using MediatR;
using System.Data;
using System.Data.Common;
using TakeoutSaaS.Application.App.Billings.Dto;
using TakeoutSaaS.Application.App.Billings.Queries;
using TakeoutSaaS.Shared.Abstractions.Constants;
using TakeoutSaaS.Shared.Abstractions.Data;
using TakeoutSaaS.Shared.Abstractions.Exceptions;
using TakeoutSaaS.Domain.Tenants.Enums;

namespace TakeoutSaaS.Application.App.Billings.Handlers;

/// <summary>
/// 查询账单支付记录处理器。
/// </summary>
public sealed class GetBillingPaymentsQueryHandler(
    IDapperExecutor dapperExecutor)
    : IRequestHandler<GetBillingPaymentsQuery, List<PaymentRecordDto>>
{
    /// <summary>
    /// 处理查询账单支付记录请求。
    /// </summary>
    /// <param name="request">查询命令。</param>
    /// <param name="cancellationToken">取消标记。</param>
    /// <returns>支付记录列表 DTO。</returns>
    public async Task<List<PaymentRecordDto>> Handle(GetBillingPaymentsQuery request, CancellationToken cancellationToken)
    {
        // 1. 校验账单是否存在
        return await dapperExecutor.QueryAsync(
            DatabaseConstants.AppDataSource,
            DatabaseConnectionRole.Read,
            async (connection, token) =>
            {
                // 1.1 校验账单存在
                var exists = await ExecuteScalarIntAsync(
                    connection,
                    """
                    select 1
                    from public.tenant_billing_statements b
                    where b."DeletedAt" is null
                      and b."Id" = @billingId
                    limit 1;
                    """,
                    [
                        ("billingId", request.BillingId)
                    ],
                    token);

                if (exists == 0)
                {
                    throw new BusinessException(ErrorCodes.NotFound, "账单不存在");
                }

                // 1.2 查询支付记录
                await using var command = CreateCommand(
                    connection,
                    """
                    select
                      p."Id",
                      p."TenantId",
                      p."BillingStatementId",
                      p."Amount",
                      p."Method",
                      p."Status",
                      p."TransactionNo",
                      p."ProofUrl",
                      p."Notes",
                      p."VerifiedBy",
                      p."VerifiedAt",
                      p."RefundReason",
                      p."RefundedAt",
                      p."PaidAt",
                      p."CreatedAt"
                    from public.tenant_payments p
                    where p."DeletedAt" is null
                      and p."BillingStatementId" = @billingId
                    order by p."CreatedAt" desc;
                    """,
                    [
                        ("billingId", request.BillingId)
                    ]);

                await using var reader = await command.ExecuteReaderAsync(token);
                var results = new List<PaymentRecordDto>();
                while (await reader.ReadAsync(token))
                {
                    results.Add(new PaymentRecordDto
                    {
                        Id = reader.GetInt64(0),
                        TenantId = reader.GetInt64(1),
                        BillingId = reader.GetInt64(2),
                        Amount = reader.GetDecimal(3),
                        Method = (TenantPaymentMethod)reader.GetInt32(4),
                        Status = (TenantPaymentStatus)reader.GetInt32(5),
                        TransactionNo = reader.IsDBNull(6) ? null : reader.GetString(6),
                        ProofUrl = reader.IsDBNull(7) ? null : reader.GetString(7),
                        Notes = reader.IsDBNull(8) ? null : reader.GetString(8),
                        VerifiedBy = reader.IsDBNull(9) ? null : reader.GetInt64(9),
                        VerifiedAt = reader.IsDBNull(10) ? null : reader.GetDateTime(10),
                        RefundReason = reader.IsDBNull(11) ? null : reader.GetString(11),
                        RefundedAt = reader.IsDBNull(12) ? null : reader.GetDateTime(12),
                        PaidAt = reader.IsDBNull(13) ? null : reader.GetDateTime(13),
                        IsVerified = !reader.IsDBNull(10),
                        CreatedAt = reader.GetDateTime(14)
                    });
                }

                return results;
            },
            cancellationToken);
    }

    private static async Task<int> ExecuteScalarIntAsync(
        IDbConnection connection,
        string sql,
        (string Name, object? Value)[] parameters,
        CancellationToken cancellationToken)
    {
        await using var command = CreateCommand(connection, sql, parameters);
        var result = await command.ExecuteScalarAsync(cancellationToken);
        return result is null or DBNull ? 0 : Convert.ToInt32(result);
    }

    private static DbCommand CreateCommand(IDbConnection connection, string sql, (string Name, object? Value)[] parameters)
    {
        var command = connection.CreateCommand();
        command.CommandText = sql;

        foreach (var (name, value) in parameters)
        {
            var p = command.CreateParameter();
            p.ParameterName = name;
            p.Value = value ?? DBNull.Value;
            command.Parameters.Add(p);
        }

        return (DbCommand)command;
    }
}