main.go

// Copyright 2022 Google LLC
//
// 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 (
	"context"
	"flag"
	"fmt"
	"io"
	"os"
	"sort"

	"cloud.google.com/go/storage"
	"github.com/googlecloudplatform/pi-delivery/pkg/resultset"
	"github.com/googlecloudplatform/pi-delivery/pkg/ycd"
	"go.uber.org/zap"
	"google.golang.org/api/iterator"
	"google.golang.org/api/option"
)

// All the YCD files I tested are smaller than 256 bytes so let's just fetch the first
// one kilobyte. This program fails if a header is somehow bigger than this limit.
const maxHeaderLength = 1024

var logger *zap.SugaredLogger

var bucketName = flag.String("bucket", "", "bucket name (e.g. pi-delivery-public)")
var hexPrefix = flag.String("hex", "Pi - Hex - Chudnovsky", "prefix for hexadecimal results")
var decPrefix = flag.String("dec", "Pi - Dec - Chudnovsky", "prefix for decimal results")
var prefix = flag.String("prefix", "", "common prefix for the result objects")

func listObjects(ctx context.Context, bucket *storage.BucketHandle, prefix string) ([]string, error) {
	logger.Infow("listObjects",
		"prefix", prefix,
	)

	query := &storage.Query{Prefix: prefix}
	query.SetAttrSelection([]string{"Name"})
	iter := bucket.Objects(ctx, query)
	objects := []string{}
	for {
		attrs, err := iter.Next()
		if err == iterator.Done {
			break
		}
		if err != nil {
			logger.Errorw("failed to list objects",
				"prefix", prefix,
				"error", err,
			)
			return nil, err
		}
		logger.Infow("object found",
			"name", attrs.Name,
		)
		objects = append(objects, attrs.Name)
	}
	logger.Infow("listObjects finished",
		"prefix", prefix,
		"objects", len(objects),
	)
	return objects, nil
}

func newStorageClient(ctx context.Context) *storage.Client {
	option.WithScopes("ScopeReadOnly")
	client, err := storage.NewClient(ctx)
	if err != nil {
		logger.Fatalw("failed to create a Storage client",
			"error", err,
		)
		os.Exit(1)
	}
	return client
}

func logYCDInfo(file *ycd.YCDFile) {
	logger.Infow("ycd file",
		"name", file.Name,
		"first digit offset", file.FirstDigitOffset,
		"version", file.Header.FileVersion,
		"radix", file.Header.Radix,
		"first digits", file.Header.FirstDigits,
		"total digits", file.Header.TotalDigits,
		"block size", file.Header.BlockSize,
		"block id", file.Header.BlockID,
		"header length", file.Header.Length,
	)
}

func fetchYCDFiles(ctx context.Context, client *storage.Client, bucketName, prefix string) resultset.ResultSet {
	bucket := client.Bucket(bucketName)
	objects, err := listObjects(ctx, bucket, prefix)
	if err != nil {
		logger.Fatalw("failed to list objects for decimal results",
			"error", err,
			"prefix", prefix,
		)
		os.Exit(1)
	}
	files := resultset.ResultSet{}
	for _, name := range objects {
		object := bucket.Object(name)
		reader, err := object.NewRangeReader(ctx, 0, maxHeaderLength)
		if err != nil {
			logger.Fatalw("creating an object reader failed",
				"error", err,
				"bucket", bucketName,
				"object", name,
			)
			os.Exit(1)
		}
		defer reader.Close()
		ycd, err := ycd.Parse(reader)
		if err != nil {
			logger.Errorw("failed to parse a ycd file",
				"error", err,
				"bucket", bucketName,
				"object", object,
			)
		}
		ycd.Name = name
		logYCDInfo(ycd)
		files = append(files, ycd)
	}
	sort.Sort(files)
	return files
}

func printIndexPrologue(w io.Writer, bucketName string) {
	fmt.Fprintln(w, `// Code generated by indexer. DO NOT EDIT.
// Run indexer/main.go to generate this file.
package index

import (
	"github.com/googlecloudplatform/pi-delivery/pkg/resultset"
	"github.com/googlecloudplatform/pi-delivery/pkg/ycd"	
)`)
	fmt.Fprintln(w)
	fmt.Fprintf(w, "const BucketName = \"%s\"\n", bucketName)
	fmt.Fprintln(w)
}

func printIndexFileList(w io.Writer, varName string, files resultset.ResultSet) {
	fmt.Fprintf(w, "var %s resultset.ResultSet = resultset.ResultSet{\n", varName)

	for _, v := range files {
		fmt.Fprintf(w, `	{
		Header: &ycd.Header{
			FileVersion: "%s",
			Radix: %d,
			FirstDigits: "%s",
			TotalDigits: int64(%d),
			BlockSize: int64(%d),
			BlockID: int64(%d),
			Length: %d,
		},
		Name: "%s",
		FirstDigitOffset: %d,
	},`,
			v.Header.FileVersion,
			v.Header.Radix,
			v.Header.FirstDigits,
			v.Header.TotalDigits,
			v.Header.BlockSize,
			v.Header.BlockID,
			v.Header.Length,
			v.Name,
			v.FirstDigitOffset,
		)
		fmt.Fprintln(w)
	}
	fmt.Fprintln(w, "}")
	fmt.Fprintln(w)
}

func processDirectory(ctx context.Context, client *storage.Client, w io.Writer, varName, bucketName, prefix string) {
	files := fetchYCDFiles(ctx, client, bucketName, prefix)
	printIndexFileList(w, varName, files)
}

func main() {
	if l, err := zap.NewDevelopment(); err != nil {
		fmt.Fprintf(os.Stderr, "failed to initialize logger: %v", err)
		os.Exit(1)
	} else {
		logger = l.Sugar()
		defer logger.Sync()
	}
	flag.Parse()

	if *bucketName == "" {
		logger.Errorf("bucket name is required (--bucket)")
		os.Exit(1)
	}

	ctx := context.Background()

	client := newStorageClient(ctx)
	defer func() {
		if err := client.Close(); err != nil {
			logger.Errorw("failed to close the Storage client",
				"error", err)
		}
	}()
	printIndexPrologue(os.Stdout, *bucketName)
	processDirectory(ctx, client, os.Stdout, "Decimal", *bucketName, *prefix+*decPrefix)
	processDirectory(ctx, client, os.Stdout, "Hexadecimal", *bucketName, *prefix+*hexPrefix)
}