//! The meter on this host's own counters and GPU, where it has them: a WebGPU
//! member's runs and the CPU reference's, each in a window long enough to
//! resolve, and one run that is not.
//!
//! This is its own test binary because the first meter in a process probes
//! the GPU counter with the load it is given, once for the process's life.
//!
//! On a host with no WebGPU adapter, or where the counters are not live, the
//! test says so and checks what holds there: every window is unmetered. On a
//! host where they are live it prints `quantum-meter hardware:` lines, which a
//! CI job that expects live counters looks for.
//!
//! A GPU window can lose its figure to another process using the GPU over it,
//! which a shared host cannot prevent; the test then requires the refusal to
//! say so, and no figure.

use quantum_meter::{Declared, MIN_GPU_WINDOW, ProcessRunMeter, Refused, label, probe_load, span_of_runs};
use std::time::Duration;
use wai_quantum::quantum::{BaseGate, Circuit, Gate, Gateset};
use wai_quantum::quantum_energy::{EnergyClass, check_label};
use wai_quantum::quantum_fabric::{EnergyCalibration, RunMeter, pair_updates};
use wai_quantum::quantum_fabric_webgpu::blocking;

const DECLARED: Declared = Declared { counter_ppm: 50_000 };

/// Hadamards, a chain of controlled X, phases, Hadamards: `5n − 1` gates.
fn circuit(n: u8) -> Circuit {
    let mut c = Circuit::with_gateset(n, Gateset::V2);
    let one = |base, target, param| Gate { base, controls: Vec::new(), target, param };
    (0..n).for_each(|q| c.ops.push(one(BaseGate::H, q, 0)));
    (0..n - 1).for_each(|q| c.ops.push(Gate { base: BaseGate::X, controls: vec![q], target: q + 1, param: 0 }));
    for q in 0..n {
        c.ops.push(one(BaseGate::T, q, 0));
        c.ops.push(one(BaseGate::P, q, 1 + u16::from(q % 6)));
    }
    (0..n).for_each(|q| c.ops.push(one(BaseGate::H, q, 0)));
    c
}

#[test]
fn a_members_runs_are_metered_over_a_window_the_counters_resolve() {
    let discovery = blocking::discover().expect("discovery resolves natively");
    let Some(gpu) = discovery.found.first() else {
        eprintln!("quantum-meter: no WebGPU adapter on this host ({} refused)", discovery.refused.len());
        return;
    };
    let wide = circuit(gpu.max_qubits().min(18));
    let ops = pair_updates(&wide);
    let mut meter = ProcessRunMeter::new(
        probe_load(|| {
            let _ = blocking::simulate_from(gpu, &wide, 0);
        }),
        DECLARED,
    );
    let on_gpu = || blocking::simulate_from(gpu, &wide, 0).map(|_| ops).map_err(|e| format!("{e:?}"));
    let on_cpu = || wide.simulate_from(0).map(|_| ops).map_err(|e| format!("{e:?}"));

    if !meter.is_live() {
        eprintln!("quantum-meter: the counters are not live here (GPU counter {})", meter.gpu_liveness());
        // No window opens, and a run through the member is unmetered.
        assert!(span_of_runs(&mut meter, Duration::ZERO, on_gpu).is_err());
        assert!(matches!(meter.last(), Some(Err(Refused::NotLive(_)))), "{:?}", meter.last());
        let (_, joules_micro, class) = blocking::simulate_metered(gpu, &wide, 0, &mut meter).expect("the run itself");
        assert_eq!((joules_micro, class), (0, None));
        return;
    }

    // The member's runs, two seconds of them.
    let runs = span_of_runs(&mut meter, MIN_GPU_WINDOW * 2, on_gpu).expect("the member runs");
    assert!(runs.runs >= 1 && runs.ops == ops * runs.runs, "{runs:?}");
    match meter.last().expect("a window was closed") {
        Ok(span) => {
            assert!(span.gpu_ns > 0, "the member's runs spent GPU time: {span:?}");
            assert!(span.cpu_uj > 0, "and the host's side of them CPU energy: {span:?}");
            let (joules_micro, class) = label(span, DECLARED).expect("two seconds of GPU work is labelled");
            assert_eq!((runs.joules_micro, runs.class.clone()), (joules_micro, Some(class.clone())), "stop returned the span's label");
            assert_eq!(joules_micro, span.cpu_uj + span.gpu_uj);
            assert!(matches!(class, EnergyClass::OnChipCounter { .. }), "{class:?}");
            assert_eq!(check_label(joules_micro, &class), Ok(()));
            let mut calibration = EnergyCalibration::new();
            calibration.add(runs.ops, runs.joules_micro, runs.class.as_ref());
            let (nanojoules, _) = calibration.finish().expect("a figure");
            eprintln!(
                "quantum-meter hardware: {} on {} qubits: {} runs in {:?}, cpu {} uJ + gpu {} uJ over {} ms of GPU time -> {nanojoules} nJ/op, {} ppm",
                gpu.id(),
                wide.n_qubits,
                runs.runs,
                runs.wall,
                span.cpu_uj,
                span.gpu_uj,
                span.gpu_ns / 1_000_000,
                class.uncertainty().expect("declared").relative_ppm
            );
        }
        // The GPU was not this process's alone over the window, or its rail
        // gave no reading: no figure, and the reason kept.
        Err(why @ (Refused::NoGpuFigure(_) | Refused::Counter(_))) => {
            assert_eq!((runs.joules_micro, runs.class.clone()), (0, None), "{why}");
            eprintln!("quantum-meter hardware: {} window unmetered: {why}", gpu.id());
        }
        Err(other) => panic!("a two-second window of the member's runs was refused: {other}"),
    }

    // The CPU reference's runs, in the same domain: no GPU time, so the
    // figure is the CPU count alone.
    let runs = span_of_runs(&mut meter, Duration::from_secs(1), on_cpu).expect("the reference runs");
    match meter.last().expect("a window was closed") {
        Ok(span) => {
            assert_eq!((span.gpu_ns, span.gpu_uj), (0, 0), "the reference spends no GPU time: {span:?}");
            assert!(span.cpu_uj > 0, "{span:?}");
            assert_eq!(runs.joules_micro, span.cpu_uj);
            let class = runs.class.clone().expect("a second of CPU work is labelled");
            assert_eq!(check_label(runs.joules_micro, &class), Ok(()));
            let mut calibration = EnergyCalibration::new();
            calibration.add(runs.ops, runs.joules_micro, runs.class.as_ref());
            let (nanojoules, _) = calibration.finish().expect("a figure");
            eprintln!(
                "quantum-meter hardware: the CPU reference on {} qubits: {} runs in {:?}, cpu {} uJ -> {nanojoules} nJ/op, {} ppm",
                wide.n_qubits,
                runs.runs,
                runs.wall,
                span.cpu_uj,
                class.uncertainty().expect("declared").relative_ppm
            );
        }
        // Another process's GPU client came or went over the window: the GPU
        // counter then gives no figure, a zero included.
        Err(why @ (Refused::NoGpuFigure(_) | Refused::Counter(_))) => {
            assert_eq!((runs.joules_micro, runs.class.clone()), (0, None), "{why}");
            eprintln!("quantum-meter hardware: the CPU reference's window unmetered: {why}");
        }
        Err(other) => panic!("a one-second window of the reference's runs was refused: {other}"),
    }

    // One run of the member, in the window the fabric opens around it: far
    // under a second, so it is unmetered, never read at a resolution the rail
    // does not have.
    let small = circuit(6);
    let (_, joules_micro, class) = blocking::simulate_metered(gpu, &small, 0, &mut meter).expect("the run itself");
    assert_eq!((joules_micro, class), (0, None), "a run of {:?}", meter.last());
    match meter.last().expect("the run's window was closed") {
        Ok(span) => assert!(matches!(label(span, DECLARED), Err(Refused::TooShort { .. })), "{span:?}"),
        Err(Refused::NoGpuFigure(_) | Refused::Counter(_)) => {}
        Err(other) => panic!("{other}"),
    }
    // Every start was matched by a stop: the meter starts again.
    assert!(meter.start().is_ok());
    assert!(meter.stop().is_ok());
}