MoneyMap/MoneyMap.Mcp/Tools/MerchantTools.cs

using System.ComponentModel;
using System.Text.Json;
using Microsoft.EntityFrameworkCore;
using ModelContextProtocol.Server;
using MoneyMap.Data;

namespace MoneyMap.Mcp.Tools;

[McpServerToolType]
public static class MerchantTools
{
    private static readonly JsonSerializerOptions JsonOptions = new() { WriteIndented = true };

    [McpServerTool(Name = "list_merchants"), Description("List all merchants with transaction counts and category mapping info.")]
    public static async Task<string> ListMerchants(
        [Description("Filter merchants by name (contains)")] string? query = null,
        MoneyMapContext db = default!)
    {
        var q = db.Merchants
            .Include(m => m.Transactions)
            .Include(m => m.CategoryMappings)
            .AsQueryable();

        if (!string.IsNullOrWhiteSpace(query))
            q = q.Where(m => m.Name.Contains(query));

        var merchants = await q
            .OrderBy(m => m.Name)
            .Select(m => new
            {
                m.Id,
                m.Name,
                TransactionCount = m.Transactions.Count,
                MappingCount = m.CategoryMappings.Count,
                Categories = m.CategoryMappings.Select(cm => cm.Category).Distinct().ToList()
            })
            .ToListAsync();

        return JsonSerializer.Serialize(new { Count = merchants.Count, Merchants = merchants }, JsonOptions);
    }

    [McpServerTool(Name = "merge_merchants"), Description("Merge duplicate merchants. Reassigns all transactions and category mappings from source to target, then deletes source.")]
    public static async Task<string> MergeMerchants(
        [Description("Merchant ID to merge FROM (will be deleted)")] int sourceMerchantId,
        [Description("Merchant ID to merge INTO (will be kept)")] int targetMerchantId,
        MoneyMapContext db = default!)
    {
        if (sourceMerchantId == targetMerchantId)
            return "Source and target merchant cannot be the same";

        var source = await db.Merchants.FindAsync(sourceMerchantId);
        var target = await db.Merchants.FindAsync(targetMerchantId);

        if (source == null)
            return $"Source merchant {sourceMerchantId} not found";
        if (target == null)
            return $"Target merchant {targetMerchantId} not found";

        var transactions = await db.Transactions
            .Where(t => t.MerchantId == sourceMerchantId)
            .ToListAsync();

        foreach (var t in transactions)
            t.MerchantId = targetMerchantId;

        var sourceMappings = await db.CategoryMappings
            .Where(cm => cm.MerchantId == sourceMerchantId)
            .ToListAsync();

        var targetMappingPatterns = await db.CategoryMappings
            .Where(cm => cm.MerchantId == targetMerchantId)
            .Select(cm => cm.Pattern)
            .ToListAsync();

        foreach (var mapping in sourceMappings)
        {
            if (targetMappingPatterns.Contains(mapping.Pattern))
                db.CategoryMappings.Remove(mapping);
            else
                mapping.MerchantId = targetMerchantId;
        }

        db.Merchants.Remove(source);
        await db.SaveChangesAsync();

        return JsonSerializer.Serialize(new
        {
            Merged = true,
            Source = new { source.Id, source.Name },
            Target = new { target.Id, target.Name },
            TransactionsReassigned = transactions.Count,
            MappingsReassigned = sourceMappings.Count
        }, JsonOptions);
    }
}