import type { Kysely } from 'kysely'
import type { DB } from '../types/db.types.js'
import type { EmailService } from '../services/email.js'
import { applyBookingTransition } from './booking-status.js'

/**
 * The booking lifecycle's time-driven rules, factored out so the daily cron,
 * the manual "run now" RPC, and `triggerContractEmail` all share one
 * implementation. All calendar math is Europe/Berlin local days; every rule is
 * idempotent (guarded by `*SentAt`/`flaggedAt`/`paidOn`), so running twice in a
 * day is a no-op.
 */

type LifecycleServices = {
  kysely: Kysely<DB>
  email: EmailService
  logger: { info: (message: string) => void }
}

/** Today as a Berlin-local `YYYY-MM-DD` (sv-SE locale emits ISO date form). */
export const berlinDate = (d: Date = new Date()): string =>
  d.toLocaleDateString('sv-SE', { timeZone: 'Europe/Berlin' })

/** The Berlin-local date portion of a stored ISO timestamp. */
export const berlinDateFromIso = (iso: string): string => berlinDate(new Date(iso))

/** Whole days from `fromYmd` to `toYmd` (both `YYYY-MM-DD`, UTC-anchored so DST never skews the count). */
export const daysBetween = (fromYmd: string, toYmd: string): number =>
  Math.round((Date.parse(toYmd) - Date.parse(fromYmd)) / 86_400_000)

/** `YYYY-MM-DD` plus `n` calendar days. */
export const addDays = (ymd: string, n: number): string => {
  const d = new Date(`${ymd}T00:00:00Z`)
  d.setUTCDate(d.getUTCDate() + n)
  return d.toISOString().slice(0, 10)
}

const DEPOSIT_WINDOW_DAYS = 14
const DEPOSIT_REMINDER_DAYS = 7
/** Placeholder deposit amount (cents) until a real per-booking calc lands. */
const DEFAULT_DEPOSIT_CENTS = 30000

/**
 * Lifecycle rule R1, for a single booking: ensure a deposit invoice exists,
 * send the contract+deposit email, then stamp `contractSentAt`. The
 * invoice-existence check (not `contractSentAt`) makes the whole sequence
 * safely re-entrant even if a prior run died after the email.
 */
export async function dispatchContract(
  { kysely, email }: Pick<LifecycleServices, 'kysely' | 'email'>,
  booking: { bookingId: string; venueId: string },
  todayYmd: string,
): Promise<void> {
  const existing = await kysely
    .selectFrom('invoice')
    .where('bookingId', '=', booking.bookingId)
    .where('kind', '=', 'deposit')
    .select('invoiceId')
    .executeTakeFirst()

  if (!existing) {
    await kysely
      .insertInto('invoice')
      .values({
        invoiceId: `inv_${booking.bookingId}_dep`,
        bookingId: booking.bookingId,
        kind: 'deposit',
        invoiceNumber: `DEP-${todayYmd}-${booking.bookingId}`,
        issuedOn: todayYmd,
        dueOn: addDays(todayYmd, DEPOSIT_WINDOW_DAYS),
        paidOn: null,
        amountCents: DEFAULT_DEPOSIT_CENTS,
        status: 'outstanding',
      })
      .execute()
  }

  await email.sendContractAndDepositEmail(booking.bookingId)

  const now = new Date().toISOString()

  await kysely
    .updateTable('booking')
    .set({ contractSentAt: now })
    .where('bookingId', '=', booking.bookingId)
    .execute()

  await kysely
    .insertInto('auditLog')
    .values({
      auditId:
        globalThis.crypto?.randomUUID?.() ??
        `audit_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
      venueId: booking.venueId,
      userId: null,
      entity: 'booking',
      entityId: booking.bookingId,
      field: null,
      beforeValue: null,
      afterValue: 'sendContractAndDepositEmail',
      action: 'email_sent',
    })
    .execute()
}

export type LifecycleSummary = {
  date: string
  contractsSent: number
  reminders: number
  flagged: number
  ended: number
}

/**
 * One daily sweep over active bookings, applying rules R1–R4 (see
 * docs/booking-lifecycle.md). Returns a counts summary for logging/dev.
 */
export async function runBookingLifecycle(
  services: LifecycleServices,
): Promise<LifecycleSummary> {
  const { kysely, email, logger } = services
  const today = berlinDate()

  const bookings = await kysely
    .selectFrom('booking')
    .where('status', 'in', ['reserved', 'confirmed'])
    .select([
      'bookingId',
      'venueId',
      'status',
      'startDate',
      'endDate',
      'contractSentAt',
      'depositReminderSentAt',
      'flaggedAt',
    ])
    .execute()

  const summary: LifecycleSummary = {
    date: today,
    contractsSent: 0,
    reminders: 0,
    flagged: 0,
    ended: 0,
  }

  for (const b of bookings) {
    // Lifecycle rules are all date-driven; a booking without dates (an
    // enquiry that hasn't been scheduled yet) has nothing to act on.
    if (b.startDate == null || b.endDate == null) continue

    // R4 — auto-end a confirmed booking once its event has ended.
    if (b.status === 'confirmed') {
      if (b.endDate < today) {
        await applyBookingTransition(services, {
          bookingId: b.bookingId,
          to: 'ended',
          userId: null,
        })
        summary.ended++
      }
      continue
    }

    // status === 'reserved' below.

    // R1 — dispatch the contract ~1yr before start (daily `<=`, not `==`).
    if (!b.contractSentAt) {
      if (daysBetween(today, b.startDate) <= 365) {
        await dispatchContract(services, b, today)
        summary.contractsSent++
      }
      continue // freshly sent — reminders/flags begin on later ticks
    }

    // Contract sent → drive deposit reminders/flags off the deposit invoice.
    const deposit = await kysely
      .selectFrom('invoice')
      .where('bookingId', '=', b.bookingId)
      .where('kind', '=', 'deposit')
      .select(['dueOn', 'paidOn'])
      .executeTakeFirst()

    if (deposit?.paidOn) continue // deposit settled — nothing to chase

    // contractSentAt is a real Date via CoercionPlugin.
    const daysSinceContract = daysBetween(berlinDate(b.contractSentAt as Date), today)

    // R2 — day-7 reminder while the deposit is still unpaid.
    if (!b.depositReminderSentAt && daysSinceContract >= DEPOSIT_REMINDER_DAYS) {
      await email.sendDepositReminderEmail(b.bookingId)
      const reminderNow = new Date().toISOString()
      await kysely
        .updateTable('booking')
        .set({ depositReminderSentAt: reminderNow })
        .where('bookingId', '=', b.bookingId)
        .execute()
      await kysely
        .insertInto('auditLog')
        .values({
          auditId:
            globalThis.crypto?.randomUUID?.() ??
            `audit_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
          venueId: b.venueId,
          userId: null,
          entity: 'booking',
          entityId: b.bookingId,
          field: null,
          beforeValue: null,
          afterValue: 'sendDepositReminderEmail',
          action: 'email_sent',
        })
        .execute()
      summary.reminders++
    }

    // R3 — past due → FLAG ONLY (deadline = invoice.dueOn, admin-overridable).
    // dueOn is a Date via CoercionPlugin; convert to Berlin YYYY-MM-DD for comparison.
    if (!b.flaggedAt && deposit?.dueOn && berlinDate(deposit.dueOn as Date) < today) {
      await kysely
        .updateTable('booking')
        .set({ flaggedAt: new Date().toISOString(), flagReason: 'deposit_overdue' })
        .where('bookingId', '=', b.bookingId)
        .execute()
      summary.flagged++
    }
  }

  logger.info(`[booking-lifecycle] ${JSON.stringify(summary)}`)
  return summary
}