Sebastian Unterschütz
77 lines
2.3 KiB
Go
77 lines
2.3 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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"time"
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)
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// krokiBaseURL is the Kroki instance to use. Override with the -kroki flag.
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// Self-host: docker run -d -p 8000:8000 yuzutech/kroki
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var krokiBaseURL = "https://kroki.io"
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// krokiClient is a shared HTTP client with a short timeout so a dead Kroki
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// backend fails fast instead of hanging for ~60 s per diagram.
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var krokiClient = &http.Client{Timeout: 10 * time.Second}
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// RenderDiagramViaKroki converts a diagram source (Mermaid, PlantUML, etc.)
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// to a PNG image via a Kroki rendering service and caches the result in the
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// OS temp directory. The base URL is controlled by krokiBaseURL (-kroki flag).
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//
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// Cache key: SHA-256 of the diagram source — unchanged diagrams are not re-fetched.
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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("%s/%s/png/%s", krokiBaseURL, 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 := krokiClient.Get(url) //nolint:gosec
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if err != nil {
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return "", fmt.Errorf("kroki request failed (is %s reachable?): %w", krokiBaseURL, 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 — try a local instance: docker run -d -p 8000:8000 yuzutech/kroki", 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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_ = os.Remove(cachePath) // remove incomplete cache file
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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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