rewrite code a bit

Signed-off-by: Naman Sood <mail@nsood.in>

stylemap/stylemap.go

@@ -0,0 +1,117 @@
+package stylemap
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"prose/watcher"
+	"strings"
+	"sync"
+
+	"github.com/bep/godartsass/v2"
+)
+
+type styleMap struct {
+	mu          sync.RWMutex
+	stylesheets map[string]string
+	transpiler  *godartsass.Transpiler
+}
+
+// New returns a new styleMap.
+func New() (watcher.AutoMap[string, string], error) {
+	folder, err := os.ReadDir("styles/")
+	if err != nil {
+		return nil, fmt.Errorf("could not load styles directory: %w", err)
+	}
+
+	sassTranspiler, err := godartsass.Start(godartsass.Options{})
+	if err != nil {
+		return nil, fmt.Errorf("could not start sass transpiler: %w", err)
+	}
+
+	sm := &styleMap{
+		stylesheets: make(map[string]string),
+		transpiler:  sassTranspiler,
+	}
+
+	for _, s := range folder {
+		err := sm.fetchLocked(s.Name())
+		if err != nil {
+			return nil, fmt.Errorf("could not generate styles for %s: %w", s.Name(), err)
+		}
+		log.Printf("loaded stylesheet %q", s.Name())
+	}
+
+	go watcher.Watch("styles/", sm)
+
+	return sm, nil
+}
+
+func (sm *styleMap) Get(filename string) (string, bool) {
+	sm.mu.RLock()
+	defer sm.mu.RUnlock()
+	contents, ok := sm.stylesheets[filename]
+	return contents, ok
+}
+
+func (sm *styleMap) Delete(filename string) error {
+	sm.mu.Lock()
+	defer sm.mu.Unlock()
+	if s, ok := strings.CutSuffix(filename, ".scss"); ok {
+		filename = s + ".css"
+	}
+	delete(sm.stylesheets, filename)
+	return nil
+}
+
+func (sm *styleMap) Fetch(filename string) (err error) {
+	sm.mu.Lock()
+	defer sm.mu.Unlock()
+	return sm.fetchLocked(filename)
+}
+
+func (sm *styleMap) fetchLocked(filename string) (err error) {
+	var outfile, contents string
+	if strings.HasSuffix(filename, ".scss") {
+		outfile, contents, err = sm.loadSCSS(filename)
+	} else {
+		outfile, contents, err = sm.loadCSS(filename)
+	}
+	if err != nil {
+		return
+	}
+	sm.stylesheets[outfile] = contents
+	return
+}
+
+func (sm *styleMap) loadSCSS(filename string) (string, string, error) {
+	in, err := os.Open("styles/" + filename)
+	if err != nil {
+		return "", "", fmt.Errorf("could not open stylesheet %s: %w", filename, err)
+	}
+	stylesheet, err := io.ReadAll(in)
+	if err != nil {
+		return "", "", fmt.Errorf("could not read stylesheet %s: %w", filename, err)
+	}
+	res, err := sm.transpiler.Execute(godartsass.Args{
+		Source: string(stylesheet),
+	})
+	if err != nil {
+		return "", "", fmt.Errorf("could not generate stylesheet %s: %w", filename, err)
+	}
+	return strings.TrimSuffix(filename, ".scss") + ".css", res.CSS, nil
+}
+
+func (sm *styleMap) loadCSS(filename string) (string, string, error) {
+	in, err := os.Open("styles/" + filename)
+	if err != nil {
+		return "", "", fmt.Errorf("could not open style infile %s: %w", filename, err)
+	}
+	var buf strings.Builder
+	_, err = io.Copy(&buf, in)
+	if err != nil {
+		return "", "", fmt.Errorf("could not copy stylesheet %s: %w", filename, err)
+	}
+	return filename, buf.String(), nil
+}