/**
 * Email notifications via your own SMTP server (nodemailer).
 *
 * Required env vars:
 *   SMTP_HOST        — your mail server hostname (e.g. mail.beachpartyballoons.com)
 *   SMTP_PORT        — 587 (STARTTLS) or 465 (SSL), defaults to 587
 *   SMTP_USER        — SMTP login username
 *   SMTP_PASS        — SMTP login password
 *   ALERT_EMAIL_TO   — address that receives alerts (e.g. chris@beachpartyballoons.com)
 *   ALERT_EMAIL_FROM — sender address (e.g. shop@beachpartyballoons.com)
 */

import nodemailer from 'nodemailer'

// ── Shared helpers ─────────────────────────────────────────────────────────────

/** Format a slot as "4/14/26 2:00 PM" */
function fmtDate(iso: string): string {
  const d = new Date(iso)
  const { month, day, year, hour, minute, dayPeriod } = Object.fromEntries(
    new Intl.DateTimeFormat('en-US', {
      timeZone: 'America/New_York',
      month: 'numeric', day: 'numeric', year: '2-digit',
      hour: 'numeric', minute: '2-digit', hour12: true,
    }).formatToParts(d).map(({ type, value }) => [type, value])
  )
  return `${month}/${day}/${year} ${hour}:${minute} ${dayPeriod}`
}

/** Format a window as "4/14/26 2:00 – 5:00 PM" (shared date, shared AM/PM if same) */
function fmtWindow(startISO: string, endISO: string): string {
  const start = fmtDate(startISO)   // "4/14/26 2:00 PM"
  const endTime = new Intl.DateTimeFormat('en-US', {
    timeZone: 'America/New_York',
    hour: 'numeric', minute: '2-digit', hour12: true,
  }).format(new Date(endISO))       // "5:00 PM"
  // Strip the time portion from start and append range
  const datePart = start.replace(/ \d+:\d+ [AP]M$/, '')
  return `${datePart} ${start.match(/\d+:\d+ [AP]M$/)?.[0]} – ${endTime}`
}

// ── Shared types ───────────────────────────────────────────────────────────────

export interface EmailLineItem {
  name:       string
  quantity:   number
  priceCents: number
  colors?:    string[]
  note?:      string
  modifiers?: Array<{ name: string }>
}

function formatLineItems(lineItems: EmailLineItem[]): string {
  return lineItems.map((li) => {
    const price = `$${(li.priceCents / 100).toFixed(2)}`
    const lines = [`${li.quantity}× ${li.name} — ${price}`]
    if (li.modifiers?.length) lines.push(`  Add-ons: ${li.modifiers.map((m) => m.name).join(', ')}`)
    if (li.colors?.length)    lines.push(`  Colors: ${li.colors.join(', ')}`)
    if (li.note)              lines.push(`  Note: ${li.note}`)
    return lines.join('\n')
  }).join('\n')
}

function getTransporter() {
  const host = process.env.SMTP_HOST
  const port = parseInt(process.env.SMTP_PORT ?? '587', 10)
  const user = process.env.SMTP_USER
  const pass = process.env.SMTP_PASS

  if (!host || !user || !pass) return null

  return nodemailer.createTransport({
    host,
    port,
    secure: port === 465,
    auth: { user, pass },
  })
}

async function send(params: {
  to:           string
  subject:      string
  text:         string
  attachments?: Array<{ filename: string; content: string; contentType: string }>
}): Promise<void> {
  const from        = process.env.ALERT_EMAIL_FROM ?? 'shop@beachpartyballoons.com'
  const transporter = getTransporter()

  if (!transporter) {
    const missing = ['SMTP_HOST', 'SMTP_USER', 'SMTP_PASS'].filter((k) => !process.env[k])
    console.error('[notify] SMTP not configured — missing env vars:', missing.join(', '), '— email skipped:', params.subject)
    return
  }

  try {
    await transporter.sendMail({
      from,
      to:          params.to,
      subject:     params.subject,
      text:        params.text,
      attachments: params.attachments,
    })
    console.log('[notify] Email sent:', params.subject, '→', params.to)
  } catch (err: unknown) {
    const msg = err instanceof Error ? err.message : String(err)
    console.error('[notify] SMTP send failed:', msg, '| subject:', params.subject, '| to:', params.to)
    throw err   // re-throw so callers can handle/log it
  }
}

// ── ICS builder for customer calendar attachment ────────────────────────────

function buildCustomerICS(params: {
  uid:        string
  startISO:   string
  endISO:     string
  summary:    string
  description: string
  location?:  string
}): string {
  function toStamp(d: Date): string {
    return d.toISOString().replace(/[-:]/g, '').replace(/\.\d{3}/, '')
  }
  function toET(d: Date): string {
    const parts = new Intl.DateTimeFormat('en-US', {
      timeZone: 'America/New_York',
      year: 'numeric', month: '2-digit', day: '2-digit',
      hour: '2-digit', minute: '2-digit', second: '2-digit', hour12: false,
    }).formatToParts(d)
    const p: Record<string, string> = {}
    for (const { type, value } of parts) p[type] = value
    const h = p.hour === '24' ? '00' : p.hour
    return `${p.year}${p.month}${p.day}T${h}${p.minute}${p.second}`
  }
  function fold(s: string): string {
    const out: string[] = []
    while (s.length > 73) { out.push(s.slice(0, 73)); s = ' ' + s.slice(73) }
    out.push(s)
    return out.join('\r\n')
  }

  const start = new Date(params.startISO)
  const end   = new Date(params.endISO)
  const lines = [
    'BEGIN:VCALENDAR',
    'VERSION:2.0',
    'PRODID:-//BeachPartyBalloons//Shop//EN',
    'BEGIN:VEVENT',
    `UID:${params.uid}`,
    `DTSTAMP:${toStamp(new Date())}`,
    `DTSTART;TZID=America/New_York:${toET(start)}`,
    `DTEND;TZID=America/New_York:${toET(end)}`,
    fold(`SUMMARY:${params.summary}`),
    ...(params.location ? [fold(`LOCATION:${params.location}`)] : []),
    fold(`DESCRIPTION:${params.description}`),
    'STATUS:CONFIRMED',
    'END:VEVENT',
    'END:VCALENDAR',
  ]
  return lines.join('\r\n')
}

// ── Public helpers ─────────────────────────────────────────────────────────────

export async function sendOrderConfirmationEmail(params: {
  shortRef:       string
  orderId:        string
  customerName:   string
  customerEmail:  string
  fulfillment:    'delivery' | 'pickup'
  slotISO:        string
  slotEndISO?:    string
  address?:       string
  lineItems:      EmailLineItem[]
  colors:         string[]   // order-level color selection (when not per-item)
  subtotalCents?: number
  deliveryCents?: number
  totalCents:     bigint
}): Promise<void> {
  const isDelivery = params.fulfillment === 'delivery'
  const slotStr    = params.slotEndISO
    ? fmtWindow(params.slotISO, params.slotEndISO)
    : fmtDate(params.slotISO)
  const total      = `$${(Number(params.totalCents) / 100).toFixed(2)}`

  // Charges breakdown (only shown when subtotal is provided)
  const chargesLines: string[] = []
  if (params.subtotalCents != null) {
    chargesLines.push(`Subtotal:  $${(params.subtotalCents / 100).toFixed(2)}`)
    if (params.deliveryCents) {
      chargesLines.push(`Delivery:  $${(params.deliveryCents / 100).toFixed(2)}`)
    }
    const impliedTax = Number(params.totalCents) - (params.subtotalCents) - (params.deliveryCents ?? 0)
    if (impliedTax > 0) {
      chargesLines.push(`Tax:       $${(impliedTax / 100).toFixed(2)}`)
    }
    chargesLines.push(`Total:     ${total}`)
  } else {
    chargesLines.push(`Total:     ${total}`)
  }

  const itemsBlock  = formatLineItems(params.lineItems)
  // Order-level colors (when colors aren't set per-item)
  const hasPerItemColors = params.lineItems.some((li) => li.colors?.length)
  const orderColors = !hasPerItemColors && params.colors.length ? params.colors : []

  const lines = [
    `Hi ${params.customerName.split(' ')[0]},`,
    ``,
    `Your order is confirmed! Here's a summary:`,
    ``,
    `Order #: ${params.shortRef}`,
    ``,
    itemsBlock,
    ...(orderColors.length ? [``, `Colors: ${orderColors.join(', ')}`] : []),
    ``,
    isDelivery ? `Delivery: ${slotStr}` : `Pickup:   ${slotStr}`,
    ...(params.address ? [`Address: ${params.address}`] : []),
    ``,
    ...chargesLines,
    ``,
    isDelivery
      ? `If you need to make any changes, please call or text us as soon as possible.`
      : [
          `Pick up at 554 Boston Post Rd, Milford CT 06460.`,
          `Please bring this confirmation. If you need to reschedule, give us a call!`,
        ].join('\n'),
    ``,
    `Thank you for choosing Beach Party Balloons!`,
    ``,
    `— The Beach Party Balloons Team`,
    `beachpartyballoons.com`,
  ]

  // Build ICS calendar attachment
  const icsEndISO  = params.slotEndISO ?? new Date(new Date(params.slotISO).getTime() + 60 * 60_000).toISOString()
  const itemsSummary = params.lineItems.map((li) => `${li.quantity}× ${li.name}`).join(', ')
  const icsDesc    = [
    `Order #${params.shortRef}`,
    `Items: ${itemsSummary}`,
    ...(params.colors.length ? [`Colors: ${params.colors.join(', ')}`] : []),
    ...(params.address ? [`Address: ${params.address}`] : []),
  ].join('\\n')
  const icsSummary  = isDelivery ? 'Balloon Delivery — Beach Party Balloons' : 'Balloon Pickup — Beach Party Balloons'
  const icsContent  = buildCustomerICS({
    uid:         `customer-${params.orderId}@beachpartyballoons.com`,
    startISO:    params.slotISO,
    endISO:      icsEndISO,
    summary:     icsSummary,
    description: icsDesc,
    location:    params.address ?? (isDelivery ? undefined : '554 Boston Post Rd, Milford CT 06460'),
  })

  await send({
    to:      params.customerEmail,
    subject: `Your Beach Party Balloons order is confirmed! (#${params.shortRef})`,
    text:    lines.join('\n'),
    attachments: [{
      filename:    'appointment.ics',
      content:     icsContent,
      contentType: 'text/calendar; method=REQUEST',
    }],
  })
}

export async function sendSlotConflictAlert(params: {
  shortRef:     string
  orderId:      string
  customerName: string
  customerPhone: string
  slotISO:      string
  address:      string
  items:        string
}): Promise<void> {
  const to = process.env.ALERT_EMAIL_TO
  if (!to) { console.warn('[notify] ALERT_EMAIL_TO not set'); return }

  await send({
    to,
    subject: `🚨 ACTION REQUIRED: Slot not blocked — Order #${params.shortRef}`,
    text: [
      `URGENT — Payment succeeded but the delivery slot was NOT written to your calendar.`,
      ``,
      `You must manually block this slot immediately to prevent a double-booking.`,
      ``,
      `Order:    #${params.shortRef}  (${params.orderId})`,
      `Customer: ${params.customerName}  ${params.customerPhone}`,
      `Slot:     ${fmtDate(params.slotISO)}`,
      `Address:  ${params.address}`,
      `Items:    ${params.items}`,
      ``,
      `Steps:`,
      `  1. Block the slot in your calendar now.`,
      `  2. Confirm the booking with the customer by phone.`,
      `  3. Check Square dashboard for the full order details.`,
    ].join('\n'),
  })
}

export async function sendNewOrderAlert(params: {
  shortRef:       string
  orderId:        string
  customerName:   string
  customerPhone:  string
  customerEmail:  string
  fulfillment:    'delivery' | 'pickup'
  slotISO:        string
  slotEndISO?:    string
  address?:       string
  lineItems:      EmailLineItem[]
  colors:         string[]
  subtotalCents?: number
  deliveryCents?: number
  totalCents:     bigint
}): Promise<void> {
  const to = process.env.ALERT_EMAIL_TO
  if (!to) return

  const slotStr = params.slotEndISO
    ? fmtWindow(params.slotISO, params.slotEndISO)
    : fmtDate(params.slotISO)
  const total   = `$${(Number(params.totalCents) / 100).toFixed(2)}`

  const chargesLines: string[] = []
  if (params.subtotalCents != null) {
    chargesLines.push(`Subtotal: $${(params.subtotalCents / 100).toFixed(2)}`)
    if (params.deliveryCents) {
      chargesLines.push(`Delivery: $${(params.deliveryCents / 100).toFixed(2)}`)
    }
    const impliedTax = Number(params.totalCents) - params.subtotalCents - (params.deliveryCents ?? 0)
    if (impliedTax > 0) {
      chargesLines.push(`Tax:      $${(impliedTax / 100).toFixed(2)}`)
    }
    chargesLines.push(`Total:    ${total}`)
  } else {
    chargesLines.push(`Total:    ${total}`)
  }

  const slotLine = params.fulfillment === 'delivery'
    ? `Delivery: ${slotStr}`
    : `Pickup:   ${slotStr}`

  const itemsBlock = formatLineItems(params.lineItems)
  const hasPerItemColors = params.lineItems.some((li) => li.colors?.length)
  const orderColors = !hasPerItemColors && params.colors.length ? params.colors : []

  const lines = [
    `New ${params.fulfillment} order — #${params.shortRef}`,
    ``,
    `Customer: ${params.customerName}`,
    `Phone:    ${params.customerPhone}`,
    `Email:    ${params.customerEmail}`,
    ``,
    slotLine,
    ...(params.address ? [`Address:  ${params.address}`] : []),
    ``,
    itemsBlock,
    ...(orderColors.length ? [``, `Colors: ${orderColors.join(', ')}`] : []),
    ``,
    ...chargesLines,
    ``,
    `View in Square: https://squareup.com/dashboard/orders`,
  ]

  await send({
    to,
    subject: `🎈 New order #${params.shortRef} — ${params.customerName} (${params.fulfillment})`,
    text:    lines.join('\n'),
  })
}