cmd/specs/to_starlark.go

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"io"

	"log"
	"os"

	"fuchsia.googlesource.com/infra/infra/cmd/specs/generators"
	"github.com/google/subcommands"
)

// StarlarkCodeGenerator transforms a text protobuf message read from the given io.Reader
// into the starlark code that would generate that same message when executed by fxicfg.
// The output is written to the given io.Writer.
//
// This relies on the generated Golang protobuf API being checked in to the fxcicfg pkg.
type StarlarkCodeGenerator interface {
	Generate(io.Reader) error
}

// FuchsiaPyID is the ID used to select the Fuchsia spec generator.
const FuchsiaPyID = "fuchsia"

// ToStarlarkCommand generates starlark code from a spec.
type ToStarlarkCommand struct {
	// The selected StarlarkCodeGenerator.
	recipe string
}

func (*ToStarlarkCommand) Name() string  { return "to_starlark" }
func (*ToStarlarkCommand) Usage() string { return "cat /path/to/spec | to_starlark" }
func (*ToStarlarkCommand) Synopsis() string {
	return "Generates the fxicfg starlark code that would produce the input spec"
}

func (cmd *ToStarlarkCommand) SetFlags(f *flag.FlagSet) {
	f.StringVar(&cmd.recipe, "recipe", FuchsiaPyID, fmt.Sprintf("The recipe whose api is being generated. Options: %v", []string{
		FuchsiaPyID,
	}))
}

func (cmd *ToStarlarkCommand) Execute(ctx context.Context, f *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
	generator, err := cmd.selectGenerator(cmd.recipe)
	if err != nil {
		log.Fatalf("invalid generator: %v", cmd.recipe)
	}
	if err := generator.Generate(os.Stdin); err != nil {
		log.Fatalf("failed to generate spec: %v", err)
	}
	return subcommands.ExitFailure
}

func (cmd *ToStarlarkCommand) selectGenerator(key string) (StarlarkCodeGenerator, error) {
	switch key {
	case FuchsiaPyID:
		return generators.NewFuchsiaPySpecGenerator(os.Stdout), nil
	default:
		return nil, errors.New("generator not found")
	}
}