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Inject css rules into html document (#194)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| package cssrule | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "errors" | ||
| "fmt" | ||
| "log" | ||
| "net/http" | ||
| "regexp" | ||
| "strings" | ||
|
|
||
| "github.com/anfragment/zen/internal/hostmatch" | ||
| "github.com/anfragment/zen/internal/htmlrewrite" | ||
| "github.com/anfragment/zen/internal/logger" | ||
| ) | ||
|
|
||
| var ( | ||
| RuleRegex = regexp.MustCompile(`.*#@?\$#.+`) | ||
| primaryRuleRegex = regexp.MustCompile(`(.*?)#\$#(.*)`) | ||
| exceptionRuleRegex = regexp.MustCompile(`(.*?)#@\$#(.+)`) | ||
|
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| injectionStart = []byte("<style>") | ||
| injectionEnd = []byte("</style>") | ||
| ) | ||
|
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| type store interface { | ||
| AddPrimaryRule(hostnamePatterns string, css string) error | ||
| AddExceptionRule(hostnamePatterns string, css string) error | ||
| Get(hostname string) []string | ||
| } | ||
|
|
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| type Injector struct { | ||
| store store | ||
| } | ||
|
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| func NewInjector() *Injector { | ||
| return &Injector{ | ||
| store: hostmatch.NewHostMatcher[string](), | ||
| } | ||
| } | ||
|
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| func (inj *Injector) AddRule(rule string) error { | ||
| if match := primaryRuleRegex.FindStringSubmatch(rule); match != nil { | ||
| if err := inj.store.AddPrimaryRule(match[1], match[2]); err != nil { | ||
| return fmt.Errorf("add primary rule: %w", err) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| if match := exceptionRuleRegex.FindStringSubmatch(rule); match != nil { | ||
| if err := inj.store.AddExceptionRule(match[1], match[2]); err != nil { | ||
| return fmt.Errorf("add exception rule: %w", err) | ||
| } | ||
| return nil | ||
| } | ||
|
|
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| return errors.New("unsupported syntax") | ||
| } | ||
|
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| func (inj *Injector) Inject(req *http.Request, res *http.Response) error { | ||
| hostname := req.URL.Hostname() | ||
| cssRules := inj.store.Get(hostname) | ||
| log.Printf("got %d css rules for %q", len(cssRules), logger.Redacted(hostname)) | ||
| if len(cssRules) == 0 { | ||
| return nil | ||
| } | ||
|
|
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| var ruleInjection bytes.Buffer | ||
| ruleInjection.Write(injectionStart) | ||
| ruleInjection.WriteString(strings.Join(cssRules, "")) | ||
| ruleInjection.Write(injectionEnd) | ||
|
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| htmlrewrite.ReplaceHeadContents(res, func(match []byte) []byte { | ||
| return bytes.Join([][]byte{match, ruleInjection.Bytes()}, nil) | ||
| }) | ||
|
|
||
| return nil | ||
| } |
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