evalphobia/go-jp-text-ripper

package writer

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

// Writer writes the output to file
type Writer struct {
    fp *os.File
    w  writer
}

// NewFromFile returns initialized Writer for file
func NewFromFile(filepath string) (*Writer, error) {
    fp, err := os.Create(filepath)
    if err != nil {
        return nil, err
    }

    var w writer
    switch ext := path.Ext(filepath); ext {
    case ".tsv":
        w = newTSVWriter(fp)
    default:
        w = newCSVWriter(fp)
    }

    return &Writer{
        fp: fp,
        w:  w,
    }, nil
}

// NewDummy returns initialized Writer with dummy writer
func NewDummy() *Writer {
    return &Writer{
        fp: nil,
        w:  newDummyWriter(),
    }
}

// Write writes a line into file
func (w *Writer) Write(line []string) error {
    err := w.w.Write(line)
    if err != nil {
        return err
    }

    w.w.Flush()
    return nil
}

// Close closes file
func (w *Writer) Close() error {
    if w.fp == nil {
        return nil
    }
    return w.fp.Close()
}

// writer is interface of actual writes line into files
type writer interface {
    Write([]string) error
    Flush()
}

func newCSVWriter(fp *os.File) writer {
    w := csv.NewWriter(fp)
    return w
}

func newTSVWriter(fp *os.File) writer {
    w := csv.NewWriter(fp)
    w.Comma = '\t'
    return w
}