using BakeryErp.Infrastructure.Database;

namespace BakeryErp.Infrastructure.Repositories;

public sealed class PettyCashRepository
{
    private readonly DatabaseOptions _options;

    public PettyCashRepository(DatabaseOptions options)
    {
        _options = options;
    }

    public IReadOnlyList<LocalPettyCashTransaction> List()
    {
        return LocalDataStoreFile.Load(_options)
            .PettyCashTransactions
            .OrderByDescending(static transaction => transaction.TransactionDate)
            .ThenBy(static transaction => transaction.TransactionNumber)
            .ToList();
    }

    public LocalPettyCashTransaction? Find(Guid id)
    {
        return LocalDataStoreFile.Load(_options)
            .PettyCashTransactions
            .FirstOrDefault(transaction => transaction.Id == id);
    }

    public PettyCashReport GetReport()
    {
        var transactions = LocalDataStoreFile.Load(_options).PettyCashTransactions;
        var approvedExpenses = transactions.Where(static transaction =>
            transaction.TransactionType == LocalPettyCashTransactionType.Expense &&
            transaction.Status is LocalPettyCashStatus.Approved or LocalPettyCashStatus.MonthlyClosed);
        var replenishments = transactions.Where(static transaction =>
            transaction.TransactionType == LocalPettyCashTransactionType.Replenishment &&
            transaction.Status is LocalPettyCashStatus.Approved or LocalPettyCashStatus.Replenished);

        return new PettyCashReport(
            transactions.Count,
            transactions.Count(static transaction => transaction.Status == LocalPettyCashStatus.PendingFinanceApproval),
            approvedExpenses.Sum(static transaction => transaction.Amount),
            transactions.Count(static transaction => transaction.Status == LocalPettyCashStatus.MonthlyClosed),
            replenishments.Sum(static transaction => transaction.Amount),
            replenishments.Sum(static transaction => transaction.Amount) - approvedExpenses.Sum(static transaction => transaction.Amount));
    }

    public IReadOnlyList<StorePettyCashSummary> GetStoreSummaries()
    {
        return LocalDataStoreFile.Load(_options)
            .PettyCashTransactions
            .Where(static transaction => transaction.Status != LocalPettyCashStatus.Cancelled)
            .GroupBy(static transaction => transaction.StoreName)
            .Select(group => new StorePettyCashSummary(
                group.Key,
                group.Count(),
                group.Where(static transaction => transaction.TransactionType == LocalPettyCashTransactionType.Expense).Sum(static transaction => transaction.Amount),
                group.Where(static transaction => transaction.TransactionType == LocalPettyCashTransactionType.Replenishment).Sum(static transaction => transaction.Amount)))
            .OrderByDescending(static summary => summary.ExpenseAmount)
            .ToList();
    }

    public SavePettyCashResult Save(LocalPettyCashTransaction transaction)
    {
        var store = LocalDataStoreFile.Load(_options);
        var transactionNumber = transaction.TransactionNumber.Trim().ToUpperInvariant();

        if (string.IsNullOrWhiteSpace(transactionNumber) ||
            string.IsNullOrWhiteSpace(transaction.StoreName) ||
            string.IsNullOrWhiteSpace(transaction.ExpenseCategory))
        {
            return SavePettyCashResult.ValidationError("零用金單號、門市與分類為必填。");
        }

        if (transaction.Amount <= 0)
        {
            return SavePettyCashResult.ValidationError("金額需大於 0。");
        }

        var duplicatedNumber = store.PettyCashTransactions.Any(existing =>
            existing.Id != transaction.Id &&
            string.Equals(existing.TransactionNumber, transactionNumber, StringComparison.OrdinalIgnoreCase));
        if (duplicatedNumber)
        {
            return SavePettyCashResult.ValidationError("零用金單號已存在，請改用其他單號。");
        }

        var existingTransaction = store.PettyCashTransactions.FirstOrDefault(existing => existing.Id == transaction.Id);
        if (existingTransaction is null)
        {
            transaction.Id = transaction.Id == Guid.Empty ? Guid.NewGuid() : transaction.Id;
            transaction.TransactionNumber = transactionNumber;
            transaction.StoreName = transaction.StoreName.Trim();
            transaction.ExpenseCategory = transaction.ExpenseCategory.Trim();
            transaction.Description = BlankToNull(transaction.Description);
            transaction.Status = LocalPettyCashStatus.PendingFinanceApproval;
            transaction.CreatedAt = DateTime.UtcNow;
            store.PettyCashTransactions.Add(transaction);
        }
        else
        {
            if (existingTransaction.Status is LocalPettyCashStatus.Approved or LocalPettyCashStatus.MonthlyClosed or LocalPettyCashStatus.Replenished)
            {
                return SavePettyCashResult.ValidationError("已審核、已月結或已撥補的零用金紀錄不可編輯。");
            }

            existingTransaction.TransactionNumber = transactionNumber;
            existingTransaction.StoreName = transaction.StoreName.Trim();
            existingTransaction.TransactionDate = transaction.TransactionDate;
            existingTransaction.TransactionType = transaction.TransactionType;
            existingTransaction.ExpenseCategory = transaction.ExpenseCategory.Trim();
            existingTransaction.Amount = transaction.Amount;
            existingTransaction.Description = BlankToNull(transaction.Description);
            existingTransaction.ReceiptImagePath = BlankToNull(transaction.ReceiptImagePath) ?? existingTransaction.ReceiptImagePath;
            existingTransaction.Status = LocalPettyCashStatus.PendingFinanceApproval;
            existingTransaction.UpdatedAt = DateTime.UtcNow;
        }

        LocalDataStoreFile.Save(_options, store);
        return SavePettyCashResult.Success();
    }

    public void Approve(Guid id)
    {
        UpdateStatus(id, LocalPettyCashStatus.Approved);
    }

    public void Reject(Guid id)
    {
        UpdateStatus(id, LocalPettyCashStatus.Rejected);
    }

    public void CloseMonthly(Guid id)
    {
        UpdateStatus(id, LocalPettyCashStatus.MonthlyClosed);
    }

    public void Replenish(Guid id)
    {
        UpdateStatus(id, LocalPettyCashStatus.Replenished);
    }

    public static string GetTransactionTypeName(LocalPettyCashTransactionType type)
    {
        return type switch
        {
            LocalPettyCashTransactionType.Expense => "門市支出",
            LocalPettyCashTransactionType.Replenishment => "零用金撥補",
            LocalPettyCashTransactionType.Adjustment => "調整",
            _ => type.ToString()
        };
    }

    public static string GetStatusName(LocalPettyCashStatus status)
    {
        return status switch
        {
            LocalPettyCashStatus.Draft => "草稿",
            LocalPettyCashStatus.PendingFinanceApproval => "待財務審核",
            LocalPettyCashStatus.Approved => "已審核",
            LocalPettyCashStatus.MonthlyClosed => "已月結",
            LocalPettyCashStatus.Replenished => "已撥補",
            LocalPettyCashStatus.Rejected => "已退回",
            LocalPettyCashStatus.Cancelled => "已取消",
            _ => status.ToString()
        };
    }

    private void UpdateStatus(Guid id, LocalPettyCashStatus status)
    {
        var store = LocalDataStoreFile.Load(_options);
        var transaction = store.PettyCashTransactions.FirstOrDefault(existing => existing.Id == id);
        if (transaction is null)
        {
            return;
        }

        transaction.Status = status;
        transaction.UpdatedAt = DateTime.UtcNow;
        if (status == LocalPettyCashStatus.Approved)
        {
            transaction.ApprovedAt = DateTime.UtcNow;
        }
        if (status == LocalPettyCashStatus.MonthlyClosed)
        {
            transaction.ClosedAt = DateTime.UtcNow;
        }

        LocalDataStoreFile.Save(_options, store);
    }

    private static string? BlankToNull(string? value)
    {
        return string.IsNullOrWhiteSpace(value) ? null : value.Trim();
    }
}

public sealed record PettyCashReport(
    int TransactionCount,
    int PendingFinanceApprovalCount,
    decimal ApprovedExpenseAmount,
    int MonthlyClosedCount,
    decimal ReplenishmentAmount,
    decimal EstimatedBalance);

public sealed record StorePettyCashSummary(
    string StoreName,
    int TransactionCount,
    decimal ExpenseAmount,
    decimal ReplenishmentAmount);

public sealed record SavePettyCashResult(bool IsSuccess, string? ErrorMessage)
{
    public static SavePettyCashResult Success() => new(true, null);
    public static SavePettyCashResult ValidationError(string message) => new(false, message);
}