/**
 * Compliance Advisor Chat API — Clarity-Gate orchestration.
 *
 * Consumes the SDK/RAG /retrieve (evidence/visual_evidence/footnotes/clarity) and returns the
 * FE-facing contract (advisor-clarity-gate-contract):
 *   - clarify mode  -> short L1 general answer (no RAG) + domain context chips
 *   - answer  mode  -> L2 answer over the scoped evidence with [n] citation markers
 * Citations are generated here ([n] -> nth evidence unit). The FE renders ONLY this structured data.
 */

import { NextRequest, NextResponse } from 'next/server'
import { readSoulFile } from '@/lib/sdk/agents/soul-reader'
import { retrieveFull } from '@/lib/sdk/agents/advisor-rag'
import { completeAdvisorAnswer, streamAdvisorAnswer, type ChatMessage } from '@/lib/sdk/agents/advisor-llm'
import {
  buildCitations,
  isLegacyRequest,
  mapClarity,
  mapFootnotes,
  numberedEvidenceForPrompt,
  resolveMode,
} from '@/lib/sdk/advisor/retrieve-mapping'
import type { AdvisorResponse } from '@/lib/sdk/advisor/contract'

type Country = 'DE' | 'AT' | 'CH' | 'EU'

const COUNTRY_LABELS: Record<Country, string> = {
  DE: 'Deutschland',
  AT: 'Oesterreich',
  CH: 'Schweiz',
  EU: 'EU-weit',
}

function countryBlock(c: Country): string {
  const label = COUNTRY_LABELS[c]
  return `\n\n## Laenderspezifische Auskunft
Der Nutzer hat "${label} (${c})" gewaehlt. Beziehe dich auf ${c}-Recht + anwendbares EU-Recht und nenne das Land.`
}

// L1: general knowledge, deliberately NOT grounded (the clarify step precedes the legal retrieval).
const L1_SYSTEM = `Du bist der BreakPilot Compliance-Berater. Gib eine KURZE, allgemeine Definition/Erklaerung
des gefragten Begriffs aus Allgemeinwissen — 2 bis 4 Saetze, Markdown, neutral. NENNE KEINE Rechtsquellen,
Paragraphen, Artikel oder Fundstellen; der Nutzer waehlt anschliessend einen konkreten Kontext, erst dann
folgen belegte Quellen. Wenn der Begriff in mehreren Bereichen vorkommt, erwaehne das in einem Halbsatz.`

const FALLBACK_SYSTEM = `Du bist der BreakPilot Compliance-Berater. Antworte quellenbasiert, verstaendlich und ehrlich auf Deutsch.`

function answerSystem(
  soul: string | null,
  country: Country | undefined,
  evidenceBlock: string,
  withCitations = true,
): string {
  let s = soul || FALLBACK_SYSTEM
  if (country) s += countryBlock(country)
  s += `\n\n## Belegte Evidence (nummeriert — DEINE EINZIGEN Quellen)\n${evidenceBlock || '(keine Evidence gefunden)'}`
  s += `\n\n## Antwortformat (WICHTIG)
- Gut gegliedertes Markdown: kurze ## Ueberschriften je Aspekt, Aufzaehlungen, **Fettung** fuer Kernbegriffe.`
  if (withCitations) {
    s += `\n- Belege Kernaussagen mit [n], wobei n die NUMMER der Evidence-Quelle oben ist (z. B. [1], [2]).
- Nenne KEINE Quellen-/Fundstellen-Liste im Fliesstext — die Quellen werden dem Nutzer separat angezeigt.`
  } else {
    s += `\n- Nenne Fundstellen nur, wo sie der Antwort dienen (natuerlich im Text, KEIN [n]-Markup).`
  }
  s += `\n- Triff KEINE Aussage, die nicht durch die nummerierte Evidence belegt ist; fehlt der Beleg, sage das offen.`
  return s
}

export async function POST(request: NextRequest) {
  try {
    const body = await request.json()
    const question = String(body.question ?? body.message ?? '').trim()
    const context: string | null = body.context ?? null
    const country = (['DE', 'AT', 'CH', 'EU'] as const).includes(body.country)
      ? (body.country as Country)
      : undefined

    if (!question) {
      return NextResponse.json({ error: 'Question is required' }, { status: 400 })
    }

    const retrieved = await retrieveFull(question, context)

    // Backward-compat: legacy consumers (breakpilot-workspace) send {message} and read a plain-text
    // stream. Serve the L2 answer streamed (clean prose, no [n]); no clarify gate, no JSON.
    if (isLegacyRequest(body)) {
      const legacyEvidence = retrieved.evidence ?? []
      const legacySoul = await readSoulFile('compliance-advisor')
      const legacyStream = await streamAdvisorAnswer([
        { role: 'system', content: answerSystem(legacySoul, country, numberedEvidenceForPrompt(legacyEvidence), false) },
        { role: 'user', content: question },
      ])
      if (!legacyStream) {
        return NextResponse.json({ error: 'LLM nicht erreichbar.' }, { status: 502 })
      }
      return new NextResponse(legacyStream, {
        headers: {
          'Content-Type': 'text/plain; charset=utf-8',
          'Cache-Control': 'no-cache',
          'X-Advisor-Format': 'legacy-stream',
        },
      })
    }

    const mode = resolveMode(retrieved.clarity?.mode, !!context)

    if (mode === 'clarify') {
      const general = await completeAdvisorAnswer([
        { role: 'system', content: L1_SYSTEM },
        { role: 'user', content: question },
      ])
      if (general === null) {
        return NextResponse.json({ error: 'LLM nicht erreichbar.' }, { status: 502 })
      }
      const resp: AdvisorResponse = {
        mode: 'clarify',
        question,
        clarity: mapClarity(retrieved.clarity, 'clarify'),
        general_answer: general,
        answer: null,
        scoped_query: null,
        evidence: [],
        citations: [],
        visual_evidence: [],
        footnotes: [],
      }
      return NextResponse.json(resp)
    }

    const evidence = retrieved.evidence ?? []
    const soul = await readSoulFile('compliance-advisor')
    const messages: ChatMessage[] = [
      { role: 'system', content: answerSystem(soul, country, numberedEvidenceForPrompt(evidence)) },
      { role: 'user', content: question },
    ]
    const answer = await completeAdvisorAnswer(messages)
    if (answer === null) {
      return NextResponse.json({ error: 'LLM nicht erreichbar.' }, { status: 502 })
    }
    const resp: AdvisorResponse = {
      mode: 'answer',
      question,
      clarity: mapClarity(retrieved.clarity, 'answer'),
      general_answer: null,
      answer,
      scoped_query: context,
      evidence,
      citations: buildCitations(evidence),
      visual_evidence: retrieved.visual_evidence ?? [],
      footnotes: mapFootnotes(retrieved.footnotes),
    }
    return NextResponse.json(resp)
  } catch (error) {
    console.error('Compliance advisor chat error:', error)
    return NextResponse.json({ error: 'Verbindung zum Advisor fehlgeschlagen.' }, { status: 503 })
  }
}