go-examples/statecsv2json/main.go

package main

import "encoding/csv"
import "encoding/json"
import "io"
import "log"
import "os"
import "strconv"

type StateData struct {
	Id                      int
	Name                    string
	Abbreviation            string
	Country                 string
	Type_state              string
	Sort                    int
	Status                  string
	Occupied                string
	Notes                   string
	Fips_state              string
	Assoc_press             string
	Standard_federal_region string
	Census_region           int
	Census_region_name      string
	Census_division         int
	Census_division_name    string
	Circuit_court           int
}

func readCsvHeader(line []string) (map[string]int, error) {
	columns := make(map[string]int)
	for i, col := range line {
		columns[col] = i
	}
	return columns, nil
}

func readCsvLine(line []string, columns map[string]int) (*StateData, error) {
	var err error
	data := new(StateData)
	for i, col := range line {
		switch i {
		case columns["id"]:
			data.Id, err = strconv.Atoi(col)
			if err != nil {
				return data, err
			}
		case columns["name"]:
			data.Name = col
		case columns["abbreviation"]:
			data.Abbreviation = col
		case columns["country"]:
			data.Country = col
		case columns["type"]:
			data.Type_state = col
		case columns["sort"]:
			data.Sort, err = strconv.Atoi(col)
			if err != nil {
				return data, err
			}
		case columns["status"]:
			data.Status = col
		case columns["occupied"]:
			data.Occupied = col
		case columns["notes"]:
			data.Notes = col
		case columns["fips_state"]:
			data.Fips_state = col
		case columns["assoc_press"]:
			data.Assoc_press = col
		case columns["standard_federal_region"]:
			data.Standard_federal_region = col
		case columns["census_region"]:
			data.Census_region, err = strconv.Atoi(col)
			if err != nil {
				return data, err
			}
		case columns["census_region_name"]:
			data.Census_region_name = col
		case columns["census_division"]:
			data.Census_division, err = strconv.Atoi(col)
			if err != nil {
				return data, err
			}
		case columns["census_division_name"]:
			data.Census_division_name = col
		case columns["circuit_court"]:
			data.Circuit_court, err = strconv.Atoi(col)
			if err != nil {
				return data, err
			}
		}
	}
	return data, nil
}

func readCsv(in io.Reader) map[string]*StateData {
	data := make(map[string]*StateData)
	csvReader := csv.NewReader(in)
	var header map[string]int
	for {
		line, err := csvReader.Read()
		if err == io.EOF {
			break
		} else if err != nil {
			log.Fatal(err)
		}
		if len(header) == 0 {
			header, err = readCsvHeader(line)
			if err != nil {
				log.Fatal(err)
			}
		} else {
			d, err := readCsvLine(line, header)
			if err != nil {
				log.Println("Invalid line", err) // skip
			} else {
				data[d.Abbreviation] = d
			}
		}
	}
	return data
}

func main() {
	if len(os.Args) < 2 {
		log.Fatalln("Usage statecsv <file>")
	}

	// read input
	csv, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln("Error reading file", err)
	}
	defer csv.Close()

	// parse data
	data := readCsv(csv)

	// convert JSON
	var writer io.Writer
	if len(os.Args) > 2 {
		f, ferr := os.Create(os.Args[2])
		if ferr != nil {
			panic(ferr)
		}
		defer f.Close()
		writer = f
	} else {
		writer = os.Stdout
	}
	err = json.NewEncoder(writer).Encode(data)
	if err != nil {
		panic(err)
	}

}