import { NextRequest, NextResponse } from "next/server";
import { prisma } from "@/lib/db";
import { ALL_CITIES } from "@/lib/data/stadtwerke-cities";

const OPENROUTER_API_KEY = process.env.OPENROUTER_API_KEY || "";
const OPENROUTER_BASE = "https://openrouter.ai/api/v1";

export async function GET(req: NextRequest) {
  try {
    const { searchParams } = new URL(req.url);
    const count = Math.min(parseInt(searchParams.get("count") || "20", 10), 100);

    // Get all regions already used for stadtwerke mode
    const used = await prisma.searchHistory.findMany({
      where: { searchMode: "stadtwerke" },
      select: { region: true },
    });
    const usedRegions = new Set(used.map(u => u.region.toLowerCase().trim()));

    // Filter static list — cities not yet searched
    const remaining = ALL_CITIES.filter(city => !usedRegions.has(city.toLowerCase().trim()));

    if (remaining.length === 0) {
      // All static cities exhausted — ask AI for new suggestions
      const newCities = await generateNewCities(usedRegions);
      return NextResponse.json({ cities: newCities.slice(0, count), exhausted: true, totalRemaining: newCities.length });
    }

    return NextResponse.json({
      cities: remaining.slice(0, count),
      exhausted: false,
      totalRemaining: remaining.length,
    });
  } catch (err) {
    console.error("GET /api/stadtwerke-cities error:", err);
    return NextResponse.json({ error: "Failed to fetch cities" }, { status: 500 });
  }
}

async function generateNewCities(usedRegions: Set<string>): Promise<string[]> {
  if (!OPENROUTER_API_KEY) return [];

  const usedList = Array.from(usedRegions)
    .filter(r => r.length > 0)
    .slice(0, 150)
    .join(", ");

  try {
    const res = await fetch(`${OPENROUTER_BASE}/chat/completions`, {
      method: "POST",
      headers: {
        "Authorization": `Bearer ${OPENROUTER_API_KEY}`,
        "Content-Type": "application/json",
        "HTTP-Referer": "https://mein-solar.de",
      },
      body: JSON.stringify({
        model: "openai/gpt-4o-mini",
        messages: [
          {
            role: "system",
            content:
              "Du bist ein Experte für kommunale Energieversorger in Deutschland. Antworte ausschließlich mit einem gültigen JSON-Array aus Städtenamen, ohne Erklärungen.",
          },
          {
            role: "user",
            content: `Generiere 40 deutsche Städte und Gemeinden, in denen es lokale Stadtwerke oder kommunale Energieversorger gibt. Keine dieser Städte darf in der folgenden Liste enthalten sein:\n${usedList}\n\nGib nur ein JSON-Array zurück, z.B.: ["Landsberg am Lech", "Bühl", "Leutkirch"]`,
          },
        ],
        max_tokens: 600,
        temperature: 0.7,
      }),
    });

    const data = await res.json() as { choices?: Array<{ message?: { content?: string } }> };
    const content = data.choices?.[0]?.message?.content?.trim() || "[]";

    // Strip markdown code blocks if present
    const cleaned = content.replace(/^```(?:json)?\s*/i, "").replace(/\s*```$/, "").trim();
    const cities = JSON.parse(cleaned) as unknown;
    return Array.isArray(cities) ? (cities as string[]).filter(c => typeof c === "string") : [];
  } catch {
    return [];
  }
}