feat: Canton MCMS proposal analyzer

Author: JohnChangUK

.changeset/canton-proposal-analyzer.md

@@ -0,0 +1,5 @@
+---
+"chainlink-deployments-framework": minor
+---
+
+feat(analyzer): implement Canton MCMS proposal analyzer

experimental/analyzer/canton_analyzer.go

@@ -0,0 +1,62 @@
+package analyzer
+
+import (
+	"encoding/json"
+	"fmt"
+
+	mcmscantonsdk "github.com/smartcontractkit/mcms/sdk/canton"
+	"github.com/smartcontractkit/mcms/types"
+)
+
+func AnalyzeCantonTransactions(ctx ProposalContext, chainSelector uint64, txs []types.Transaction) ([]*DecodedCall, error) {
+	decoder := mcmscantonsdk.NewDecoder()
+	decodedTxs := make([]*DecodedCall, len(txs))
+	for i, op := range txs {
+		analyzedTransaction, err := AnalyzeCantonTransaction(ctx, decoder, chainSelector, op)
+		if err != nil {
+			return nil, fmt.Errorf("failed to analyze Canton transaction %d: %w", i, err)
+		}
+		decodedTxs[i] = analyzedTransaction
+	}
+
+	return decodedTxs, nil
+}
+
+// AnalyzeCantonTransaction decodes a single Canton MCMS transaction. Each transaction already
+// describes the target call (Daml choice or factory deploy) via its AdditionalFields, so it is decoded directly
+func AnalyzeCantonTransaction(ctx ProposalContext, decoder *mcmscantonsdk.Decoder, chainSelector uint64, mcmsTx types.Transaction) (*DecodedCall, error) {
+	contractType, contractVersion := resolveContractInfo(ctx, chainSelector, mcmsTx)
+
+	var additionalFields mcmscantonsdk.AdditionalFields
+	if err := json.Unmarshal(mcmsTx.AdditionalFields, &additionalFields); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal Canton additional fields: %w", err)
+	}
+
+	// Pass the resolved contract type as the fallback contract-type key
+	// The decoder prefers the entity name parsed from AdditionalFields.TargetTemplateID when present.
+	decodedOp, err := decoder.Decode(mcmsTx, contractType)
+	if err != nil {
+		errStr := fmt.Errorf("failed to decode Canton transaction %q: %w", additionalFields.FunctionName, err)
+
+		return &DecodedCall{
+			Address:         mcmsTx.To,
+			Method:          errStr.Error(),
+			ContractType:    contractType,
+			ContractVersion: contractVersion,
+		}, nil
+	}
+
+	namedArgs, err := toNamedFields(decodedOp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to convert decoded operation to named arguments: %w", err)
+	}
+
+	return &DecodedCall{
+		Address:         mcmsTx.To,
+		Method:          decodedOp.MethodName(),
+		Inputs:          namedArgs,
+		Outputs:         []NamedField{},
+		ContractType:    contractType,
+		ContractVersion: contractVersion,
+	}, nil
+}