config.go

package jconf

import (
	"encoding/json"
	"fmt"
	"os"
	"strings"
)

type Config struct {
	config map[string]interface{}
}

// NewConfig is used to parse configuration values from a JSON file.
func NewConfig(filename string) (*Config, error) {
	config := &Config{}
	config.config = make(map[string]interface{})
	err := config.readConfig(filename)

	return config, err
}

func (c *Config) AddConfig(filename string) error {
	return c.readConfig(filename)
}

// Internal function to read config JSON.
func (c *Config) readConfig(filename string) error {
	file, err := os.Open(filename)
	if nil != err {
		return fmt.Errorf("Could not read config %s: %s", filename, err)
	}
	fmt.Printf("Reading config file %s\n", filename)
	config := make(map[string]interface{})
	decoder := json.NewDecoder(file)
	err = decoder.Decode(&config)

	if nil != err {
		return fmt.Errorf("Could not parse config %s: %s", filename, err)
	}

	// Allow environment variable to override config setting.
	for key, _ := range config {
		fmt.Printf("Have config %s - looking for env variable overrides\n", key)
		newVal, ok := os.LookupEnv(strings.ToUpper(key))
		if ok {
			fmt.Printf("Overriding config value %s with env variable\n", key)
			//fmt.Printf("Overriding config value %s with env variable: %s\n", key, newVal)
			config[key] = newVal
		}
	}

	// Merge into main config map.
	for key, val := range config {
		//fmt.Printf("Adding config value %s:%s\n", key, val)
		c.config[key] = val
	}

	return nil
}

// The HasConfig function can be used to determine if a config value
// exists before reading.
func (c *Config) HasConfig(key string) bool {
	_, ok := c.config[key]
	return ok
}

// The GetConfig function is used to get a config value as an interface.
// nil is returned if the config value does not exist.
func (c *Config) GetConfig(key string) interface{} {
	val, _ := c.config[key]

	return val
}

// The GetConfigStr function is used to get a config value as a string.
// An empty string is returned if the config value does not exist.
func (c *Config) GetConfigStr(key string) string {
	val, ok := c.config[key]

	if ok {
		return val.(string)
	}

	return ""
}

// The GetConfigStr function is used to get a config as an integter.
// -1 is returned if the config value does not exist.
func (c *Config) GetConfigInt(key string) float64 {
	val, ok := c.config[key]

	if ok {
		return val.(float64)
	}

	return -1
}