Cache pygments rendering between runs

Fixes #1000

diff --git a/helpers/pygments.go b/helpers/pygments.go
index a615f21baff5116ecd072b87749926e55343dcf1..0f06635fc58378bcd43a6c1f8926574b6f4f96cf 100644 (file)
--- a/helpers/pygments.go
+++ b/helpers/pygments.go
@@ -15,10 +15,13 @@ package helpers
 
 import (
        "bytes"
+       "crypto/sha1"
        "fmt"
+       "io/ioutil"
        "os/exec"
        "strings"
 
+       "github.com/spf13/hugo/hugofs"
        jww "github.com/spf13/jwalterweatherman"
        "github.com/spf13/viper"
 )
@@ -42,6 +45,33 @@ func Highlight(code string, lexer string) string {
                return code
        }
 
+       fs := hugofs.OsFs
+
+       // Try to read from cache first
+       hash := sha1.Sum([]byte(code))
+       cachefile := fmt.Sprintf("%s/pygments-%s-%x", viper.GetString("CacheDir"), lexer, hash)
+       exists, err := Exists(cachefile, fs)
+       if err != nil {
+               jww.ERROR.Print(err.Error())
+               return code
+       }
+       if exists {
+               f, err := fs.Open(cachefile)
+               if err != nil {
+                       jww.ERROR.Print(err.Error())
+                       return code
+               }
+
+               s, err := ioutil.ReadAll(f)
+               if err != nil {
+                       jww.ERROR.Print(err.Error())
+                       return code
+               }
+
+               return string(s)
+       }
+
+       // No cache file, render and cache it
        var out bytes.Buffer
        var stderr bytes.Buffer
        style := viper.GetString("PygmentsStyle")
@@ -62,5 +92,10 @@ func Highlight(code string, lexer string) string {
                return code
        }
 
+       // Write cache file
+       if err := WriteToDisk(cachefile, bytes.NewReader(out.Bytes()), fs); err != nil {
+               jww.ERROR.Print(stderr.String())
+       }
+
        return out.String()
 }