evalphobia/go-jp-text-ripper

package reader

import (
    "encoding/csv"
    "fmt"
    "os"
    "path"
)

// Reader reads file
type Reader struct {
    fp       *os.File
    r        reader
    position int
}

// NewFromFile returns initialized Reader for file
func NewFromFile(filepath string) (*Reader, error) {
    /* #nosec G304 */
    fp, err := os.Open(filepath)
    if err != nil {
        return nil, err
    }

    var r reader
    switch ext := path.Ext(filepath); ext {
    case ".csv":
        r = newCSVReader(fp)
    case ".tsv":
        r = newTSVReader(fp)
    default:
        return nil, fmt.Errorf("non supported file format: %s", ext)
    }

    return &Reader{
        fp: fp,
        r:  r,
    }, nil
}

// Read returns []string and count up current position
func (r *Reader) Read() ([]string, error) {
    line, err := r.r.Read()
    if err != nil {
        return nil, err
    }

    r.position++
    return line, nil
}

// Close closes file
func (r *Reader) Close() error {
    return r.fp.Close()
}

// GetPosition returns position(read line number)
func (r *Reader) GetPosition() int {
    return r.position
}

// reader is interface of actual reads line from files
type reader interface {
    Read() ([]string, error)
}

func newCSVReader(fp *os.File) reader {
    r := csv.NewReader(fp)
    r.FieldsPerRecord = -1
    return r
}

func newTSVReader(fp *os.File) reader {
    r := csv.NewReader(fp)
    r.Comma = '\t'
    r.LazyQuotes = true
    r.FieldsPerRecord = -1
    return r
}