/**
 * Dedicated Current Understanding synthesis API route.
 *
 * Route: POST /api/cases/synthesis
 *
 * Follows the thin route pattern established by cases/start and cases/update routes:
 *   parse request → invoke domain seam → return validated result → map failure status
 *
 * No synthesis business logic belongs in this file.
 */

import { getProvider, getProviderModelName } from "@/lib/llm/provider.js";
import { synthesizeCurrentUnderstanding } from "@/lib/graph/current-understanding-synthesis.js";
import { withAuthenticatedApi } from "@/lib/supabase/api-auth.js";

async function post(request) {
  try {
    const body = await request.json();

    // ── Parse / validate input contract ───────────────────────
    if (!body || typeof body !== "object") {
      return Response.json(
        { success: false, stage: "request_validation", error: "Invalid request body" },
        { status: 400 }
      );
    }

    const { situationGraph, findings } = body;

    if (!situationGraph) {
      return Response.json(
        { success: false, stage: "request_validation", error: "Missing situationGraph" },
        { status: 400 }
      );
    }

    // ── Invoke domain seam with configured model ──────────────
    const result = await synthesizeCurrentUnderstanding(
      { situationGraph, findings },
      {
        provider: getProvider(),
        modelName: getProviderModelName(),
      }
    );

    return Response.json({ success: true, currentUnderstanding: result.currentUnderstanding }, { status: 200 });
  } catch (error) {
    if (error instanceof SyntaxError) {
      return Response.json(
        { success: false, stage: "request_validation", error: "Invalid JSON request body" },
        { status: 400 }
      );
    }

    if (error.statusCode) {
      return Response.json(
        {
          success: false,
          stage: error.statusCode === 400 ? "request_validation" : "provider",
          error: error.message ?? "Synthesis failed",
        },
        { status: error.statusCode }
      );
    }

    // Unexpected error
    return Response.json(
      { success: false, stage: "internal", error: "Internal server error" },
      { status: 500 }
    );
  }
}

export const POST = withAuthenticatedApi(post);