using Deal.Ai.Llm;

namespace Deal.Ai.Tests.Ai;

/// <summary>
/// Unit-тесты оценки токенов
/// </summary>
public sealed class TokenEstimatorTests
{
    /// <summary>
    /// Usage провайдера проходит без изменений, включая total ≠ сумме
    /// </summary>
    [Fact]
    public void Resolve_WithProviderUsage_PassesThrough()
    {
        var provider = new ProviderUsage(PromptTokens: 11, CompletionTokens: 5, TotalTokens: 16);

        LlmUsage usage = TokenEstimator.Resolve(provider, "system", "text");

        Assert.Equal(11, usage.PromptTokens);
        Assert.Equal(5, usage.CompletionTokens);
        Assert.Equal(16, usage.TotalTokens);
    }

    /// <summary>
    /// Нет usage провайдера — оценка по символам
    /// </summary>
    [Fact]
    public void Resolve_WithoutProviderUsage_EstimatesByChars()
    {
        // prompt-текст = 8 символов → 2 токена; completion-текст = 13 символов → ceil(13/4) = 4.
        LlmUsage usage = TokenEstimator.Resolve(null, "12345678", """{"pass": true}""");

        Assert.Equal(2, usage.PromptTokens);
        Assert.Equal(4, usage.CompletionTokens);
        Assert.Equal(6, usage.TotalTokens);
    }

    /// <summary>
    /// Округление вверх
    /// </summary>
    [Fact]
    public void Resolve_WithoutProviderUsage_RoundsUp()
    {
        LlmUsage fourChars = TokenEstimator.Resolve(null, "abcd", string.Empty);
        LlmUsage fiveChars = TokenEstimator.Resolve(null, "abcde", string.Empty);

        Assert.Equal(1, fourChars.PromptTokens);
        Assert.Equal(2, fiveChars.PromptTokens);
    }

    /// <summary>
    /// Пустые тексты дают нулевую оценку
    /// </summary>
    [Fact]
    public void Resolve_EmptyTexts_ReturnsZeroTokens()
    {
        LlmUsage usage = TokenEstimator.Resolve(null, string.Empty, string.Empty);

        Assert.Equal(0, usage.PromptTokens);
        Assert.Equal(0, usage.CompletionTokens);
        Assert.Equal(0, usage.TotalTokens);
    }
}