Add systemd resource budgets with TOML profiles

internal/budget/files.go

@@ -0,0 +1,59 @@
+package budget
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
+type paths struct {
+	config string
+	units  string
+	state  string
+}
+
+func homePaths(home string) paths {
+	return paths{
+		config: filepath.Join(home, ".config/budget/profiles.toml"),
+		units:  filepath.Join(home, ".config/systemd/user"),
+		state:  filepath.Join(home, ".local/state/budget"),
+	}
+}
+
+func writeFiles(p paths, files map[string]string) error {
+	if err := os.MkdirAll(p.state, 0755); err != nil {
+		return err
+	}
+	manifest := filepath.Join(p.state, "files.json")
+	previous := []string{}
+	data, err := os.ReadFile(manifest)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	if err == nil {
+		if err := json.Unmarshal(data, &previous); err != nil {
+			return err
+		}
+	}
+	for _, relative := range previous {
+		if _, keep := files[relative]; !keep {
+			if err := os.Remove(filepath.Join(p.units, relative)); err != nil {
+				return err
+			}
+		}
+	}
+	for _, relative := range keys(files) {
+		target := filepath.Join(p.units, relative)
+		if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
+			return err
+		}
+		if err := os.WriteFile(target, []byte(files[relative]), 0644); err != nil {
+			return err
+		}
+	}
+	data, err = json.MarshalIndent(keys(files), "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(manifest, append(data, '\n'), 0644)
+}