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// Package casing helps convert between CamelCase, snake_case, and others. It | ||
// includes an intelligent `Split` function to take almost any input and then | ||
// convert it to any type of casing. | ||
package casing | ||
|
||
import ( | ||
"strconv" | ||
"strings" | ||
"unicode" | ||
) | ||
|
||
// Borrowed from Go lint (https://github.com/golang/lint) | ||
var commonInitialisms = map[string]bool{ | ||
"ACL": true, | ||
"API": true, | ||
"ASCII": true, | ||
"CPU": true, | ||
"CSS": true, | ||
"DNS": true, | ||
"EOF": true, | ||
"GUID": true, | ||
"HTML": true, | ||
"HTTP": true, | ||
"HTTPS": true, | ||
"ID": true, | ||
"IP": true, | ||
"JSON": true, | ||
"LHS": true, | ||
"QPS": true, | ||
"RAM": true, | ||
"RHS": true, | ||
"RPC": true, | ||
"SLA": true, | ||
"SMTP": true, | ||
"SQL": true, | ||
"SSH": true, | ||
"TCP": true, | ||
"TLS": true, | ||
"TTL": true, | ||
"UDP": true, | ||
"UI": true, | ||
"UID": true, | ||
"UUID": true, | ||
"URI": true, | ||
"URL": true, | ||
"UTF8": true, | ||
"VM": true, | ||
"XML": true, | ||
"XMPP": true, | ||
"XSRF": true, | ||
"XSS": true, | ||
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// Media initialisms | ||
"1080P": true, | ||
"2D": true, | ||
"3D": true, | ||
"4K": true, | ||
"8K": true, | ||
"AAC": true, | ||
"AC3": true, | ||
"CDN": true, | ||
"DASH": true, | ||
"DRM": true, | ||
"DVR": true, | ||
"EAC3": true, | ||
"FPS": true, | ||
"GOP": true, | ||
"H264": true, | ||
"H265": true, | ||
"HD": true, | ||
"HLS": true, | ||
"MJPEG": true, | ||
"MP2T": true, | ||
"MP3": true, | ||
"MP4": true, | ||
"MPEG2": true, | ||
"MPEG4": true, | ||
"NTSC": true, | ||
"PCM": true, | ||
"RGB": true, | ||
"RGBA": true, | ||
"RTMP": true, | ||
"RTP": true, | ||
"SCTE": true, | ||
"SCTE35": true, | ||
"SMPTE": true, | ||
"UPID": true, | ||
"UPIDS": true, | ||
"VOD": true, | ||
"YUV420": true, | ||
"YUV422": true, | ||
"YUV444": true, | ||
} | ||
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var commonSuffixes = map[string]bool{ | ||
// E.g. 2D, 3D | ||
"D": true, | ||
// E.g. 100GB | ||
"GB": true, | ||
// E.g. 4K, 8K | ||
"K": true, | ||
// E.g. 100KB | ||
"KB": true, | ||
// E.g. 64kbps | ||
"KBPS": true, | ||
// E.g. 100MB | ||
"MB": true, | ||
// E.g. 2500mbps | ||
"MPBS": true, | ||
// E.g. 1080P | ||
"P": true, | ||
// E.g. 100TB | ||
"TB": true, | ||
} | ||
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// TransformFunc is used to transform parts of a split string during joining. | ||
type TransformFunc func(string) string | ||
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// Identity is the identity transformation function. | ||
func Identity(part string) string { | ||
return part | ||
} | ||
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// Initialism converts common initialisms like ID and HTTP to uppercase. | ||
func Initialism(part string) string { | ||
if u := strings.ToUpper(part); commonInitialisms[u] { | ||
return u | ||
} | ||
return part | ||
} | ||
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// State machine for splitting. | ||
const ( | ||
stateNone = 0 | ||
stateLower = 1 | ||
stateFirstUpper = 2 | ||
stateUpper = 3 | ||
stateSymbol = 4 | ||
) | ||
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// Split a value intelligently, taking into account different casing styles, | ||
// numbers, symbols, etc. | ||
// | ||
// // Returns: ["HTTP", "Server", "2020"] | ||
// casing.Split("HTTPServer_2020") | ||
func Split(value string) []string { | ||
results := []string{} | ||
start := 0 | ||
state := stateNone | ||
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for i, c := range value { | ||
// Regardless of state, these always break words. Handles kabob and snake | ||
// casing, respectively. | ||
if unicode.IsSpace(c) || unicode.IsPunct(c) { | ||
if i-start > 0 { | ||
results = append(results, value[start:i]) | ||
} | ||
start = i + 1 | ||
state = stateNone | ||
continue | ||
} | ||
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switch { | ||
case state != stateFirstUpper && state != stateUpper && unicode.IsUpper(c): | ||
// Initial uppercase, might start a word, e.g. Camel | ||
if start != i { | ||
results = append(results, value[start:i]) | ||
start = i | ||
} | ||
state = stateFirstUpper | ||
case state == stateFirstUpper && unicode.IsUpper(c): | ||
// String of uppercase to be grouped, e.g. HTTP | ||
state = stateUpper | ||
case state != stateSymbol && !unicode.IsLetter(c): | ||
// Anything -> non-letter | ||
if start != i { | ||
results = append(results, value[start:i]) | ||
start = i | ||
} | ||
state = stateSymbol | ||
case state != stateLower && unicode.IsLower(c): | ||
if state == stateUpper { | ||
// Multi-character uppercase to lowercase. Last item in the uppercase | ||
// is part of the lowercase string, e.g. HTTPServer. | ||
if i > 0 && start != i-1 { | ||
results = append(results, value[start:i-1]) | ||
start = i - 1 | ||
} | ||
} else if state != stateFirstUpper { | ||
// End of a non-uppercase or non-lowercase string. Ignore the first | ||
// upper state as it's part of the same word. | ||
if i > 0 && start != i { | ||
results = append(results, value[start:i]) | ||
start = i | ||
} | ||
} | ||
state = stateLower | ||
} | ||
} | ||
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// Include whatever is at the end of the string. | ||
if start < len(value) { | ||
results = append(results, value[start:]) | ||
} | ||
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return results | ||
} | ||
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// Join will combine split parts back together with the given separator and | ||
// optional transform functions. | ||
func Join(parts []string, sep string, transform ...TransformFunc) string { | ||
for i := 0; i < len(parts); i++ { | ||
for _, t := range transform { | ||
parts[i] = t(parts[i]) | ||
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if parts[i] == "" { | ||
// Transformer completely removed this part. | ||
parts = append(parts[:i], parts[i+1:]...) | ||
i-- | ||
} | ||
} | ||
} | ||
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return strings.Join(parts, sep) | ||
} | ||
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// MergeNumbers will merge some number parts with their adjacent letter parts | ||
// to support a smarter delimited join. For example, `h264` instead of `h_264` | ||
// or `mp3-player` instead of `mp-3-player`. You can pass suffixes for right | ||
// aligning certain items, e.g. `K` to get `MODE_4K` instead of `MODE4_K`. If | ||
// no suffixes are passed, then a default set of common ones is used. Pass an | ||
// empty string to disable the default. | ||
func MergeNumbers(parts []string, suffixes ...string) []string { | ||
// TODO: should we do this in-place instead? | ||
results := make([]string, 0, len(parts)) | ||
prevNum := false | ||
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suffixLookup := map[string]bool{} | ||
for _, word := range suffixes { | ||
suffixLookup[strings.ToUpper(word)] = true | ||
} | ||
if len(suffixes) == 0 { | ||
suffixLookup = commonSuffixes | ||
} | ||
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for i := 0; i < len(parts); i++ { | ||
part := parts[i] | ||
if _, err := strconv.Atoi(part); err == nil { | ||
// This part is a number! | ||
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// Special case: right aligned word | ||
if i < len(parts)-1 && suffixLookup[strings.ToUpper(parts[i+1])] { | ||
results = append(results, part+parts[i+1]) | ||
i++ | ||
continue | ||
} | ||
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if !prevNum { | ||
if i == 0 { | ||
// First item must always append. | ||
results = append(results, part) | ||
} else { | ||
// Concatenate the number to the previous non-number piece. | ||
results[len(results)-1] += part | ||
} | ||
prevNum = true | ||
continue | ||
} | ||
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prevNum = true | ||
} else { | ||
// Special case: first part is a number, second part is not. | ||
if i == 1 && prevNum { | ||
results[0] += part | ||
prevNum = false | ||
continue | ||
} | ||
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prevNum = false | ||
} | ||
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results = append(results, part) | ||
} | ||
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return results | ||
} | ||
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// Camel returns a CamelCase version of the input. If no transformation | ||
// functions are passed in, then strings.ToLower is used. This can be disabled | ||
// by passing in the identity function. | ||
func Camel(value string, transform ...TransformFunc) string { | ||
if transform == nil { | ||
transform = []TransformFunc{strings.ToLower} | ||
} | ||
t := append(transform, strings.Title) //nolint:staticcheck | ||
return Join(Split(value), "", t...) | ||
} | ||
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// LowerCamel returns a lowerCamelCase version of the input. | ||
func LowerCamel(value string, transform ...TransformFunc) string { | ||
runes := []rune(Camel(value, transform...)) | ||
runes[0] = unicode.ToLower(runes[0]) | ||
return string(runes) | ||
} | ||
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// Snake returns a snake_case version of the input. | ||
func Snake(value string, transform ...TransformFunc) string { | ||
if transform == nil { | ||
transform = []TransformFunc{strings.ToLower} | ||
} | ||
return Join(MergeNumbers(Split(value)), "_", transform...) | ||
} | ||
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// Kebab returns a kabob-case version of the input. | ||
func Kebab(value string, transform ...TransformFunc) string { | ||
if transform == nil { | ||
transform = []TransformFunc{strings.ToLower} | ||
} | ||
return Join(MergeNumbers(Split(value)), "-", transform...) | ||
} |
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