feat(prospective-parachains): Implement FragmentChain

dot/parachain/prospective-parachains/fragment-chain/errors.go

@@ -0,0 +1,82 @@
+package fragmentchain
+
+import (
+	"errors"
+	"fmt"
+
+	parachaintypes "github.com/ChainSafe/gossamer/dot/parachain/types"
+	"github.com/ChainSafe/gossamer/lib/common"
+)
+
+var (
+	ErrCandidateAlradyKnown            = errors.New("candidate already known")
+	ErrZeroLengthCycle                 = errors.New("candidate's parent head is equal to its output head. Would introduce a cycle")
+	ErrCycle                           = errors.New("candidate would introduce a cycle")
+	ErrMultiplePaths                   = errors.New("candidate would introduce two paths to the same output state")
+	ErrIntroduceBackedCandidate        = errors.New("attempting to directly introduce a Backed candidate. It should first be introduced as Seconded")
+	ErrParentCandidateNotFound         = errors.New("could not find parent of the candidate")
+	ErrRelayParentMovedBackwards       = errors.New("relay parent would move backwards from the latest candidate in the chain")
+	ErrPersistedValidationDataMismatch = errors.New("candidate does not match the persisted validation data provided alongside it")
+	ErrCandidateEntryZeroLengthCycle   = errors.New("candidate's parent head is equal to its output head. Would introduce a cycle")
+)
+
+type ErrRelayParentPrecedesCandidatePendingAvailability struct {
+	relayParentA, relayParentB common.Hash
+}
+
+func (e ErrRelayParentPrecedesCandidatePendingAvailability) Error() string {
+	return fmt.Sprintf("relay parent %x of the candidate precedes the relay parent %x of a pending availability candidate",
+		e.relayParentA, e.relayParentB)
+}
+
+type ErrForkWithCandidatePendingAvailability struct {
+	candidateHash parachaintypes.CandidateHash
+}
+
+func (e ErrForkWithCandidatePendingAvailability) Error() string {
+	return fmt.Sprintf("candidate would introduce a fork with a pending availability candidate: %x", e.candidateHash.Value)
+}
+
+type ErrForkChoiceRule struct {
+	candidateHash parachaintypes.CandidateHash
+}
+
+func (e ErrForkChoiceRule) Error() string {
+	return fmt.Sprintf("fork selection rule favours another candidate: %x", e.candidateHash.Value)
+}
+
+type ErrComputeConstraints struct {
+	modificationErr error
+}
+
+func (e ErrComputeConstraints) Error() string {
+	return fmt.Sprintf("could not compute candidate constraints: %s", e.modificationErr)
+}
+
+type ErrCheckAgainstConstraints struct {
+	fragmentValidityErr error
+}
+
+func (e ErrCheckAgainstConstraints) Error() string {
+	return fmt.Sprintf("candidate violates constraints: %s", e.fragmentValidityErr)
+}
+
+type ErrRelayParentNotInScope struct {
+	relayParentA, relayParentB common.Hash
+}
+
+func (e ErrRelayParentNotInScope) Error() string {
+	return fmt.Sprintf("relay parent %s not in scope, earliest relay parent allowed %s",
+		e.relayParentA.String(), e.relayParentB.String())
+}
+
+type ErrUnexpectedAncestor struct {
+	// The block number that this error occurred at
+	Number uint
+	// The previous seen block number, which did not match `number`.
+	Prev uint
+}
+
+func (e ErrUnexpectedAncestor) Error() string {
+	return fmt.Sprintf("unexpected ancestor %d, expected %d", e.Number, e.Prev)
+}