// Copyright 2020-2026 Buf Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"bytes"
	"cmp"
	"context"
	"errors"
	"fmt"
	"go/format"
	"io"
	"path/filepath"
	"sort"
	"strings"

	"buf.build/go/app"
	"buf.build/go/app/appcmd"
	"buf.build/go/app/appext"
	"buf.build/go/standard/xslices"
	"github.com/bufbuild/buf/private/bufpkg/bufanalysis"
	"github.com/bufbuild/buf/private/bufpkg/bufimage"
	"github.com/bufbuild/buf/private/bufpkg/bufmodule"
	"github.com/bufbuild/buf/private/bufpkg/bufprotosource"
	"github.com/bufbuild/buf/private/pkg/slogapp"
	"github.com/bufbuild/buf/private/pkg/storage"
	"github.com/bufbuild/buf/private/pkg/storage/storageos"
	"github.com/spf13/pflag"
)

const (
	programName             = "wkt-go-data"
	pkgFlagName             = "package"
	protobufVersionFlagName = "protobuf-version"
	bytesPerLine            = 20
)

var failedError = app.NewError( /* exitCode */ 100, "something went wrong")

func main() {
	// TODO: The datawkt machinery would be WAY simpler if it just used go:embed instead.
	appcmd.Main(context.Background(), newCommand())
}

func newCommand() *appcmd.Command {
	flags := newFlags()
	builder := appext.NewBuilder(
		programName,
		appext.BuilderWithLoggerProvider(slogapp.LoggerProvider),
	)
	return &appcmd.Command{
		Use:  fmt.Sprintf("%s path/to/google/protobuf/include", programName),
		Args: appcmd.ExactArgs(1),
		Run: builder.NewRunFunc(
			func(ctx context.Context, container appext.Container) error {
				return run(ctx, container, flags)
			},
		),
		BindFlags: flags.Bind,
	}
}

type flags struct {
	Pkg             string
	ProtobufVersion string
}

func newFlags() *flags {
	return &flags{}
}

func (f *flags) Bind(flagSet *pflag.FlagSet) {
	flagSet.StringVar(
		&f.Pkg,
		pkgFlagName,
		"",
		"The name of the generated package.",
	)
	flagSet.StringVar(
		&f.ProtobufVersion,
		protobufVersionFlagName,
		"",
		"The version of protobuf used to get the Well-Known Types.",
	)
}

func run(ctx context.Context, container appext.Container, flags *flags) error {
	dirPath := container.Arg(0)
	packageName := flags.Pkg
	if packageName == "" {
		packageName = filepath.Base(dirPath)
	}
	protobufVersion := flags.ProtobufVersion
	if protobufVersion == "" {
		return appcmd.NewInvalidArgumentErrorf("--%s is required", protobufVersionFlagName)
	}
	readWriteBucket, err := storageos.NewProvider(storageos.ProviderWithSymlinks()).NewReadWriteBucket(dirPath, storageos.ReadWriteBucketWithSymlinksIfSupported())
	if err != nil {
		return err
	}
	pathToData, err := getPathToData(ctx, readWriteBucket)
	if err != nil {
		return err
	}
	protosourceFiles, err := getProtosourceFiles(ctx, container, readWriteBucket)
	if err != nil {
		return err
	}
	fullNameToMessage, err := bufprotosource.FullNameToMessage(protosourceFiles...)
	if err != nil {
		return err
	}
	fullNameToEnum, err := bufprotosource.FullNameToEnum(protosourceFiles...)
	if err != nil {
		return err
	}
	pathToFile, err := bufprotosource.FilePathToFile(protosourceFiles...)
	if err != nil {
		return err
	}
	pathToImports := make(map[string][]string, len(pathToFile))
	for path, file := range pathToFile {
		imports := xslices.Map(
			file.FileImports(),
			func(fileImport bufprotosource.FileImport) string {
				return fileImport.Import()
			},
		)
		sort.Strings(imports)
		pathToImports[path] = imports
	}
	golangFileData, err := getGolangFileData(
		protobufVersion,
		pathToData,
		fullNameToMessage,
		fullNameToEnum,
		pathToImports,
		packageName,
	)
	if err != nil {
		return err
	}
	_, err = container.Stdout().Write(golangFileData)
	return err
}

func getPathToData(ctx context.Context, bucket storage.ReadBucket) (map[string][]byte, error) {
	pathToData := make(map[string][]byte)
	if err := storage.WalkReadObjects(
		ctx,
		bucket,
		"",
		func(readObject storage.ReadObject) error {
			data, err := io.ReadAll(readObject)
			if err != nil {
				return err
			}
			pathToData[readObject.Path()] = data
			return nil
		},
	); err != nil {
		return nil, err
	}
	return pathToData, nil
}

func getProtosourceFiles(
	ctx context.Context,
	container appext.Container,
	bucket storage.ReadBucket,
) ([]bufprotosource.File, error) {
	moduleSet, err := bufmodule.NewModuleSetBuilder(
		ctx,
		container.Logger(),
		bufmodule.NopModuleDataProvider,
		bufmodule.NopCommitProvider,
	).AddLocalModule(
		bucket,
		".",
		true,
	).Build()
	if err != nil {
		return nil, err
	}
	module := bufmodule.ModuleSetToModuleReadBucketWithOnlyProtoFiles(moduleSet)
	image, err := bufimage.BuildImage(
		ctx,
		container.Logger(),
		module,
		bufimage.WithExcludeSourceCodeInfo(),
	)
	if err != nil {
		var fileAnnotationSet bufanalysis.FileAnnotationSet
		if errors.As(err, &fileAnnotationSet) {
			// stderr since we do output to stdout
			if err := bufanalysis.PrintFileAnnotationSet(
				container.Stderr(),
				fileAnnotationSet,
				"text",
			); err != nil {
				return nil, err
			}
			return nil, failedError
		}
		return nil, err
	}
	return bufprotosource.NewFiles(ctx, image.Files(), image.Resolver())
}

func getGolangFileData(
	protobufVersion string,
	pathToData map[string][]byte,
	fullNameToMessage map[string]bufprotosource.Message,
	fullNameToEnum map[string]bufprotosource.Enum,
	// imports are sorted
	pathToImports map[string][]string,
	packageName string,
) ([]byte, error) {
	paths := make([]string, 0, len(pathToData))
	for path := range pathToData {
		paths = append(paths, path)
	}
	sort.Strings(paths)

	buffer := bytes.NewBuffer(nil)
	p := func(s string) {
		_, _ = buffer.WriteString(s)
	}

	p(`// Code generated by `)
	p(programName)
	p(`. DO NOT EDIT.`)
	p("\n\n")
	p(`// Package `)
	p(packageName)
	p(` stores the sources of the Well-Known Types, and provides helper functionality around them.`)
	p("\n")
	p(`package `)
	p(packageName)
	p(`

import (
	"github.com/bufbuild/buf/private/pkg/storage"
	"github.com/bufbuild/buf/private/pkg/storage/storagemem"
	"github.com/bufbuild/buf/private/pkg/normalpath"
)`)
	p("\n\n")
	p(`// Version is the version of github.com/protocolbuffers/protobuf used to extract the Well-Known Types.
const Version = "`)
	p(protobufVersion)
	p(`"`)
	p("\n\n")
	p(`var (
	// ReadBucket is the storage.ReadBucket with the static data generated for this package.
	ReadBucket storage.ReadBucket`)
	p("\n\n")
	p(`// AllFilePaths are all Well-Known Type file paths in sorted order.`)
	p("\n")
	p(`AllFilePaths = []string{`)
	p("\n")
	for _, path := range paths {
		p(`"`)
		p(path)
		p(`",`)
		p("\n")
	}
	p(`}`)
	p("\n\n")
	p(`filePathToData = map[string][]byte{
`)
	for _, path := range paths {
		p(`"`)
		p(path)
		p(`": {
`)
		data := pathToData[path]
		for len(data) > 0 {
			n := min(bytesPerLine, len(data))
			var accum strings.Builder
			for _, elem := range data[:n] {
				_, _ = fmt.Fprintf(&accum, "0x%02x,", elem)
			}
			p(accum.String())
			p("\n")
			data = data[n:]
		}
		p(`},
`)
	}
	p(`}`)
	p("\n\n")
	p(`filePathToImports = map[string][]string{
`)
	for _, pathToImportsPair := range sortedPairs(pathToImports) {
		p(`"`)
		p(pathToImportsPair.key)
		p(`": {`)
		p("\n")
		for _, imp := range pathToImportsPair.val {
			p(`"`)
			p(imp)
			p(`",`)
			p("\n")
		}
		p(`},`)
		p("\n")
	}
	p(`}`)
	p("\n\n")
	p(`messageNameToFilePath = map[string]string{
`)
	for _, fullNameToMessagePair := range sortedPairs(fullNameToMessage) {
		p(`"`)
		p(fullNameToMessagePair.key)
		p(`": "`)
		p(fullNameToMessagePair.val.File().Path())
		p(`",`)
		p("\n")
	}
	p(`}`)
	p("\n\n")
	p(`enumNameToFilePath = map[string]string{
`)
	for _, fullNameToEnumPair := range sortedPairs(fullNameToEnum) {
		p(`"`)
		p(fullNameToEnumPair.key)
		p(`": "`)
		p(fullNameToEnumPair.val.File().Path())
		p(`",`)
		p("\n")
	}
	p(`}`)
	p("\n")
	p(`)`)
	p("\n\n")
	p(`func init() {
	readBucket, err := storagemem.NewReadBucket(filePathToData)
	if err != nil {
		panic(err.Error())
	}
	ReadBucket = readBucket
}

// Exists returns true if the given path exists in the static data.
//
// The path is normalized within this function.
func Exists(filePath string) bool {
	_, ok := filePathToData[normalpath.Normalize(filePath)]
	return ok
}

// FileImports gets the imports for the given file path, if the file path exists.
func FileImports(filePath string) ([]string, bool) {
	imports, ok := filePathToImports[filePath]
	if !ok {
		return nil, false
	}
	c := make([]string, len(imports))
	copy(c, imports)
	return c, true
}

// MessageFilePath gets the file path for the given message, if the message exists.
func MessageFilePath(messageName string) (string, bool) {
	filePath, ok := messageNameToFilePath[messageName]
	return filePath, ok
}

// EnumFilePath gets the file path for the given enum, if the enum exists.
func EnumFilePath(enumName string) (string, bool) {
	filePath, ok := enumNameToFilePath[enumName]
	return filePath, ok
}
`)
	formatted, err := format.Source(buffer.Bytes())
	if err != nil {
		return nil, fmt.Errorf("could not format: %w\n%s", err, buffer.String())
	}
	return formatted, nil
}

type keyValPair[K any, V any] struct {
	key K
	val V
}

func sortedPairs[K cmp.Ordered, V any](m map[K]V) []keyValPair[K, V] {
	ret := make([]keyValPair[K, V], 0, len(m))
	for key := range m {
		ret = append(ret, keyValPair[K, V]{key: key, val: m[key]})
	}
	sort.Slice(ret, func(i, j int) bool {
		return ret[i].key < ret[j].key
	})
	return ret
}
