feat: Add means to fetch schema (sourcenetwork#2006)

## Relevant issue(s)

Resolves sourcenetwork#1993

## Description

Adds means to fetch schema.

Adds a bunch of funcs to the clients to allow fetching of
schema(versions) defined in the system. When the set-default stuff got
merged, users were no longer guaranteed (at least on init) to be able to
view the schema ids they have created, this change allows them to view
them when ever they like.

cli/cli.go

@@ -59,6 +59,7 @@ func NewDefraCommand(cfg *config.Config) *cobra.Command {
 		MakeSchemaAddCommand(),
 		MakeSchemaPatchCommand(),
 		MakeSchemaSetDefaultCommand(),
+		MakeSchemaDescribeCommand(),
 		schema_migrate,
 	)
 

cli/schema_describe.go

@@ -0,0 +1,82 @@
+// Copyright 2023 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package cli
+
+import (
+	"github.com/spf13/cobra"
+
+	"github.com/sourcenetwork/defradb/client"
+)
+
+func MakeSchemaDescribeCommand() *cobra.Command {
+	var name string
+	var root string
+	var versionID string
+
+	var cmd = &cobra.Command{
+		Use:   "describe",
+		Short: "View schema descriptions.",
+		Long: `Introspect schema types.
+
+Example: view all schemas
+  defradb client schema describe
+		
+Example: view schemas by name
+  defradb client schema describe --name User
+		
+Example: view schemas by root
+  defradb client schema describe --root bae123
+		
+Example: view a single schema by version id
+  defradb client schema describe --version bae123
+		`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			store := mustGetStoreContext(cmd)
+
+			var schemas []client.SchemaDescription
+			switch {
+			case versionID != "":
+				schema, err := store.GetSchemaByVersionID(cmd.Context(), versionID)
+				if err != nil {
+					return err
+				}
+				return writeJSON(cmd, schema)
+
+			case root != "":
+				s, err := store.GetSchemasByRoot(cmd.Context(), root)
+				if err != nil {
+					return err
+				}
+				schemas = s
+
+			case name != "":
+				s, err := store.GetSchemasByName(cmd.Context(), name)
+				if err != nil {
+					return err
+				}
+				schemas = s
+
+			default:
+				s, err := store.GetAllSchemas(cmd.Context())
+				if err != nil {
+					return err
+				}
+				schemas = s
+			}
+
+			return writeJSON(cmd, schemas)
+		},
+	}
+	cmd.PersistentFlags().StringVar(&name, "name", "", "Schema name")
+	cmd.PersistentFlags().StringVar(&root, "root", "", "Schema root")
+	cmd.PersistentFlags().StringVar(&versionID, "version", "", "Schema Version ID")
+	return cmd
+}

client/db.go

@@ -161,6 +161,22 @@ type Store interface {
 	// this [Store].
 	GetAllCollections(context.Context) ([]Collection, error)
 
+	// GetSchemasByName returns the all schema versions with the given name.
+	GetSchemasByName(context.Context, string) ([]SchemaDescription, error)
+
+	// GetSchemaByVersionID returns the schema description for the schema version of the
+	// ID provided.
+	//
+	// Will return an error if it is not found.
+	GetSchemaByVersionID(context.Context, string) (SchemaDescription, error)
+
+	// GetSchemasByRoot returns the all schema versions for the given root.
+	GetSchemasByRoot(context.Context, string) ([]SchemaDescription, error)
+
+	// GetAllSchemas returns all schema versions that currently exist within
+	// this [Store].
+	GetAllSchemas(context.Context) ([]SchemaDescription, error)
+
 	// GetAllIndexes returns all the indexes that currently exist within this [Store].
 	GetAllIndexes(context.Context) (map[CollectionName][]IndexDescription, error)