//! Attestations (spec §14.4): signed statements about references and batches
//! of changes, and runs (receipts, §14.6).

use crate::cbor::{self, Value};
use crate::hash::{hash_object, ChangeHash, KeyId, ObjectRef, ObjectType};
use crate::objects::{
    array, bytes, check_version, field, map, oref, text, uint, Hlc, ObjectError, FORMAT_VERSION,
};

pub const MAX_SEAL_HASHES: usize = 4096;

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum AttestBody {
    /// A bookmark moved from `old_state` to `new_state` (spec §10.2).
    Ref {
        name: String,
        old_state: ObjectRef,
        new_state: ObjectRef,
        serial: u64,
    },
    /// One signature covering a batch of changes (spec §14.4).
    Seal { hashes: Vec<ChangeHash> },
    /// An immutable named state (spec §10.1).
    Tag {
        name: String,
        state: ObjectRef,
        message: String,
    },
    /// The signing key's identity was replaced by `new` (spec §14.2).
    Rotate { new: KeyId },
    /// `key` must no longer be trusted (spec §14.2).
    Revoke { key: KeyId, reason: String },
    /// A runner ran the job of `receipt` on `state` (spec §14.6); `run`
    /// names the run, usually by URL.
    Receipt {
        receipt: ObjectRef,
        state: ObjectRef,
        run: String,
    },
    /// A person approved (or rejected) one job of one run (OxygenFlow
    /// approval gates; oxygenhub#235): the job as hashed with its sandbox,
    /// on that state, taking exactly those input blobs (a reviewed plan),
    /// for that environment. It approves nothing else.
    Approval {
        run: String,
        job: String,
        job_hash: ObjectRef,
        state: ObjectRef,
        inputs: Vec<ObjectRef>,
        environment: String,
        approve: bool,
    },
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Attest {
    /// Repository ID chosen at init.
    pub repo: [u8; 16],
    pub hlc: Hlc,
    pub body: AttestBody,
}

impl Attest {
    pub fn kind(&self) -> &'static str {
        match self.body {
            AttestBody::Ref { .. } => "ref",
            AttestBody::Seal { .. } => "seal",
            AttestBody::Tag { .. } => "tag",
            AttestBody::Rotate { .. } => "rotate",
            AttestBody::Revoke { .. } => "revoke",
            AttestBody::Receipt { .. } => "receipt",
            AttestBody::Approval { .. } => "approval",
        }
    }

    pub fn seal(repo: [u8; 16], mut hashes: Vec<ChangeHash>) -> Attest {
        hashes.sort();
        hashes.dedup();
        Attest {
            repo,
            hlc: Hlc::now(),
            body: AttestBody::Seal { hashes },
        }
    }

    pub fn to_value(&self) -> Value {
        let body = match &self.body {
            AttestBody::Ref {
                name,
                old_state,
                new_state,
                serial,
            } => Value::map([
                (0, Value::Text(name.clone())),
                (1, Value::Bytes(old_state.0.to_vec())),
                (2, Value::Bytes(new_state.0.to_vec())),
                (3, Value::Uint(*serial)),
            ]),
            AttestBody::Seal { hashes } => Value::map([(
                0,
                Value::Array(hashes.iter().map(|h| Value::Bytes(h.0.to_vec())).collect()),
            )]),
            AttestBody::Tag {
                name,
                state,
                message,
            } => Value::map([
                (0, Value::Text(name.clone())),
                (1, Value::Bytes(state.0.to_vec())),
                (2, Value::Text(message.clone())),
            ]),
            AttestBody::Rotate { new } => Value::map([(0, Value::Bytes(new.0.to_vec()))]),
            AttestBody::Revoke { key, reason } => Value::map([
                (0, Value::Bytes(key.0.to_vec())),
                (1, Value::Text(reason.clone())),
            ]),
            AttestBody::Receipt {
                receipt,
                state,
                run,
            } => Value::map([
                (0, Value::Bytes(receipt.0.to_vec())),
                (1, Value::Bytes(state.0.to_vec())),
                (2, Value::Text(run.clone())),
            ]),
            AttestBody::Approval {
                run,
                job,
                job_hash,
                state,
                inputs,
                environment,
                approve,
            } => Value::map([
                (0, Value::Text(run.clone())),
                (1, Value::Text(job.clone())),
                (2, Value::Bytes(job_hash.0.to_vec())),
                (3, Value::Bytes(state.0.to_vec())),
                (
                    4,
                    Value::Array(inputs.iter().map(|i| Value::Bytes(i.0.to_vec())).collect()),
                ),
                (5, Value::Text(environment.clone())),
                (6, Value::Uint(u64::from(*approve))),
            ]),
        };
        Value::map([
            (0, Value::Uint(FORMAT_VERSION)),
            (1, Value::Text(self.kind().into())),
            (2, Value::Bytes(self.repo.to_vec())),
            (3, self.hlc.to_value()),
            (4, body),
        ])
    }

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

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

    pub fn decode(b: &[u8]) -> Result<Attest, ObjectError> {
        let v = cbor::decode(b)?;
        let m = map(&v, "attest")?;
        check_version(m)?;
        let kind = text(field(m, 1, "kind")?, "kind")?;
        let repo: [u8; 16] = bytes(field(m, 2, "repo")?, "repo")?
            .try_into()
            .map_err(|_| ObjectError::Schema("repo: expected 16 bytes".into()))?;
        let hlc = Hlc::from_value(field(m, 3, "hlc")?)?;
        let b = map(field(m, 4, "body")?, "body")?;
        let body = match kind {
            "ref" => AttestBody::Ref {
                name: text(field(b, 0, "name")?, "name")?.to_owned(),
                old_state: oref(field(b, 1, "old_state")?, "old_state")?,
                new_state: oref(field(b, 2, "new_state")?, "new_state")?,
                serial: uint(field(b, 3, "serial")?, "serial")?,
            },
            "seal" => {
                let hashes = array(field(b, 0, "hashes")?, "hashes")?
                    .iter()
                    .map(|h| oref(h, "hash"))
                    .collect::<Result<Vec<_>, _>>()?;
                if hashes.is_empty()
                    || hashes.len() > MAX_SEAL_HASHES
                    || !hashes.windows(2).all(|w| w[0] < w[1])
                {
                    return Err(ObjectError::Schema(
                        "seal: hashes must be 1..4096, sorted and unique".into(),
                    ));
                }
                AttestBody::Seal { hashes }
            }
            "tag" => AttestBody::Tag {
                name: text(field(b, 0, "name")?, "name")?.to_owned(),
                state: oref(field(b, 1, "state")?, "state")?,
                message: text(field(b, 2, "message")?, "message")?.to_owned(),
            },
            "rotate" => AttestBody::Rotate {
                new: oref(field(b, 0, "new")?, "new")?,
            },
            "revoke" => AttestBody::Revoke {
                key: oref(field(b, 0, "key")?, "key")?,
                reason: text(field(b, 1, "reason")?, "reason")?.to_owned(),
            },
            "receipt" => AttestBody::Receipt {
                receipt: oref(field(b, 0, "receipt")?, "receipt")?,
                state: oref(field(b, 1, "state")?, "state")?,
                run: text(field(b, 2, "run")?, "run")?.to_owned(),
            },
            "approval" => {
                let inputs = array(field(b, 4, "inputs")?, "inputs")?
                    .iter()
                    .map(|h| oref(h, "input"))
                    .collect::<Result<Vec<_>, _>>()?;
                if !inputs.windows(2).all(|w| w[0] < w[1]) {
                    return Err(ObjectError::Schema(
                        "approval: inputs must be sorted and unique".into(),
                    ));
                }
                AttestBody::Approval {
                    run: text(field(b, 0, "run")?, "run")?.to_owned(),
                    job: text(field(b, 1, "job")?, "job")?.to_owned(),
                    job_hash: oref(field(b, 2, "job_hash")?, "job_hash")?,
                    state: oref(field(b, 3, "state")?, "state")?,
                    inputs,
                    environment: text(field(b, 5, "environment")?, "environment")?.to_owned(),
                    approve: match uint(field(b, 6, "approve")?, "approve")? {
                        0 => false,
                        1 => true,
                        _ => return Err(ObjectError::Schema("approval: approve is 0 or 1".into())),
                    },
                }
            }
            other => {
                return Err(ObjectError::Schema(format!(
                    "unknown attestation kind {other:?}"
                )))
            }
        };
        Ok(Attest { repo, hlc, body })
    }
}

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

    #[test]
    fn round_trips() {
        let r = Attest {
            repo: [1; 16],
            hlc: Hlc {
                wall_ms: 3,
                logical: 0,
            },
            body: AttestBody::Ref {
                name: "main".into(),
                old_state: ObjectRef([1; 32]),
                new_state: ObjectRef([2; 32]),
                serial: 7,
            },
        };
        assert_eq!(Attest::decode(&r.encode()).unwrap(), r);
        assert_eq!(r.kind(), "ref");
        let s = Attest::seal(
            [1; 16],
            vec![ObjectRef([9; 32]), ObjectRef([3; 32]), ObjectRef([9; 32])],
        );
        let d = Attest::decode(&s.encode()).unwrap();
        assert!(
            matches!(&d.body, AttestBody::Seal { hashes } if hashes == &vec![ObjectRef([3; 32]), ObjectRef([9; 32])])
        );
        assert_ne!(s.hash(), r.hash());
        let t = Attest {
            repo: [1; 16],
            hlc: Hlc::default(),
            body: AttestBody::Tag {
                name: "v1".into(),
                state: ObjectRef([5; 32]),
                message: "release".into(),
            },
        };
        assert_eq!(Attest::decode(&t.encode()).unwrap(), t);
        assert_eq!(t.kind(), "tag");
    }

    #[test]
    fn rejects_bad_seals() {
        let empty = Attest {
            repo: [0; 16],
            hlc: Hlc::default(),
            body: AttestBody::Seal { hashes: vec![] },
        };
        assert!(Attest::decode(&empty.encode()).is_err());
        let unsorted = Attest {
            repo: [0; 16],
            hlc: Hlc::default(),
            body: AttestBody::Seal {
                hashes: vec![ObjectRef([2; 32]), ObjectRef([1; 32])],
            },
        };
        assert!(Attest::decode(&unsorted.encode()).is_err());
    }
}