server/config.go

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/user"
	"strings"
)

type Config struct {
	Tick      int     `json:"tick"` // ms
	Timescale float32 `json:"timescale"`
	Width     int     `json:"width"`
	Height    int     `json:"height"`
	Obstacles int     `json:"obstacles"`
	MaxPoints int     `json:"max_points"`
	Mode      string  `json:"mode"`
}

const (
	TICK         = 60
	TIMESCALE    = 1.0
	WIDTH        = 800
	HEIGHT       = 550
	OBSTACLES    = 5
	MAX_POINTS   = 500 // allowing for 50 pts in every category
	DEFAULT_MODE = "deathmatch"
)

func loadConfig(filename string) (Config, error) {
	c := Config{
		Tick:      TICK,
		Timescale: TIMESCALE,
		Width:     WIDTH,
		Height:    HEIGHT,
		Obstacles: OBSTACLES,
		MaxPoints: MAX_POINTS,
		Mode:      DEFAULT_MODE,
	}
	u, err := user.Current()
	if err != nil {
		return c, err
	}
	if len(filename) > 1 && filename[:2] == "~/" {
		filename = strings.Replace(filename, "~", u.HomeDir, 1)
	}
	if _, err := os.Stat(filename); os.IsNotExist(err) {
		log.Printf("%+v not found, using defaults", filename)
	} else {
		log.Printf("found config file: %s", filename)
		f, err := ioutil.ReadFile(filename)
		if err != nil {
			return c, err
		}
		err = json.Unmarshal(f, &c)
		if err != nil {
			return c, errors.New(fmt.Sprintf("config parse error: %s", err))
		}
	}
	log.Printf("final config: %+v", c)
	return c, nil
}