import { NextResponse } from 'next/server'
import { createClient } from '@/lib/supabase/server'
import { sendTextMessage, sendTemplateMessage } from '@/lib/whatsapp/meta-api'
import { decrypt } from '@/lib/whatsapp/encryption'
import {
  sanitizePhoneForMeta,
  isValidE164,
  phoneVariants,
  isRecipientNotAllowedError,
} from '@/lib/whatsapp/phone-utils'

export async function POST(request: Request) {
  try {
    const supabase = await createClient()

    const {
      data: { user },
      error: authError,
    } = await supabase.auth.getUser()

    if (authError || !user) {
      return NextResponse.json(
        { error: 'Unauthorized' },
        { status: 401 }
      )
    }

    const body = await request.json()
    const {
      conversation_id,
      message_type,
      content_text,
      media_url,
      template_name,
      template_params,
    } = body

    if (!conversation_id || !message_type) {
      return NextResponse.json(
        { error: 'conversation_id and message_type are required' },
        { status: 400 }
      )
    }

    if (message_type === 'text' && !content_text) {
      return NextResponse.json(
        { error: 'content_text is required for text messages' },
        { status: 400 }
      )
    }

    if (message_type === 'template' && !template_name) {
      return NextResponse.json(
        { error: 'template_name is required for template messages' },
        { status: 400 }
      )
    }

    // Fetch conversation and contact
    const { data: conversation, error: convError } = await supabase
      .from('conversations')
      .select('*, contact:contacts(*)')
      .eq('id', conversation_id)
      .eq('user_id', user.id)
      .single()

    if (convError || !conversation) {
      return NextResponse.json(
        { error: 'Conversation not found' },
        { status: 404 }
      )
    }

    const contact = conversation.contact
    if (!contact?.phone) {
      return NextResponse.json(
        { error: 'Contact phone number not found' },
        { status: 400 }
      )
    }

    // Sanitize and validate phone
    const sanitizedPhone = sanitizePhoneForMeta(contact.phone)
    if (!isValidE164(sanitizedPhone)) {
      return NextResponse.json(
        { error: 'Invalid phone number format' },
        { status: 400 }
      )
    }

    // Fetch and decrypt WhatsApp config
    const { data: config, error: configError } = await supabase
      .from('whatsapp_config')
      .select('*')
      .eq('user_id', user.id)
      .single()

    if (configError || !config) {
      return NextResponse.json(
        { error: 'WhatsApp not configured. Please set up your WhatsApp integration first.' },
        { status: 400 }
      )
    }

    const accessToken = decrypt(config.access_token)

    // Send via Meta API — retry with phone-number variants if Meta rejects
    // with "recipient not in allowed list" (common in sandbox / when a
    // number was registered with/without a trunk 0). If an alternate
    // format succeeds, we persist it back to the contact row so the
    // next send goes through on the first attempt.
    let waMessageId = ''
    let workingPhone = sanitizedPhone

    const attempt = async (phone: string): Promise<string> => {
      if (message_type === 'template') {
        const result = await sendTemplateMessage(
          config.phone_number_id,
          accessToken,
          phone,
          template_name,
          undefined, // default language (en_US)
          template_params || []
        )
        return result.messageId
      }
      const result = await sendTextMessage(
        config.phone_number_id,
        accessToken,
        phone,
        content_text
      )
      return result.messageId
    }

    try {
      const variants = phoneVariants(sanitizedPhone)
      let lastError: unknown = null

      for (const variant of variants) {
        try {
          waMessageId = await attempt(variant)
          workingPhone = variant
          lastError = null
          break
        } catch (err) {
          const message = err instanceof Error ? err.message : String(err)
          // Only retry when the failure is specifically that the
          // recipient isn't in Meta's allowed list. Any other error
          // (bad token, invalid template, etc.) bubbles up immediately.
          if (!isRecipientNotAllowedError(message)) {
            throw err
          }
          lastError = err
          console.warn(`[whatsapp/send] variant "${variant}" rejected by Meta, trying next…`)
        }
      }

      if (lastError) throw lastError
    } catch (err) {
      const message = err instanceof Error ? err.message : 'Unknown Meta API error'
      console.error('Meta API send failed for all variants:', message)
      return NextResponse.json(
        { error: `Meta API error: ${message}` },
        { status: 502 }
      )
    }

    // If a non-original variant succeeded, update the contact so future
    // sends go straight through. sanitizePhoneForMeta on workingPhone
    // will yield workingPhone itself, so re-storing preserves it.
    if (workingPhone !== sanitizedPhone) {
      console.log(
        `[whatsapp/send] Auto-corrected contact phone: ${sanitizedPhone} → ${workingPhone}`
      )
      await supabase
        .from('contacts')
        .update({ phone: workingPhone })
        .eq('id', contact.id)
    }

    // Insert message into DB — field names MUST match the messages schema
    // (see supabase/migrations/001_initial_schema.sql):
    //   conversation_id, sender_type, content_type, content_text,
    //   media_url, template_name, message_id, status, created_at
    const { data: messageRecord, error: msgError } = await supabase
      .from('messages')
      .insert({
        conversation_id,
        sender_type: 'agent',
        content_type: message_type,
        content_text: content_text || null,
        media_url: media_url || null,
        template_name: template_name || null,
        message_id: waMessageId,
        status: 'sent',
      })
      .select()
      .single()

    if (msgError) {
      console.error('Error inserting sent message:', msgError)
      return NextResponse.json(
        { error: `Message sent to Meta but failed to save to DB: ${msgError.message}` },
        { status: 500 }
      )
    }

    // Update conversation
    await supabase
      .from('conversations')
      .update({
        last_message_text: content_text || `[${message_type}]`,
        last_message_at: new Date().toISOString(),
        updated_at: new Date().toISOString(),
      })
      .eq('id', conversation_id)

    return NextResponse.json({
      success: true,
      message_id: messageRecord.id,
      whatsapp_message_id: waMessageId,
    })
  } catch (error) {
    console.error('Error in WhatsApp send POST:', error)
    return NextResponse.json(
      { error: 'Failed to send message' },
      { status: 500 }
    )
  }
}