// Embranchement : duplique la conversation jusqu'à un message donné.
import { NextResponse } from "next/server";
import { z } from "zod";
import { apiError, parseBody } from "@/lib/api.ts";
import { assertSameOrigin, requireUser } from "@/lib/auth/session.ts";
import { all, get, run, transaction } from "@/lib/db/index.ts";

const schema = z.object({ upToMessageId: z.number().int().positive() });

export async function POST(req: Request, ctx: { params: Promise<{ id: string }> }) {
  try {
    await assertSameOrigin();
    const user = await requireUser();
    const id = parseInt((await ctx.params).id, 10);
    const conv = get<{ id: number; title: string; course_code: string | null; mode: string; knowledge_mode: string; model: string }>(
      "SELECT id, title, course_code, mode, knowledge_mode, model FROM conversations WHERE id = ? AND user_id = ?",
      id, user.id
    );
    if (!conv) return NextResponse.json({ error: "Conversation introuvable." }, { status: 404 });
    const { upToMessageId } = await parseBody(req, schema);

    const newId = transaction(() => {
      const r = run(
        `INSERT INTO conversations (user_id, course_code, title, mode, knowledge_mode, model, parent_conversation_id, branched_from_message_id)
         VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
        user.id, conv.course_code, conv.title + " (branche)", conv.mode, conv.knowledge_mode, conv.model, conv.id, upToMessageId
      );
      const nid = Number(r.lastInsertRowid);
      const msgs = all<{ role: string; content: string; citations: string; attachments: string; model: string; mode: string; knowledge_mode: string }>(
        "SELECT role, content, citations, attachments, model, mode, knowledge_mode FROM messages WHERE conversation_id = ? AND id <= ? ORDER BY id",
        conv.id, upToMessageId
      );
      for (const m of msgs) {
        run(
          "INSERT INTO messages (conversation_id, role, content, citations, attachments, model, mode, knowledge_mode) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
          nid, m.role, m.content, m.citations, m.attachments, m.model, m.mode, m.knowledge_mode
        );
      }
      return nid;
    });
    return NextResponse.json({ ok: true, conversationId: newId });
  } catch (e) {
    return apiError(e);
  }
}