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element.go
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element.go
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package terminal
import (
"encoding/base64"
"errors"
"fmt"
"mime"
"strings"
)
const (
ELEMENT_ITERM_IMAGE = iota
ELEMENT_IMAGE = iota
ELEMENT_LINK = iota
ELEMENT_BK = iota
)
type element struct {
url string
alt string
contentType string
content string
height string
width string
elementType int
bk map[string]string
}
var errUnsupportedElementSequence = errors.New("Unsupported element sequence")
func (i *element) asHTML() string {
if i.elementType == ELEMENT_LINK {
content := i.content
if content == "" {
content = i.url
}
return fmt.Sprintf(`<a href="%s">%s</a>`, i.url, content)
}
if i.elementType == ELEMENT_BK {
output := `<?bk`
for key, value := range i.bk {
output = output + ` ` + key + `="` + strings.Replace(value, `"`, """, -1) + `"`
}
return output + `?>`
}
alt := i.alt
if alt == "" {
alt = i.url
}
parts := []string{fmt.Sprintf(`alt="%s"`, alt)}
if i.elementType == ELEMENT_ITERM_IMAGE {
parts = append(parts, fmt.Sprintf(`src="data:%s;base64,%s"`, i.contentType, i.content))
} else {
parts = append(parts, fmt.Sprintf(`src="%s"`, i.url))
}
if i.width != "" {
parts = append(parts, fmt.Sprintf(`width="%s"`, i.width))
}
if i.height != "" {
parts = append(parts, fmt.Sprintf(`height="%s"`, i.height))
}
return fmt.Sprintf(`<img %s>`, strings.Join(parts, " "))
}
func parseElementSequence(sequence string) (*element, error) {
// Expect 1337;File=name=1.gif;inline=1:BASE64
args, elementType, content, err := splitAndVerifyElementSequence(sequence)
if err != nil {
if err == errUnsupportedElementSequence {
err = nil
}
return nil, err
}
args = strings.Map(htmlStripper, args)
tokens, err := tokenizeString(args, ';', '\\')
if err != nil {
return nil, err
}
imageInline := false
elem := &element{content: content, elementType: elementType}
for _, token := range tokens {
parts := strings.SplitN(token, "=", 2)
if len(parts) != 2 {
continue
}
key := parts[0]
val := parts[1]
switch strings.ToLower(key) {
case "name":
nameBytes, err := base64.StdEncoding.DecodeString(val)
if err != nil {
return nil, fmt.Errorf("name= value of %q is not valid base64", val)
}
elem.url = strings.Map(htmlStripper, string(nameBytes))
elem.contentType = contentTypeForFile(elem.url)
case "url":
elem.url = val
case "content":
elem.content = val
case "inline":
imageInline = val == "1"
case "width":
elem.width = parseImageDimension(val)
case "height":
elem.height = parseImageDimension(val)
case "alt":
elem.alt = val
}
}
if elem.elementType == ELEMENT_ITERM_IMAGE {
if elem.url == "" {
return nil, fmt.Errorf("name= argument not supplied, required to determine content type")
}
if elem.contentType == "" {
return nil, fmt.Errorf("can't determine content type for %q", elem.url)
}
} else {
if elem.url == "" {
return nil, fmt.Errorf("url= argument not supplied")
}
}
if elem.elementType == ELEMENT_ITERM_IMAGE && !imageInline {
// in iTerm2, if you don't specify inline=1, the image is merely downloaded
// and not displayed.
elem = nil
}
return elem, nil
}
func contentTypeForFile(filename string) string {
dot := strings.LastIndex(filename, ".")
if dot == -1 {
return ""
}
return mime.TypeByExtension(filename[dot:])
}
func parseImageDimension(s string) string {
s = strings.ToLower(s)
if !strings.HasSuffix(s, "px") && !strings.HasSuffix(s, "%") {
return s + "em"
} else {
return s
}
}
func htmlStripper(r rune) rune {
switch r {
case '<', '>', '\'', '"':
return -1
default:
return r
}
}
func splitAndVerifyElementSequence(s string) (arguments string, elementType int, content string, err error) {
if strings.HasPrefix(s, "1338;") {
return s[len("1338;"):], ELEMENT_IMAGE, "", nil
}
if strings.HasPrefix(s, "1339;") {
return s[len("1339;"):], ELEMENT_LINK, "", nil
}
prefixLen := len("1337;File=")
if !strings.HasPrefix(s, "1337;File=") {
return "", 0, "", errUnsupportedElementSequence
}
s = s[prefixLen:]
parts := strings.Split(s, ":")
if len(parts) != 2 {
return "", 0, "", fmt.Errorf("expected sequence to have one arguments part and one content part, got %d part(s)", len(parts))
}
elementType = ELEMENT_ITERM_IMAGE
arguments = parts[0]
content = parts[1]
if len(content) == 0 {
return "", 0, "", fmt.Errorf("image content missing")
}
_, err = base64.StdEncoding.DecodeString(content)
if err != nil {
return "", 0, "", fmt.Errorf("expected content part to be valid Base64")
}
return
}
func parseBuildkiteElementSequence(sequence string) (*element, error) {
// Expect bk;t=123123234234234;llamas=blah
if !strings.HasPrefix(sequence, "bk;") {
return nil, nil
}
tokens, err := tokenizeString(sequence[3:], ';', '\\')
if err != nil {
return nil, err
}
params := map[string]string{}
for _, token := range tokens {
tokenParts := strings.SplitN(token, "=", 2)
if len(tokenParts) != 2 {
return nil, fmt.Errorf("Failed to read key=value from token %q", token)
}
params[tokenParts[0]] = tokenParts[1]
}
return &element{elementType: ELEMENT_BK, bk: params}, nil
}
func tokenizeString(s string, sep, escape rune) (tokens []string, err error) {
var runes []rune
inEscape := false
for _, r := range s {
switch {
case inEscape:
inEscape = false
fallthrough
default:
runes = append(runes, r)
case r == escape:
inEscape = true
case r == sep:
tokens = append(tokens, string(runes))
runes = runes[:0]
}
}
tokens = append(tokens, string(runes))
if inEscape {
err = errors.New("invalid terminal escape")
}
return tokens, err
}