using ClawdDotNet.Core.Api.Models;
using ClawdDotNet.Core.Config;
using ClawdDotNet.Core.Engine;
using ClawdDotNet.Core.Tests.Infrastructure;
using Shouldly;

namespace ClawdDotNet.Core.Tests.Engine;

/// <summary>
/// #605: In continuous operation compaction started at every step and stayed ineffective -
/// stage 1 checked with the raw instead of the calibrated estimate, compacted only to just
/// below the threshold, and the summarization call was not booked.
/// </summary>
public sealed class CompactionMarginTests
{
    private const string Model = "test/model";

    private static (ContextCompactor Compactor, FakeChatClient Client) Create()
    {
        var client = new FakeChatClient().AlwaysRespondsWithText("- Der Agent hat Daten geprueft.");
        return (new ContextCompactor(client, TestLogging.Factory), client);
    }

    /// <summary>
    /// The raw estimate as it would look after stage 1 - rebuilt in order to choose thresholds
    /// at which the old and new check decide differently. Values as in the
    /// ContextCompactor: the last 6 messages protected, tool results at 2,000 characters.
    /// </summary>
    private static int RawAfterStage1(List<ChatMessage> messages)
    {
        var copy = messages
            .Select(m => new ChatMessage { Role = m.Role, Content = m.Content, ToolCallId = m.ToolCallId, ToolCalls = m.ToolCalls })
            .ToList();

        var protection = Math.Max(0, copy.Count - 6);
        for (var i = 0; i < protection; i++)
        {
            if (copy[i].Role == "tool" && copy[i].Content is { Length: > 2_000 } content)
                copy[i].Content = content[..2_000] + "\n\n[... Ergebnis gekürzt ...]";
        }

        return ContextCompactor.EstimateTokens(copy);
    }

    private static List<ChatMessage> LongHistory()
        => Conversation.Start().Repeat(times: 6, toolCallsPerCycle: 1, resultLength: 8_000).Build();

    [Fact]
    public async Task After_stage_1_the_calibrated_estimate_decides()
    {
        var (compactor, client) = Create();

        // This model counts about three times as many tokens as chars/4 suggests.
        for (var i = 0; i < 12; i++)
            compactor.Calibrate(Model, 1_000, 3_000);

        var messages = LongHistory();
        var rawAfter = RawAfterStage1(messages);

        // Raw, stage 1 lies below the threshold, calibrated clearly above it.
        var threshold = (int)(rawAfter * 1.5);
        var guard = new LoopGuardConfig { MaxContextTokens = threshold * 2, CompactionThreshold = 0.5 };

        await compactor.CompactIfNeededAsync(messages, guard, Model, default);

        client.CallCount.ShouldBe(1, "die rohe Zahl meldete faelschlich 'unter der Schwelle' und Stufe 2 lief nie");
        ContextInvariants.AssertValid(messages);
    }

    [Fact]
    public async Task Just_below_the_threshold_is_not_enough_compaction_keeps_a_margin()
    {
        var (compactor, client) = Create();
        var messages = LongHistory();
        var rawAfter = RawAfterStage1(messages);

        // Stage 1 brings it just below the threshold (90 %), but not below the target (55 %).
        var threshold = (int)(rawAfter * 1.2);
        var guard = new LoopGuardConfig { MaxContextTokens = (int)(threshold / 0.9), CompactionThreshold = 0.9 };

        await compactor.CompactIfNeededAsync(messages, guard, Model, default);

        client.CallCount.ShouldBe(1, "knapp unter der Schwelle waere beim naechsten Schritt wieder darueber");
        ContextInvariants.AssertValid(messages);
    }

    [Fact]
    public async Task The_summary_call_is_booked()
    {
        var (compactor, _) = Create();
        var booked = new List<Usage>();
        var messages = Conversation.Start().Repeat(15).Build();

        await compactor.CompactIfNeededAsync(
            messages, new LoopGuardConfig { MaxContextTokens = 1_000, CompactionThreshold = 0.5 }, Model, default, booked.Add);

        booked.ShouldHaveSingleItem().PromptTokens.ShouldBe(100);
    }

    [Fact]
    public async Task Below_the_threshold_nothing_is_booked()
    {
        var (compactor, client) = Create();
        var booked = new List<Usage>();

        await compactor.CompactIfNeededAsync(
            Conversation.Start().Repeat(2).Build(),
            new LoopGuardConfig { MaxContextTokens = 10_000_000, CompactionThreshold = 0.9 }, Model, default, booked.Add);

        booked.ShouldBeEmpty();
        client.CallCount.ShouldBe(0);
    }
}