//! Consume the published `proof.receipt/1` conformance pack.
//!
//! `gen-vectors` writes `proof/conformance/v1/` and nothing read it back — the
//! crate's `soundness.rs` does no file IO, so the published receipts were never
//! checked against the implementation that claims to produce them.
//!
//! Three things are checked here, deliberately separated:
//!
//! 1. **Drift** — the generator still emits exactly the published files, run into a
//!    temporary directory so the pack itself is never touched.
//! 2. **Signatures, independently** — each envelope is verified from the pack and
//!    RFC 9052 alone, with a hand-built CBOR encoder rather than the crate's own
//!    COSE code, which is what a third-party verifier would have to do.
//! 3. **The cascade's accounting** — the economics the receipts record, recomputed
//!    across tiers rather than read back one at a time.

use ed25519_dalek::{Signature, Verifier, VerifyingKey};
use serde_json::Value;
use std::path::{Path, PathBuf};

fn pack_dir() -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("../../../conformance/v1")
        .canonicalize()
        .expect("the conformance pack must exist next to the spec")
}

fn receipts_in(dir: &Path) -> Vec<Value> {
    let raw = std::fs::read_to_string(dir.join("receipts.jsonl")).expect("read receipts.jsonl");
    raw.lines()
        .filter(|l| !l.trim().is_empty())
        .map(|l| serde_json::from_str(l).expect("each line must parse"))
        .collect()
}

fn meta() -> Value {
    serde_json::from_slice(&std::fs::read(pack_dir().join("meta.json")).expect("read meta.json"))
        .expect("meta.json must parse")
}

// --- minimal CBOR (RFC 8949), independent of the crate's own COSE code ----------

fn head(major: u8, len: u64) -> Vec<u8> {
    let m = major << 5;
    match len {
        0..=23 => vec![m | len as u8],
        24..=0xff => vec![m | 24, len as u8],
        0x100..=0xffff => {
            let mut v = vec![m | 25];
            v.extend_from_slice(&(len as u16).to_be_bytes());
            v
        }
        _ => {
            let mut v = vec![m | 26];
            v.extend_from_slice(&(len as u32).to_be_bytes());
            v
        }
    }
}
fn bstr(b: &[u8]) -> Vec<u8> {
    let mut v = head(2, b.len() as u64);
    v.extend_from_slice(b);
    v
}
fn tstr(s: &str) -> Vec<u8> {
    let mut v = head(3, s.len() as u64);
    v.extend_from_slice(s.as_bytes());
    v
}
/// `{1: -8, 4: <steward bytes>}` — EdDSA with the steward as `kid`.
fn protected_header(kid: &str) -> Vec<u8> {
    let mut v = head(5, 2);
    v.push(0x01);
    v.push(0x27); // -8
    v.push(0x04);
    v.extend(bstr(kid.as_bytes()));
    v
}
/// RFC 9052 §4.4.
fn sig_structure(protected: &[u8], payload: &[u8]) -> Vec<u8> {
    let mut v = head(4, 4);
    v.extend(tstr("Signature1"));
    v.extend(bstr(protected));
    v.extend(bstr(&[]));
    v.extend(bstr(payload));
    v
}

/// The generator still emits exactly the published pack.
///
/// Run into a temp directory — `gen-vectors` takes an output path, so the
/// comparison never risks the published files.
#[test]
fn the_generator_still_emits_the_published_pack() {
    let tmp = std::env::temp_dir().join(format!("proof-pack-{}", std::process::id()));
    let _ = std::fs::remove_dir_all(&tmp);
    std::fs::create_dir_all(&tmp).expect("create temp dir");

    let out = std::process::Command::new(env!("CARGO_BIN_EXE_gen-vectors"))
        .arg(&tmp)
        .output()
        .expect("gen-vectors must run");
    assert!(out.status.success(), "gen-vectors failed: {}", String::from_utf8_lossy(&out.stderr));

    for f in ["meta.json", "receipts.jsonl"] {
        assert_eq!(
            std::fs::read(tmp.join(f)).unwrap(),
            std::fs::read(pack_dir().join(f)).unwrap(),
            "{f} has drifted from what the implementation emits"
        );
    }
    let _ = std::fs::remove_dir_all(&tmp);
}

/// Every published envelope verifies under the published key, checked from the pack
/// and RFC 9052 alone.
#[test]
fn every_published_envelope_verifies_under_the_published_key() {
    let m = meta();
    let steward = m["steward"].as_str().expect("meta names the steward");
    let pubkey: [u8; 32] = hex::decode(m["pubkey_hex"].as_str().unwrap())
        .unwrap()
        .try_into()
        .expect("a 32-byte Ed25519 key");
    let vk = VerifyingKey::from_bytes(&pubkey).unwrap();
    let protected = protected_header(steward);

    let receipts = receipts_in(&pack_dir());
    assert_eq!(receipts.len(), 4, "the pack records one receipt per cascade tier");

    for r in &receipts {
        let tier = r["closed_by"].as_str().unwrap();
        let core = hex::decode(r["signed_core_hex"].as_str().unwrap()).unwrap();
        let envelope = hex::decode(r["envelope_hex"].as_str().unwrap()).unwrap();
        let sig = Signature::from_slice(&envelope[envelope.len() - 64..]).unwrap();
        vk.verify(&sig_structure(&protected, &core), &sig)
            .unwrap_or_else(|e| panic!("{tier}: published envelope does not verify: {e}"));

        // the envelope really does carry the published core, not some other payload
        assert!(
            envelope.windows(core.len()).any(|w| w == core),
            "{tier}: the envelope does not contain its published signed core"
        );
        assert_eq!(r["wire"]["steward"], m["steward"], "{tier}: wire steward disagrees with meta");
        assert_eq!(r["wire"]["closed_by"], r["closed_by"], "{tier}: wire tier disagrees");
        let goal_id = r["wire"]["goal_id"].as_str().expect("wire carries a goal id");
        assert_eq!(goal_id.len(), 64, "{tier}: goal id is not a 32-byte hash");
        assert!(goal_id.bytes().all(|b| b.is_ascii_hexdigit()), "{tier}: goal id is not hex");
    }

    // Distinct goals must address distinctly, or the receipts would be
    // interchangeable and the pack would prove nothing about which goal closed.
    let goals: Vec<&str> = receipts.iter().map(|r| r["goal"].as_str().unwrap()).collect();
    let ids: Vec<&str> = receipts.iter().map(|r| r["wire"]["goal_id"].as_str().unwrap()).collect();
    for i in 0..receipts.len() {
        for j in i + 1..receipts.len() {
            assert_eq!(
                goals[i] == goals[j],
                ids[i] == ids[j],
                "goal text and goal id disagree about whether {i} and {j} are the same goal"
            );
        }
    }
}

/// The verification above is not vacuous.
#[test]
fn a_tampered_core_or_a_wrong_key_does_not_verify() {
    let m = meta();
    let steward = m["steward"].as_str().unwrap();
    let pubkey: [u8; 32] =
        hex::decode(m["pubkey_hex"].as_str().unwrap()).unwrap().try_into().unwrap();
    let protected = protected_header(steward);
    let r = &receipts_in(&pack_dir())[0];
    let envelope = hex::decode(r["envelope_hex"].as_str().unwrap()).unwrap();
    let sig = Signature::from_slice(&envelope[envelope.len() - 64..]).unwrap();

    let mut core = hex::decode(r["signed_core_hex"].as_str().unwrap()).unwrap();
    let mid = core.len() / 2;
    core[mid] ^= 0x01;
    assert!(
        VerifyingKey::from_bytes(&pubkey)
            .unwrap()
            .verify(&sig_structure(&protected, &core), &sig)
            .is_err(),
        "a tampered signed core verified"
    );

    let core = hex::decode(r["signed_core_hex"].as_str().unwrap()).unwrap();
    let stranger = ed25519_dalek::SigningKey::from_bytes(&[0x42; 32]).verifying_key();
    assert!(
        stranger.verify(&sig_structure(&protected, &core), &sig).is_err(),
        "the envelope verified under a key that did not seal it"
    );
}

/// The cascade's accounting, recomputed across the whole pack.
///
/// Two properties the receipts assert together and neither states alone: the waste
/// recorded at a tier is exactly what the tiers before it consumed, and escalating
/// all the way costs **more** than the baseline it is measured against. The cascade
/// saves energy by closing early, not by existing.
#[test]
fn the_cascade_accounting_holds_across_the_tiers() {
    let receipts = receipts_in(&pack_dir());
    let tiers: Vec<&str> = receipts.iter().map(|r| r["closed_by"].as_str().unwrap()).collect();
    assert_eq!(tiers, ["T0", "T1", "T2", "T3"], "the pack must cover every cascade tier");

    let total = |r: &Value| r["wire"]["total_uj"].as_u64().unwrap();
    let wasted = |r: &Value| r["wire"]["wasted_uj"].as_u64().unwrap();
    let baseline = receipts[0]["wire"]["baseline_uj"].as_u64().unwrap();

    assert_eq!(wasted(&receipts[0]), 0, "closing at T0 wastes nothing");
    for i in 1..receipts.len() {
        assert_eq!(
            wasted(&receipts[i]),
            total(&receipts[i - 1]),
            "{}: waste must be exactly what the earlier tiers consumed",
            tiers[i]
        );
        assert!(total(&receipts[i]) > total(&receipts[i - 1]), "{}: cost must rise", tiers[i]);
    }

    for r in &receipts[..3] {
        assert!(total(r) < baseline, "closing early must beat the baseline");
    }
    assert!(
        total(&receipts[3]) > baseline,
        "escalating to T3 costs more than the baseline — if this ever passes, the \
         honest limit of the cascade has been quietly re-described"
    );

    // Every verdict here was closed by a stand-in, and the pack says so rather than
    // hiding it. That marking is the property worth holding onto.
    for (r, tier) in receipts.iter().zip(&tiers) {
        assert_eq!(r["wire"]["verdict"], "proved", "{tier}");
        assert_eq!(r["wire"]["closed_by_stub"], 1, "{tier}: a stub close must be recorded as one");
    }
}