//! Execution receipts in a repository (spec §14.6): kept beside the state
//! they were made on, with the runner's identity and signature.

use super::*;
use crate::receipt::SignedReceipt;

/// A stored receipt and what verifying it found.
#[derive(Clone, Debug)]
pub struct ReceiptInfo {
    /// The receipt attestation's ObjectRef, which names it.
    pub attest: ObjectRef,
    pub signed: SignedReceipt,
    /// Why it does not verify, if it does not.
    pub problem: Option<String>,
    /// The runner's key was revoked (spec §14.2).
    pub revoked: bool,
}

impl Repo {
    /// Verify `sr` and keep it: the receipt, the attestation with its
    /// signatures, and the runner's identity. Returns the attestation's
    /// ObjectRef. Receipts for another repository are refused.
    pub fn add_receipt(&self, sr: &SignedReceipt) -> Result<ObjectRef> {
        sr.verify()
            .map_err(|e| RepoError::Msg(format!("receipt does not verify: {e}")))?;
        if sr.attest.repo != self.id()? {
            return fail("that receipt is for another repository");
        }
        self.store.put_identity(&sr.runner)?;
        self.store.put_receipt(&sr.receipt)?;
        let r = self.store.put_attest(&sr.attest)?;
        for sig in &sr.sigs {
            self.store.put_signature(&r, sig)?;
        }
        self.store.index_receipt(&sr.state(), &r)?;
        Ok(r)
    }

    /// The receipt named by attestation `r`, verified again from the store.
    pub fn receipt(&self, r: &ObjectRef) -> Result<ReceiptInfo> {
        let attest = self.store.get_attest(r)?;
        let AttestBody::Receipt { receipt, .. } = &attest.body else {
            return fail(format!("#{} is not a receipt", r.short(12)));
        };
        let receipt = self.store.get_receipt(receipt)?;
        let sigs = self.store.signatures(r)?;
        let Some(key) = sigs.first().map(|s| s.key) else {
            return fail(format!("receipt #{} has no signature", r.short(12)));
        };
        let runner = self.store.get_identity(&key)?;
        let signed = SignedReceipt {
            receipt,
            attest,
            sigs,
            runner,
        };
        let problem = signed.verify().err().map(|e| e.to_string());
        Ok(ReceiptInfo {
            attest: *r,
            revoked: self.is_revoked(&key)?,
            signed,
            problem,
        })
    }

    /// Every receipt kept for the state of `heads`, oldest first.
    pub fn receipts(&self, heads: &[ChangeHash]) -> Result<Vec<ReceiptInfo>> {
        let state = hash_object(
            ObjectType::State,
            &StateObject::new(heads.to_vec()).encode(),
        );
        let mut out = self
            .store
            .receipts_for(&state)?
            .iter()
            .map(|r| self.receipt(r))
            .collect::<Result<Vec<_>>>()?;
        out.sort_by_key(|i| i.signed.attest.hlc);
        Ok(out)
    }

    /// Receipts to keep through garbage collection: those whose state's
    /// heads `keep` holds, with their receipts, runners and outputs.
    /// Keep a signed approval (oxygenhub#235): verified, for this repository,
    /// with the signer's identity and indexed by the state it approves, so
    /// garbage collection keeps it while that state lives. Who may approve is
    /// the caller's rule.
    pub fn add_approval(&self, sa: &crate::approval::SignedApproval) -> Result<ObjectRef> {
        sa.verify()
            .map_err(|e| RepoError::Msg(format!("approval does not verify: {e}")))?;
        if sa.attest.repo != self.id()? {
            return fail("that approval is for another repository");
        }
        let state = sa
            .statement()
            .map_err(|e| RepoError::Msg(e.to_string()))?
            .state;
        self.store.put_identity(&sa.signer)?;
        let r = self.store.put_attest(&sa.attest)?;
        for sig in &sa.sigs {
            self.store.put_signature(&r, sig)?;
        }
        self.store.index_approval(&state, &r)?;
        Ok(r)
    }

    /// Approvals of states garbage collection keeps are kept, with their
    /// signatures and signers.
    pub(crate) fn reachable_approvals(&self, keep: &mut HashSet<ObjectRef>) -> Result<()> {
        for state in self.store.approval_states()? {
            if !keep.contains(&state) {
                let heads = match self.store.get_state(&state) {
                    Ok(s) => s.heads,
                    Err(StoreError::NotFound(_)) => vec![],
                    Err(e) => return Err(e.into()),
                };
                if !heads.iter().all(|h| keep.contains(h)) {
                    continue;
                }
                keep.insert(state);
            }
            for a in self.store.approvals_for(&state)? {
                keep.insert(a);
                for sig in self.store.signatures(&a)? {
                    keep.insert(sig.key);
                }
            }
        }
        Ok(())
    }

    pub(crate) fn reachable_receipts(&self, keep: &mut HashSet<ObjectRef>) -> Result<()> {
        for state in self.store.receipt_states()? {
            let heads = match self.store.get_state(&state) {
                Ok(s) => s.heads,
                // A receipt may arrive before its state object; its heads
                // are unknown, so keep it.
                Err(StoreError::NotFound(_)) => vec![],
                Err(e) => return Err(e.into()),
            };
            if !heads.iter().all(|h| keep.contains(h)) {
                continue;
            }
            keep.insert(state);
            for a in self.store.receipts_for(&state)? {
                keep.insert(a);
                for sig in self.store.signatures(&a)? {
                    keep.insert(sig.key);
                }
                let Ok(attest) = self.store.get_attest(&a) else {
                    continue;
                };
                let AttestBody::Receipt { receipt, .. } = attest.body else {
                    continue;
                };
                keep.insert(receipt);
                let Ok(r) = self.store.get_receipt(&receipt) else {
                    continue;
                };
                for b in r.outputs.iter().chain(&r.inputs) {
                    if keep.insert(*b) {
                        if let Ok(bytes) = self.store.get_typed(b, ObjectType::Blob) {
                            keep.extend(Blob::decode(&bytes)?.chunks);
                        }
                    }
                }
            }
        }
        Ok(())
    }
}