using BS.Shared.Exceptions;
using BS.Shared.Interface.Feature.AICore;
using System;
using System.Collections.Generic;
using System.Linq;

namespace BS.Shared.Core
{
	public static class AiUtils
	{
		private const double MAX_TOKENS_SYSTEM_PERCENTAGE = 40.0d;
		private const double MAX_TOKENS_USER_PERCENTAGE = 10.0d;
		private const double MAX_TOKENS_CONVERSATION_PERCENTAGE = 80.0d;

		public static bool CheckSystemMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
		{
			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_SYSTEM_PERCENTAGE, out error);
		}

		public static bool CheckUserFirstMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
		{
			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_SYSTEM_PERCENTAGE + MAX_TOKENS_USER_PERCENTAGE, out error);
		}

		public static bool CheckUserAllMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
		{
			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_CONVERSATION_PERCENTAGE, out error);
		}

		private static bool CheckContextSize(IEnumerable<string> messages, string modelName, int max_context_size, double maximum, out string error)
		{
			error = null;

			if (max_context_size < 0)
				throw new ArgumentOutOfRangeException(nameof(max_context_size));

			if (max_context_size == 0)
				return false;

			var tokens_count = CalculateTokensByModel(messages, modelName);

			var percentage = (double)tokens_count * 100 / max_context_size;

			var success = percentage <= maximum;

			if (!success)
			{
				error = $"Windowsize exceeded: {tokens_count}/{max_context_size} ({percentage}%>{maximum}%)";
			}

			return success;
		}

		private static int CalculateTokensByModel(IEnumerable<string> messages, string modelName)
		{
			var count = 0;

			foreach (var message in messages)
			{
				count += 4;
				count += message.Length / 2;
			}

			return count;
		}

	}
}