using OrderSupportTicket.Models;
using OrderSupportTicket.Models.Api;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace OrderSupportTicket.Services;

/// <summary>
/// 启动时从服务端工单列表和历史本地缓存计算未读消息。
/// </summary>
public sealed class WorkOrderUnreadService
{
    private const int PageSize = 100;
    private const int MaxPages = 20;
    private readonly TicketApiService _api;
    private readonly WorkOrderCacheService _cache;

    /// <summary>
    /// 使用默认工单 API 和缓存服务创建未读计算服务。
    /// </summary>
    public WorkOrderUnreadService()
        : this(new TicketApiService(), new WorkOrderCacheService())
    {
    }

    /// <summary>
    /// 创建未读计算服务。
    /// </summary>
    public WorkOrderUnreadService(
        TicketApiService api,
        WorkOrderCacheService cache)
    {
        _api = api ?? throw new ArgumentNullException(nameof(api));
        _cache = cache ?? throw new ArgumentNullException(nameof(cache));
    }

    /// <summary>
    /// 获取每个工单的未读消息数。返回值的键为 "appId|wechatOrderId"。
    /// </summary>
    public async Task<Dictionary<string, int>> GetUnreadByTicketAsync(
        TicketClientOptions options)
    {
        if (options == null)
            throw new ArgumentNullException(nameof(options));

        TicketApiService.ValidateOptions(options);
        var cache = _cache.Load(options.UserName);
        var workOrders = new List<WorkOrderSummaryDto>();
        string cursor = null;
        var page = 0;

        do
        {
            var response = await _api.GetWorkOrdersAsync(
                options,
                limit: PageSize,
                cursor: cursor).ConfigureAwait(false);
            if (response?.Items != null)
                workOrders.AddRange(response.Items);

            cursor = response?.NextCursor;
            page++;
            if (response == null
                || !response.HasMore
                || string.IsNullOrWhiteSpace(cursor))
            {
                break;
            }
        }
        while (page < MaxPages);

        return _cache.BuildUnreadMap(workOrders, cache);
    }
}