//! End-to-end: a small task runs here, this host's meter reads its energy, the
//! figure is attested inside a TEE, committed into an `efficiency/1` receipt,
//! and then independently re-verified from scratch — deriving the trust level,
//! never asserting it. This is the whole frontier composed in one runnable flow.
//!
//!   cargo run -p sandbox-tee --example attested_efficiency
//!
//! **What the figure is.** The task is a bounded SHA-512 chain on this thread,
//! metered by [`PowerMeter::detect_in_process`] (the work runs on this
//! process's own threads). The attested counter class and the receipt's grade
//! both follow how the figure was obtained:
//!
//! - where a vendor counter read this process's CPU work over the span (the
//!   kernel's per-process count on macOS, a RAPL package on Linux, IOReport's
//!   CPU rails on Apple Silicon where they are live), the statement names that
//!   counter's class and the receipt seals the reading, `HwShunt`;
//! - where none did (no live counter, or one that did not advance over the
//!   span), the figure is the meter's estimate: attested as
//!   [`CounterClass::Estimator`] and sealed `Estimator`.
//!
//! Either way the derived trust level is `IntegrityAttested`: a software-grounded
//! report binds the figure, as it was obtained, to a measured environment. What
//! the figure itself is — a reading or an estimate — is the counter class the
//! report binds, printed beside it.

use ed25519_dalek::SigningKey;
use jcp_efficiency::{verify as verify_efficiency, Efficiency, EfficiencyReceipt};
use jcp_schema::{ContentId, Energy};
use sandbox_meter::{Measurement, PowerMeter, Provenance};
use sandbox_schema::DeviceClass;
use sandbox_tee::energy::{
    attest_energy, verify_attested_energy, AttestTrust, AttestedEnergy, CounterClass, EnergyStatement,
};
use sandbox_tee::provider::LocalSnpProvider;
use sandbox_tee::Grounding;
use sha2::{Digest, Sha512};

/// Links in the task's SHA-512 chain: a fixed amount of real CPU work, some
/// hundreds of milliseconds in a debug build and a few in a release one. A
/// span too short for the counter to advance over it is not a reading, and
/// comes back as the meter's estimate.
pub const CHAIN_LINKS: u64 = 20_000;

/// The task: a SHA-512 chain of [`CHAIN_LINKS`] links from a fixed seed. Its
/// output is the last link, so the work cannot be optimised away.
pub fn task() -> [u8; 64] {
    let mut link = [0x5au8; 64];
    for _ in 0..CHAIN_LINKS {
        let next = Sha512::digest(link);
        link.copy_from_slice(&next);
    }
    link
}

/// The counter class of the probe among `sources` (a [`PowerMeter`]'s live
/// hardware probes) that reads CPU energy: only a known one is named. `None`
/// for a probe set with no CPU counter this example can name.
pub fn cpu_counter(sources: &[&str]) -> Option<CounterClass> {
    sources.iter().find_map(|s| match *s {
        "process-energy" => Some(CounterClass::ProcessEnergy),
        "rapl-powercap" => Some(CounterClass::Rapl),
        "ioreport-energy-model" => Some(CounterClass::IoReport),
        _ => None,
    })
}

/// The figure to attest for span `m` on `meter`, and the class that obtained
/// it. A hardware reading of the CPU work — the span's `HwShunt` CPU records,
/// from a counter this example can name — is attested under that counter's
/// class and sealed as a reading. Anything else is the meter's estimate of the
/// span ([`PowerMeter::estimate`]): attested as `Estimator`, sealed as one.
pub fn figure(meter: &PowerMeter, m: &Measurement) -> (CounterClass, Energy) {
    if m.reads_cpu() {
        if let Some(class) = cpu_counter(&meter.sources()) {
            let cpu_uj: u64 = m
                .devices
                .iter()
                .filter(|d| d.class == DeviceClass::Cpu && d.provenance == Provenance::HwShunt)
                .filter_map(|d| d.measured_uj)
                .sum();
            return (class, Energy::measured(cpu_uj));
        }
    }
    (CounterClass::Estimator, Energy::estimator(meter.estimate(m.wall).total_uj()))
}

/// One run of the composed flow.
pub struct Run {
    /// The meter's live hardware probes (empty: the estimator alone).
    pub sources: Vec<&'static str>,
    /// The span over the task, as the meter recorded it.
    pub measurement: Measurement,
    /// The attested statement and its report.
    pub attested: AttestedEnergy,
    /// The `efficiency/1` receipt, as a relying party verified it.
    pub receipt: EfficiencyReceipt,
    /// The trust level derived from the attestation.
    pub trust: AttestTrust,
    /// The task's output.
    pub output: [u8; 64],
    /// Whether a tampered joule figure failed attestation verification.
    pub tamper_rejected: bool,
}

/// Run the task, meter it, attest the figure, seal the receipt, and verify the
/// composition from scratch.
pub fn run() -> Run {
    // ── 1. The task runs here, metered as it runs.
    let mut meter = PowerMeter::detect_in_process();
    let sources = meter.sources();
    let (output, measurement) = meter.measure(task);
    let (counter, energy) = figure(&meter, &measurement);
    let window_ns = u64::try_from(measurement.wall.as_nanos()).unwrap_or(u64::MAX);

    // ── 2. A verifier issues a fresh nonce; we attest the figure inside a TEE,
    //       under the class that obtained it. The LocalSnpProvider mints a real
    //       ECDSA-P384 report — software-grounded.
    let nonce = [0x5au8; 32];
    let measurement_digest = [0x11u8; 48];
    let provider = LocalSnpProvider::new(measurement_digest, 7);
    let statement = EnergyStatement { counter, energy_uj: energy.uj(), window_ns, nonce };
    let attested = attest_energy(statement, &provider).expect("attest the figure");

    // ── 3. Seal the efficiency/1 receipt at the figure's own grade, committing
    //       to the attestation by content id. Its output units are the chain's
    //       links; no value figure is stated (none is invented).
    let sk = SigningKey::from_bytes(&[0xefu8; 32]);
    let steward = "did:jcp:attested-efficiency-demo";
    let eff = Efficiency {
        task: "sha512-chain".into(),
        completed: true,
        verdict: "chain-computed".into(),
        tokens_in: 1,
        tokens_out: CHAIN_LINKS,
        energy,
        wall_ns: window_ns,
        value_uusd: None,
        energy_attestation: None,
    }
    .with_energy_attestation(&attested.report);
    let envelope = eff.seal(0, &ContentId([0u8; 32]), &sk, steward);

    // ── 4. A relying party runs the COMPOSED verification, from scratch:
    // (a) the receipt verifies under the steward key.
    let receipt =
        verify_efficiency(&envelope, steward, &sk.verifying_key().to_bytes()).expect("efficiency/1 verifies");
    // (b) its commitment resolves to the attestation we hold.
    let commitment = receipt.energy_attestation.as_deref().expect("receipt carries an attestation commitment");
    assert_eq!(commitment, ContentId::of_bytes(&attested.report).to_hex(), "commitment must match the attestation");
    // (c) the attestation verifies — deriving the trust level from evidence.
    let trust = verify_attested_energy(&attested, measurement_digest, &nonce, &provider.vcek(), Grounding::Software)
        .expect("attestation verifies");
    // (d) the attested joules equal the sealed joules.
    assert_eq!(attested.statement.energy_uj, receipt.energy_uj, "attested energy must match the receipt");

    // Tampering is caught: rewrite the attested energy figure downstream.
    let mut forged = attested.clone();
    forged.statement.energy_uj = forged.statement.energy_uj.wrapping_add(1);
    let tamper_rejected =
        verify_attested_energy(&forged, measurement_digest, &nonce, &provider.vcek(), Grounding::Software).is_err();

    Run { sources, measurement, attested, receipt, trust, output, tamper_rejected }
}

fn main() {
    let r = run();
    let counter = r.attested.statement.counter;
    let sources = if r.sources.is_empty() { "none — the estimator".to_string() } else { r.sources.join(", ") };

    println!("task '{}' ran here: {} SHA-512 links in {:?}", r.receipt.task, CHAIN_LINKS, r.measurement.wall);
    println!("  meter's live counters : {sources}");
    println!(
        "  sealed efficiency/1   : {} µJ [{}] over {} links\n",
        r.receipt.energy_uj, r.receipt.provenance, r.receipt.tokens_out
    );

    println!("composed verification ✓");
    println!("  receipt          : verified under the steward key");
    println!("  commitment       : matches the attestation");
    println!(
        "  attested energy  : {} µJ ({})  ==  receipt energy {} µJ [{}]",
        r.attested.statement.energy_uj,
        counter.tag(),
        r.receipt.energy_uj,
        r.receipt.provenance
    );
    println!("  nonce            : fresh (matches the issued challenge)");
    println!(
        "  efficiency       : {} µJ / link",
        r.receipt
            .uj_per_accepted_token
            .map_or_else(|| "—".to_string(), |uj| uj.to_string())
    );
    println!("  TRUST LEVEL      : {:?}, over a `{}` figure", r.trust, counter.tag());
    println!();

    assert_eq!(r.trust, AttestTrust::IntegrityAttested);
    if counter == CounterClass::Estimator {
        println!(
            "This is IntegrityAttested over an ESTIMATE: no counter on this host read the\n\
             task's CPU work over the span, so the figure is the meter's estimate, attested\n\
             under the `estimator` class and sealed `Estimator`. The report binds the figure\n\
             to a measured environment; it does not make the figure a reading."
        );
    } else {
        println!(
            "This is IntegrityAttested, not PhysicallyRooted: a software-grounded report\n\
             over a platform-self-reported counter (`{}`) attests an honest *relay* inside\n\
             a measured environment — not a reading rooted independently of the platform.\n\
             (Not a claim that the counter is inaccurate: it is a real sensor reading;\n\
             nothing binds it to the sensor.) An independent root needs a dedicated sensor\n\
             signed at the source (a shunt) on confidential hardware — derived, never asserted.",
            counter.tag()
        );
    }

    assert!(r.tamper_rejected, "a tampered energy figure must fail attestation verification");
    println!("\n(a tampered joule figure fails attestation verification — checked.)");
    std::hint::black_box(r.output);
}