Sebastian Unterschütz
69 lines
1.8 KiB
Go
69 lines
1.8 KiB
Go
package main
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import (
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"bytes"
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"compress/zlib"
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"crypto/sha256"
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"encoding/base64"
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"fmt"
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"io"
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"net/http"
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"os"
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"path/filepath"
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)
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// RenderDiagramViaKroki converts a diagram source (Mermaid, PlantUML, etc.)
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// to a PNG image using the Kroki.io public rendering service and caches the
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// result in the OS temp directory.
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//
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// The cache key is the SHA-256 hash of the diagram source, so unchanged
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// diagrams are not re-fetched between runs.
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//
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// Supported languages: "mermaid", "plantuml" / "puml"
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func RenderDiagramViaKroki(lang, code string) (string, error) {
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if lang == "puml" {
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lang = "plantuml"
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}
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// Kroki encoding: deflate (zlib) then base64url
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var buf bytes.Buffer
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w := zlib.NewWriter(&buf)
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if _, err := w.Write([]byte(code)); err != nil {
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return "", fmt.Errorf("zlib write: %w", err)
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}
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if err := w.Close(); err != nil {
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return "", fmt.Errorf("zlib close: %w", err)
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}
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encoded := base64.URLEncoding.EncodeToString(buf.Bytes())
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url := fmt.Sprintf("https://kroki.io/%s/png/%s", lang, encoded)
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// Deterministic cache path based on content hash
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hash := fmt.Sprintf("%x", sha256.Sum256([]byte(code)))
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cachePath := filepath.Join(os.TempDir(), "ihk_kroki_"+hash+".png")
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if _, err := os.Stat(cachePath); err == nil {
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return cachePath, nil // cache hit
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}
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resp, err := http.Get(url) //nolint:gosec // URL is constructed from user content, acceptable here
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if err != nil {
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return "", fmt.Errorf("kroki request: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return "", fmt.Errorf("kroki returned HTTP %d", resp.StatusCode)
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}
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out, err := os.Create(cachePath)
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if err != nil {
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return "", fmt.Errorf("cache file create: %w", err)
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}
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defer out.Close()
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if _, err = io.Copy(out, resp.Body); err != nil {
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return "", fmt.Errorf("cache file write: %w", err)
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}
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return cachePath, nil
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}
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