// Flashcards : file de révision (dues + nouvelles), création manuelle, génération IA.
import { NextResponse } from "next/server";
import { z } from "zod";
import { apiError, parseBody, requireEnrollment } from "@/lib/api.ts";
import { assertSameOrigin, requireUser } from "@/lib/auth/session.ts";
import { all, get, run } from "@/lib/db/index.ts";
import { normalizeCourse } from "@/lib/learning/helpers.ts";
import { getPrompt } from "@/lib/prompts.ts";
import { completeChat } from "@/lib/openrouter/client.ts";
import { resolvePreset, getModel, estimateCost } from "@/lib/openrouter/registry.ts";
import { hybridSearch, buildContext } from "@/lib/rag/search.ts";
import { checkBudget, logUsage } from "@/lib/usage.ts";

export async function GET(req: Request, ctx: { params: Promise<{ course: string }> }) {
  try {
    const user = await requireUser();
    const course = normalizeCourse((await ctx.params).course);
    requireEnrollment(user.id, course);
    const url = new URL(req.url);
    const conceptSlug = url.searchParams.get("concept");
    const conceptFilter = conceptSlug
      ? "AND f.concept_id = (SELECT id FROM concepts WHERE course_code = ? AND slug = ?)"
      : "";
    const params: unknown[] = [user.id, course];
    if (conceptSlug) params.push(course, conceptSlug);

    // Cartes dues (état existant) puis nouvelles (jamais vues), plafonnées.
    const due = all(
      `SELECT f.id, f.type, f.front, f.back, f.concept_id, c.name as concept_name, cs.ef, cs.interval_days, cs.reps, cs.due_at, cs.favorite
       FROM card_states cs JOIN flashcards f ON f.id = cs.card_id LEFT JOIN concepts c ON c.id = f.concept_id
       WHERE cs.user_id = ? AND f.course_code = ? ${conceptFilter} AND cs.suspended = 0 AND cs.due_at <= datetime('now')
       ORDER BY cs.due_at LIMIT 40`,
      ...params
    );
    const fresh = all(
      `SELECT f.id, f.type, f.front, f.back, f.concept_id, c.name as concept_name
       FROM flashcards f LEFT JOIN concepts c ON c.id = f.concept_id
       WHERE f.course_code = ? ${conceptSlug ? "AND f.concept_id = (SELECT id FROM concepts WHERE course_code = ? AND slug = ?)" : ""}
         AND (f.owner_user_id IS NULL OR f.owner_user_id = ?)
         AND f.id NOT IN (SELECT card_id FROM card_states WHERE user_id = ?)
       ORDER BY f.id LIMIT 15`,
      ...(conceptSlug ? [course, course, conceptSlug, user.id, user.id] : [course, user.id, user.id])
    );
    const stats = {
      total: get<{ n: number }>(
        "SELECT COUNT(*) as n FROM flashcards WHERE course_code = ? AND (owner_user_id IS NULL OR owner_user_id = ?)", course, user.id
      )?.n ?? 0,
      learned: get<{ n: number }>(
        `SELECT COUNT(*) as n FROM card_states cs JOIN flashcards f ON f.id = cs.card_id WHERE cs.user_id = ? AND f.course_code = ? AND cs.reps >= 2`,
        user.id, course
      )?.n ?? 0,
      suspended: get<{ n: number }>(
        `SELECT COUNT(*) as n FROM card_states cs JOIN flashcards f ON f.id = cs.card_id WHERE cs.user_id = ? AND f.course_code = ? AND cs.suspended = 1`,
        user.id, course
      )?.n ?? 0,
    };
    return NextResponse.json({ due, fresh, stats });
  } catch (e) {
    return apiError(e);
  }
}

const createSchema = z.object({
  action: z.literal("create"),
  conceptSlug: z.string().max(120).nullable(),
  type: z.enum(["qa", "definition", "formula", "error", "comparison", "calc"]).default("qa"),
  front: z.string().min(3).max(2000),
  back: z.string().min(1).max(4000),
});
const generateSchema = z.object({
  action: z.literal("generate"),
  conceptSlug: z.string().min(1).max(120),
  count: z.number().int().min(2).max(10).default(5),
});

export async function POST(req: Request, ctx: { params: Promise<{ course: string }> }) {
  try {
    await assertSameOrigin();
    const user = await requireUser();
    const course = normalizeCourse((await ctx.params).course);
    requireEnrollment(user.id, course);
    const body = await parseBody(req, z.discriminatedUnion("action", [createSchema, generateSchema]));

    if (body.action === "create") {
      const conceptId = body.conceptSlug
        ? get<{ id: number }>("SELECT id FROM concepts WHERE course_code = ? AND slug = ?", course, body.conceptSlug)?.id ?? null
        : null;
      const r = run(
        `INSERT INTO flashcards (course_code, concept_id, type, front, back, created_by, owner_user_id, validated)
         VALUES (?, ?, ?, ?, ?, 'user', ?, 0)`,
        course, conceptId, body.type, body.front, body.back, user.id
      );
      return NextResponse.json({ ok: true, cardId: Number(r.lastInsertRowid) });
    }

    // Génération IA fondée sur le matériel du cours (RAG) — cartes privées à l'étudiant.
    const budget = checkBudget(user.id);
    if (!budget.ok) return NextResponse.json({ error: budget.reason }, { status: 429 });
    const concept = get<{ id: number; name: string; description: string }>(
      "SELECT id, name, description FROM concepts WHERE course_code = ? AND slug = ?", course, body.conceptSlug
    );
    if (!concept) return NextResponse.json({ error: "Concept inconnu." }, { status: 404 });

    const results = await hybridSearch({ query: concept.name + " " + concept.description, spaces: [`official-${course.toLowerCase()}`], k: 6 });
    const context = buildContext(results, 8000);
    const model = await resolvePreset("economique");
    const t0 = Date.now();
    const { text, promptTokens, completionTokens } = await completeChat({
      model,
      messages: [
        { role: "system", content: [getPrompt("base-system"), course === "IMM1003" ? getPrompt("course-imm1003") : getPrompt("course-imm1033"), getPrompt("flashcard-generation")].join("\n\n---\n\n") },
        { role: "user", content: `Concept ciblé : « ${concept.name} » (slug: ${body.conceptSlug}). Produis ${body.count} cartes.\n\nMatériel du cours :\n${context.text}` },
      ],
      jsonMode: true,
      temperature: 0.5,
    });
    const mi = await getModel(model);
    logUsage({ userId: user.id, model, kind: "flashcard-gen", tokensIn: promptTokens, tokensOut: completionTokens, cost: mi ? estimateCost(mi, promptTokens, completionTokens) : 0, latencyMs: Date.now() - t0 });

    let cards: { type?: string; front?: string; back?: string }[] = [];
    try {
      const parsed = JSON.parse(text.replace(/^```json?\s*|\s*```$/g, ""));
      cards = Array.isArray(parsed.flashcards) ? parsed.flashcards : [];
    } catch {
      return NextResponse.json({ error: "La génération a produit un format invalide. Réessayez." }, { status: 502 });
    }
    const created: number[] = [];
    for (const c of cards.slice(0, body.count)) {
      if (!c.front || !c.back) continue;
      const r = run(
        `INSERT INTO flashcards (course_code, concept_id, type, front, back, created_by, owner_user_id, validated)
         VALUES (?, ?, ?, ?, ?, 'ai', ?, 0)`,
        course, concept.id, ["qa", "definition", "formula", "error", "comparison", "calc"].includes(c.type ?? "") ? c.type : "qa",
        String(c.front).slice(0, 2000), String(c.back).slice(0, 4000), user.id
      );
      created.push(Number(r.lastInsertRowid));
    }
    return NextResponse.json({ ok: true, created: created.length });
  } catch (e) {
    return apiError(e);
  }
}