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

namespace MoneyMap.Mcp.Tools;

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

    [McpServerTool(Name = "list_categories"), Description("List all categories with transaction counts.")]
    public static async Task<string> ListCategories(
        MoneyMapContext db = default!)
    {
        var categories = await db.Transactions
            .Where(t => t.Category != null && t.Category != "")
            .GroupBy(t => t.Category!)
            .Select(g => new { Category = g.Key, Count = g.Count(), TotalSpent = g.Where(t => t.Amount < 0).Sum(t => Math.Abs(t.Amount)) })
            .OrderByDescending(x => x.Count)
            .ToListAsync();

        var uncategorized = await db.Transactions
            .CountAsync(t => t.Category == null || t.Category == "");

        return JsonSerializer.Serialize(new { Categories = categories, UncategorizedCount = uncategorized }, JsonOptions);
    }

    [McpServerTool(Name = "get_category_mappings"), Description("Get auto-categorization pattern rules (CategoryMappings).")]
    public static async Task<string> GetCategoryMappings(
        [Description("Filter mappings to a specific category")] string? category = null,
        ITransactionCategorizer categorizer = default!)
    {
        var mappings = await categorizer.GetAllMappingsAsync();

        if (!string.IsNullOrWhiteSpace(category))
            mappings = mappings.Where(m => m.Category.Equals(category, StringComparison.OrdinalIgnoreCase)).ToList();

        var result = mappings.Select(m => new
        {
            m.Id,
            m.Pattern,
            m.Category,
            m.MerchantId,
            m.Priority
        }).OrderBy(m => m.Category).ThenByDescending(m => m.Priority).ToList();

        return JsonSerializer.Serialize(result, JsonOptions);
    }

    [McpServerTool(Name = "add_category_mapping"), Description("Add a new auto-categorization rule that maps transaction name patterns to categories.")]
    public static async Task<string> AddCategoryMapping(
        [Description("Pattern to match in transaction name (case-insensitive)")] string pattern,
        [Description("Category to assign when pattern matches")] string category,
        [Description("Merchant name to assign (creates if new)")] string? merchantName = null,
        [Description("Priority (higher = checked first, default 0)")] int priority = 0,
        MoneyMapContext db = default!,
        IMerchantService merchantService = default!)
    {
        int? merchantId = null;
        if (!string.IsNullOrWhiteSpace(merchantName))
            merchantId = await merchantService.GetOrCreateIdAsync(merchantName);

        var mapping = new MoneyMap.Models.CategoryMapping
        {
            Pattern = pattern,
            Category = category,
            MerchantId = merchantId,
            Priority = priority
        };

        db.CategoryMappings.Add(mapping);
        await db.SaveChangesAsync();

        return JsonSerializer.Serialize(new { Created = true, mapping.Id, mapping.Pattern, mapping.Category, Merchant = merchantName, mapping.Priority }, JsonOptions);
    }
}