//! Execution receipts (spec §14.6): what a runner ran, in what, on which
//! inputs and with what result. A receipt names no state, so the same
//! receipt serves every state whose scope is unchanged; an attestation of
//! kind `receipt`, signed by the runner, binds it to the state it ran on.

use crate::attest::{Attest, AttestBody};
use crate::cbor::{self, Value};
use crate::hash::{hash_object, ObjectRef, ObjectType};
use crate::identity::{verify, Domain, Identity, SecretKey, Signature};
use crate::objects::{array, bytes, check_version, field, map, oref, text, uint, Hlc, ObjectError};

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Receipt {
    pub job_name: String,
    /// The pipeline definition the job came from.
    pub pipeline_hash: ObjectRef,
    /// BLAKE3 over the sorted (path, content) of the files the job's scope
    /// matches; the whole tree when it has no scope.
    pub scope_tree_hash: ObjectRef,
    /// Artifacts and other inputs consumed beyond the tree.
    pub inputs: Vec<ObjectRef>,
    /// What the job ran in: isolation tier, rootfs, argv and environment.
    pub environment: ObjectRef,
    /// Blobs the job produced.
    pub outputs: Vec<ObjectRef>,
    pub exit_code: u32,
    pub duration_ms: u64,
}

fn refs(v: &[ObjectRef]) -> Value {
    Value::Array(v.iter().map(|h| Value::Bytes(h.0.to_vec())).collect())
}

fn refs_from(v: &Value, what: &str) -> Result<Vec<ObjectRef>, ObjectError> {
    array(v, what)?.iter().map(|h| oref(h, what)).collect()
}

impl Receipt {
    pub fn passed(&self) -> bool {
        self.exit_code == 0
    }

    pub fn to_value(&self) -> Value {
        Value::map([
            (0, Value::Uint(1)),
            (1, Value::Text(self.job_name.clone())),
            (2, Value::Bytes(self.pipeline_hash.0.to_vec())),
            (3, Value::Bytes(self.scope_tree_hash.0.to_vec())),
            (4, refs(&self.inputs)),
            (5, Value::Bytes(self.environment.0.to_vec())),
            (6, refs(&self.outputs)),
            (7, Value::Uint(self.exit_code as u64)),
            (8, Value::Uint(self.duration_ms)),
        ])
    }

    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&self.to_value())
    }

    pub fn hash(&self) -> ObjectRef {
        hash_object(ObjectType::Receipt, &self.encode())
    }

    pub fn decode(b: &[u8]) -> Result<Receipt, ObjectError> {
        let v = cbor::decode(b)?;
        let m = map(&v, "receipt")?;
        check_version(m)?;
        let exit_code = uint(field(m, 7, "exit_code")?, "exit_code")?;
        Ok(Receipt {
            job_name: text(field(m, 1, "job_name")?, "job_name")?.to_owned(),
            pipeline_hash: oref(field(m, 2, "pipeline_hash")?, "pipeline_hash")?,
            scope_tree_hash: oref(field(m, 3, "scope_tree_hash")?, "scope_tree_hash")?,
            inputs: refs_from(field(m, 4, "inputs")?, "inputs")?,
            environment: oref(field(m, 5, "environment")?, "environment")?,
            outputs: refs_from(field(m, 6, "outputs")?, "outputs")?,
            exit_code: u32::try_from(exit_code)
                .map_err(|_| ObjectError::Schema("exit_code: expected u32".into()))?,
            duration_ms: uint(field(m, 8, "duration_ms")?, "duration_ms")?,
        })
    }
}

#[derive(Clone, Debug, PartialEq, Eq, thiserror::Error)]
pub enum ReceiptError {
    #[error("the attestation is not of kind receipt")]
    NotReceipt,
    #[error("the attestation names a different receipt")]
    WrongReceipt,
    #[error("no signature by the runner {0}")]
    Unsigned(String),
    #[error("the runner's signature does not verify: {0}")]
    BadSignature(String),
    #[error("{0}")]
    Schema(String),
}

impl From<ObjectError> for ReceiptError {
    fn from(e: ObjectError) -> Self {
        ReceiptError::Schema(e.to_string())
    }
}

/// A receipt as a runner hands it over: the receipt, the attestation
/// binding it to a state, the runner's signature over that attestation, and
/// the runner's identity, so it verifies with nothing else.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SignedReceipt {
    pub receipt: Receipt,
    pub attest: Attest,
    pub sigs: Vec<Signature>,
    pub runner: Identity,
}

impl SignedReceipt {
    /// Bind `receipt` to `state` of repository `repo` for run `run` (a URL
    /// or other name of the run), signed by `runner` with `sk`.
    pub fn sign(
        receipt: Receipt,
        repo: [u8; 16],
        state: ObjectRef,
        run: &str,
        runner: &Identity,
        sk: &SecretKey,
    ) -> SignedReceipt {
        let attest = Attest {
            repo,
            hlc: Hlc::now(),
            body: AttestBody::Receipt {
                receipt: receipt.hash(),
                state,
                run: run.into(),
            },
        };
        let sig = sk.sign(Domain::Attest, &runner.hash(), &attest.hash());
        SignedReceipt {
            receipt,
            attest,
            sigs: vec![sig],
            runner: runner.clone(),
        }
    }

    /// The state the receipt was made on.
    pub fn state(&self) -> ObjectRef {
        match &self.attest.body {
            AttestBody::Receipt { state, .. } => *state,
            _ => ObjectRef([0; 32]),
        }
    }

    pub fn run(&self) -> &str {
        match &self.attest.body {
            AttestBody::Receipt { run, .. } => run,
            _ => "",
        }
    }

    /// The attestation is a receipt attestation for this receipt, and the
    /// runner signed it. Whether to trust the runner is the reader's call.
    pub fn verify(&self) -> Result<(), ReceiptError> {
        let AttestBody::Receipt { receipt, .. } = &self.attest.body else {
            return Err(ReceiptError::NotReceipt);
        };
        if *receipt != self.receipt.hash() {
            return Err(ReceiptError::WrongReceipt);
        }
        let key = self.runner.hash();
        let target = self.attest.hash();
        let sig = self
            .sigs
            .iter()
            .find(|s| s.key == key)
            .ok_or_else(|| ReceiptError::Unsigned(key.short(12)))?;
        verify(&self.runner, sig, Domain::Attest, &target)
            .map_err(|e| ReceiptError::BadSignature(e.to_string()))
    }

    /// `[receipt, attest, [Signature], identity]`, each object as its bytes.
    pub fn encode(&self) -> Vec<u8> {
        cbor::encode(&Value::Array(vec![
            Value::Bytes(self.receipt.encode()),
            Value::Bytes(self.attest.encode()),
            Value::Array(self.sigs.iter().map(|s| s.to_value()).collect()),
            Value::Bytes(self.runner.encode()),
        ]))
    }

    pub fn decode(b: &[u8]) -> Result<SignedReceipt, ReceiptError> {
        let v = cbor::decode(b).map_err(ObjectError::from)?;
        let a = array(&v, "signed receipt")?;
        if a.len() != 4 {
            return Err(ReceiptError::Schema(
                "signed receipt: expected [receipt, attest, sigs, identity]".into(),
            ));
        }
        Ok(SignedReceipt {
            receipt: Receipt::decode(bytes(&a[0], "receipt")?)?,
            attest: Attest::decode(bytes(&a[1], "attest")?)?,
            sigs: array(&a[2], "sigs")?
                .iter()
                .map(Signature::from_value)
                .collect::<Result<_, _>>()?,
            runner: Identity::decode(bytes(&a[3], "identity")?)?,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    pub(crate) fn sample() -> Receipt {
        Receipt {
            job_name: "test".into(),
            pipeline_hash: ObjectRef([1; 32]),
            scope_tree_hash: ObjectRef([2; 32]),
            inputs: vec![],
            environment: ObjectRef([3; 32]),
            outputs: vec![ObjectRef([4; 32])],
            exit_code: 0,
            duration_ms: 1500,
        }
    }

    #[test]
    fn receipts_round_trip_and_hash_as_receipt_objects() {
        let r = sample();
        assert_eq!(Receipt::decode(&r.encode()).unwrap(), r);
        let mut h = blake3::Hasher::new();
        h.update(format!("oxy1 receipt {}\0", r.encode().len()).as_bytes());
        h.update(&r.encode());
        assert_eq!(
            r.hash().0,
            *h.finalize().as_bytes(),
            "OxygenFlow's receipt hash"
        );
        assert!(r.passed());
    }

    #[test]
    fn a_signed_receipt_verifies_and_tampering_does_not() {
        let sk = SecretKey::generate();
        let runner = sk.identity("earth-1", "runner@earth", 1);
        let sr = SignedReceipt::sign(
            sample(),
            [7; 16],
            ObjectRef([9; 32]),
            "andy/demo#3",
            &runner,
            &sk,
        );
        sr.verify().unwrap();
        let back = SignedReceipt::decode(&sr.encode()).unwrap();
        assert_eq!(back, sr);
        assert_eq!(back.state(), ObjectRef([9; 32]));
        assert_eq!(back.run(), "andy/demo#3");

        let mut forged = sr.clone();
        forged.receipt.exit_code = 0;
        forged.receipt.duration_ms = 1;
        assert_eq!(forged.verify(), Err(ReceiptError::WrongReceipt));

        let mut moved = sr.clone();
        if let AttestBody::Receipt { state, .. } = &mut moved.attest.body {
            *state = ObjectRef([8; 32]);
        }
        assert!(matches!(moved.verify(), Err(ReceiptError::BadSignature(_))));

        let other = SecretKey::generate().identity("mallory", "m@x", 1);
        let mut swapped = sr.clone();
        swapped.runner = other;
        assert!(matches!(swapped.verify(), Err(ReceiptError::Unsigned(_))));
    }
}