using System.Text.Json;
using Backend.DatabaseHandler;
using Backend.Interface;

namespace Backend.ServiceHander;

public sealed class PercentChangeEvaluator : IAlertEvaluator
{
	public string AlertType => "percent_change";

	public Task<AlertEvaluation> EvaluateAsync(AlertRecord alert, MarketDataService marketData)
	{
		var parameters = JsonSerializer.Deserialize<PercentChangeParameters>(alert.Parameters)
			?? throw new InvalidOperationException($"Invalid parameters for alert {alert.Id}");

		var snapshot = marketData.GetLiveQuote(alert.Symbol);

		if (!snapshot.LastPrice.HasValue || !snapshot.PreviousClose.HasValue || snapshot.PreviousClose.Value == 0)
		{
			return Task.FromResult(new AlertEvaluation { Triggered = false });
		}

		double price = snapshot.LastPrice.Value;
		double prevClose = snapshot.PreviousClose.Value;
		double percentChange = (price - prevClose) / prevClose * 100.0;

		bool triggered = parameters.PercentThreshold >= 0
			? percentChange >= parameters.PercentThreshold
			: percentChange <= parameters.PercentThreshold;

		string updatedState = JsonSerializer.Serialize(new { lastPrice = price, percentChange });

		return Task.FromResult(new AlertEvaluation
		{
			Triggered = triggered,
			UpdatedLastState = updatedState
		});
	}

	private sealed class PercentChangeParameters
	{
		public double PercentThreshold { get; set; }
	}
}