// app/api/progress/route.ts
import { NextResponse } from 'next/server';
import { getServerSession } from 'next-auth';
import { authOptions } from '@/lib/auth-options';
import { prisma } from '@/lib/prisma';
import {
  UNLOCK_THRESHOLD_PERCENT,
  mergeRanges,
  sanitizeRanges,
  totalSeconds,
  unlockNextVideo,
  type SecRange,
} from '@/lib/watch-progress';

export async function GET(req: Request) {
  try {
    const session = await getServerSession(authOptions);
    if (!session?.user?.email)
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });

    const userEmail = session.user.email;
    const { searchParams } = new URL(req.url);
    const videoId = searchParams.get('videoId');

    if (!videoId)
      return NextResponse.json({ error: 'videoId required' }, { status: 400 });

    const user = await prisma.user.findUnique({ where: { email: userEmail } });
    if (!user)
      return NextResponse.json({ error: 'user not found' }, { status: 404 });

    // Validate that the video exists
    const video = await prisma.video.findUnique({ where: { id: videoId } });
    if (!video) {
      console.debug(`[PROGRESS] Video not found: ${videoId} (likely deleted video with cached browser reference)`);
      return NextResponse.json({ error: 'video not found' }, { status: 404 });
    }

    const progress = await prisma.videoProgress.findUnique({
      where: { userId_videoId: { userId: user.id, videoId } },
      select: { percent: true, lastPos: true, watchedSec: true },
    });

    return NextResponse.json({ 
      percent: progress?.percent ?? 0,
      lastPos: progress?.lastPos ?? 0,
      watchedSec: progress?.watchedSec ?? 0,
    });
  } catch (err: any) {
    console.error('progress GET error', err);
    return NextResponse.json(
      { error: err?.message ?? 'server error' },
      { status: 500 }
    );
  }
}

export async function POST(req: Request) {
  try {
    const session = await getServerSession(authOptions);
    if (!session?.user?.email)
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });

    const userEmail = session.user.email;

    const body = await req.json().catch(() => ({}));
    const { videoId, watchedSec, lastPos, duration } = body ?? {};

    if (!videoId || typeof videoId !== 'string')
      return NextResponse.json({ error: 'videoId required' }, { status: 400 });

    // look up user id
    const user = await prisma.user.findUnique({
      where: { email: userEmail },
      select: { id: true },
    });
    if (!user)
      return NextResponse.json({ error: 'user not found' }, { status: 404 });

    // Validate that the video exists
    const video = await prisma.video.findUnique({
      where: { id: videoId },
      select: { id: true, playlistId: true, durationSec: true },
    });
    if (!video) {
      // Log at debug level since this is expected when users have old cached references
      console.debug(`[PROGRESS] Video not found: ${videoId} (likely deleted video with cached browser reference)`);
      return NextResponse.json({ error: 'video not found' }, { status: 404 });
    }

    // The stored duration wins; the player's value is only a fallback for
    // videos uploaded without one.
    const dur =
      video.durationSec && video.durationSec > 0 ? video.durationSec : Number(duration);
    if (!Number.isFinite(dur) || dur <= 0)
      return NextResponse.json({ error: 'duration required' }, { status: 400 });

    const lastPosition = Math.max(0, Math.floor(Number(lastPos ?? 0)) || 0);

    // Current players send the ranges actually played. Tabs still running the
    // previous player only send a total, from which one range is inferred.
    let incoming: SecRange[];
    if (Array.isArray(body?.ranges)) {
      incoming = sanitizeRanges(body.ranges, dur);
    } else {
      const watched = Number(watchedSec ?? 0);
      incoming = sanitizeRanges(
        watched > 0 ? [[lastPosition - watched, lastPosition]] : [],
        dur
      );
    }

    const where = { userId_videoId: { userId: user.id, videoId } };

    const { progress, segments } = await prisma.$transaction(async (tx) => {
      const existingProgress = await tx.videoProgress.upsert({
        where,
        update: {},
        create: {
          userId: user.id,
          videoId,
          watchedSec: 0,
          lastPos: 0,
          percent: 0,
          durationSec: Math.round(dur),
        },
      });

      const existing = await tx.videoWatchSegment.findMany({
        where: { userId: user.id, videoId },
        select: { startSec: true, endSec: true, watchedAt: true },
        orderBy: { startSec: 'asc' },
      });

      // Keep one row per distinct watched stretch instead of one per update.
      const now = new Date();
      const merged = mergeRanges([
        ...existing,
        ...incoming.map((r) => ({ ...r, watchedAt: now })),
      ]);
      const unchanged =
        merged.length === existing.length &&
        merged.every(
          (m, i) => m.startSec === existing[i].startSec && m.endSec === existing[i].endSec
        );
      if (!unchanged) {
        await tx.videoWatchSegment.deleteMany({ where: { userId: user.id, videoId } });
        await tx.videoWatchSegment.createMany({
          data: merged.map((m) => ({
            userId: user.id,
            videoId,
            startSec: m.startSec,
            endSec: m.endSec,
            watchedAt: m.watchedAt ?? now,
          })),
        });
      }

      // Progress never goes backwards, even if segment rows were pruned.
      const mergedSec = totalSeconds(merged);
      const percent = Math.max(
        existingProgress.percent,
        Math.min(100, Math.round((mergedSec / dur) * 100))
      );
      const completed =
        existingProgress.completed || percent >= UNLOCK_THRESHOLD_PERCENT;

      const updated = await tx.videoProgress.update({
        where,
        data: {
          watchedSec: Math.max(existingProgress.watchedSec, mergedSec),
          lastPos: Math.max(existingProgress.lastPos ?? 0, lastPosition),
          percent,
          durationSec: Math.round(dur),
          completed,
          updatedAt: now,
        },
      });

      return { progress: updated, segments: merged };
    });

    // Completing a video unlocks the next one in its playlist for this user.
    const unlockedNext = progress.completed
      ? await unlockNextVideo(user.id, video)
      : null;

    return NextResponse.json({ ok: true, progress, unlockedNext, segments });
  } catch (err: any) {
    console.error('progress error', err);

    return NextResponse.json(
      { error: err?.message ?? 'server error' },
      { status: 500 }
    );
  }
}