import crypto from 'crypto'
import { createLogger } from '@sim/logger'
import { safeCompare } from '@sim/security/compare'
import { NextResponse } from 'next/server'
import { getNotificationUrl, getProviderConfig } from '@/lib/webhooks/provider-subscription-utils'
import type {
  AuthContext,
  DeleteSubscriptionContext,
  EventMatchContext,
  FormatInputContext,
  FormatInputResult,
  SubscriptionContext,
  SubscriptionResult,
  WebhookProviderHandler,
} from '@/lib/webhooks/providers/types'

const logger = createLogger('WebhookProvider:Zendesk')

function asRecord(value: unknown): Record<string, unknown> {
  return (value as Record<string, unknown>) || {}
}

/** Zendesk API base for a subdomain. */
function zendeskApiBase(subdomain: string): string {
  return `https://${subdomain}.zendesk.com/api/v2`
}

/**
 * Zendesk subdomains are bare hostname labels (letters, digits, internal hyphens).
 * Rejecting anything else prevents the value from escaping the host portion of the
 * interpolated URL (e.g. a subdomain containing `/` would redirect the request —
 * and its Basic-auth admin credentials — to an attacker-controlled host).
 */
const ZENDESK_SUBDOMAIN_PATTERN = /^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?$/i

function isValidZendeskSubdomain(subdomain: string): boolean {
  return ZENDESK_SUBDOMAIN_PATTERN.test(subdomain)
}

/** Basic auth header for the Zendesk API-token scheme (`email/token:apiToken`). */
function zendeskAuthHeader(email: string, apiToken: string): string {
  return `Basic ${Buffer.from(`${email}/token:${apiToken}`).toString('base64')}`
}

/** Best-effort delete used to avoid orphaning a webhook when post-create setup fails. */
async function deleteZendeskWebhookQuietly(
  apiBase: string,
  authHeader: string,
  webhookId: string
): Promise<void> {
  await fetch(`${apiBase}/webhooks/${webhookId}`, {
    method: 'DELETE',
    headers: { Authorization: authHeader },
  }).catch(() => {})
}

/** Maximum allowed clock skew (5 minutes) between Zendesk's signed timestamp and now, per Zendesk docs. */
const ZENDESK_TIMESTAMP_MAX_SKEW_MS = 5 * 60 * 1000

/**
 * Verify the signed timestamp is recent to prevent replay of captured deliveries.
 * Zendesk sends `X-Zendesk-Webhook-Signature-Timestamp` as an ISO-8601 string
 * (e.g. `2025-01-24T15:30:00.000Z`), so it is parsed with `Date.parse`.
 */
function isZendeskTimestampFresh(timestamp: string): boolean {
  const signedAt = Date.parse(timestamp)
  if (Number.isNaN(signedAt)) return false
  return Math.abs(Date.now() - signedAt) <= ZENDESK_TIMESTAMP_MAX_SKEW_MS
}

/**
 * Zendesk signs `timestamp + rawBody` (no separator) with HMAC-SHA256 keyed by
 * the webhook's signing secret, then base64-encodes it into
 * `X-Zendesk-Webhook-Signature`. The timestamp is sent in a separate header.
 */
function validateZendeskSignature(
  secret: string,
  signature: string,
  timestamp: string,
  body: string
): boolean {
  if (!secret || !signature || !timestamp) return false
  const computed = crypto
    .createHmac('sha256', secret)
    .update(timestamp + body, 'utf8')
    .digest('base64')
  return safeCompare(computed, signature)
}

export const zendeskHandler: WebhookProviderHandler = {
  verifyAuth({ request, rawBody, requestId, providerConfig }: AuthContext) {
    const secret = providerConfig.webhookSecret as string | undefined
    if (!secret) {
      logger.warn(`[${requestId}] Zendesk webhook secret not configured`)
      return new NextResponse('Unauthorized - Missing Zendesk webhook secret', { status: 401 })
    }

    const signature = request.headers.get('X-Zendesk-Webhook-Signature')
    const timestamp = request.headers.get('X-Zendesk-Webhook-Signature-Timestamp')
    if (!signature || !timestamp) {
      logger.warn(`[${requestId}] Zendesk webhook missing signature headers`)
      return new NextResponse('Unauthorized - Missing Zendesk signature', { status: 401 })
    }

    if (!isZendeskTimestampFresh(timestamp)) {
      logger.warn(`[${requestId}] Zendesk webhook timestamp outside the allowed window`, {
        timestamp,
      })
      return new NextResponse('Unauthorized - Stale Zendesk timestamp', { status: 401 })
    }

    if (!validateZendeskSignature(secret, signature, timestamp, rawBody)) {
      logger.warn(`[${requestId}] Zendesk signature verification failed`)
      return new NextResponse('Unauthorized - Invalid Zendesk signature', { status: 401 })
    }

    return null
  },

  async matchEvent({ body, requestId, providerConfig }: EventMatchContext) {
    const triggerId = providerConfig.triggerId as string | undefined
    if (!triggerId || triggerId === 'zendesk_webhook') return true

    const eventType = asRecord(body).type as string | undefined

    const { isZendeskEventMatch } = await import('@/triggers/zendesk/utils')
    if (!isZendeskEventMatch(triggerId, eventType || '')) {
      logger.debug(
        `[${requestId}] Zendesk event '${eventType}' does not match trigger ${triggerId}, skipping`
      )
      return false
    }
    return true
  },

  async formatInput({ body }: FormatInputContext): Promise<FormatInputResult> {
    const b = asRecord(body)
    const detail = asRecord(b.detail)
    const via = asRecord(detail.via)

    return {
      input: {
        event_id: b.id,
        event_type: b.type,
        time: b.time,
        account_id: b.account_id,
        ticket: {
          id: detail.id,
          subject: detail.subject,
          status: detail.status,
          priority: detail.priority,
          ticket_type: detail.type,
          description: detail.description,
          requester_id: detail.requester_id,
          assignee_id: detail.assignee_id,
          group_id: detail.group_id,
          organization_id: detail.organization_id,
          tags: Array.isArray(detail.tags) ? detail.tags : [],
          via_channel: via.channel,
          is_public: detail.is_public,
          created_at: detail.created_at,
          updated_at: detail.updated_at,
        },
        event: b.event ?? null,
      },
    }
  },

  extractIdempotencyId(body: unknown) {
    return (asRecord(body).id as string | undefined) || null
  },

  async createSubscription(ctx: SubscriptionContext): Promise<SubscriptionResult | undefined> {
    const config = getProviderConfig(ctx.webhook)
    const subdomain = config.subdomain as string | undefined
    const email = config.email as string | undefined
    const apiToken = config.apiToken as string | undefined
    const triggerId = config.triggerId as string | undefined

    if (!subdomain) throw new Error('Zendesk subdomain is required to create the webhook.')
    if (!isValidZendeskSubdomain(subdomain)) {
      throw new Error(
        'Zendesk subdomain must contain only letters, numbers, and hyphens (e.g. "yourcompany").'
      )
    }
    if (!email) throw new Error('Zendesk admin email is required to create the webhook.')
    if (!apiToken) throw new Error('Zendesk API token is required to create the webhook.')

    const { getZendeskSubscriptions } = await import('@/triggers/zendesk/utils')
    const apiBase = zendeskApiBase(subdomain)
    const authHeader = zendeskAuthHeader(email, apiToken)

    const createRes = await fetch(`${apiBase}/webhooks`, {
      method: 'POST',
      headers: { Authorization: authHeader, 'Content-Type': 'application/json' },
      body: JSON.stringify({
        webhook: {
          name: `Sim webhook (${ctx.webhook.id})`,
          endpoint: getNotificationUrl(ctx.webhook),
          http_method: 'POST',
          request_format: 'json',
          status: 'active',
          subscriptions: getZendeskSubscriptions(triggerId ?? 'zendesk_webhook'),
        },
      }),
    })

    if (!createRes.ok) {
      const detail = await createRes.text().catch(() => '')
      logger.error(`[${ctx.requestId}] Failed to create Zendesk webhook (${createRes.status})`, {
        detail,
      })
      if (createRes.status === 401 || createRes.status === 403) {
        throw new Error(
          'Zendesk authentication failed. Verify the subdomain, admin email, and API token.'
        )
      }
      throw new Error(`Failed to create Zendesk webhook: ${createRes.status}`)
    }

    const created = asRecord((await createRes.json().catch(() => ({}))) as unknown)
    const externalId = asRecord(created.webhook).id as string | undefined
    if (!externalId) throw new Error('Zendesk webhook created but no webhook ID was returned.')

    const secretRes = await fetch(`${apiBase}/webhooks/${externalId}/signing_secret`, {
      headers: { Authorization: authHeader },
    })
    if (!secretRes.ok) {
      const detail = await secretRes.text().catch(() => '')
      logger.error(
        `[${ctx.requestId}] Created Zendesk webhook ${externalId} but failed to fetch signing secret (${secretRes.status})`,
        { detail }
      )
      await deleteZendeskWebhookQuietly(apiBase, authHeader, externalId)
      throw new Error(`Failed to fetch Zendesk signing secret: ${secretRes.status}`)
    }

    const secretBody = asRecord((await secretRes.json().catch(() => ({}))) as unknown)
    const secret = asRecord(secretBody.signing_secret).secret as string | undefined
    if (!secret) {
      await deleteZendeskWebhookQuietly(apiBase, authHeader, externalId)
      throw new Error('Zendesk did not return a signing secret for the webhook.')
    }

    logger.info(`[${ctx.requestId}] Created Zendesk webhook ${externalId}`)
    return { providerConfigUpdates: { externalId, webhookSecret: secret } }
  },

  async deleteSubscription(ctx: DeleteSubscriptionContext): Promise<void> {
    const config = getProviderConfig(ctx.webhook)
    const subdomain = config.subdomain as string | undefined
    const email = config.email as string | undefined
    const apiToken = config.apiToken as string | undefined
    const externalId = config.externalId as string | undefined

    if (!subdomain || !email || !apiToken || !externalId) {
      if (ctx.strict) throw new Error('Missing Zendesk credentials or webhook ID for deletion.')
      logger.warn(
        `[${ctx.requestId}] Skipping Zendesk webhook cleanup — missing credentials or webhook ID`
      )
      return
    }

    if (!isValidZendeskSubdomain(subdomain)) {
      if (ctx.strict) throw new Error('Invalid Zendesk subdomain for deletion.')
      logger.warn(`[${ctx.requestId}] Skipping Zendesk webhook cleanup — invalid subdomain`)
      return
    }

    const res = await fetch(`${zendeskApiBase(subdomain)}/webhooks/${externalId}`, {
      method: 'DELETE',
      headers: { Authorization: zendeskAuthHeader(email, apiToken) },
    })

    if (!res.ok && res.status !== 404) {
      if (ctx.strict) throw new Error(`Failed to delete Zendesk webhook: ${res.status}`)
      logger.warn(
        `[${ctx.requestId}] Failed to delete Zendesk webhook ${externalId} (non-fatal): ${res.status}`
      )
      return
    }
    logger.info(`[${ctx.requestId}] Deleted Zendesk webhook ${externalId}`)
  },
}