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 TransactionTools
{
    private static readonly JsonSerializerOptions JsonOptions = new() { WriteIndented = true };

    [McpServerTool(Name = "search_transactions"), Description("Search and filter transactions. Returns matching transactions with details.")]
    public static async Task<string> SearchTransactions(
        [Description("Full-text search across name, memo, and category")] string? query = null,
        [Description("Start date (inclusive), e.g. 2026-01-01")] string? startDate = null,
        [Description("End date (inclusive), e.g. 2026-01-31")] string? endDate = null,
        [Description("Filter by category name (exact match)")] string? category = null,
        [Description("Filter by merchant name (contains)")] string? merchantName = null,
        [Description("Minimum amount (absolute value)")] decimal? minAmount = null,
        [Description("Maximum amount (absolute value)")] decimal? maxAmount = null,
        [Description("Filter by account ID")] int? accountId = null,
        [Description("Filter by card ID")] int? cardId = null,
        [Description("Filter by type: 'debit' or 'credit'")] string? type = null,
        [Description("Only show uncategorized transactions")] bool? uncategorizedOnly = null,
        [Description("Max results to return (default 50)")] int? limit = null,
        MoneyMapContext db = default!)
    {
        var q = db.Transactions
            .Include(t => t.Merchant)
            .Include(t => t.Card)
            .Include(t => t.Account)
            .Include(t => t.Receipts)
            .AsQueryable();

        if (!string.IsNullOrWhiteSpace(query))
            q = q.Where(t => t.Name.Contains(query) || (t.Memo != null && t.Memo.Contains(query)) || (t.Category != null && t.Category.Contains(query)));

        if (!string.IsNullOrWhiteSpace(startDate) && DateTime.TryParse(startDate, out var start))
            q = q.Where(t => t.Date >= start);

        if (!string.IsNullOrWhiteSpace(endDate) && DateTime.TryParse(endDate, out var end))
            q = q.Where(t => t.Date <= end);

        if (!string.IsNullOrWhiteSpace(category))
            q = q.Where(t => t.Category == category);

        if (!string.IsNullOrWhiteSpace(merchantName))
            q = q.Where(t => t.Merchant != null && t.Merchant.Name.Contains(merchantName));

        if (minAmount.HasValue)
            q = q.Where(t => Math.Abs(t.Amount) >= minAmount.Value);

        if (maxAmount.HasValue)
            q = q.Where(t => Math.Abs(t.Amount) <= maxAmount.Value);

        if (accountId.HasValue)
            q = q.Where(t => t.AccountId == accountId.Value);

        if (cardId.HasValue)
            q = q.Where(t => t.CardId == cardId.Value);

        if (type?.ToLower() == "debit")
            q = q.Where(t => t.Amount < 0);
        else if (type?.ToLower() == "credit")
            q = q.Where(t => t.Amount > 0);

        if (uncategorizedOnly == true)
            q = q.Where(t => t.Category == null || t.Category == "");

        var results = await q
            .OrderByDescending(t => t.Date).ThenByDescending(t => t.Id)
            .Take(limit ?? 50)
            .Select(t => new
            {
                t.Id,
                t.Date,
                t.Name,
                t.Memo,
                t.Amount,
                t.Category,
                Merchant = t.Merchant != null ? t.Merchant.Name : null,
                Account = t.Account!.Institution + " " + t.Account.Last4,
                Card = t.Card != null ? t.Card.Issuer + " " + t.Card.Last4 : null,
                ReceiptCount = t.Receipts.Count,
                t.TransferToAccountId
            })
            .ToListAsync();

        return JsonSerializer.Serialize(new { Count = results.Count, Transactions = results }, JsonOptions);
    }

    [McpServerTool(Name = "get_transaction"), Description("Get a single transaction with all details including receipts.")]
    public static async Task<string> GetTransaction(
        [Description("Transaction ID")] long transactionId,
        MoneyMapContext db = default!)
    {
        var t = await db.Transactions
            .Include(t => t.Merchant)
            .Include(t => t.Card)
            .Include(t => t.Account)
            .Include(t => t.Receipts)
            .Where(t => t.Id == transactionId)
            .Select(t => new
            {
                t.Id,
                t.Date,
                t.Name,
                t.Memo,
                t.Amount,
                t.TransactionType,
                t.Category,
                Merchant = t.Merchant != null ? t.Merchant.Name : null,
                MerchantId = t.MerchantId,
                Account = t.Account!.Institution + " " + t.Account.Last4,
                AccountId = t.AccountId,
                Card = t.Card != null ? t.Card.Issuer + " " + t.Card.Last4 : null,
                CardId = t.CardId,
                t.Notes,
                t.TransferToAccountId,
                Receipts = t.Receipts.Select(r => new { r.Id, r.FileName, r.ParseStatus, r.Merchant, r.Total }).ToList()
            })
            .FirstOrDefaultAsync();

        if (t == null)
            return "Transaction not found";

        return JsonSerializer.Serialize(t, JsonOptions);
    }

    [McpServerTool(Name = "get_spending_summary"), Description("Get spending totals grouped by category for a date range. Excludes transfers.")]
    public static async Task<string> GetSpendingSummary(
        [Description("Start date (inclusive), e.g. 2026-01-01")] string startDate,
        [Description("End date (inclusive), e.g. 2026-01-31")] string endDate,
        [Description("Filter to specific account ID")] int? accountId = null,
        MoneyMapContext db = default!)
    {
        var start = DateTime.Parse(startDate);
        var end = DateTime.Parse(endDate);

        var q = db.Transactions
            .Where(t => t.Date >= start && t.Date <= end)
            .Where(t => t.Amount < 0)
            .Where(t => t.TransferToAccountId == null)
            .ExcludeTransfers();

        if (accountId.HasValue)
            q = q.Where(t => t.AccountId == accountId.Value);

        var summary = await q
            .GroupBy(t => t.Category ?? "Uncategorized")
            .Select(g => new { Category = g.Key, Total = g.Sum(t => Math.Abs(t.Amount)), Count = g.Count() })
            .OrderByDescending(x => x.Total)
            .ToListAsync();

        var grandTotal = summary.Sum(x => x.Total);

        return JsonSerializer.Serialize(new { Period = $"{startDate} to {endDate}", GrandTotal = grandTotal, Categories = summary }, JsonOptions);
    }

    [McpServerTool(Name = "get_income_summary"), Description("Get income (credits) grouped by source/name for a date range.")]
    public static async Task<string> GetIncomeSummary(
        [Description("Start date (inclusive), e.g. 2026-01-01")] string startDate,
        [Description("End date (inclusive), e.g. 2026-01-31")] string endDate,
        [Description("Filter to specific account ID")] int? accountId = null,
        MoneyMapContext db = default!)
    {
        var start = DateTime.Parse(startDate);
        var end = DateTime.Parse(endDate);

        var q = db.Transactions
            .Where(t => t.Date >= start && t.Date <= end)
            .Where(t => t.Amount > 0)
            .Where(t => t.TransferToAccountId == null)
            .ExcludeTransfers();

        if (accountId.HasValue)
            q = q.Where(t => t.AccountId == accountId.Value);

        var summary = await q
            .GroupBy(t => t.Name)
            .Select(g => new { Source = g.Key, Total = g.Sum(t => t.Amount), Count = g.Count() })
            .OrderByDescending(x => x.Total)
            .ToListAsync();

        var grandTotal = summary.Sum(x => x.Total);

        return JsonSerializer.Serialize(new { Period = $"{startDate} to {endDate}", GrandTotal = grandTotal, Sources = summary }, JsonOptions);
    }

    [McpServerTool(Name = "update_transaction_category"), Description("Update the category (and optionally merchant) on one or more transactions.")]
    public static async Task<string> UpdateTransactionCategory(
        [Description("Array of transaction IDs to update")] long[] transactionIds,
        [Description("New category to assign")] string category,
        [Description("Merchant name to assign (creates if new)")] string? merchantName = null,
        MoneyMapContext db = default!,
        IMerchantService merchantService = default!)
    {
        var transactions = await db.Transactions
            .Where(t => transactionIds.Contains(t.Id))
            .ToListAsync();

        if (!transactions.Any())
            return "No transactions found with the provided IDs";

        int? merchantId = null;
        if (!string.IsNullOrWhiteSpace(merchantName))
            merchantId = await merchantService.GetOrCreateIdAsync(merchantName);

        foreach (var t in transactions)
        {
            t.Category = category;
            if (merchantId.HasValue)
                t.MerchantId = merchantId;
        }

        await db.SaveChangesAsync();

        return JsonSerializer.Serialize(new { Updated = transactions.Count, Category = category, Merchant = merchantName }, JsonOptions);
    }

    [McpServerTool(Name = "bulk_recategorize"), Description("Recategorize all transactions matching a name pattern. Use dryRun=true (default) to preview changes first.")]
    public static async Task<string> BulkRecategorize(
        [Description("Pattern to match in transaction name (case-insensitive contains)")] string namePattern,
        [Description("New category to assign")] string toCategory,
        [Description("Only recategorize transactions currently in this category")] string? fromCategory = null,
        [Description("Merchant name to assign (creates if new)")] string? merchantName = null,
        [Description("If true (default), only shows what would change without applying")] bool dryRun = true,
        MoneyMapContext db = default!,
        IMerchantService merchantService = default!)
    {
        var q = db.Transactions
            .Where(t => t.Name.Contains(namePattern));

        if (!string.IsNullOrWhiteSpace(fromCategory))
            q = q.Where(t => t.Category == fromCategory);

        var transactions = await q.ToListAsync();

        if (!transactions.Any())
            return JsonSerializer.Serialize(new { Message = "No transactions match the pattern", Pattern = namePattern, FromCategory = fromCategory }, JsonOptions);

        if (dryRun)
        {
            var preview = transactions.Take(20).Select(t => new { t.Id, t.Date, t.Name, t.Amount, CurrentCategory = t.Category }).ToList();
            return JsonSerializer.Serialize(new { DryRun = true, TotalMatches = transactions.Count, Preview = preview, ToCategory = toCategory }, JsonOptions);
        }

        int? merchantId = null;
        if (!string.IsNullOrWhiteSpace(merchantName))
            merchantId = await merchantService.GetOrCreateIdAsync(merchantName);

        foreach (var t in transactions)
        {
            t.Category = toCategory;
            if (merchantId.HasValue)
                t.MerchantId = merchantId;
        }

        await db.SaveChangesAsync();

        return JsonSerializer.Serialize(new { Applied = true, Updated = transactions.Count, ToCategory = toCategory, Merchant = merchantName }, JsonOptions);
    }
}