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writer.go
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114 lines (100 loc) · 2.54 KB
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package csv
import (
"bytes"
"encoding/csv"
"io"
"net/http"
"sort"
)
// Header represents a CSV's header line.
type Header []string
// Value represents a CSV's value (non-header row).
type Value []string
// Writer is the interface for something that writes to CSV files.
type Writer interface {
AddValue(value Value)
Write(w http.ResponseWriter, filename string)
}
// GenericWriter is a generic CSV Writer.
type GenericWriter struct {
header Header
values []Value
// If set true, will sort before writing out
// Sorting is done lexicographically, giving preference to earlier columns
sort bool
}
// NewGenericWriter creates a new CSV Writer using the given header.
func NewGenericWriter(header Header, sort bool) *GenericWriter {
return &GenericWriter{header: header, sort: sort}
}
// AddValue adds a CSV value (row) to the CSV file.
func (c *GenericWriter) AddValue(value Value) {
c.values = append(c.values, value)
}
// Append to value
func (c *GenericWriter) AppendToValue(value *Value, field string) {
*value = append(*value, field)
}
// IsEmpty returns true if there are no values.
func (c *GenericWriter) IsEmpty() bool {
return len(c.values) == 0
}
// WriteBytes writes out csv header and values to the provided buffer
func (c *GenericWriter) WriteBytes(buf *bytes.Buffer) error {
cw := csv.NewWriter(buf)
cw.UseCRLF = true
_ = cw.Write(c.header)
for _, v := range c.values {
if err := cw.Write(v); err != nil {
return err
}
}
cw.Flush()
return nil
}
// WriteCSVwrites out csv header and values to the provided IO writer
func (c *GenericWriter) WriteCSV(w io.Writer) error {
cw := csv.NewWriter(w)
cw.UseCRLF = true
_ = cw.Write(c.header)
for _, v := range c.values {
if err := cw.Write(v); err != nil {
return err
}
}
cw.Flush()
return nil
}
// Write writes back the CSV file contents into the http.ResponseWriter.
func (c *GenericWriter) Write(w http.ResponseWriter, filename string) {
writeHeaders(w, filename)
if c.sort {
sort.Slice(c.values, func(i, j int) bool {
first, second := c.values[i], c.values[j]
for len(first) > 0 {
// first has more values, so greater
if len(second) == 0 {
return false
}
if first[0] < second[0] {
return true
}
if first[0] > second[0] {
return false
}
first = first[1:]
second = second[1:]
}
// second has more values, so first is lesser
return len(second) > 0
})
}
_, _ = w.Write([]byte(utf8BOM))
cw := csv.NewWriter(w)
cw.UseCRLF = true
_ = cw.Write(c.header)
for _, v := range c.values {
_ = cw.Write(v)
}
cw.Flush()
}