import { NextRequest, NextResponse } from "next/server"
import { prisma } from "@/lib/db"
import { buildFsrsCard, gradeCard, skillCodeFromGrade } from "@/lib/fsrs"

export async function POST(request: NextRequest) {
  try {
    const { childId, exerciseId, skillCode, correct, promptLevel, responseMs, errorType, stage } = await request.json()

    if (!childId || !exerciseId || !skillCode) {
      return NextResponse.json({ error: "Missing required fields" }, { status: 400 })
    }

    // Auto-create session log if none exists (so SkillAttempts are always stored)
    let sessionLog = await prisma.sessionLog.findFirst({
      where: { childId },
      orderBy: { startedAt: "desc" },
    })

    if (!sessionLog) {
      sessionLog = await prisma.sessionLog.create({
        data: { childId, startedAt: new Date() },
      })
    }

    await prisma.skillAttempt.create({
      data: {
        sessionLogId: sessionLog.id,
        skillCode,
        promptLevel: promptLevel ?? 0,
        correct,
        responseMs: responseMs ?? null,
        errorType: errorType ?? null,
        exerciseId,
        stage: stage ?? null,
      },
    })

    // Update/create FSRS card so due-date sorting works in the engine
    const existingCard = await prisma.fsrsCard.findFirst({
      where: { childId, skillCode },
    })

    const grade = skillCodeFromGrade(correct, responseMs ?? 5000)
    const baseCard = buildFsrsCard({
      stability: existingCard?.stability,
      difficulty: existingCard?.difficulty,
      reps: existingCard?.reps,
      lapses: existingCard?.lapses,
      due: existingCard?.dueAt,
    })

    const { card: updatedCard } = gradeCard(baseCard, grade)

    if (existingCard) {
      await prisma.fsrsCard.update({
        where: { id: existingCard.id },
        data: {
          dueAt: updatedCard.due,
          stability: updatedCard.stability,
          difficulty: updatedCard.difficulty,
          reps: updatedCard.reps,
          lapses: updatedCard.lapses,
        },
      })
    } else {
      await prisma.fsrsCard.create({
        data: {
          childId,
          skillCode,
          dueAt: updatedCard.due,
          stability: updatedCard.stability,
          difficulty: updatedCard.difficulty,
          reps: updatedCard.reps,
          lapses: updatedCard.lapses,
        },
      })
    }

    return NextResponse.json({ success: true })
  } catch (error) {
    console.error("Curriculum grade error:", error)
    return NextResponse.json({ error: "Internal error" }, { status: 500 })
  }
}