refactor: expose generated code and client business logic to share with Kapacitor (#103)

* refactor: take clients out of internal

* refactor: move stdio to pkg

* Move internal/api to api

* refactor: final changes for Kapacitor to access shared functionality

* chore: regenerate mocks

* fix: bad automated refactor

* chore: extra formatting not caught by make fmt

clients/helpers.go

@@ -0,0 +1,56 @@
+package clients
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+
+	"github.com/urfave/cli/v2"
+)
+
+// ReadQuery reads a Flux query into memory from a --file argument, args, or stdin
+func ReadQuery(ctx *cli.Context) (string, error) {
+	nargs := ctx.NArg()
+	file := ctx.String("file")
+
+	if nargs > 1 {
+		return "", fmt.Errorf("at most 1 query string can be specified over the CLI, got %d", ctx.NArg())
+	}
+	if nargs == 1 && file != "" {
+		return "", fmt.Errorf("query can be specified via --file or over the CLI, not both")
+	}
+
+	readFile := func(path string) (string, error) {
+		queryBytes, err := ioutil.ReadFile(path)
+		if err != nil {
+			return "", fmt.Errorf("failed to read query from %q: %w", path, err)
+		}
+		return string(queryBytes), nil
+	}
+
+	readStdin := func() (string, error) {
+		queryBytes, err := ioutil.ReadAll(os.Stdin)
+		if err != nil {
+			return "", fmt.Errorf("failed to read query from stdin: %w", err)
+		}
+		return string(queryBytes), err
+	}
+
+	if file != "" {
+		return readFile(file)
+	}
+	if nargs == 0 {
+		return readStdin()
+	}
+
+	arg := ctx.Args().Get(0)
+	// Backwards compatibility.
+	if strings.HasPrefix(arg, "@") {
+		return readFile(arg[1:])
+	} else if arg == "-" {
+		return readStdin()
+	} else {
+		return arg, nil
+	}
+}