EmailBill/Service/EmailParseServices/IEmailParseServices.cs

namespace Service.EmailParseServices;

public interface IEmailParseServices
{
    bool CanParse(string from, string subject, string body);

    /// <summary>
    /// 解析邮件内容，提取交易信息
    /// </summary>
    Task<(
        string card,
        string reason,
        decimal amount,
        decimal balance,
        TransactionType type,
        DateTime? occurredAt
    )[]> ParseAsync(string emailContent);
}

public abstract class EmailParseServicesBase(
    ILogger<EmailParseServicesBase> logger,
    IOpenAiService openAiService
) : IEmailParseServices
{
    public abstract bool CanParse(string from, string subject, string body);

    public async Task<(
        string card,
        string reason,
        decimal amount,
        decimal balance,
        TransactionType type,
        DateTime? occurredAt
    )[]> ParseAsync(string emailContent)
    {
        var result = await ParseEmailContentAsync(emailContent);

        if (result.Length > 0)
        {
            logger.LogInformation("使用规则成功解析邮件内容，提取到 {Count} 条交易记录", result.Length);
            return result;
        }

        logger.LogInformation("规则解析邮件内容失败，尝试使用AI进行解析");
        // AI兜底
        result = await ParseByAiAsync(emailContent) ?? [];

        if(result.Length == 0)
        {
            logger.LogWarning("AI解析邮件内容也未能提取到任何交易记录");
        }

        return result;
    }

    public abstract Task<(
        string card,
        string reason,
        decimal amount,
        decimal balance,
        TransactionType type,
        DateTime? occurredAt
    )[]> ParseEmailContentAsync(string emailContent);

    private async Task<(
        string card, 
        string reason, 
        decimal amount, 
        decimal balance, 
        TransactionType type,
        DateTime? occurredAt
    )[]?> ParseByAiAsync(string body)
    {
        var systemPrompt = "你是一个信息抽取助手。仅输出严格的JSON数组，不要包含任何多余文本。每个交易记录包含字段: card(字符串), reason(字符串), amount(数字), balance(数字), type(字符串，值为'收入'或'支出'), occurredAt(字符串，yyyy-MM-dd HH:mm:ss格式日期时间)。如果缺失，请推断或置空。";
        var userPrompt = $"从下面这封银行账单相关邮件正文中提取所有交易记录，返回JSON数组格式，每个元素包含: card, reason, amount, balance, type(收入或支出), occurredAt(非必要)。正文如下:\n\n{body}";

        var contentText = await openAiService.ChatAsync(systemPrompt, userPrompt);
        if (string.IsNullOrWhiteSpace(contentText))
        {
            logger.LogWarning("AI未返回任何内容，无法解析邮件");
            return null;
        }

        logger.LogDebug("AI返回的内容: {Content}", contentText);
        // 清理可能的 markdown 代码块标记
        contentText = contentText.Trim();
        if (contentText.StartsWith("```"))
        {
            // 移除开头的 ```json 或 ```
            var firstNewLine = contentText.IndexOf('\n');
            if (firstNewLine > 0)
            {
                contentText = contentText.Substring(firstNewLine + 1);
            }

            // 移除结尾的 ```
            if (contentText.EndsWith("```"))
            {
                contentText = contentText.Substring(0, contentText.Length - 3);
            }

            contentText = contentText.Trim();
        }

        // contentText 期望是 JSON 数组
        using var jsonDoc = JsonDocument.Parse(contentText);
        var arrayElement = jsonDoc.RootElement;

        // 如果返回的是单个对象而不是数组，尝试兼容处理
        if (arrayElement.ValueKind == JsonValueKind.Object)
        {
            logger.LogWarning("AI返回的内容是单个对象而非数组，尝试兼容处理");
            var result = ParseSingleRecord(arrayElement);
            return result != null ? [result.Value] : null;
        }

        if (arrayElement.ValueKind != JsonValueKind.Array)
        {
            logger.LogWarning("AI返回的内容不是JSON数组，无法解析邮件");
            return null;
        }

        var results = new List<(string card, string reason, decimal amount, decimal balance, TransactionType type, DateTime? occurredAt)>();

        foreach (var obj in arrayElement.EnumerateArray())
        {
            var record = ParseSingleRecord(obj);
            if (record != null)
            {
                logger.LogInformation("解析到一条交易记录: {@Record}", record.Value);
                results.Add(record.Value);
            }
        }

        logger.LogInformation("使用AI成功解析邮件内容，提取到 {Count} 条交易记录", results.Count);
        return results.Count > 0 ? results.ToArray() : null;
    }

    private (string card, string reason, decimal amount, decimal balance, TransactionType type, DateTime? occurredAt)? ParseSingleRecord(JsonElement obj)
    {
        string card = obj.TryGetProperty("card", out var pCard) ? pCard.GetString() ?? string.Empty : string.Empty;
        string reason = obj.TryGetProperty("reason", out var pReason) ? pReason.GetString() ?? string.Empty : string.Empty;
        string typeStr = obj.TryGetProperty("type", out var pType) ? pType.GetString() ?? string.Empty : string.Empty;
        string occurredAtStr = obj.TryGetProperty("occurredAt", out var pOccurredAt) ? pOccurredAt.GetString() ?? string.Empty : string.Empty;

        decimal amount = 0m;
        if (obj.TryGetProperty("amount", out var pAmount))
        {
            if (pAmount.ValueKind == JsonValueKind.Number && pAmount.TryGetDecimal(out var d)) amount = d;
            else if (pAmount.ValueKind == JsonValueKind.String && decimal.TryParse(pAmount.GetString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var ds)) amount = ds;
        }

        decimal balance = 0m;
        if (obj.TryGetProperty("balance", out var pBalance))
        {
            if (pBalance.ValueKind == JsonValueKind.Number && pBalance.TryGetDecimal(out var d2)) balance = d2;
            else if (pBalance.ValueKind == JsonValueKind.String && decimal.TryParse(pBalance.GetString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var ds2)) balance = ds2;
        }

        if (string.IsNullOrWhiteSpace(card) || string.IsNullOrWhiteSpace(reason))
        {
            return null;
        }

        var occurredAt = (DateTime?)null;
        if(DateTime.TryParse(occurredAtStr, out var occurredAtValue))
        {
            occurredAt = occurredAtValue;
        }

        var type = DetermineTransactionType(typeStr, reason, amount);
        return (card, reason, amount, balance, type, occurredAt);
    }

    /// <summary>
    /// 判断交易类型
    /// </summary>
    protected TransactionType DetermineTransactionType(string typeStr, string reason, decimal amount)
    {
        // 优先使用明确的类型字符串
        if (!string.IsNullOrWhiteSpace(typeStr))
        {
            if (typeStr.Contains("收入") || typeStr.Contains("income") || typeStr.Equals("收", StringComparison.OrdinalIgnoreCase))
                return TransactionType.Income;
            if (typeStr.Contains("支出") || typeStr.Contains("expense") || typeStr.Equals("支", StringComparison.OrdinalIgnoreCase))
                return TransactionType.Expense;
        }

        // 根据交易原因中的关键词判断
        var lowerReason = reason.ToLower();

        // 收入关键词
        string[] incomeKeywords = { "工资", "奖金", "退款", "返现", "收入", "转入", "存入", "利息", "分红" };
        if (incomeKeywords.Any(k => lowerReason.Contains(k)))
            return TransactionType.Income;

        // 支出关键词
        string[] expenseKeywords = { "消费", "支付", "购买", "转出", "取款", "支出", "扣款", "缴费" };
        if (expenseKeywords.Any(k => lowerReason.Contains(k)))
            return TransactionType.Expense;

        // 根据金额正负判断（如果金额为负数，可能是支出）
        if (amount < 0)
            return TransactionType.Expense;
        if (amount > 0)
            return TransactionType.Income;

        // 默认为支出
        return TransactionType.Expense;
    }
}