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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package csv

import (
        "bufio"
        "io"
        "strings"
        "unicode"
        "unicode/utf8"
)

// A Writer writes records to a CSV encoded file.
//
// As returned by NewWriter, a Writer writes records terminated by a
// newline and uses ',' as the field delimiter.  The exported fields can be
// changed to customize the details before the first call to Write or WriteAll.
//
// Comma is the field delimiter.
//
// If UseCRLF is true, the Writer ends each record with \r\n instead of \n.
type Writer struct {
        Comma   rune // Field delimiter (set to to ',' by NewWriter)
        UseCRLF bool // True to use \r\n as the line terminator
        w       *bufio.Writer
}

// NewWriter returns a new Writer that writes to w.
func NewWriter(w io.Writer) *Writer {
        return &Writer{
                Comma: ',',
                w:     bufio.NewWriter(w),
        }
}

// Writer writes a single CSV record to w along with any necessary quoting.
// A record is a slice of strings with each string being one field.
func (w *Writer) Write(record []string) (err error) {
        for n, field := range record {
                if n > 0 {
                        if _, err = w.w.WriteRune(w.Comma); err != nil {
                                return
                        }
                }

                // If we don't have to have a quoted field then just
                // write out the field and continue to the next field.
                if !w.fieldNeedsQuotes(field) {
                        if _, err = w.w.WriteString(field); err != nil {
                                return
                        }
                        continue
                }
                if err = w.w.WriteByte('"'); err != nil {
                        return
                }

                for _, r1 := range field {
                        switch r1 {
                        case '"':
                                _, err = w.w.WriteString(`""`)
                        case '\r':
                                if !w.UseCRLF {
                                        err = w.w.WriteByte('\r')
                                }
                        case '\n':
                                if w.UseCRLF {
                                        _, err = w.w.WriteString("\r\n")
                                } else {
                                        err = w.w.WriteByte('\n')
                                }
                        default:
                                _, err = w.w.WriteRune(r1)
                        }
                        if err != nil {
                                return
                        }
                }

                if err = w.w.WriteByte('"'); err != nil {
                        return
                }
        }
        if w.UseCRLF {
                _, err = w.w.WriteString("\r\n")
        } else {
                err = w.w.WriteByte('\n')
        }
        return
}

// Flush writes any buffered data to the underlying io.Writer.
func (w *Writer) Flush() {
        w.w.Flush()
}

// WriteAll writes multiple CSV records to w using Write and then calls Flush.
func (w *Writer) WriteAll(records [][]string) (err error) {
        for _, record := range records {
                err = w.Write(record)
                if err != nil {
                        break
                }
        }
        w.Flush()
        return nil
}

// fieldNeedsQuotes returns true if our field must be enclosed in quotes.
// Empty fields, files with a Comma, fields with a quote or newline, and
// fields which start with a space must be enclosed in quotes.
func (w *Writer) fieldNeedsQuotes(field string) bool {
        if len(field) == 0 || strings.IndexRune(field, w.Comma) >= 0 || strings.IndexAny(field, "\"\r\n") >= 0 {
                return true
        }

        r1, _ := utf8.DecodeRuneInString(field)
        return unicode.IsSpace(r1)
}