break up Generate

generate/main.go

@@ -0,0 +1,63 @@
+package generate
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+func outputWriter(filename string) (io.Writer, error) {
+	if filename == "-" {
+		return os.Stdout, nil
+	}
+
+	f, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return nil, fmt.Errorf("could not open generated file %v: %v",
+			filename, err)
+	}
+	return f, nil
+}
+
+func ParseGenerateAndWrite(specFilename, schemaFilename string, out io.Writer) error {
+	schema, err := getSchema(schemaFilename)
+	if err != nil {
+		return err
+	}
+
+	document, err := getAndValidateQueries(specFilename, schema)
+	if err != nil {
+		return err
+	}
+
+	code, err := Generate(schema, document)
+	if err != nil {
+		return err
+	}
+
+	_, err = out.Write(code)
+	return err
+}
+
+func Main() {
+	var err error
+	defer func() {
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+	}()
+
+	if len(os.Args) != 4 {
+		err = fmt.Errorf("usage: %s queries.graphql schema.graphql generated.go",
+			os.Args[0])
+		return
+	}
+
+	out, err := outputWriter(os.Args[3])
+	if err != nil {
+		return
+	}
+
+	err = ParseGenerateAndWrite(os.Args[1], os.Args[2], out)
+}