flatten nested json strings

flatten.go

// use:
// cat nested.json | go run . > flattenned.json 
package main

import (
	"bytes"
	"compress/gzip"
	"encoding/base64"
	"fmt"
	"io"
	"log"
	"os"
	"testing"
	"time"

	"github.com/jeremywohl/flatten/v2"
)

const (
	maxBufferSize = 102400
)

func main() {
	b := make([]byte, 1)
	c := make(chan byte, 2)
	fd := os.Stdout
	go start(c, fd)
	for {
		n, err := os.Stdin.Read(b)
		if err != nil && err != io.EOF {
			log.Fatal(err)
		}
		if n == 0 {
			// sleep for a bit
			time.Sleep(100 * time.Millisecond)
			break
		}
		c <- b[0]
	}
}

func start(c chan byte, fd io.Writer) {
	buf := make([]byte, maxBufferSize)
	openBracket := 0
	count := 0
	inObject := false
	// Read stdin into buffer
	for ch := range c {
		if ch == '\n' || ch == '\r' || ch == ' ' || ch == '\t' {
			continue
		}
		if ch == '{' {
			openBracket++
			inObject = true
		}
		if ch == '}' {
			openBracket--
		}
		if !inObject && (ch == '[' || ch == ']') {
			continue
		}
		if ch == ',' && !inObject {
			continue
		}
		buf[count] = ch
		count++
		if openBracket == 0 && inObject {
			// flatten buffer and print
			flat, err := flatten.FlattenString(string(buf[:count]), "", flatten.DotStyle)
			if err != nil {
				log.Println(err, string(buf[:count]))
			}
			fmt.Fprintln(fd, flat)
			buf = make([]byte, maxBufferSize)
			inObject = false
			count = 0
		}

	}
}

var testJSON1BB64GZ = "H4sIAAAAAAACA+2QvQ6CQBCE+3uKzdZQiD+FNdHEwgasCMUBK7fJcZfAUhDiu3tijIWFPoBbbPPtzGammJGHyuEecJWs4812FydJghGAAtSjGN8HpiDMvGwAtHoQpzt6iFJPGL3Alfs3OWlHuJBbpJAali9WWcdifjELUFjsAnJDcLHCnRaCVIuu9ECQydhMcBy5oWcUwDoctL6fgqjAs3fxgWth7wLHnGrjvPXthKUKH/6dfHRSqjuB6mvcKgIAAA=="

func gzipDecode(data []byte) ([]byte, error) {
	gz, err := gzip.NewReader(bytes.NewReader(data))
	if err != nil {
		return nil, err
	}
	defer gz.Close()
	return io.ReadAll(gz)
}

func BenchmarkMain(b *testing.B) {
	//un-base64 and un-gzip the test data
	testJSON1B, _ := base64.StdEncoding.DecodeString(testJSON1BB64GZ)
	testJSON1B, _ = gzipDecode(testJSON1B)
	c := make(chan byte)

	go func() {
		for _, ch := range testJSON1B {
			c <- ch
		}
		close(c)
	}()
	nullOut := io.Discard

	for i := 0; i < b.N; i++ {
		start(c, nullOut)
	}
}