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package cors
import (
"net/http"
"strconv"
"strings"
"time"
)
type converter func(string) string
func generateNormalHeaders(c Config) http.Header {
headers := make(http.Header)
if c.AllowCredentials {
headers.Set("Access-Control-Allow-Credentials", "true")
}
if len(c.ExposeHeaders) > 0 {
exposeHeaders := convert(normalize(c.ExposeHeaders), http.CanonicalHeaderKey)
headers.Set("Access-Control-Expose-Headers", strings.Join(exposeHeaders, ","))
}
if c.AllowAllOrigins {
headers.Set("Access-Control-Allow-Origin", "*")
} else {
headers.Set("Vary", "Origin")
}
return headers
}
func generatePreflightHeaders(c Config) http.Header {
headers := make(http.Header)
if c.AllowCredentials {
headers.Set("Access-Control-Allow-Credentials", "true")
}
if len(c.AllowMethods) > 0 {
allowMethods := convert(normalize(c.AllowMethods), strings.ToUpper)
value := strings.Join(allowMethods, ",")
headers.Set("Access-Control-Allow-Methods", value)
}
if len(c.AllowHeaders) > 0 {
allowHeaders := convert(normalize(c.AllowHeaders), http.CanonicalHeaderKey)
value := strings.Join(allowHeaders, ",")
headers.Set("Access-Control-Allow-Headers", value)
}
if c.MaxAge > time.Duration(0) {
value := strconv.FormatInt(int64(c.MaxAge/time.Second), 10)
headers.Set("Access-Control-Max-Age", value)
}
if c.AllowPrivateNetwork {
headers.Set("Access-Control-Allow-Private-Network", "true")
}
if c.AllowAllOrigins {
headers.Set("Access-Control-Allow-Origin", "*")
} else {
// Always set Vary headers
// see https://github.com/rs/cors/issues/10,
// https://github.com/rs/cors/commit/dbdca4d95feaa7511a46e6f1efb3b3aa505bc43f#commitcomment-12352001
headers.Add("Vary", "Origin")
headers.Add("Vary", "Access-Control-Request-Method")
headers.Add("Vary", "Access-Control-Request-Headers")
}
return headers
}
func normalize(values []string) []string {
if values == nil {
return nil
}
distinctMap := make(map[string]bool, len(values))
normalized := make([]string, 0, len(values))
for _, value := range values {
value = strings.TrimSpace(value)
value = strings.ToLower(value)
if _, seen := distinctMap[value]; !seen {
normalized = append(normalized, value)
distinctMap[value] = true
}
}
return normalized
}
func convert(s []string, c converter) []string {
var out []string
for _, i := range s {
out = append(out, c(i))
}
return out
}
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