// 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"
	"strconv"
	"strings"

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

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)
					generateIdentifiers(gen, file)
					generateSourceContextStringer(gen, file)
				}
			}
			gen.SupportedFeatures = gengo.SupportedFeatures
			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
		pkgPaths map[string]string // mapping of .proto path to Go package path
		annotate map[string]bool   // .proto files to annotate
		exclude  map[string]bool   // .proto files to exclude from generation
	}{{
		path:     "cmd/protoc-gen-go/testdata",
		pkgPaths: map[string]string{"cmd/protoc-gen-go/testdata/nopackage/nopackage.proto": "google.golang.org/protobuf/cmd/protoc-gen-go/testdata/nopackage"},
		annotate: 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/.*/`)
	for _, d := range dirs {
		subDirs := map[string]bool{}

		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 := "module=" + modulePath
			for protoPath, goPkgPath := range d.pkgPaths {
				opts += fmt.Sprintf(",M%v=%v", protoPath, goPkgPath)
			}
			if d.annotate[filepath.ToSlash(relPath)] {
				opts += ",annotate_code"
			}
			protoc("-I"+filepath.Join(protoRoot, "src"), "-I"+repoRoot, "--go_out="+opts+":"+tmpDir, 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, goPkgPath string }{
		// Well-known protos.
		{"src", "google/protobuf/any.proto", ""},
		{"src", "google/protobuf/api.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/timestamp.proto", ""},
		{"src", "google/protobuf/type.proto", ""},
		{"src", "google/protobuf/wrappers.proto", ""},

		// Compiler protos.
		{"src", "google/protobuf/compiler/plugin.proto", ""},
		{"src", "google/protobuf/descriptor.proto", ""},

		// Conformance protos.
		{"", "conformance/conformance.proto", "google.golang.org/protobuf/internal/testprotos/conformance;conformance"},
		{"src", "google/protobuf/test_messages_proto2.proto", "google.golang.org/protobuf/internal/testprotos/conformance;conformance"},
		{"src", "google/protobuf/test_messages_proto3.proto", "google.golang.org/protobuf/internal/testprotos/conformance;conformance"},

		// Benchmark protos.
		// TODO: The protobuf repo no longer includes benchmarks.
		//       CL removing them says they are superceded by google/fleetbench:
		//         https://github.com/protocolbuffers/protobuf/commit/83c499de86224538e5d59adc3d0fa7fdb45b2c72
		//       But that project's proto benchmark files are very different:
		//         https://github.com/google/fleetbench/tree/main/fleetbench/proto
		//       For now, commenting these out until benchmarks in this repo can be
		//       reconciled with new fleetbench stuff.
		//{"benchmarks", "benchmarks.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks;benchmarks"},
		//{"benchmarks", "datasets/google_message1/proto2/benchmark_message1_proto2.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message1/proto2;proto2"},
		//{"benchmarks", "datasets/google_message1/proto3/benchmark_message1_proto3.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message1/proto3;proto3"},
		//{"benchmarks", "datasets/google_message2/benchmark_message2.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message2;google_message2"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_1.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_2.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_3.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_4.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_5.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_6.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_7.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message3/benchmark_message3_8.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message3;google_message3"},
		//{"benchmarks", "datasets/google_message4/benchmark_message4.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message4;google_message4"},
		//{"benchmarks", "datasets/google_message4/benchmark_message4_1.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message4;google_message4"},
		//{"benchmarks", "datasets/google_message4/benchmark_message4_2.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message4;google_message4"},
		//{"benchmarks", "datasets/google_message4/benchmark_message4_3.proto", "google.golang.org/protobuf/internal/testprotos/benchmarks/datasets/google_message4;google_message4"},
	}

	opts := "module=" + modulePath
	for _, file := range files {
		if file.goPkgPath != "" {
			opts += fmt.Sprintf(",M%v=%v", file.path, file.goPkgPath)
		}
	}
	for _, f := range files {
		protoc("-I"+filepath.Join(protoRoot, f.prefix), "--go_out="+opts+":"+tmpDir, f.path)
	}

	syncOutput(repoRoot, tmpDir)
}

func protoc(args ...string) {
	// TODO: Remove --experimental_allow_proto3_optional flag.
	cmd := exec.Command("protoc", "--plugin=protoc-gen-go="+os.Args[0], "--experimental_allow_proto3_optional")
	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)
}

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

	importPath := modulePath + "/internal/genid"
	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()

	g.P("const ", file.GoDescriptorIdent.GoName, " = ", strconv.Quote(file.Desc.Path()))
	g.P()

	var processEnums func([]*protogen.Enum)
	var processMessages func([]*protogen.Message)
	const protoreflectPackage = protogen.GoImportPath("google.golang.org/protobuf/reflect/protoreflect")
	processEnums = func(enums []*protogen.Enum) {
		for _, enum := range enums {
			g.P("// Full and short names for ", enum.Desc.FullName(), ".")
			g.P("const (")
			g.P(enum.GoIdent.GoName, "_enum_fullname = ", strconv.Quote(string(enum.Desc.FullName())))
			g.P(enum.GoIdent.GoName, "_enum_name = ", strconv.Quote(string(enum.Desc.Name())))
			g.P(")")
			g.P()
		}
	}
	processMessages = func(messages []*protogen.Message) {
		for _, message := range messages {
			g.P("// Names for ", message.Desc.FullName(), ".")
			g.P("const (")
			g.P(message.GoIdent.GoName, "_message_name ", protoreflectPackage.Ident("Name"), " = ", strconv.Quote(string(message.Desc.Name())))
			g.P(message.GoIdent.GoName, "_message_fullname ", protoreflectPackage.Ident("FullName"), " = ", strconv.Quote(string(message.Desc.FullName())))
			g.P(")")
			g.P()

			if len(message.Fields) > 0 {
				g.P("// Field names for ", message.Desc.FullName(), ".")
				g.P("const (")
				for _, field := range message.Fields {
					g.P(message.GoIdent.GoName, "_", field.GoName, "_field_name ", protoreflectPackage.Ident("Name"), " = ", strconv.Quote(string(field.Desc.Name())))
				}
				g.P()
				for _, field := range message.Fields {
					g.P(message.GoIdent.GoName, "_", field.GoName, "_field_fullname ", protoreflectPackage.Ident("FullName"), " = ", strconv.Quote(string(field.Desc.FullName())))
				}
				g.P(")")
				g.P()

				g.P("// Field numbers for ", message.Desc.FullName(), ".")
				g.P("const (")
				for _, field := range message.Fields {
					g.P(message.GoIdent.GoName, "_", field.GoName, "_field_number ", protoreflectPackage.Ident("FieldNumber"), " = ", field.Desc.Number())
				}
				g.P(")")
				g.P()
			}

			if len(message.Oneofs) > 0 {
				g.P("// Oneof names for ", message.Desc.FullName(), ".")
				g.P("const (")
				for _, oneof := range message.Oneofs {
					g.P(message.GoIdent.GoName, "_", oneof.GoName, "_oneof_name ", protoreflectPackage.Ident("Name"), " = ", strconv.Quote(string(oneof.Desc.Name())))
				}
				g.P()
				for _, oneof := range message.Oneofs {
					g.P(message.GoIdent.GoName, "_", oneof.GoName, "_oneof_fullname ", protoreflectPackage.Ident("FullName"), " = ", strconv.Quote(string(oneof.Desc.FullName())))
				}
				g.P(")")
				g.P()
			}

			processEnums(message.Enums)
			processMessages(message.Messages)
		}
	}
	processEnums(file.Enums)
	processMessages(file.Messages)
}

// generateSourceContextStringer generates the implementation for the
// protoreflect.SourcePath.String method by using information present
// in the descriptor.proto.
func generateSourceContextStringer(gen *protogen.Plugin, file *protogen.File) {
	if file.Desc.Path() != "google/protobuf/descriptor.proto" {
		return
	}

	importPath := modulePath + "/reflect/protoreflect"
	g := gen.NewGeneratedFile(importPath+"/source_gen.go", protogen.GoImportPath(importPath))
	for _, s := range generatedPreamble {
		g.P(s)
	}
	g.P("package ", path.Base(importPath))
	g.P()

	var messages []*protogen.Message
	for _, message := range file.Messages {
		if message.Desc.Name() == "FileDescriptorProto" {
			messages = append(messages, message)
		}
	}
	seen := make(map[*protogen.Message]bool)

	for len(messages) > 0 {
		m := messages[0]
		messages = messages[1:]
		if seen[m] {
			continue
		}
		seen[m] = true

		g.P("func (p *SourcePath) append", m.GoIdent.GoName, "(b []byte) []byte {")
		g.P("if len(*p) == 0 { return b }")
		g.P("switch (*p)[0] {")
		for _, f := range m.Fields {
			g.P("case ", f.Desc.Number(), ":")
			var cardinality string
			switch {
			case f.Desc.IsMap():
				panic("maps are not supported")
			case f.Desc.IsList():
				cardinality = "Repeated"
			default:
				cardinality = "Singular"
			}
			nextAppender := "nil"
			if f.Message != nil {
				nextAppender = "(*SourcePath).append" + f.Message.GoIdent.GoName
				messages = append(messages, f.Message)
			}
			g.P("b = p.append", cardinality, "Field(b, ", strconv.Quote(string(f.Desc.Name())), ", ", nextAppender, ")")
		}
		g.P("}")
		g.P("return b")
		g.P("}")
		g.P()
	}
}

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