Mats Törnberg
f5014fe906
Co-authored-by: matst80 <mats.tornberg@gmail.com> Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4 Co-authored-by: Mats Törnberg <mats@tornberg.me> Co-committed-by: Mats Törnberg <mats@tornberg.me>
70 lines
1.7 KiB
Go
70 lines
1.7 KiB
Go
package main
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import (
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"bytes"
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"crypto/sha256"
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_ "embed"
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"encoding/hex"
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"net/http"
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"sync"
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)
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// openapi_embed.go: Provides embedded OpenAPI spec and helper to mount handler.
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//go:embed openapi.json
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var openapiJSON []byte
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var (
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openapiOnce sync.Once
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openapiETag string
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)
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// initOpenAPIMetadata computes immutable metadata for the embedded spec.
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func initOpenAPIMetadata() {
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sum := sha256.Sum256(openapiJSON)
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openapiETag = `W/"` + hex.EncodeToString(sum[:8]) + `"` // weak ETag with first 8 bytes
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}
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// ServeEmbeddedOpenAPI serves the embedded OpenAPI JSON spec at /openapi.json.
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// It supports GET and HEAD and implements basic ETag caching.
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func ServeEmbeddedOpenAPI(w http.ResponseWriter, r *http.Request) {
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if r.Method != http.MethodGet && r.Method != http.MethodHead {
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w.Header().Set("Allow", "GET, HEAD")
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http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
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return
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}
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openapiOnce.Do(initOpenAPIMetadata)
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w.Header().Set("Content-Type", "application/json; charset=utf-8")
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w.Header().Set("Cache-Control", "no-cache")
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w.Header().Set("Access-Control-Allow-Origin", "*")
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w.Header().Set("ETag", openapiETag)
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if match := r.Header.Get("If-None-Match"); match != "" {
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if bytes.Contains([]byte(match), []byte(openapiETag)) {
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w.WriteHeader(http.StatusNotModified)
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return
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}
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}
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if r.Method == http.MethodHead {
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w.WriteHeader(http.StatusOK)
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return
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}
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w.WriteHeader(http.StatusOK)
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_, _ = w.Write(openapiJSON)
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}
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// Optional: function to access raw spec bytes programmatically.
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func OpenAPISpecBytes() []byte {
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return openapiJSON
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}
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// Optional: function to access current ETag.
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func OpenAPIETag() string {
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openapiOnce.Do(initOpenAPIMetadata)
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return openapiETag
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}
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