src/controllers/blog-related.controller.ts

import { Request, Response } from 'express';
import prisma from '../models/prisma';

// Type for blog post with author
type BlogPostWithAuthor = {
    id: string;
    title: string;
    slug: string;
    content: string;
    excerpt: string | null;
    featuredImage: string | null;
    tags: string | null;
    status: string;
    publishedAt: Date | null;
    createdAt: Date;
    updatedAt: Date;
    authorId: string;
    author: { name: string | null } | null;
};

// GET /api/blog/:slug/related (Public)
export const getRelatedPosts = async (req: Request, res: Response) => {
    try {
        const { slug } = req.params;

        // Find the current post to get its tags
        const currentPost = await prisma.blogPost.findFirst({
            where: { slug }
        });

        if (!currentPost) {
            return res.status(404).json({ error: 'Post not found' });
        }

        // Parse tags
        let tags: string[] = [];
        try {
            if (currentPost.tags) tags = JSON.parse(currentPost.tags);
        } catch (e) {
            // ignore
        }

        // If no tags, just return 3 latest posts excluding current
        if (tags.length === 0) {
            const latest = await prisma.blogPost.findMany({
                where: {
                    status: 'PUBLISHED',
                    slug: { not: slug },
                    publishedAt: { lte: new Date() }
                },
                orderBy: { publishedAt: 'desc' },
                take: 3,
                include: { author: { select: { name: true } } }
            });
            return res.status(200).json(latest);
        }

        // SQLite doesn't natively support querying inside JSON arrays easily without raw queries or specific extensions,
        // so we'll fetch recently published posts and manually filter/score them by tag overlap.
        // For a production app with Postgres, you'd use a raw query or better JSON filtering.

        const allOtherPosts = await prisma.blogPost.findMany({
            where: {
                status: 'PUBLISHED',
                slug: { not: slug },
                publishedAt: { lte: new Date() }
            },
            orderBy: {
                publishedAt: 'desc'
            },
            take: 50, // Limit to recent 50 to avoid massive memory usage
            include: { author: { select: { name: true } } }
        });

        // Score based on shared tags
        const scoredPosts: { post: BlogPostWithAuthor; score: number }[] = allOtherPosts.map((post: BlogPostWithAuthor) => {
            let postTags: string[] = [];
            try {
                if (post.tags) postTags = JSON.parse(post.tags);
            } catch (e) { }

            const intersection = tags.filter(t => postTags.includes(t));
            return { post, score: intersection.length };
        });

        // Sort by score (desc), then date (desc) implicitly from the DB query
        scoredPosts.sort((a: { post: BlogPostWithAuthor; score: number }, b: { post: BlogPostWithAuthor; score: number }) => b.score - a.score);

        // Take top 3
        const related = scoredPosts.slice(0, 3).map((s: { post: BlogPostWithAuthor; score: number }) => s.post);

        return res.status(200).json(related);
    } catch (error) {
        console.error('Error fetching related posts:', error);
        return res.status(500).json({ error: 'Internal server error' });
    }
}