import { getDb } from '../db/client.js'
import { getMaxCustomersPerMitra, getPairingBlastTimeoutSeconds, getReturningChatConfirmationTimeoutSeconds } from './config.service.js'
import { sendToUser } from '../plugins/websocket.js'
import { sendPushNotification } from './notification.service.js'
import { startSessionTimer } from './session-timer.service.js'
import { startSessionListener } from './chat-handler.service.js'
import { consumePaymentSession, failPaymentSession, getPaymentSession, recordIntermediateFailure } from './payment.service.js'
import { isMitraReachable, isMitraInActiveSessionWithCustomer, getMitraActiveSessionCount } from './mitra-status.service.js'
import {
  UserType,
  SessionStatus,
  NotificationResponse,
  TransactionType,
  WsMessage,
  TopicSensitivity,
  PaymentSessionStatus,
  PairingFailureCause,
  PairingRequestType,
} from '../constants.js'

const sql = getDb()

// Timeout map for active pairing requests (sessionId → timeoutId)
const pairingTimeouts = new Map()

// Send notification to mitra via WebSocket, fall back to FCM if offline
const notifyMitra = async (mitraId, data) => {
  const sent = sendToUser(UserType.MITRA, mitraId, data)
  if (!sent) {
    // Mitra not connected via WebSocket — send FCM push
    if (data.type === WsMessage.CHAT_REQUEST) {
      await sendPushNotification(UserType.MITRA, mitraId, {
        title: 'Permintaan Chat Baru',
        body: 'Ada pelanggan yang ingin curhat! Ketuk untuk menerima.',
        data: {
          type: WsMessage.CHAT_REQUEST,
          session_id: data.session_id,
          request_type: data.request_type || PairingRequestType.GENERAL,
          action: 'open_accept',
        },
      })
    }
  }
}

// Send notification to customer via WebSocket, fall back to FCM if offline
const notifyCustomer = async (customerId, data) => {
  const sent = sendToUser(UserType.CUSTOMER, customerId, data)
  console.log(`[notifyCustomer] customerId=${customerId} type=${data.type} ws_sent=${sent}`)
  if (!sent) {
    if (data.type === WsMessage.PAIRED) {
      await sendPushNotification(UserType.CUSTOMER, customerId, {
        title: 'Bestie Ditemukan!',
        body: `${data.mitra_display_name} siap menemanimu curhat`,
        data: { type: WsMessage.PAIRED, session_id: data.session_id },
      })
    } else if (data.type === WsMessage.SESSION_EXPIRED) {
      await sendPushNotification(UserType.CUSTOMER, customerId, {
        title: 'Tidak Ada Bestie',
        body: 'Maaf, tidak ada bestie yang tersedia saat ini.',
        data: { type: WsMessage.SESSION_EXPIRED, session_id: data.session_id },
      })
    } else if (data.type === WsMessage.PAIRING_FAILED) {
      // Terminal pairing failure on a confirmed payment. Push so the customer
      // can come back to the app and see the failed-pairing screen / contact support.
      await sendPushNotification(UserType.CUSTOMER, customerId, {
        title: 'Sesi gagal',
        body: 'Maaf, kami tidak bisa menemukan bestie untuk sesimu. Tim kami akan menghubungimu segera.',
        data: {
          type: WsMessage.PAIRING_FAILED,
          payment_session_id: data.payment_session_id || '',
          cause_tag: data.cause_tag || '',
        },
      })
    }
  }
}

export const findAvailableMitras = async () => {
  const { max_customers_per_mitra } = await getMaxCustomersPerMitra()
  // Project active_session_count alongside the mitra row so the blast loop doesn't
  // need a per-mitra COUNT roundtrip later.
  const mitras = await sql`
    SELECT m.id, m.display_name, sub.active_session_count
    FROM mitras m
    INNER JOIN mitra_online_status s ON s.mitra_id = m.id
    INNER JOIN LATERAL (
      SELECT COUNT(*)::int AS active_session_count
      FROM chat_sessions cs
      WHERE cs.mitra_id = m.id AND cs.status IN (${SessionStatus.ACTIVE}, ${SessionStatus.PENDING_PAYMENT})
    ) sub ON true
    WHERE m.is_active = true
      AND s.is_online = true
      AND sub.active_session_count < ${max_customers_per_mitra}
  `
  return mitras
}

/**
 * Validate that a payment session is owned by the customer, confirmed, and not yet consumed.
 * Throws on mismatch. Returns the loaded payment session row.
 */
const requireConfirmedPaymentSession = async (paymentSessionId, customerId, { allowExtension = false } = {}) => {
  if (!paymentSessionId) {
    throw Object.assign(new Error('payment_session_id is required'), {
      code: 'VALIDATION_ERROR', statusCode: 422,
    })
  }
  const paySession = await getPaymentSession(paymentSessionId)
  if (!paySession) {
    throw Object.assign(new Error('Payment session not found'), { code: 'NOT_FOUND', statusCode: 404 })
  }
  if (paySession.customer_id !== customerId) {
    throw Object.assign(new Error('Payment session does not belong to this customer'), {
      code: 'FORBIDDEN', statusCode: 403,
    })
  }
  if (paySession.status !== PaymentSessionStatus.CONFIRMED) {
    throw Object.assign(new Error(`Payment session is ${paySession.status}, must be confirmed`), {
      code: 'INVALID_STATE', statusCode: 409,
    })
  }
  if (paySession.is_extension && !allowExtension) {
    throw Object.assign(new Error('Extension payment session cannot be used to start a new chat'), {
      code: 'INVALID_STATE', statusCode: 409,
    })
  }
  if (new Date(paySession.expires_at) <= new Date()) {
    // Check expiry inline at every state transition (defense in depth vs. the background sweeper).
    await failPaymentSession(paymentSessionId, PairingFailureCause.PAYMENT_SESSION_EXPIRED)
    throw Object.assign(new Error('Payment session has expired'), { code: 'EXPIRED', statusCode: 409 })
  }
  return paySession
}

/**
 * General-blast pairing request. Requires a confirmed payment_session_id.
 *
 * The duration_minutes / price / is_first_session_discount values for the chat_session row are
 * sourced from the payment session — the client does not dictate pricing here.
 *
 * `allowTargetedPayment` is set true by the fallback-to-blast path: the original payment
 * was created with a `targeted_mitra_id` for "Curhat lagi" but the customer chose to
 * fall back to general blast on the same payment. The flag bypasses the
 * "use returning-chat endpoint" guard in that exact case.
 */
export const createPairingRequest = async (customerId, { paymentSessionId, topic_sensitivity, allowTargetedPayment = false } = {}) => {
  const paySession = await requireConfirmedPaymentSession(paymentSessionId, customerId)

  // Targeted payment session must use createTargetedPairingRequest unless we're
  // explicitly invoked by the fallback-to-blast path.
  if (paySession.targeted_mitra_id && !allowTargetedPayment) {
    throw Object.assign(new Error('Payment session is targeted to a specific mitra; use returning-chat endpoint'), {
      code: 'INVALID_STATE', statusCode: 409,
    })
  }

  // Check for existing active session or request
  const [existing] = await sql`
    SELECT id, status FROM chat_sessions
    WHERE customer_id = ${customerId}
      AND status IN (${SessionStatus.SEARCHING}, ${SessionStatus.PENDING_ACCEPTANCE}, ${SessionStatus.PENDING_PAYMENT}, ${SessionStatus.ACTIVE})
  `
  if (existing) {
    throw Object.assign(new Error('Customer already has an active session or request'), {
      code: 'ALREADY_ACTIVE', statusCode: 409,
    })
  }

  const availableMitras = await findAvailableMitras()
  if (availableMitras.length === 0) {
    // No mitras to blast to — fail the payment immediately.
    await failPaymentSession(paymentSessionId, PairingFailureCause.NO_MITRA_AVAILABLE)
    throw Object.assign(new Error('No bestie available'), {
      code: 'NO_MITRA_AVAILABLE', statusCode: 404,
    })
  }

  const resolvedTopic = topic_sensitivity === TopicSensitivity.SENSITIVE
    ? TopicSensitivity.SENSITIVE
    : TopicSensitivity.REGULAR

  // Create session sourced from the payment session.
  const [session] = await sql`
    INSERT INTO chat_sessions (
      customer_id, status, duration_minutes, price, is_first_session_discount, topic_sensitivity, payment_session_id
    )
    VALUES (
      ${customerId}, ${SessionStatus.PENDING_ACCEPTANCE},
      ${paySession.duration_minutes}, ${paySession.amount}, ${paySession.is_first_session_discount},
      ${resolvedTopic}, ${paymentSessionId}
    )
    RETURNING id, customer_id, status, duration_minutes, price, is_first_session_discount, topic_sensitivity, payment_session_id, created_at
  `

  // Fan out to all available mitras in parallel — DB inserts and notifications are
  // independent per mitra. active_session_count was already projected by findAvailableMitras.
  await Promise.all(availableMitras.map(async (mitra) => {
    await sql`
      INSERT INTO chat_request_notifications (session_id, mitra_id, active_session_count)
      VALUES (${session.id}, ${mitra.id}, ${mitra.active_session_count})
    `
    await notifyMitra(mitra.id, {
      type: WsMessage.CHAT_REQUEST,
      session_id: session.id,
      request_type: PairingRequestType.GENERAL,
      created_at: session.created_at,
      duration_minutes: session.duration_minutes,
      is_first_session_discount: session.is_first_session_discount,
      topic_sensitivity: session.topic_sensitivity,
    })
  }))

  // Start blast timeout (configurable via app_config)
  const { pairing_blast_timeout_seconds } = await getPairingBlastTimeoutSeconds()
  const timeoutId = setTimeout(async () => {
    try {
      await expirePairingRequest(session.id, PairingFailureCause.NO_MITRA_AVAILABLE)
    } catch (err) {
      console.error('expirePairingRequest failed', { sessionId: session.id, err })
    }
  }, pairing_blast_timeout_seconds * 1000)
  pairingTimeouts.set(session.id, timeoutId)

  return session
}

/**
 * Targeted pairing request for "Curhat lagi" (returning chat).
 *
 *   - Pre-check targeted mitra reachability + capacity. If unreachable or at-capacity-and-not-mid-session
 *     with this customer → fail payment immediately and return 409 with `reason: 'targeted_mitra_offline'`.
 *   - Fire ONE notification to the targeted mitra.
 *   - Start a server-side timer of `returning_chat_confirmation_timeout_seconds`. On expiry,
 *     mark request auto-rejected, fail payment with `targeted_mitra_timeout`, push WS event.
 *   - On explicit decline by mitra: fail payment with `targeted_mitra_rejected`, push WS event.
 *   - On accept: existing accept path runs (consumes payment session as for general blast).
 */
export const createTargetedPairingRequest = async (customerId, { paymentSessionId, targetedMitraId, topic_sensitivity } = {}) => {
  const paySession = await requireConfirmedPaymentSession(paymentSessionId, customerId)

  if (!targetedMitraId) {
    throw Object.assign(new Error('targetedMitraId is required'), { code: 'VALIDATION_ERROR', statusCode: 422 })
  }
  // Cross-check: payment_session.targeted_mitra_id should match (if set).
  if (paySession.targeted_mitra_id && paySession.targeted_mitra_id !== targetedMitraId) {
    throw Object.assign(new Error('targetedMitraId does not match payment session'), {
      code: 'INVALID_STATE', statusCode: 409,
    })
  }

  // Check for existing active session or request
  const [existing] = await sql`
    SELECT id, status FROM chat_sessions
    WHERE customer_id = ${customerId}
      AND status IN (${SessionStatus.SEARCHING}, ${SessionStatus.PENDING_ACCEPTANCE}, ${SessionStatus.PENDING_PAYMENT}, ${SessionStatus.ACTIVE})
  `
  if (existing) {
    throw Object.assign(new Error('Customer already has an active session or request'), {
      code: 'ALREADY_ACTIVE', statusCode: 409,
    })
  }

  // Pre-check: mitra reachable?
  const reachable = await isMitraReachable(targetedMitraId)
  if (!reachable) {
    // Intermediate failure: audit row written, payment stays `confirmed` so the customer
    // can choose to fall back to general blast (or cancel, which terminates).
    await recordIntermediateFailure({
      paymentSessionId,
      customerId,
      targetedMitraId,
      causeTag: PairingFailureCause.TARGETED_MITRA_OFFLINE,
      amount: paySession.amount,
    })
    throw Object.assign(new Error('Targeted mitra is offline'), {
      code: 'TARGETED_MITRA_OFFLINE', statusCode: 409, reason: 'targeted_mitra_offline',
    })
  }

  // Pre-check: mitra at capacity AND not mid-session with this customer?
  const { max_customers_per_mitra } = await getMaxCustomersPerMitra()
  const activeCount = await getMitraActiveSessionCount(targetedMitraId)
  if (activeCount >= max_customers_per_mitra) {
    const midSessionWithCustomer = await isMitraInActiveSessionWithCustomer(targetedMitraId, customerId)
    if (!midSessionWithCustomer) {
      await recordIntermediateFailure({
        paymentSessionId,
        customerId,
        targetedMitraId,
        causeTag: PairingFailureCause.TARGETED_MITRA_OFFLINE,
        amount: paySession.amount,
      })
      throw Object.assign(new Error('Targeted mitra is at capacity'), {
        code: 'TARGETED_MITRA_OFFLINE', statusCode: 409, reason: 'targeted_mitra_offline',
      })
    }
    // Else: at-capacity but mid-session with the requesting customer — request allowed through.
  }

  const resolvedTopic = topic_sensitivity === TopicSensitivity.SENSITIVE
    ? TopicSensitivity.SENSITIVE
    : TopicSensitivity.REGULAR

  // Create session sourced from the payment session, status = pending_acceptance.
  const [session] = await sql`
    INSERT INTO chat_sessions (
      customer_id, status, duration_minutes, price, is_first_session_discount, topic_sensitivity, payment_session_id
    )
    VALUES (
      ${customerId}, ${SessionStatus.PENDING_ACCEPTANCE},
      ${paySession.duration_minutes}, ${paySession.amount}, ${paySession.is_first_session_discount},
      ${resolvedTopic}, ${paymentSessionId}
    )
    RETURNING id, customer_id, status, duration_minutes, price, is_first_session_discount, topic_sensitivity, payment_session_id, created_at
  `

  // Single notification to the targeted mitra
  await sql`
    INSERT INTO chat_request_notifications (session_id, mitra_id, active_session_count)
    VALUES (${session.id}, ${targetedMitraId}, ${activeCount})
  `
  // Server-side timer (configurable, default 20s) — also surfaced in the WS payload so the mitra
  // app countdown UI matches what the server is enforcing.
  const { returning_chat_confirmation_timeout_seconds } = await getReturningChatConfirmationTimeoutSeconds()

  await notifyMitra(targetedMitraId, {
    type: WsMessage.CHAT_REQUEST,
    session_id: session.id,
    request_type: PairingRequestType.RETURNING,
    created_at: session.created_at,
    duration_minutes: session.duration_minutes,
    is_first_session_discount: session.is_first_session_discount,
    topic_sensitivity: session.topic_sensitivity,
    confirmation_timeout_seconds: returning_chat_confirmation_timeout_seconds,
  })

  const timeoutId = setTimeout(async () => {
    try {
      await expireTargetedPairingRequest(session.id)
    } catch (err) {
      console.error('expireTargetedPairingRequest failed', { sessionId: session.id, err })
    }
  }, returning_chat_confirmation_timeout_seconds * 1000)
  pairingTimeouts.set(session.id, timeoutId)

  // Surface the timeout to the customer so the targeted-waiting overlay countdown
  // matches the server-side timer exactly (CC-configurable; never stale).
  return { ...session, confirmation_timeout_seconds: returning_chat_confirmation_timeout_seconds }
}

export const acceptPairingRequest = async (sessionId, mitraId) => {
  // Use a transaction-like approach: update only if status is still pending_acceptance
  const [session] = await sql`
    UPDATE chat_sessions
    SET mitra_id = ${mitraId}, status = ${SessionStatus.PENDING_PAYMENT}, paired_at = NOW()
    WHERE id = ${sessionId} AND status = ${SessionStatus.PENDING_ACCEPTANCE} AND mitra_id IS NULL
    RETURNING id, customer_id, mitra_id, status, paired_at, payment_session_id
  `

  if (!session) {
    throw Object.assign(new Error('Request already accepted or expired'), {
      code: 'REQUEST_UNAVAILABLE', statusCode: 409,
    })
  }

  // Mark this mitra's notification as accepted
  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.ACCEPTED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND mitra_id = ${mitraId}
  `

  // Mark other mitras' notifications as missed (another mitra accepted)
  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.MISSED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND mitra_id != ${mitraId} AND response IS NULL
  `

  // Clear timeout
  const timeoutId = pairingTimeouts.get(sessionId)
  if (timeoutId) {
    clearTimeout(timeoutId)
    pairingTimeouts.delete(sessionId)
  }

  // Consume the payment session at the moment of acceptance.
  if (session.payment_session_id) {
    await consumePaymentSession(session.payment_session_id)
  }

  // Activate the session and set expires_at.
  const [activeSession] = await sql`
    UPDATE chat_sessions
    SET status = ${SessionStatus.ACTIVE},
        expires_at = CASE
          WHEN duration_minutes IS NOT NULL THEN NOW() + (duration_minutes || ' minutes')::interval
          ELSE NULL
        END
    WHERE id = ${sessionId}
    RETURNING id, customer_id, mitra_id, status, paired_at, duration_minutes, price, is_first_session_discount, expires_at, payment_session_id
  `

  // Record transaction
  if (activeSession.duration_minutes) {
    const txType = activeSession.is_first_session_discount ? TransactionType.FIRST_SESSION_DISCOUNT : TransactionType.PAID
    await sql`
      INSERT INTO customer_transactions (customer_id, session_id, type, amount)
      VALUES (${activeSession.customer_id}, ${sessionId}, ${txType}, ${activeSession.price || 0})
    `
  }

  // Start session timer if duration is set
  if (activeSession.expires_at) {
    startSessionTimer(sessionId, activeSession.expires_at)
  }

  // Start chat message listener for this session
  startSessionListener(sessionId)

  // Get mitra display name for customer notification
  const [mitra] = await sql`
    SELECT display_name FROM mitras WHERE id = ${mitraId}
  `

  // Notify customer via WebSocket (FCM fallback)
  await notifyCustomer(activeSession.customer_id, {
    type: WsMessage.PAIRED,
    session_id: sessionId,
    mitra_display_name: mitra.display_name,
    status: SessionStatus.ACTIVE,
  })

  // Notify other mitras to dismiss the request — independent fan-out, run in parallel.
  const notifications = await sql`
    SELECT mitra_id FROM chat_request_notifications
    WHERE session_id = ${sessionId} AND mitra_id != ${mitraId}
  `
  await Promise.all(notifications.map((n) => notifyMitra(n.mitra_id, {
    type: WsMessage.CHAT_REQUEST_CLOSED,
    session_id: sessionId,
    reason: 'accepted_by_other',
  })))

  return activeSession
}

export const declinePairingRequest = async (sessionId, mitraId) => {
  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.DECLINED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND mitra_id = ${mitraId} AND response IS NULL
  `

  // Targeted-vs-general is determined by the payment_session.targeted_mitra_id, not by
  // notification count — a general blast with only one online mitra also has length=1.
  const [targetCheck] = await sql`
    SELECT ps.targeted_mitra_id
    FROM chat_sessions cs
    LEFT JOIN payment_sessions ps ON ps.id = cs.payment_session_id
    WHERE cs.id = ${sessionId}
  `
  const isTargeted = !!targetCheck?.targeted_mitra_id

  if (isTargeted) {
    // Mark the chat_session as expired (the targeted attempt is over) — but keep the
    // payment_session in `confirmed` so the customer can fall back to general blast on
    // the same payment, or cancel (which then terminates).
    const [session] = await sql`
      UPDATE chat_sessions
      SET status = ${SessionStatus.EXPIRED}
      WHERE id = ${sessionId} AND status = ${SessionStatus.PENDING_ACCEPTANCE}
      RETURNING id, customer_id, payment_session_id
    `
    if (session) {
      // Clear the 20s timer if still pending.
      const timeoutId = pairingTimeouts.get(sessionId)
      if (timeoutId) {
        clearTimeout(timeoutId)
        pairingTimeouts.delete(sessionId)
      }

      // Audit row only; payment session stays `confirmed`.
      if (session.payment_session_id) {
        const paySession = await getPaymentSession(session.payment_session_id)
        if (paySession) {
          await recordIntermediateFailure({
            paymentSessionId: session.payment_session_id,
            customerId: session.customer_id,
            targetedMitraId: mitraId,
            causeTag: PairingFailureCause.TARGETED_MITRA_REJECTED,
            amount: paySession.amount,
          })
        }
      }

      // Push a returning-chat-rejected WS event to the customer (fall-through to fallback flow).
      await notifyCustomer(session.customer_id, {
        type: WsMessage.RETURNING_CHAT_REJECTED,
        session_id: sessionId,
        payment_session_id: session.payment_session_id,
      })
    }
    return
  }

  // General-blast: if all notifications now have a non-null DECLINED response → treat as
  // every-mitra-rejected (terminal, distinct from blast-window-timeout). Empty-array guard
  // prevents a misfire when the SELECT happens to return zero rows.
  const notifications = await sql`
    SELECT response FROM chat_request_notifications WHERE session_id = ${sessionId}
  `
  const allDeclined = notifications.length > 0
    && notifications.every((n) => n.response === NotificationResponse.DECLINED)
  if (allDeclined) {
    const [session] = await sql`
      UPDATE chat_sessions
      SET status = ${SessionStatus.EXPIRED}
      WHERE id = ${sessionId} AND status = ${SessionStatus.PENDING_ACCEPTANCE}
      RETURNING id, customer_id, payment_session_id
    `
    if (session) {
      const timeoutId = pairingTimeouts.get(sessionId)
      if (timeoutId) {
        clearTimeout(timeoutId)
        pairingTimeouts.delete(sessionId)
      }

      if (session.payment_session_id) {
        await failPaymentSession(session.payment_session_id, PairingFailureCause.ALL_MITRAS_REJECTED)
      }

      // Terminal: customer is in a searching state and the search just ended with no chat.
      await notifyCustomer(session.customer_id, {
        type: WsMessage.PAIRING_FAILED,
        session_id: sessionId,
        payment_session_id: session.payment_session_id,
        cause_tag: PairingFailureCause.ALL_MITRAS_REJECTED,
      })
    }
  }
}

export const cancelPairingRequest = async (sessionId, customerId) => {
  const [session] = await sql`
    UPDATE chat_sessions
    SET status = ${SessionStatus.CANCELLED}
    WHERE id = ${sessionId} AND customer_id = ${customerId}
      AND status IN (${SessionStatus.SEARCHING}, ${SessionStatus.PENDING_ACCEPTANCE})
    RETURNING id, customer_id, status, payment_session_id
  `

  if (!session) {
    throw Object.assign(new Error('Cannot cancel this request'), {
      code: 'CANNOT_CANCEL', statusCode: 409,
    })
  }

  // Clear timeout
  const timeoutId = pairingTimeouts.get(sessionId)
  if (timeoutId) {
    clearTimeout(timeoutId)
    pairingTimeouts.delete(sessionId)
  }

  // Mark all notifications as ignored
  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.IGNORED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND response IS NULL
  `

  // Notify mitras to dismiss (customer cancelled) — independent fan-out, run in parallel.
  const notifications = await sql`
    SELECT mitra_id FROM chat_request_notifications WHERE session_id = ${sessionId}
  `
  await Promise.all(notifications.map((n) => notifyMitra(n.mitra_id, {
    type: WsMessage.CHAT_REQUEST_CLOSED,
    session_id: sessionId,
    reason: 'cancelled_by_customer',
  })))

  // Customer initiated this cancel; the calling client already navigates home. Do not
  // push PAIRING_FAILED for customer-initiated cancels — surfacing it as a "failure"
  // event (especially via FCM if backgrounded) misframes the user's own action.
  if (session.payment_session_id) {
    await failPaymentSession(session.payment_session_id, PairingFailureCause.CUSTOMER_CANCELLED)
  }

  return session
}

/**
 * Customer-initiated cancel during a payment-search.
 *
 * Use this when the customer is sitting on the searching/waiting screen with a confirmed
 * payment but no chat-session row yet exists, OR when they're in a returning-chat 20s wait.
 * If a chat_session was already created (general blast in flight, or targeted request out),
 * we cancel that too.
 */
export const cancelPaymentSearch = async (paymentSessionId, customerId) => {
  const paySession = await getPaymentSession(paymentSessionId)
  if (!paySession) {
    throw Object.assign(new Error('Payment session not found'), { code: 'NOT_FOUND', statusCode: 404 })
  }
  if (paySession.customer_id !== customerId) {
    throw Object.assign(new Error('Payment session does not belong to this customer'), {
      code: 'FORBIDDEN', statusCode: 403,
    })
  }

  // If a chat_session exists for this payment in pending_acceptance/searching, cancel it.
  const [linkedSession] = await sql`
    SELECT id FROM chat_sessions
    WHERE payment_session_id = ${paymentSessionId}
      AND status IN (${SessionStatus.SEARCHING}, ${SessionStatus.PENDING_ACCEPTANCE})
  `
  if (linkedSession) {
    // cancelPairingRequest also fails the payment session — short-circuit to avoid double work.
    return cancelPairingRequest(linkedSession.id, customerId)
  }

  // Otherwise fail the payment directly. Covers the case where the customer cancels after
  // the targeted attempt already expired/rejected (chat_session no longer pending_acceptance)
  // but the payment is still `confirmed`. No customer-side WS push — see cancelPairingRequest.
  if (paySession.status === PaymentSessionStatus.CONFIRMED) {
    await failPaymentSession(paymentSessionId, PairingFailureCause.CUSTOMER_CANCELLED)
  }
  return { id: paymentSessionId, payment_session_id: paymentSessionId }
}

/**
 * After a returning-chat fail, customer taps "Chat dengan bestie lain".
 *
 * The original payment_session stays in `confirmed` for the entire returning-chat flow —
 * targeted reject/timeout writes an audit-only `pairing_failures` row but does NOT terminate.
 * So when the customer falls back to general blast, we reuse the same `payment_session_id`
 * directly. Multiple `pairing_failures` rows may FK from one payment_session — that's the
 * desired CC UX (one row per failed attempt). Termination happens only at the actual end
 * of the flow (chat starts → consumed; cancel/blast-exhaust → failed_pairing).
 *
 * The targeted_mitra_id flag on the original row is left as-is (it records the customer's
 * original intent); the general blast happens regardless.
 */
export const fallbackToGeneralBlast = async (paymentSessionId, customerId, { topic_sensitivity } = {}) => {
  const paySession = await getPaymentSession(paymentSessionId)
  if (!paySession) {
    throw Object.assign(new Error('Payment session not found'), { code: 'NOT_FOUND', statusCode: 404 })
  }
  if (paySession.customer_id !== customerId) {
    throw Object.assign(new Error('Payment session does not belong to this customer'), {
      code: 'FORBIDDEN', statusCode: 403,
    })
  }
  if (paySession.status !== PaymentSessionStatus.CONFIRMED) {
    throw Object.assign(new Error(`Cannot fallback from payment in status ${paySession.status}`), {
      code: 'INVALID_STATE', statusCode: 409,
    })
  }

  // Run the general blast against the SAME payment session. Pass `allowTargetedPayment`
  // so the targeted_mitra_id on the payment session doesn't trip the general-blast guard.
  return createPairingRequest(customerId, {
    paymentSessionId,
    topic_sensitivity,
    allowTargetedPayment: true,
  })
}

export const expirePairingRequest = async (sessionId, causeTag = PairingFailureCause.NO_MITRA_AVAILABLE) => {
  const [session] = await sql`
    UPDATE chat_sessions
    SET status = ${SessionStatus.EXPIRED}
    WHERE id = ${sessionId} AND status = ${SessionStatus.PENDING_ACCEPTANCE}
    RETURNING id, customer_id, status, payment_session_id
  `
  if (!session) return null

  pairingTimeouts.delete(sessionId)

  // Mark all pending notifications as ignored
  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.IGNORED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND response IS NULL
  `

  // Fail the payment session (if any) — terminal.
  if (session.payment_session_id) {
    await failPaymentSession(session.payment_session_id, causeTag)
  }

  // Notify customer via WebSocket (FCM fallback). Terminal pairing failure → PAIRING_FAILED
  // so the client can route to the failed-pairing screen consistently with the other
  // terminal paths (cancel / all-rejected / payment-expired-mid-search).
  await notifyCustomer(session.customer_id, {
    type: WsMessage.PAIRING_FAILED,
    session_id: sessionId,
    payment_session_id: session.payment_session_id,
    cause_tag: causeTag,
  })

  // Notify mitras to dismiss (request expired) — independent fan-out, run in parallel.
  const notifications = await sql`
    SELECT mitra_id FROM chat_request_notifications WHERE session_id = ${sessionId}
  `
  await Promise.all(notifications.map((n) => notifyMitra(n.mitra_id, {
    type: WsMessage.CHAT_REQUEST_CLOSED,
    session_id: sessionId,
    reason: 'expired',
  })))

  return session
}

/**
 * Targeted-request timer fired with no mitra response.
 *
 * INTERMEDIATE failure: the chat_session is marked expired (the targeted attempt is over)
 * but the payment_session stays `confirmed` so the customer can fall back to general blast
 * on the same payment, or cancel (which then terminates).
 *
 *   - cause_tag is targeted_mitra_timeout (audit row only)
 *   - WS event sent to customer is RETURNING_CHAT_TIMEOUT (not PAIRING_FAILED)
 */
const expireTargetedPairingRequest = async (sessionId) => {
  const [session] = await sql`
    UPDATE chat_sessions
    SET status = ${SessionStatus.EXPIRED}
    WHERE id = ${sessionId} AND status = ${SessionStatus.PENDING_ACCEPTANCE}
    RETURNING id, customer_id, status, payment_session_id
  `
  if (!session) return null

  pairingTimeouts.delete(sessionId)

  // Capture which mitra was targeted (for the audit row).
  const [notif] = await sql`
    SELECT mitra_id FROM chat_request_notifications WHERE session_id = ${sessionId} LIMIT 1
  `

  await sql`
    UPDATE chat_request_notifications
    SET response = ${NotificationResponse.IGNORED}, responded_at = NOW()
    WHERE session_id = ${sessionId} AND response IS NULL
  `

  if (session.payment_session_id) {
    const paySession = await getPaymentSession(session.payment_session_id)
    if (paySession) {
      await recordIntermediateFailure({
        paymentSessionId: session.payment_session_id,
        customerId: session.customer_id,
        targetedMitraId: notif?.mitra_id ?? null,
        causeTag: PairingFailureCause.TARGETED_MITRA_TIMEOUT,
        amount: paySession.amount,
      })
    }
  }

  await notifyCustomer(session.customer_id, {
    type: WsMessage.RETURNING_CHAT_TIMEOUT,
    session_id: sessionId,
    payment_session_id: session.payment_session_id,
  })

  // Notify the targeted mitra that the card is no longer actionable — fan-out in parallel
  // (single recipient today, but cheap to future-proof).
  const notifications = await sql`
    SELECT mitra_id FROM chat_request_notifications WHERE session_id = ${sessionId}
  `
  await Promise.all(notifications.map((n) => notifyMitra(n.mitra_id, {
    type: WsMessage.CHAT_REQUEST_CLOSED,
    session_id: sessionId,
    reason: 'timeout',
  })))

  return session
}

export const getPendingRequestsForMitra = async (mitraId) => {
  // Distinguish general blast from "Curhat lagi" returning requests via payment_session.targeted_mitra_id.
  // For returning requests, surface the configured timeout so the cold-start (FCM-tap) path can render
  // the countdown overlay — same field the WS payload provides for the live path.
  const rows = await sql`
    SELECT
      cs.id AS session_id,
      cs.duration_minutes,
      cs.is_first_session_discount,
      cs.topic_sensitivity,
      cs.created_at,
      CASE
        WHEN ps.targeted_mitra_id IS NOT NULL THEN ${PairingRequestType.RETURNING}
        ELSE ${PairingRequestType.GENERAL}
      END AS request_type
    FROM chat_request_notifications crn
    JOIN chat_sessions cs ON cs.id = crn.session_id
    LEFT JOIN payment_sessions ps ON ps.id = cs.payment_session_id
    WHERE crn.mitra_id = ${mitraId}
      AND crn.response IS NULL
      AND cs.status = ${SessionStatus.PENDING_ACCEPTANCE}
    ORDER BY cs.created_at ASC
  `

  if (!rows.some((r) => r.request_type === PairingRequestType.RETURNING)) {
    return rows
  }

  // At least one returning row — fetch the timeout config once and attach.
  const { returning_chat_confirmation_timeout_seconds } = await getReturningChatConfirmationTimeoutSeconds()
  return rows.map((r) =>
    r.request_type === PairingRequestType.RETURNING
      ? { ...r, confirmation_timeout_seconds: returning_chat_confirmation_timeout_seconds }
      : r
  )
}

export const getSessionStatus = async (sessionId) => {
  const [session] = await sql`
    SELECT cs.id, cs.customer_id, cs.mitra_id, cs.status, cs.topic_sensitivity,
      cs.created_at, cs.paired_at, cs.ended_at, cs.ended_by,
      m.display_name AS mitra_display_name
    FROM chat_sessions cs
    LEFT JOIN mitras m ON m.id = cs.mitra_id
    WHERE cs.id = ${sessionId}
  `
  return session
}