
  REFERENCE_DATE,
  type Member,
  type Subscription,
} from "@/lib/sample-data"

// The plans are reference rows nothing writes. The subscriptions and the
// accounts are read per call, never held at module scope: a cancellation or a
// new account since the server started is in the next book.
const PLANS = new Map(db.plans.all().map((plan) => [plan.id, plan]))
const subscriptions = (): Subscription[] => db.subscriptions.all()
const accountsById = () => new Map(db.customers.all().map((customer) => [customer.id, customer]))

// What a tier charges a seat a month, read off the accounts paying it today.
// A churned account's own `mrrCents` is zeroed the moment it churns, so the
// rate has to come from an account still on that tier — otherwise every
// cancellation would be worth nothing and churn would read as zero.
function seatPrices(): Map<string, number> {
  const prices = new Map<string, number>()
  for (const customer of db.customers.all()) {
    if (customer.mrrCents > 0 && !prices.has(customer.plan)) {
      prices.set(customer.plan, customer.mrrCents / customer.seats)
    }
  }
  return prices
}

/** What a subscription bills a month, in cents. A trial bills nothing. */
function billedCents(subscription: Subscription, prices: Map<string, number>): number {
  if (subscription.status === "trialing") return 0
  const tier = (PLANS.get(subscription.planId)?.name ?? "").toLowerCase()
  return subscription.seats * (prices.get(tier) ?? 0)
}

const DAY_MS = 86_400_000

const dollars = (cents: number): number => cents / 100

/** Midnight UTC on the first of the month `k` months before the current one. */
function monthStart(k: number): Date {
  return new Date(Date.UTC(REFERENCE_DATE.getUTCFullYear(), REFERENCE_DATE.getUTCMonth() - k, 1))
}

/** Whether a subscription was on the book at an instant. */
function live(subscription: Subscription, at: Date): boolean {
  if (subscription.startedAt > at) return false
  return !subscription.cancelledAt || subscription.cancelledAt > at
}

/** The book at an instant, in dollars. */
function bookAt(at: Date): number {
  const prices = seatPrices()
  return dollars(
    subscriptions()
      .filter((subscription) => live(subscription, at))
      .reduce((total, subscription) => total + billedCents(subscription, prices), 0)
  )
}

/** How many months of movement the waterfall covers. */
export const WINDOW_MONTHS = 12

const OPENED_AT = monthStart(WINDOW_MONTHS)

/**
 * How the book got from one close to the next. Two movements, not the usual
 * four: an account moving up or down a tier leaves no trace in the rows, and
 * an invented expansion would need an invented contraction to cancel it — so
 * opening plus new minus churn closes on the book to the cent.
 */
export function mrrMovements(): { label: string; value: number; isTotal?: boolean }[] {
  let won = 0
  let lost = 0
  const prices = seatPrices()
  for (const subscription of subscriptions()) {
    if (subscription.startedAt > OPENED_AT) won += billedCents(subscription, prices)
    const { cancelledAt } = subscription
    if (cancelledAt && cancelledAt > OPENED_AT) lost += billedCents(subscription, prices)
  }

  return [
    { label: "Opening", value: Math.round(bookAt(OPENED_AT)) },
    { label: "New", value: Math.round(dollars(won)) },
    { label: "Churn", value: -Math.round(dollars(lost)) },
    { label: "Closing", value: 0, isTotal: true },
  ]
}

const liveNow = () => subscriptions().filter((subscription) => live(subscription, REFERENCE_DATE))
const trialing = () => liveNow().filter((subscription) => subscription.status === "trialing")

export type SubscriptionStat = {
  key: string
  label: string
  value: number
  description: string
  format: "currency" | "number"
}

/** The four headline numbers: what the book is worth, and who is on it. */
export function subscriptionStats(): SubscriptionStat[] {
  const prices = seatPrices()
  const book = subscriptions()
  const onBook = book.filter((subscription) => live(subscription, REFERENCE_DATE))
  const billing = onBook.filter((subscription) => billedCents(subscription, prices) > 0)
  const closing = bookAt(REFERENCE_DATE)

  return [
    {
      key: "mrr",
      label: "MRR",
      value: Math.round(closing),
      description: `across ${billing.length} paying subscriptions`,
      format: "currency",
    },
    {
      key: "live",
      label: "Live subscriptions",
      value: onBook.length,
      description: `of ${book.length} ever opened`,
      format: "number",
    },
    {
      key: "trials",
      label: "In trial",
      value: onBook.filter((subscription) => subscription.status === "trialing").length,
      description: "not billing yet",
      format: "number",
    },
    {
      key: "arpa",
      label: "Average account",
      value: billing.length > 0 ? Math.round(closing / billing.length) : 0,
      description: "a month, across the accounts that pay",
      format: "currency",
    },
  ]
}

/** How the live book splits across the four tiers, largest first. */
export function planMix(): { name: string; value: number }[] {
  const counts = new Map<string, number>()
  for (const subscription of liveNow()) {
    const name = PLANS.get(subscription.planId)?.name ?? "Unknown"
    counts.set(name, (counts.get(name) ?? 0) + 1)
  }
  return [...counts]
    .map(([name, value]) => ({ name, value }))
    .sort((a, b) => b.value - a.value)
}

/** How many subscriptions are on the book right now, for the middle of the donut. */
export function liveTotal(): number {
  return liveNow().length
}

/** How many monthly cohorts the heatmap shows, and how far each is followed. */
export const COHORTS = 12

const COHORT_LABEL = new Intl.DateTimeFormat("en-US", {
  month: "short",
  year: "2-digit",
  timeZone: "UTC",
})

/** `months` months after `from`, on the same day of the month. */
function monthsAfter(from: Date, months: number): Date {
  return new Date(
    Date.UTC(
      from.getUTCFullYear(),
      from.getUTCMonth() + months,
      from.getUTCDate(),
      from.getUTCHours(),
      from.getUTCMinutes()
    )
  )
}

export type Cohorts = { rows: string[]; columns: string[]; values: number[][] }

/**
 * Retention by signup cohort. A cohort is the accounts that opened in one
 * month; a cell is the share of them still on the book that many months later.
 * A month a cohort has not lived through yet is left empty rather than counted
 * as a loss — the grid draws those as "no data".
 */
export function churnCohorts(): Cohorts {
  const starts = Array.from({ length: COHORTS }, (_, index) => monthStart(COHORTS - index))
  const book = subscriptions()

  return {
    rows: starts.map((start) => COHORT_LABEL.format(start)),
    columns: Array.from({ length: COHORTS }, (_, month) => `M${month}`),
    values: starts.map((start, index) => {
      const end = monthStart(COHORTS - index - 1)
      const cohort = book.filter(
        (subscription) => subscription.startedAt >= start && subscription.startedAt < end
      )

      return Array.from({ length: COHORTS }, (_, month) => {
        // Read at the close of the month, not its start: a cohort's own month
        // opens before its accounts exist, and "M0" is how many of them made it
        // to the end of the month they arrived in.
        const at = monthsAfter(start, month + 1)
        // The future has no retention to report.
        if (at > REFERENCE_DATE || cohort.length === 0) return Number.NaN
        const kept = cohort.filter((subscription) => live(subscription, at)).length
        return (kept / cohort.length) * 100
      })
    }),
  }
}

// The trial the data itself describes: every account in trial was opened
// somewhere in the last three weeks, so three weeks is the window it is on.
const TRIAL_DAYS = 21

export type Trial = {
  id: string
  company: string
  contact: string
  contactAvatar?: string
  plan: string
  seats: number
  endsAt: Date
  daysLeft: number
}

/** The trials closest to running out, soonest first. */
export function trialsExpiring(): Trial[] {
  const accounts = accountsById()
  return trialing()
    .map((subscription) => {
      const account = accounts.get(subscription.customerId)
      const endsAt = new Date(subscription.startedAt.getTime() + TRIAL_DAYS * DAY_MS)

      return {
        id: subscription.id,
        company: account?.company ?? subscription.customerId,
        contact: account?.name ?? "Unknown",
        contactAvatar: account?.avatarUrl,
        plan: PLANS.get(subscription.planId)?.name ?? "Unknown",
        seats: subscription.seats,
        endsAt,
        daysLeft: Math.max(0, Math.ceil((endsAt.getTime() - REFERENCE_DATE.getTime()) / DAY_MS)),
      }
    })
    .sort((a, b) => a.endsAt.getTime() - b.endsAt.getTime())
    .slice(0, 6)
}

export type SubscriptionRow = {
  id: string
  company: string
  plan: string
  status: Subscription["status"]
  seats: number
  mrr: number
  startedAt: Date
  renewsAt: Date
}

/** Every subscription ever opened, newest first. */
export function subscriptionRows(): SubscriptionRow[] {
  const accounts = accountsById()
  return subscriptions()
    .map((subscription) => ({
      id: subscription.id,
      company: accounts.get(subscription.customerId)?.company ?? subscription.customerId,
      plan: PLANS.get(subscription.planId)?.name ?? "Unknown",
      status: subscription.status,
      seats: subscription.seats,
      mrr: dollars(subscription.mrrCents),
      startedAt: subscription.startedAt,
      renewsAt: subscription.renewsAt,
    }))
    .sort((a, b) => b.startedAt.getTime() - a.startedAt.getTime())
}

/** The bell's contents: the newest notifications, unread first in the panel. */
export function shellNotifications() {
  return db.notifications
    .all()
    .sort((a, b) => b.at.getTime() - a.at.getTime())
    .slice(0, 6)
    .map(({ id, title, description, at, read, href }) => ({ id, title, description, at, read, href }))
}

function ownerRow(): Member {
  return db.members.all().find((member) => member.role === "owner") ?? db.members.all()[0]
}

/** The person looking at the page: whoever owns this workspace. */
export function currentUser() {
  const owner = ownerRow()
  return { name: owner.name, email: owner.email, initials: getInitials(owner.name), avatarUrl: owner.avatarUrl }
}

const MONTH_NAME = new Intl.DateTimeFormat("en-US", {
  month: "long",
  year: "numeric",
  timeZone: "UTC",
})

/** The window the movements cover. */
export function lastUpdated(): string {
  return `${WINDOW_MONTHS} months to ${MONTH_NAME.format(REFERENCE_DATE)}`
}