import { createHash, randomBytes } from 'node:crypto';

import { Injectable, NotFoundException } from '@nestjs/common';
import {
  FEED_TOKEN_PREFIX,
  type CreateFeedTokenInput,
  type FeedTokenCreatedView,
  type FeedTokenView,
} from '@dorfteich/shared';
import { FeedToken, User } from '@prisma/client';

import { PrismaService } from '../prisma/prisma.service';

/**
 * Feed-token lifecycle (issue #149). Mirrors the API-token mechanics — the
 * secret (`dt_feed_<random>`) is shown once and only its SHA-256 lands in the
 * database — but the token is read-only by construction: the sole consumer is
 * {@link FeedService}, which resolves it to a user for the two feed endpoints.
 */
@Injectable()
export class FeedTokensService {
  constructor(private readonly prisma: PrismaService) {}

  async list(user: User): Promise<FeedTokenView[]> {
    const rows = await this.prisma.feedToken.findMany({
      where: { userId: user.id },
      orderBy: { createdAt: 'desc' },
    });
    return rows.map((row) => this.view(row));
  }

  async create(user: User, input: CreateFeedTokenInput): Promise<FeedTokenCreatedView> {
    const secret = `${FEED_TOKEN_PREFIX}${randomBytes(24).toString('hex')}`;
    const row = await this.prisma.feedToken.create({
      data: { userId: user.id, name: input.name, tokenHash: hashFeedToken(secret) },
    });
    return { ...this.view(row), token: secret };
  }

  async remove(user: User, id: string): Promise<void> {
    const { count } = await this.prisma.feedToken.deleteMany({
      where: { id, userId: user.id },
    });
    if (count === 0) throw new NotFoundException();
  }

  /** The token's user, or null for a missing/invalid secret. */
  async resolve(secret: string): Promise<User | null> {
    if (!secret.startsWith(FEED_TOKEN_PREFIX)) return null;
    const row = await this.prisma.feedToken.findUnique({
      where: { tokenHash: hashFeedToken(secret) },
      include: { user: true },
    });
    if (!row) return null;
    // Best-effort usage stamp; a lost update here is harmless.
    await this.prisma.feedToken
      .update({ where: { id: row.id }, data: { lastUsedAt: new Date() } })
      .catch(() => undefined);
    return row.user;
  }

  private view(row: FeedToken): FeedTokenView {
    return {
      id: row.id,
      name: row.name,
      lastUsedAt: row.lastUsedAt?.toISOString() ?? null,
      createdAt: row.createdAt.toISOString(),
    };
  }
}

function hashFeedToken(raw: string): string {
  return createHash('sha256').update(raw).digest('hex');
}