read config

go.mod

@@ -1,3 +1,5 @@
 module git.tilde.town/tildetown/bbj2
 
 go 1.18
+
+require gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b

server/cmd/main.go

@@ -1,7 +1,96 @@
 package main
 
-import "fmt"
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+const (
+	defaultPort         = 7099
+	defaultInstanceName = "BBJ"
+	defaultHost         = "127.0.0.1"
+)
+
+type Config struct {
+	Admins       []string
+	Port         int
+	Host         string
+	InstanceName string `yaml:"instance_name"`
+	AllowAnon    bool
+	Debug        bool
+}
+
+type iostreams struct {
+	Err io.Writer
+	Out io.Writer
+}
+
+type Opts struct {
+	ConfigPath string
+	IO         iostreams
+}
 
 func main() {
-	fmt.Println("bbj2 server")
+	var configFlag = flag.String("config", "config.yml", "A path to a config file.")
+	flag.Parse()
+	opts := Opts{
+		ConfigPath: *configFlag,
+		IO: iostreams{
+			Err: os.Stderr,
+			Out: os.Stdout,
+		},
+	}
+
+	err := _main(opts)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed: %s", err)
+	}
+}
+
+func _main(opts Opts) error {
+	cfg, err := parseConfig(opts.ConfigPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not read config file '%s'", opts.ConfigPath)
+		os.Exit(1)
+	}
+
+	fmt.Printf("DBG %#v\n", cfg.InstanceName)
+
+	return nil
+}
+
+func parseConfig(configPath string) (*Config, error) {
+	cfgBytes, err := os.ReadFile(configPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read config file: %w", err)
+	}
+
+	fmt.Printf("DBG %#v\n", string(cfgBytes))
+
+	var cfg Config
+
+	if err := yaml.Unmarshal(cfgBytes, &cfg); err != nil {
+		return nil, fmt.Errorf("failed to parse config: %w", err)
+	}
+
+	fmt.Printf("DBG %#v\n", cfg)
+
+	if cfg.Port == 0 {
+		cfg.Port = defaultPort
+	}
+
+	if cfg.InstanceName == "" {
+		cfg.InstanceName = defaultInstanceName
+
+	}
+
+	if cfg.Host == "" {
+		cfg.Host = defaultHost
+	}
+
+	return &cfg, nil
 }