MVP: Go daemon, password auth, persistent PTY terminals, React/xterm UI, PWA

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/config/config.go

@@ -0,0 +1,55 @@
+// Package config loads and saves hamlet's JSON config file.
+package config
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+type Config struct {
+	Listen       string `json:"listen"`
+	PasswordHash string `json:"password_hash"`
+
+	path string
+}
+
+func Default(path string) *Config {
+	return &Config{Listen: "127.0.0.1:8100", path: path}
+}
+
+// Load reads the config at path. A missing file yields the defaults.
+func Load(path string) (*Config, error) {
+	c := Default(path)
+	b, err := os.ReadFile(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return c, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	if err := json.Unmarshal(b, c); err != nil {
+		return nil, fmt.Errorf("parse %s: %w", path, err)
+	}
+	return c, nil
+}
+
+func (c *Config) Path() string    { return c.path }
+func (c *Config) DataDir() string { return filepath.Dir(c.path) }
+
+func (c *Config) Save() error {
+	if err := os.MkdirAll(c.DataDir(), 0o700); err != nil {
+		return err
+	}
+	b, err := json.MarshalIndent(c, "", "  ")
+	if err != nil {
+		return err
+	}
+	tmp := c.path + ".tmp"
+	if err := os.WriteFile(tmp, append(b, '\n'), 0o600); err != nil {
+		return err
+	}
+	return os.Rename(tmp, c.path)
+}