using ClawdDotNet.Core.Config;
using Shouldly;

namespace ClawdDotNet.Core.Tests.Config;

/// <summary>
/// Old configurations contain "maxTokens" — a value that was meant as a context limit,
/// but counted cumulatively over all steps and aborted runs prematurely (bug B3).
/// The migration must not take over this value unchanged as the cost budget.
/// </summary>
public sealed class ConfigMigrationTests
{
    private static InstanceConfig WithLegacyMaxTokens(int? legacy) => new()
    {
        OpenRouterApiKey = "sk-test",
        Agents =
        [
            new AgentConfig
            {
                AgentId = "test",
                LoopGuard = new LoopGuardConfig { LegacyMaxTokens = legacy }
            }
        ]
    };

    [Fact]
    public void An_old_too_tight_maxTokens_is_replaced_by_the_new_default()
    {
        var config = WithLegacyMaxTokens(80_000);   // the old, problematic value

        ConfigLoader.Migrate(config);

        var guard = config.Agents[0].LoopGuard;
        guard.MaxCumulativeTokens.ShouldBe(500_000);
        guard.LegacyMaxTokens.ShouldBeNull();
    }

    [Fact]
    public void A_deliberately_generous_maxTokens_is_kept()
    {
        var config = WithLegacyMaxTokens(2_000_000);

        ConfigLoader.Migrate(config);

        config.Agents[0].LoopGuard.MaxCumulativeTokens.ShouldBe(2_000_000);
    }

    [Fact]
    public void Without_old_field_the_default_stays_unchanged()
    {
        var config = WithLegacyMaxTokens(null);

        ConfigLoader.Migrate(config);

        config.Agents[0].LoopGuard.MaxCumulativeTokens.ShouldBe(500_000);
    }

    [Fact]
    public void Migration_can_be_applied_repeatedly()
    {
        var config = WithLegacyMaxTokens(80_000);

        ConfigLoader.Migrate(config);
        ConfigLoader.Migrate(config);

        config.Agents[0].LoopGuard.MaxCumulativeTokens.ShouldBe(500_000);
    }
}