From 93a6bd988779711f6e3c6a88100601a259b5c0b9 Mon Sep 17 00:00:00 2001
From: Tyler Helmuth <12352919+TylerHelmuth@users.noreply.github.com>
Date: Thu, 5 Sep 2024 12:06:04 -0600
Subject: [PATCH] [chore] Share encoding overrides (#35029)

**Description:**
Follow up to
https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/33942.
I'd like to share the exact override key strings so that they don't get
out of sync. Maybe this is too much effort, but wanted to discuss

It looks like there is some more reuse between textutils and stanza, but
that could be done in a separate PR.
---
 internal/coreinternal/textutils/encoding.go | 11 ++++++++++-
 pkg/ottl/ottlfuncs/func_decode.go           | 15 ++-------------
 pkg/stanza/decode/decode.go                 | 16 +++-------------
 3 files changed, 15 insertions(+), 27 deletions(-)

diff --git a/internal/coreinternal/textutils/encoding.go b/internal/coreinternal/textutils/encoding.go
index 209c2cbc7754..512b6a6f7da4 100644
--- a/internal/coreinternal/textutils/encoding.go
+++ b/internal/coreinternal/textutils/encoding.go
@@ -74,7 +74,7 @@ var encodingOverrides = map[string]encoding.Encoding{
 }
 
 func lookupEncoding(enc string) (encoding.Encoding, error) {
-	if e, ok := encodingOverrides[strings.ToLower(enc)]; ok {
+	if e, ok := EncodingOverridesMap.Get(strings.ToLower(enc)); ok {
 		return e, nil
 	}
 	e, err := ianaindex.IANA.Encoding(enc)
@@ -94,3 +94,12 @@ func IsNop(enc string) bool {
 	}
 	return e == encoding.Nop
 }
+
+var EncodingOverridesMap = encodingOverridesMap{}
+
+type encodingOverridesMap struct{}
+
+func (e *encodingOverridesMap) Get(key string) (encoding.Encoding, bool) {
+	v, ok := encodingOverrides[key]
+	return v, ok
+}
diff --git a/pkg/ottl/ottlfuncs/func_decode.go b/pkg/ottl/ottlfuncs/func_decode.go
index 374bb897de79..d6dc5efc0364 100644
--- a/pkg/ottl/ottlfuncs/func_decode.go
+++ b/pkg/ottl/ottlfuncs/func_decode.go
@@ -12,8 +12,8 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"golang.org/x/text/encoding"
 	"golang.org/x/text/encoding/ianaindex"
-	"golang.org/x/text/encoding/unicode"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/textutils"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
 )
 
@@ -87,7 +87,7 @@ func Decode[K any](target ottl.Getter[K], encoding string) (ottl.ExprFunc[K], er
 }
 
 func getEncoding(encoding string) (encoding.Encoding, error) {
-	if e, ok := encodingOverrides[strings.ToLower(encoding)]; ok {
+	if e, ok := textutils.EncodingOverridesMap.Get(strings.ToLower(encoding)); ok {
 		return e, nil
 	}
 	e, err := ianaindex.IANA.Encoding(encoding)
@@ -101,14 +101,3 @@ func getEncoding(encoding string) (encoding.Encoding, error) {
 	}
 	return e, nil
 }
-
-var encodingOverrides = map[string]encoding.Encoding{
-	"":         unicode.UTF8,
-	"nop":      encoding.Nop,
-	"ascii":    unicode.UTF8,
-	"us-ascii": unicode.UTF8,
-	"utf8":     unicode.UTF8,
-	"utf-8":    unicode.UTF8,
-	"utf16":    unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM),
-	"utf-16":   unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM),
-}
diff --git a/pkg/stanza/decode/decode.go b/pkg/stanza/decode/decode.go
index af40643a0cc6..0af0e3f3c361 100644
--- a/pkg/stanza/decode/decode.go
+++ b/pkg/stanza/decode/decode.go
@@ -10,8 +10,9 @@ import (
 
 	"golang.org/x/text/encoding"
 	"golang.org/x/text/encoding/ianaindex"
-	"golang.org/x/text/encoding/unicode"
 	"golang.org/x/text/transform"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/coreinternal/textutils"
 )
 
 type Decoder struct {
@@ -46,20 +47,9 @@ func (d *Decoder) Decode(msgBuf []byte) ([]byte, error) {
 	}
 }
 
-var encodingOverrides = map[string]encoding.Encoding{
-	"":         unicode.UTF8,
-	"nop":      encoding.Nop,
-	"ascii":    unicode.UTF8,
-	"us-ascii": unicode.UTF8,
-	"utf8":     unicode.UTF8,
-	"utf-8":    unicode.UTF8,
-	"utf16":    unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM),
-	"utf-16":   unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM),
-}
-
 // LookupEncoding attempts to match the string name provided with a character set encoding.
 func LookupEncoding(enc string) (encoding.Encoding, error) {
-	if e, ok := encodingOverrides[strings.ToLower(enc)]; ok {
+	if e, ok := textutils.EncodingOverridesMap.Get(strings.ToLower(enc)); ok {
 		return e, nil
 	}
 	e, err := ianaindex.IANA.Encoding(enc)