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standard_filters.go
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/
standard_filters.go
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// Package filters defines the standard Liquid filters.
package filters
import (
"encoding/json"
"fmt"
"html"
"math"
"net/url"
"reflect"
"regexp"
"strings"
"time"
"unicode"
"unicode/utf8"
"github.com/osteele/liquid/evaluator"
"github.com/osteele/liquid/strftime"
)
// A FilterDictionary holds filters.
type FilterDictionary interface {
AddFilter(string, interface{})
}
// AddStandardFilters defines the standard Liquid filters.
func AddStandardFilters(fd FilterDictionary) { // nolint: gocyclo
// values
fd.AddFilter("default", func(value, defaultValue interface{}) interface{} {
if value == nil || value == false || evaluator.IsEmpty(value) {
value = defaultValue
}
return value
})
// arrays
fd.AddFilter("compact", func(array []interface{}) interface{} {
out := []interface{}{}
for _, item := range array {
if item != nil {
out = append(out, item)
}
}
return out
})
fd.AddFilter("join", joinFilter)
fd.AddFilter("map", func(array []map[string]interface{}, key string) interface{} {
out := []interface{}{}
for _, obj := range array {
out = append(out, obj[key])
}
return out
})
fd.AddFilter("reverse", reverseFilter)
fd.AddFilter("sort", sortFilter)
// https://shopify.github.io/liquid/ does not demonstrate first and last as filters,
// but https://help.shopify.com/themes/liquid/filters/array-filters does
fd.AddFilter("first", func(array []interface{}) interface{} {
if len(array) == 0 {
return nil
}
return array[0]
})
fd.AddFilter("last", func(array []interface{}) interface{} {
if len(array) == 0 {
return nil
}
return array[len(array)-1]
})
fd.AddFilter("uniq", uniqFilter)
// dates
fd.AddFilter("date", func(t time.Time, format func(string) string) (string, error) {
f := format("%a, %b %d, %y")
// TODO %\d*N -> truncated fractional seconds, default 9
f = strings.Replace(f, "%N", "", -1)
return strftime.Strftime(f, t)
})
// numbers
fd.AddFilter("abs", math.Abs)
fd.AddFilter("ceil", math.Ceil)
fd.AddFilter("floor", math.Floor)
fd.AddFilter("modulo", math.Mod)
fd.AddFilter("minus", func(a, b float64) float64 {
return a - b
})
fd.AddFilter("plus", func(a, b float64) float64 {
return a + b
})
fd.AddFilter("times", func(a, b float64) float64 {
return a * b
})
fd.AddFilter("divided_by", func(a float64, b interface{}) interface{} {
switch q := b.(type) {
case int, int16, int32, int64:
return int(a) / q.(int)
case float32, float64:
return a / b.(float64)
default:
return nil
}
})
fd.AddFilter("round", func(n float64, places func(int) int) float64 {
pl := places(0)
exp := math.Pow10(pl)
return math.Floor(n*exp+0.5) / exp
})
// sequences
fd.AddFilter("size", evaluator.Length)
// strings
fd.AddFilter("append", func(s, suffix string) string {
return s + suffix
})
fd.AddFilter("capitalize", func(s, suffix string) string {
if len(s) < 1 {
return s
}
return strings.ToUpper(s[:1]) + s[1:]
})
fd.AddFilter("downcase", func(s, suffix string) string {
return strings.ToLower(s)
})
fd.AddFilter("escape", html.EscapeString)
fd.AddFilter("escape_once", func(s, suffix string) string {
return html.EscapeString(html.UnescapeString(s))
})
fd.AddFilter("newline_to_br", func(s string) string {
return strings.Replace(s, "\n", "<br />", -1)
})
fd.AddFilter("prepend", func(s, prefix string) string {
return prefix + s
})
fd.AddFilter("remove", func(s, old string) string {
return strings.Replace(s, old, "", -1)
})
fd.AddFilter("remove_first", func(s, old string) string {
return strings.Replace(s, old, "", 1)
})
fd.AddFilter("replace", func(s, old, new string) string {
return strings.Replace(s, old, new, -1)
})
fd.AddFilter("replace_first", func(s, old, new string) string {
return strings.Replace(s, old, new, 1)
})
fd.AddFilter("sort_natural", sortNaturalFilter)
fd.AddFilter("slice", func(s string, start int, length func(int) int) string {
// runes aren't bytes; don't use slice
n := length(1)
if start < 0 {
start = utf8.RuneCountInString(s) + start
}
p := regexp.MustCompile(fmt.Sprintf(`^.{%d}(.{0,%d}).*$`, start, n))
return p.ReplaceAllString(s, "$1")
})
fd.AddFilter("split", splitFilter)
fd.AddFilter("strip_html", func(s string) string {
// TODO this probably isn't sufficient
return regexp.MustCompile(`<.*?>`).ReplaceAllString(s, "")
})
// TODO test case for this
fd.AddFilter("strip_newlines", func(s string) string {
return strings.Replace(s, "\n", "", -1)
})
fd.AddFilter("strip", strings.TrimSpace)
fd.AddFilter("lstrip", func(s string) string {
return strings.TrimLeftFunc(s, unicode.IsSpace)
})
fd.AddFilter("rstrip", func(s string) string {
return strings.TrimRightFunc(s, unicode.IsSpace)
})
fd.AddFilter("truncate", func(s string, length func(int) int, ellipsis func(string) string) string {
n := length(50)
el := ellipsis("...")
// runes aren't bytes; don't use slice
re := regexp.MustCompile(fmt.Sprintf(`^(.{%d})..{%d,}`, n-len(el), len(el)))
return re.ReplaceAllString(s, `$1`+el)
})
fd.AddFilter("truncatewords", func(s string, length func(int) int, ellipsis func(string) string) string {
el := ellipsis("...")
n := length(15)
// re := regexp.MustCompile(fmt.Sprintf(`^\s*(?:\S+\s+){%d}`, n))
re := regexp.MustCompile(fmt.Sprintf(`^(?:\s*\S+){%d}`, n))
m := re.FindString(s)
if m == "" {
return s
}
return m + el
})
fd.AddFilter("upcase", func(s, suffix string) string {
return strings.ToUpper(s)
})
fd.AddFilter("url_encode", url.QueryEscape)
fd.AddFilter("url_decode", url.QueryUnescape)
// debugging extensions
// inspect is from Jekyll
fd.AddFilter("inspect", func(value interface{}) string {
s, err := json.Marshal(value)
if err != nil {
return fmt.Sprintf("%#v", value)
}
return string(s)
})
fd.AddFilter("type", func(value interface{}) string {
return reflect.TypeOf(value).String()
})
}
func joinFilter(array []interface{}, sep func(string) string) interface{} {
a := make([]string, len(array))
s := sep(", ")
for i, x := range array {
a[i] = fmt.Sprint(x)
}
return strings.Join(a, s)
}
func reverseFilter(array []interface{}) interface{} {
result := make([]interface{}, len(array))
for i, x := range array {
result[len(result)-1-i] = x
}
return result
}
func splitFilter(s, sep string) interface{} {
result := strings.Split(s, sep)
// This matches Jekyll's observed behavior.
// TODO test case
if len(result) > 0 && result[len(result)-1] == "" {
result = result[:len(result)-1]
}
return result
}
func uniqFilter(array []interface{}) (result []interface{}) {
seenMap := map[interface{}]bool{}
seen := func(item interface{}) bool {
if k := reflect.TypeOf(item).Kind(); k < reflect.Array || k == reflect.Ptr || k == reflect.UnsafePointer {
if seenMap[item] {
return true
}
seenMap[item] = true
return false
}
// the O(n^2) case:
for _, other := range result {
if eqItems(item, other) {
return true
}
}
return false
}
for _, item := range array {
if !seen(item) {
result = append(result, item)
}
}
return
}
func eqItems(a, b interface{}) bool {
if reflect.TypeOf(a).Comparable() && reflect.TypeOf(b).Comparable() {
return a == b
}
return reflect.DeepEqual(a, b)
}