intern.go

package main

import (
	"bufio"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"flag"
	"fmt"
	"log"
	"os"
	"sort"

	"github.com/reactivex/rxgo/v2"
)

type line struct {
	text string
	num  int
}

func main() {
	flag.Parse()
	if len(flag.Args()) != 1 {
		log.Fatal("please input filepath")
	}
	file, err := os.Open(flag.Arg(0))
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	lines := make(chan rxgo.Item)
	go func() {
		defer close(lines)
		scanner := bufio.NewScanner(file)
		for i := 0; scanner.Scan(); i++ {
			lines <- rxgo.Of(line{scanner.Text(), i})
		}
	}()

	result, err := rxgo.FromChannel(lines).Map(func(ctx context.Context, i interface{}) (interface{}, error) {
		l := i.(line)
		sum := sha256.Sum256([]byte(l.text))
		return line{
			hex.EncodeToString(sum[:]),
			l.num,
		}, nil
	}, rxgo.WithCPUPool()).ToSlice(0)
	if err != nil {
		log.Fatal(err)
	}
	sort.Slice(result, func(i, j int) bool {
		return result[i].(line).num < result[j].(line).num
	})
	for _, r := range result {
		fmt.Printf("%d: %s\n", r.(line).num, r.(line).text)
	}
}