//! End-to-end Mesh demo: mint a JCP grant, serve a metered inference through the
//! cheapest-sufficient backend, and print the sealed JCR-1 receipt.
//!
//! Run with the always-available estimator meter (honest `Estimator`
//! provenance):
//!
//! ```text
//! cargo run -p mesh-core --example demo
//! ```
//!
//! On Linux with RAPL (or a CUDA box with NVML), enable a hardware meter to get
//! a measured `HwShunt` span instead:
//!
//! ```text
//! cargo run -p mesh-core --example demo --features hw-meter-rapl
//! ```

use ed25519_dalek::SigningKey;
use jcp_schema::{Capability, Did, Grant};
use mesh_core::{Mesh, Presentation, INFER_ACTION};
use mesh_engine::ReferenceEngine;
use mesh_meter::Meter;
use mesh_router::BackendSpec;
use mesh_schema::{ContentId, Fidelity, ServeRequest};

fn main() {
    // --- the steward (the mesh endpoint that seals receipts) ---
    let steward_sk = SigningKey::from_bytes(&[7u8; 32]);
    let steward = Did::from_verifying_key(&steward_sk.verifying_key()).to_did_key();

    // --- the meter: hardware-backed when a feature selects one, else estimator ---
    #[cfg(feature = "hw-meter")]
    let meter = mesh_meter::HwMeter::detect();
    #[cfg(not(feature = "hw-meter"))]
    let meter = mesh_meter::EstimatorMeter::new(15.0);
    println!("meter:    {}", meter.name());

    // --- build the mesh: a fidelity cascade of backends ---
    let mut mesh = Mesh::new(&meter, steward_sk, steward.clone());
    mesh.register(
        BackendSpec::new("cache", "result-lut", Fidelity::F0, 10),
        Box::new(ReferenceEngine::new("cache", "result-lut", Fidelity::F0, 10, 8)),
    );
    mesh.register(
        BackendSpec::new("tiny", "ssm-1b", Fidelity::F1, 50_000),
        Box::new(ReferenceEngine::new("tiny", "ssm-1b", Fidelity::F1, 50_000, 4096)),
    );
    mesh.register(
        BackendSpec::new("merge", "evo-merge-8b", Fidelity::F2, 200_000),
        Box::new(ReferenceEngine::new(
            "merge", "evo-merge-8b", Fidelity::F2, 200_000, 8192,
        )),
    );
    mesh.register(
        BackendSpec::new("frontier", "wire-rpc", Fidelity::F4, 5_000_000),
        Box::new(ReferenceEngine::new(
            "frontier", "wire-rpc", Fidelity::F4, 5_000_000, 16384,
        )),
    );

    // --- the request: 64 output tokens, must be at least F1, ≤ 8 J ---
    let req = ServeRequest {
        prompt_hash: ContentId::of_bytes(b"What is the capital of France?"),
        prompt_tokens: 7,
        max_tokens: 64,
        fidelity_floor: Fidelity::F1,
        joule_ceiling_uj: 8_000_000, // 8 J
        decision: None,              // a generation, not a typed decision
        funds_ceiling: None,
    };

    // --- the caller mints a JCP grant: capability(infer over this request) ⊗ budget ---
    let caller_sk = SigningKey::from_bytes(&[42u8; 32]);
    let caller = Did::from_verifying_key(&caller_sk.verifying_key());
    let grant = Grant {
        issuer: caller,
        subject: Did::from_verifying_key(&SigningKey::from_bytes(&[7u8; 32]).verifying_key()),
        capability: Capability::new(req.id(), [INFER_ACTION]),
        budget_uj: 8_000_000,
        // Root grant: a joule ceiling only, no money ceiling and no caveats.
        budget_funds: None,
        caveats: Vec::new(),
        expiry: 0,
        parent: None,
        delegate_depth: None,
        nonce: [0u8; 16],
    };
    let signed = jcp_grant::issue(&caller_sk, grant).expect("issue grant");
    // The caller presents it, signing for this request: the steward spends a
    // grant only for its issuer, and each presentation only once.
    let presented = Presentation::sign(vec![signed], &req, &caller_sk, [1u8; 16]);

    // --- serve ---
    // The prompt token payload travels with the serve call (here a small fixed
    // stand-in) but is never sealed into the receipt — only `prompt_hash` is.
    let prompt_tokens: Vec<u32> = vec![1, 2, 3, 4, 5, 6, 7];
    let resp = mesh.serve(&req, &prompt_tokens, Some(&presented)).expect("serve");

    println!("\nroute:    {}", resp.route.justification);
    for c in &resp.route.candidates {
        let mark = if Some(&c.backend) == resp.route.chosen.as_ref() {
            "→"
        } else if c.admissible {
            " "
        } else {
            "✗"
        };
        println!(
            "  {mark} {:<9} {} est {} µJ{}",
            c.backend.0,
            c.fidelity.label(),
            c.est_total_uj,
            c.reason.as_ref().map(|r| format!("  ({r})")).unwrap_or_default()
        );
    }

    println!(
        "\nserved:   {} tokens, fidelity_met={}, provenance={}",
        resp.outcome.tokens_out,
        resp.receipt.fidelity_met,
        resp.energy.provenance.jcr1_label()
    );
    println!("energy:   {} µJ ({} J)", resp.energy.uj(), resp.energy.uj() as f64 / 1e6);
    match resp.uj_per_accepted_token() {
        Some(jpt) => println!("WEDGE:    {jpt} µJ per accepted token"),
        None => println!("WEDGE:    no tokens accepted"),
    }

    // --- the sealed JCR-1 receipt (mesh/1 profile) ---
    let wire = resp.receipt.to_jcr1_wire(mesh.steward());
    println!("\nreceipt (mesh/1):\n{}", serde_json::to_string_pretty(&wire).unwrap());

    // --- verify the seal ---
    let ok = resp
        .receipt
        .verify_envelope(&resp.envelope, mesh.steward(), &mesh.verifying_key())
        .is_ok();
    println!(
        "\nsealed envelope: {} bytes, verifies under steward key: {ok}",
        resp.envelope.len()
    );
}