using AyCode.Core.Serializers.Binaries;
using AyCode.Core.Tests.TestModels;
using System.Runtime.CompilerServices;
using System.Text;

namespace AyCode.Core.Serializers.Console;

/// <summary>
/// Configuration state for the benchmark application. Holds compile-time and runtime constants,
/// per-run mutable settings (WireMode, charset, iteration counts), and the attribute-flag
/// aggregation that drives the per-row Options column. Split out from <c>Program.cs</c> so the
/// entry-point file can focus on UX-flow and benchmark orchestration; everything in this class
/// is config / state — no benchmark logic. Single instance (static class) — the application is
/// a one-shot process, no multi-tenant state isolation needed.
/// </summary>
internal static class Configuration
{
#if AYCODE_NATIVEAOT
    internal const string BuildConfiguration = "NativeAOT";
#elif DEBUG
    internal const string BuildConfiguration = "Debug";
#elif SGEN_ONLY
    internal const string BuildConfiguration = "SGenOnly";
#else
    internal const string BuildConfiguration = "Release";
#endif

#if DEBUG
    internal static int WarmupIterations = 0;
    internal static int TestIterations = 1;
    internal static int BenchmarkSamples = 1;       // Debug: single sample, fast iteration
#else
    internal static int WarmupIterations = 5000; //10000 — per-phase (Ser AND Des get their own warmup separately)
    internal static int TestIterations = 1000; //1000
    internal static int BenchmarkSamples = 10;
#endif

    // Interactive settings: selected AcBinary wire mode for benchmark runs.
    // 1 = Compact, 2 = Fast
    internal static WireMode SelectedWireMode = WireMode.Compact;

    // Engine / IO mode / Dispatch mode identifiers → Benchmarks/BenchmarkEnums.cs (typed enums with ToDisplay)

    // Single source of truth for the chunk size used by ALL pipe-related benchmarks (NamedPipe PipeChunk,
    // NamedPipe PipeRaw, in-memory Pipe, in-memory RawMem) AND the NamedPipe server's inBufferSize/outBufferSize.
    // Same value across both layers ensures apples-to-apples comparison: chunked-streaming chunk-on-wire size
    // matches the kernel pipe-buffer slot exactly. Tweak HERE when experimenting; do NOT scatter chunkSize
    // overrides across individual benchmark rows.
    internal const int PipeChunkSize = 4096;

    // Per-cell adaptive iteration target wall-clock duration. Each Ser/Des function calibrates its
    // own iteration count post-warmup so the sample batch lands in this range — equalizes the
    // per-sample window across cells of vastly different per-op cost (Small ~6 ns/op vs Large
    // ~140 µs/op). Below ~100 ms Stopwatch precision and OS preempt spikes start to dominate.
    internal const int TargetSampleMs = 250;

    // CV (coefficient of variation = stddev / mean) threshold above which a row's range is flagged
    // as "unstable" in the markdown output (⚠️ marker). 3% is a reasonable noise-floor expectation
    // for stabilized in-memory benchmarks; rows above it should be discounted when reading
    // sub-3% inter-engine deltas.
    internal const double UnstableCVThreshold = 0.03;

    // Lower-bound CV threshold for micro-optimization measurement reliability. Rows with CV in
    // the (MicroOptCVThreshold, UnstableCVThreshold] range get a softer "⚠️micro" flag — they are
    // not unstable enough to be entirely dismissable, but sub-2% inter-engine deltas observed on
    // such a row are at the edge of the noise floor and should be cross-checked (re-run, BDN).
    // Use case: micro-opt sprints where a ~1-2% signal lives below the unstable threshold but the
    // row's own CV is still high enough to make that signal suspect.
    internal const double MicroOptCVThreshold = 0.015;

    // Inter-sample cool-down delay (ms) inserted between recorded samples in the timed loop.
    // Mitigates CPU thermal-throttling drift across a sustained burst (e.g. 10×250ms = 2.5 sec):
    // without it, boost-clock can drop mid-batch on thermally-constrained hosts (laptops esp.),
    // and the later samples in the batch read systematically slower than the early ones. 50ms is
    // enough for boost-clock state to settle but cheap in total (~500ms / cell) — quick-bench
    // workflow is not meaningfully slower.
    internal const int InterSampleSettleMs = 50;

    // JIT-tier-promotion drain delay between warmup and measurement.
    // - JIT mode (RuntimeFeature.IsDynamicCodeCompiled == true): tiered JIT promotes hot methods
    //   in a background thread; we wait briefly for the queue to drain so the first measurement
    //   sample doesn't catch a Tier-0 → Tier-1 transition mid-flight.
    // - AOT mode (NativeAOT publish): no dynamic compilation happens; the sleep is pure noise.
    // 250ms (vs the historical 3000ms) is sufficient for a few-method working set under .NET 9's
    // tiered JIT — empirically the queue drains in <100ms for the bench's hot path.
    internal static int JitSleep => RuntimeFeature.IsDynamicCodeCompiled ? 250 : 0;

    // OptionsPreset values are passed per-instance (constructor argument), not constants —
    // each CreateSerializers call line specifies its own preset name (e.g. "FastMode", "NoIntern").

    internal static readonly UTF8Encoding Utf8NoBom = new(encoderShouldEmitUTF8Identifier: false);

    /// <summary>
    /// Returns a human-readable name for the currently-active <c>BenchmarkTestDataProvider.LongStringSuffix</c>
    /// charset. Returns "Custom" when the suffix doesn't match any of the predefined
    /// <see cref="CharsetSuffixes"/> constants. Used in menu state display, console run header, and
    /// the .LLM / .log output headers so per-charset bench files are self-documenting.
    /// </summary>
    internal static string GetCurrentCharsetName()
    {
        var s = BenchmarkTestDataProvider.LongStringSuffix;

        return s switch
        {
            CharsetSuffixes.AsciiFix => nameof(CharsetSuffixes.AsciiFix),
            CharsetSuffixes.AsciiShort => nameof(CharsetSuffixes.AsciiShort),
            CharsetSuffixes.AsciiLong => nameof(CharsetSuffixes.AsciiLong),
            CharsetSuffixes.Latin1Fix => nameof(CharsetSuffixes.Latin1Fix),
            CharsetSuffixes.Latin1Short => nameof(CharsetSuffixes.Latin1Short),
            CharsetSuffixes.Latin1Long => nameof(CharsetSuffixes.Latin1Long),
            CharsetSuffixes.CjkBmpShort => nameof(CharsetSuffixes.CjkBmpShort),
            CharsetSuffixes.CjkBmpLong => nameof(CharsetSuffixes.CjkBmpLong),
            CharsetSuffixes.CyrillicShort => nameof(CharsetSuffixes.CyrillicShort),
            CharsetSuffixes.CyrillicLong => nameof(CharsetSuffixes.CyrillicLong),
            CharsetSuffixes.MixedShort => nameof(CharsetSuffixes.MixedShort),
            CharsetSuffixes.MixedLong => nameof(CharsetSuffixes.MixedLong),
            _ => "Custom"
        };
    }
}