import { NextResponse } from 'next/server'
import { z } from 'zod'
import { withRouteContext } from '@/lib/api/with-route-context'
import { checkAgentRateLimit, agentRateLimitResponseBody } from '@/lib/rate-limits/agent'
import { guardSandbox } from '@/lib/sandbox/guard'
import { requireCapability } from '@/lib/entitlements/has-capability'
import { CAPABILITY } from '@/lib/entitlements/keys'
import { getAiStatus } from '@/lib/ai'
import { gatherCandidates } from '@/lib/agent/categorize/candidates'
import { gatherUnderlag } from '@/lib/agent/categorize/underlag'
import { selectAccount } from '@/lib/agent/categorize/select-account'
import { getErrorMessage as getUserErrorMessage } from '@/lib/errors/get-error-message'
import type { EntityType, Transaction } from '@/types'

/**
 * POST /api/agent/categorize: a provider-agnostic booking proposal for one
 * transaction — the auto-booking cascade end to end (Tier 1 retrieval → Tier 2
 * selector), minus the write.
 *
 * It gathers the deterministic candidate accounts (counterparty templates,
 * rules, history) with NO model call, then has the model SELECT among them
 * (self-consistency sampled), and returns the proposed account + VAT +
 * confidence + reasoning + the candidate slate. It never posts anything: the
 * caller (the transaction row) renders the proposal as an approval card.
 *
 * Runs on any configured backend (Bedrock or a local model), so it is gated on
 * `configured`, not `assistantAvailable` — same as /api/agent/ask.
 */

const Schema = z.object({
  transaction_id: z.string().uuid(),
  company_id: z.string().uuid().optional(),
  /** Extracted receipt/invoice text, if the caller already has it. */
  underlag: z.string().max(24_000).optional(),
  /** Self-consistency samples (default 3). */
  samples: z.number().int().min(1).max(5).optional(),
})

// withRouteContext enforces auth (MFA on hosted) and resolves the active
// company; the body may still name another company the caller belongs to.
export const POST = withRouteContext(
  'agent.categorize',
  async (request, { user, supabase, companyId: activeCompanyId }) => {
    const rate = await checkAgentRateLimit(supabase, user.id)
    if (!rate.ok) return NextResponse.json(agentRateLimitResponseBody(rate), { status: 429 })

    let body: unknown
    try {
      body = await request.json()
    } catch {
      return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 })
    }
    const parsed = Schema.safeParse(body)
    if (!parsed.success) {
      return NextResponse.json({ error: 'Ogiltig förfrågan.', type: 'validation_error' }, { status: 400 })
    }

    const companyId = parsed.data.company_id ?? activeCompanyId

    // The wrapper already guarantees membership of the active company; an
    // explicit company_id override must be verified the same way.
    if (companyId !== activeCompanyId) {
      const { data: membership } = await supabase
        .from('company_members')
        .select('user_id')
        .eq('company_id', companyId)
        .eq('user_id', user.id)
        .maybeSingle()
      if (!membership) return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
    }

    const blocked = await guardSandbox(supabase, companyId)
    if (blocked) return blocked

    const capBlocked = await requireCapability(supabase, companyId, CAPABILITY.ai)
    if (capBlocked) return capBlocked

    if (!getAiStatus().configured) {
      return NextResponse.json(
        { error: 'Assistenten är inte konfigurerad på den här installationen.', code: 'ai_unconfigured' },
        { status: 503 },
      )
    }

    const { data: tx } = await supabase
      .from('transactions')
      .select('id, merchant_name, description, original_description, amount, date, currency, category, is_business, document_id')
      .eq('id', parsed.data.transaction_id)
      .eq('company_id', companyId)
      .maybeSingle()
    if (!tx) return NextResponse.json({ error: 'Transaktionen hittades inte.' }, { status: 404 })

    const [{ data: company }, { data: settings }] = await Promise.all([
      supabase.from('companies').select('entity_type').eq('id', companyId).maybeSingle(),
      supabase.from('company_settings').select('vat_registered').eq('company_id', companyId).maybeSingle(),
    ])

    try {
      // Gather the matched receipt/invoice text when the caller didn't supply it:
      // this is what lifts the cold-start case — the model reads the actual
      // supplier + line items, not just the bank line. Best-effort; '' if none.
      const underlag =
        parsed.data.underlag ??
        (await gatherUnderlag(
          supabase,
          companyId,
          (tx as Transaction).id,
          (tx as { document_id?: string | null }).document_id,
        ))

      const candidates = await gatherCandidates(supabase, companyId, tx as Transaction)
      const selection = await selectAccount({
        transaction: {
          merchantName: (tx as Transaction).merchant_name,
          description: (tx as Transaction).description,
          amount: (tx as Transaction).amount,
          date: (tx as Transaction).date,
          currency: (tx as Transaction).currency,
        },
        underlag,
        candidates,
        entityType: ((company?.entity_type as EntityType | undefined) ?? 'enskild_firma'),
        vatRegistered: settings?.vat_registered ?? false,
        samples: parsed.data.samples,
      })
      return NextResponse.json({ data: { ...selection, candidates } })
    } catch (err) {
      return NextResponse.json({ error: getUserErrorMessage(err) }, { status: 500 })
    }
  },
)