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

//go:generate go run . -execute

package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/format"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	gengo "google.golang.org/protobuf/cmd/protoc-gen-go/internal_gengo"
	"google.golang.org/protobuf/compiler/protogen"
	"google.golang.org/protobuf/internal/detrand"
	"google.golang.org/protobuf/reflect/protoreflect"
)

// Override the location of the Go package for various source files.
// TOOD: Commit these changes upstream.
var protoPackages = map[string]string{
	// Locally override field_mask.proto to an internal copy.
	// We need this package as a dependency of several tests,
	// but it currently lives in google.golang.org/genproto, which
	// we do not want a dependency on.
	//
	// TODO: Move the canonical package into this module.
	"google/protobuf/field_mask.proto": "google.golang.org/protobuf/internal/testprotos/fieldmaskpb",

	"google/protobuf/any.proto":                  "google.golang.org/protobuf/types/known/anypb",
	"google/protobuf/duration.proto":             "google.golang.org/protobuf/types/known/durationpb",
	"google/protobuf/empty.proto":                "google.golang.org/protobuf/types/known/emptypb",
	"google/protobuf/struct.proto":               "google.golang.org/protobuf/types/known/structpb",
	"google/protobuf/timestamp.proto":            "google.golang.org/protobuf/types/known/timestamppb",
	"google/protobuf/wrappers.proto":             "google.golang.org/protobuf/types/known/wrapperspb",
	"google/protobuf/descriptor.proto":           "google.golang.org/protobuf/types/descriptorpb",
	"google/protobuf/compiler/plugin.proto":      "google.golang.org/protobuf/types/pluginpb",
	"conformance/conformance.proto":              "google.golang.org/protobuf/internal/testprotos/conformance",
	"google/protobuf/test_messages_proto2.proto": "google.golang.org/protobuf/internal/testprotos/conformance",
	"google/protobuf/test_messages_proto3.proto": "google.golang.org/protobuf/internal/testprotos/conformance",
}

func init() {
	// Determine repository root path.
	out, err := exec.Command("git", "rev-parse", "--show-toplevel").CombinedOutput()
	check(err)
	repoRoot = strings.TrimSpace(string(out))

	// Determine the module path.
	cmd := exec.Command("go", "list", "-m", "-f", "{{.Path}}")
	cmd.Dir = repoRoot
	out, err = cmd.CombinedOutput()
	check(err)
	modulePath = strings.TrimSpace(string(out))

	// When the environment variable RUN_AS_PROTOC_PLUGIN is set,
	// we skip running main and instead act as a protoc plugin.
	// This allows the binary to pass itself to protoc.
	if plugin := os.Getenv("RUN_AS_PROTOC_PLUGIN"); plugin != "" {
		// Disable deliberate output instability for generated files.
		// This is reasonable since we fully control the output.
		detrand.Disable()

		protogen.Options{}.Run(func(gen *protogen.Plugin) error {
			for _, file := range gen.Files {
				if file.Generate {
					gengo.GenerateVersionMarkers = false
					gengo.GenerateFile(gen, file)
					generateFieldNumbers(gen, file)
				}
			}
			return nil
		})
		os.Exit(0)
	}
}

var (
	run        bool
	protoRoot  string
	repoRoot   string
	modulePath string

	generatedPreamble = []string{
		"// Copyright 2019 The Go Authors. All rights reserved.",
		"// Use of this source code is governed by a BSD-style",
		"// license that can be found in the LICENSE file.",
		"",
		"// Code generated by generate-protos. DO NOT EDIT.",
		"",
	}
)

func main() {
	flag.BoolVar(&run, "execute", false, "Write generated files to destination.")
	flag.StringVar(&protoRoot, "protoroot", os.Getenv("PROTOBUF_ROOT"), "The root of the protobuf source tree.")
	flag.Parse()
	if protoRoot == "" {
		panic("protobuf source root is not set")
	}

	generateLocalProtos()
	generateRemoteProtos()
}

func generateLocalProtos() {
	tmpDir, err := ioutil.TempDir(repoRoot, "tmp")
	check(err)
	defer os.RemoveAll(tmpDir)

	// Generate all local proto files (except version-locked files).
	dirs := []struct {
		path        string
		annotateFor map[string]bool
		exclude     map[string]bool
	}{
		{path: "cmd/protoc-gen-go/testdata", annotateFor: map[string]bool{
			"cmd/protoc-gen-go/testdata/annotations/annotations.proto": true},
		},
		{path: "internal/testprotos", exclude: map[string]bool{
			"internal/testprotos/irregular/irregular.proto": true,
		}},
	}
	excludeRx := regexp.MustCompile(`legacy/proto[23]_[0-9]{8}_[0-9a-f]{8}/`)
	for _, d := range dirs {
		subDirs := map[string]bool{}

		dstDir := tmpDir
		check(os.MkdirAll(dstDir, 0775))

		srcDir := filepath.Join(repoRoot, filepath.FromSlash(d.path))
		filepath.Walk(srcDir, func(srcPath string, _ os.FileInfo, _ error) error {
			if !strings.HasSuffix(srcPath, ".proto") || excludeRx.MatchString(srcPath) {
				return nil
			}
			relPath, err := filepath.Rel(repoRoot, srcPath)
			check(err)

			srcRelPath, err := filepath.Rel(srcDir, srcPath)
			check(err)
			subDirs[filepath.Dir(srcRelPath)] = true

			if d.exclude[filepath.ToSlash(relPath)] {
				return nil
			}

			opts := "paths=source_relative," + protoMapOpt()

			// Emit a .meta file for certain files.
			if d.annotateFor[filepath.ToSlash(relPath)] {
				opts += ",annotate_code"
			}

			protoc("-I"+filepath.Join(protoRoot, "src"), "-I"+repoRoot, "--go_out="+opts+":"+dstDir, relPath)
			return nil
		})

		// For directories in testdata, generate a test that links in all
		// generated packages to ensure that it builds and initializes properly.
		// This is done because "go build ./..." does not build sub-packages
		// under testdata.
		if filepath.Base(d.path) == "testdata" {
			var imports []string
			for sd := range subDirs {
				imports = append(imports, fmt.Sprintf("_ %q", path.Join(modulePath, d.path, filepath.ToSlash(sd))))
			}
			sort.Strings(imports)

			s := strings.Join(append(generatedPreamble, []string{
				"package main",
				"",
				"import (" + strings.Join(imports, "\n") + ")",
			}...), "\n")
			b, err := format.Source([]byte(s))
			check(err)
			check(ioutil.WriteFile(filepath.Join(tmpDir, filepath.FromSlash(d.path+"/gen_test.go")), b, 0664))
		}
	}

	syncOutput(repoRoot, tmpDir)
}

func generateRemoteProtos() {
	tmpDir, err := ioutil.TempDir(repoRoot, "tmp")
	check(err)
	defer os.RemoveAll(tmpDir)

	// Generate all remote proto files.
	files := []struct{ prefix, path string }{
		{"", "conformance/conformance.proto"},
		{"benchmarks", "benchmarks.proto"},
		{"benchmarks", "datasets/google_message1/proto2/benchmark_message1_proto2.proto"},
		{"benchmarks", "datasets/google_message1/proto3/benchmark_message1_proto3.proto"},
		{"benchmarks", "datasets/google_message2/benchmark_message2.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_1.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_2.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_3.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_4.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_5.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_6.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_7.proto"},
		{"benchmarks", "datasets/google_message3/benchmark_message3_8.proto"},
		{"benchmarks", "datasets/google_message4/benchmark_message4.proto"},
		{"benchmarks", "datasets/google_message4/benchmark_message4_1.proto"},
		{"benchmarks", "datasets/google_message4/benchmark_message4_2.proto"},
		{"benchmarks", "datasets/google_message4/benchmark_message4_3.proto"},
		// TODO: The commented-out entires below are currently part of
		// google.golang.org/genproto. Move them into this module.
		{"src", "google/protobuf/any.proto"},
		//{"src", "google/protobuf/api.proto"},
		{"src", "google/protobuf/compiler/plugin.proto"},
		{"src", "google/protobuf/descriptor.proto"},
		{"src", "google/protobuf/duration.proto"},
		{"src", "google/protobuf/empty.proto"},
		{"src", "google/protobuf/field_mask.proto"},
		//{"src", "google/protobuf/source_context.proto"},
		{"src", "google/protobuf/struct.proto"},
		{"src", "google/protobuf/test_messages_proto2.proto"},
		{"src", "google/protobuf/test_messages_proto3.proto"},
		{"src", "google/protobuf/timestamp.proto"},
		//{"src", "google/protobuf/type.proto"},
		{"src", "google/protobuf/wrappers.proto"},
	}
	for _, f := range files {
		protoc("-I"+filepath.Join(protoRoot, f.prefix), "--go_out="+protoMapOpt()+":"+tmpDir, f.path)
	}

	// Special-case: Generate field_mask.proto into a local test-only capy.
	copyFile(
		filepath.Join(tmpDir, "google.golang.org/protobuf/internal/testprotos/fieldmaskpb/field_mask.pb.go"),
		filepath.Join(tmpDir, "google.golang.org/genproto/protobuf/field_mask/field_mask.pb.go"),
	)

	syncOutput(repoRoot, filepath.Join(tmpDir, modulePath))
}

func protoc(args ...string) {
	cmd := exec.Command("protoc", "--plugin=protoc-gen-go="+os.Args[0])
	cmd.Args = append(cmd.Args, args...)
	cmd.Env = append(os.Environ(), "RUN_AS_PROTOC_PLUGIN=1")
	out, err := cmd.CombinedOutput()
	if err != nil {
		fmt.Printf("executing: %v\n%s\n", strings.Join(cmd.Args, " "), out)
	}
	check(err)
}

// generateFieldNumbers generates an internal package for descriptor.proto
// and well-known types.
func generateFieldNumbers(gen *protogen.Plugin, file *protogen.File) {
	if file.Desc.Package() != "google.protobuf" {
		return
	}

	importPath := modulePath + "/internal/fieldnum"
	base := strings.TrimSuffix(path.Base(file.Desc.Path()), ".proto")
	g := gen.NewGeneratedFile(importPath+"/"+base+"_gen.go", protogen.GoImportPath(importPath))
	for _, s := range generatedPreamble {
		g.P(s)
	}
	g.P("package ", path.Base(importPath))
	g.P("")

	var processMessages func([]*protogen.Message)
	processMessages = func(messages []*protogen.Message) {
		for _, message := range messages {
			g.P("// Field numbers for ", message.Desc.FullName(), ".")
			g.P("const (")
			for _, field := range message.Fields {
				fd := field.Desc
				typeName := fd.Kind().String()
				switch fd.Kind() {
				case protoreflect.EnumKind:
					typeName = string(fd.Enum().FullName())
				case protoreflect.MessageKind, protoreflect.GroupKind:
					typeName = string(fd.Message().FullName())
				}
				g.P(message.GoIdent.GoName, "_", field.GoName, "=", fd.Number(), "// ", fd.Cardinality(), " ", typeName)
			}
			g.P(")")
			processMessages(message.Messages)
		}
	}
	processMessages(file.Messages)
}

func syncOutput(dstDir, srcDir string) {
	filepath.Walk(srcDir, func(srcPath string, _ os.FileInfo, _ error) error {
		if !strings.HasSuffix(srcPath, ".go") && !strings.HasSuffix(srcPath, ".meta") {
			return nil
		}
		relPath, err := filepath.Rel(srcDir, srcPath)
		check(err)
		dstPath := filepath.Join(dstDir, relPath)

		if run {
			if copyFile(dstPath, srcPath) {
				fmt.Println("#", relPath)
			}
		} else {
			cmd := exec.Command("diff", dstPath, srcPath, "-N", "-u")
			cmd.Stdout = os.Stdout
			cmd.Run()
		}
		return nil
	})
}

func copyFile(dstPath, srcPath string) (changed bool) {
	src, err := ioutil.ReadFile(srcPath)
	check(err)
	check(os.MkdirAll(filepath.Dir(dstPath), 0775))
	dst, _ := ioutil.ReadFile(dstPath)
	if bytes.Equal(src, dst) {
		return false
	}
	check(ioutil.WriteFile(dstPath, src, 0664))
	return true
}

func protoMapOpt() string {
	var opts []string
	for k, v := range protoPackages {
		opts = append(opts, fmt.Sprintf("M%v=%v", k, v))
	}
	return strings.Join(opts, ",")
}

func check(err error) {
	if err != nil {
		panic(err)
	}
}