[CLOSED] VIN codes extractor from hotline server

hotvin.go

package main

// Author: Ali Shanaakh <hi@shal.dev>

import (
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"net/url"
	"time"

	"github.com/go-pg/pg"
)

const (
	NumberOfWorkers = 10
	Buffer          = 100
)

var (
	baseURL = "https://hotline.finance/api/insurance/osago/carDataByNumber/"
)

// Payload is representation of API response.
type Payload struct {
	//Type  string `json:"carType"`
	Vin string `json:"vin"`
	//Brand string `json:"markName"`
	//Model string `json:"modelName"`
}

// PlatesToVIN returns VIN code by car plates.
func PlatesToVIN(number string) (string, error) {
	payload := new(Payload)
	encoded := url.QueryEscape(number)

	resp, err := http.Get(baseURL + encoded)
	if err != nil {
		return "", err
	}

	if err := json.NewDecoder(resp.Body).Decode(payload); err != nil {
		return "", err
	}

	return payload.Vin, nil
}

// Operation represents public registrations of transport.
type Operation struct {
	Number string `db:"number,notnull"`
	VIN    string `db:"number"`
}

func Worker(numbers <-chan string, vins chan Operation, errs chan error) {
	for {
		number, open := <-numbers
		// On channel close.
		if !open {
			return
		}

		vin, err := PlatesToVIN(number)
		if err != nil {
			errs <- err
		}

		vins <- Operation{
			Number: number,
			VIN:    vin,
		}
	}
}

func SQLBatcher(vins <-chan Operation, errs chan error) {
	db := pg.Connect(&pg.Options{
		User:     "postgres",
		Password: "postgres",
		Database: "opencars",
	})

	for {
		op, open := <-vins
		// On channel close.
		if !open {
			db.Close()
			errs <- errors.New("closed")
			return
		}

		log.Println(op.Number, "-", op.VIN)

		_, err := db.Model((*Operation)(nil)).
			Set("vin_code = ?", op.VIN).
			Where("number = ?", op.Number).
			Update()

		if err != nil {
			errs <- err
			return
		}
	}
}

func Feeder(numbers chan string, errs chan error) {
	db := pg.Connect(&pg.Options{
		User:     "postgres",
		Password: "postgres",
		Database: "opencars",
	})

	offset := 0
	size := 100

	for {
		var rows []string

		err := db.Model((*Operation)(nil)).
			Column("number").
			Where("number LIKE 'А%'").
			Where("vin_code != ''").
			Group("number", "date").
			Order("date ASC").
			Limit(size).
			Offset(offset).
			Select(&rows)

		if err != nil {
			errs <- err
			return
		}

		for _, row := range rows {
			numbers <- row
		}

		offset += size
	}
}

func main() {
	numbers := make(chan string, Buffer)
	vins := make(chan Operation, Buffer)
	errs := make(chan error)

	go Feeder(numbers, errs)

	for i := 0; i < NumberOfWorkers; i++ {
		go Worker(numbers, vins, errs)
	}

	for i := 0; i < NumberOfWorkers; i++ {
		go SQLBatcher(vins, errs)
	}

	for {
		<-errs
		time.Sleep(10)
	}
}