T120B165/T120B165-ImgBoard/Services/PostService.cs

using System.Text.RegularExpressions;
using Microsoft.EntityFrameworkCore;
using T120B165_ImgBoard.Data;
using T120B165_ImgBoard.Models;
using T120B165_ImgBoard.Utils;
using File = T120B165_ImgBoard.Models.File;

namespace T120B165_ImgBoard.Services;

public interface IPostService
{
    Task<CreatedPost> Create(
        string title, string description, List<Tag> tags, User author,
        string fileName, string fileContentType, long fileSize);
    Task<Post?> GetById(int postId, bool includeUnfinished = false);
    public Task<PagedList<Post>> FindAll(string? query, int pageNumber = 1);
    Task<bool> Delete(Post post);
    Task<Post> Update(Post post);
}

public record CreatedPost(Post Post, File File);

public class PostService(ImgBoardContext context): IPostService
{
    private const int PageSize = 8;
    public async Task<CreatedPost> Create(
        string title,
        string description,
        List<Tag> tags,
        User author,
        string fileName,
        string fileContentType,
        long fileSize
        )
    {
        var file = new File
        {
            OriginalFileName = fileName,
            Size = fileSize,
            ContentType = fileContentType,
            FilePath = Path.GetTempFileName(),
            CreatedDate = DateTime.Now,
        };
        await context.Files.AddAsync(file);
        
        var entry = new Post
        {
            Title = title,
            Description = description,
            Author = author,
            Created = DateTime.Now,
            Tags = tags,
            File = file
        };
        await context.Posts.AddAsync(entry);
        await context.SaveChangesAsync();
        return new CreatedPost(entry, file);
    }

    public async Task<Post?> GetById(int postId, bool includeUnfinished = false)
    {
        var query = context.Posts.Where(t => t.Id == postId);
        if (!includeUnfinished)
        {
            query = query.Where(t => t.File.FinishedDate != null);
        }
            
        return await query.Include(b => b.Author)
            .Include(b => b.Tags)
            .Include(b => b.File)
            .FirstOrDefaultAsync();
    }
    
    public async Task<PagedList<Post>> FindAll(string? query, int pageNumber = 1)
    {
        var postsQuery = context.Posts
            .Where(p => p.File.FinishedDate != null);

        // Apply query filtering if the query string is not null or empty
        if (!string.IsNullOrWhiteSpace(query))
        {
            // Parse the query string into required and excluded tags
            var (requiredTags, excludedTags) = ParseTagQuery(query);

            // Filter for required tags (Post must have ALL of these tags)
            foreach (var requiredTag in requiredTags)
            {
                // Where the post's Tags collection contains ANY tag whose name matches the requiredTag.
                postsQuery = postsQuery.Where(p => p.Tags.Any(t => t.Name == requiredTag));
            }

            // Filter out excluded tags (Post must NOT have ANY of these tags)
            foreach (var excludedTag in excludedTags)
            {
                // Where the post's Tags collection does NOT contain ANY tag whose name matches the excludedTag.
                postsQuery = postsQuery.Where(p => p.Tags.All(t => t.Name != excludedTag));
            }
        }
        
        var totalCount = await postsQuery.CountAsync();
        var items = await postsQuery
            .Skip((pageNumber - 1) * PageSize)
            .Take(PageSize)
            .Include(b => b.Author)
            .Include(b => b.Tags)
            .Include(b => b.File)
            .ToListAsync();
        return new PagedList<Post>(items, pageNumber, PageSize, totalCount);
    }
    
    private static (List<string> requiredTags, List<string> excludedTags) ParseTagQuery(string query)
    {
        var requiredTags = new List<string>();
        var excludedTags = new List<string>();

        // Regex to find all "+tag" or "-tag" segments
        var matches = Regex.Matches(query, @"([+-])([\w-]+)");

        foreach (Match match in matches)
        {
            var type = match.Groups[1].Value; // "+" or "-"
            var tag = match.Groups[2].Value; // The tag name

            switch (type)
            {
                case "+":
                    requiredTags.Add(tag);
                    break;
                case "-":
                    excludedTags.Add(tag);
                    break;
            }
        }

        return (requiredTags, excludedTags);
    }

    public async Task<bool> Delete(Post post)
    {
        context.Posts.Remove(post);
        await context.SaveChangesAsync();
        return true;
    }

    public async Task<Post> Update(Post post)
    {
        context.Posts.Update(post);
        await context.SaveChangesAsync();
        return post;
    }
}