feat: implement PoolDistrResult (#1256)

Signed-off-by: Jenita <jkawan@blinklabs.io>
Co-authored-by: Jenita <jkawan@blinklabs.io>

Author: jkawan

cmd/gouroboros/query.go

@@ -315,6 +315,31 @@ func testQuery(f *globalFlags) {
 			os.Exit(1)
 		}
 		fmt.Printf("proposed-protocol-params-updates: %v\n", *proposedUpdates)
+	case "pool-distr":
+		// GetPoolDistr without specific pool IDs to get all pools distribution
+		poolDistr, err := o.LocalStateQuery().Client.GetPoolDistr(nil)
+		if err != nil {
+			fmt.Printf(
+				"ERROR: failure querying pool distribution: %s\n",
+				err,
+			)
+			os.Exit(1)
+		}
+		fmt.Printf("pool-distr (raw): %#v\n", poolDistr)
+
+		// Build a JSON-friendly view: map pool ID (hex) -> entry
+		jsonResults := make(map[string]any, len(poolDistr.Results))
+		for poolID, entry := range poolDistr.Results {
+			// PoolId is [28]byte; represent as hex for debugging
+			jsonKey := hex.EncodeToString(poolID[:])
+			jsonResults[jsonKey] = entry
+		}
+		jsonData, err := json.Marshal(jsonResults)
+		if err != nil {
+			fmt.Printf("pool-distr (JSON marshaling failed): %s\n", err)
+		} else {
+			fmt.Printf("pool-distr (JSON): %s\n", string(jsonData))
+		}
 	default:
 		fmt.Printf("ERROR: unknown query: %s\n", queryFlags.flagset.Args()[0])
 		os.Exit(1)

protocol/localstatequery/client.go

@@ -836,10 +836,18 @@ func (c *Client) GetPoolDistr(poolIds []any) (*PoolDistrResult, error) {
 	if err != nil {
 		return nil, err
 	}
+	// GetPoolDistr always requires a pool set parameter according to the Haskell implementation
+	// The query expects (len=2, tag=21) format: [21, Set(poolIds)]
+	// If no pool IDs specified, use an empty set to query all pools
+	var params []any
+	if poolIds == nil {
+		poolIds = []any{}
+	}
+	params = append(params, poolIds)
 	query := buildShelleyQuery(
 		currentEra,
 		QueryTypeShelleyPoolDistr,
-		// TODO: add args (#870)
+		params...,
 	)
 	var result PoolDistrResult
 	if err := c.runQuery(query, &result); err != nil {

protocol/localstatequery/queries.go

@@ -722,5 +722,13 @@ type PoolStateResult any
 // TODO (#869)
 type StakeSnapshotsResult any
 
-// TODO (#870)
-type PoolDistrResult any
+// PoolDistrResult represents the pool distribution result
+// It contains a map of pool IDs to their stake distribution (fraction and VRF hash)
+type PoolDistrResult struct {
+	cbor.StructAsArray
+	Results map[ledger.PoolId]struct {
+		cbor.StructAsArray
+		StakeFraction *cbor.Rat
+		VrfHash       ledger.Blake2b256
+	}
+}