Added a configuration system

config/config.go

@@ -0,0 +1,179 @@
+package config
+
+import "os"
+import "bufio"
+import "errors"
+import "strings"
+import "strconv"
+import "image/color"
+import "path/filepath"
+
+// Type represents the data type of a configuration parameter.
+type Type int
+
+const (
+	// string
+	TypeString Type = iota
+
+	// image/color.RGBA
+	TypeColor
+
+	// int
+	TypeInteger
+
+	// float64
+	TypeFloat
+
+	// bool
+	TypeBoolean
+)
+
+// Config holds a list of configuration parameters.
+type Config struct {
+	// LegalParameters holds the names and types of all parameters that can
+	// be parsed. If the parser runs into a parameter that is not listed
+	// here, it will print out an error message and keep on parsing.
+	LegalParameters map[string] Type
+
+	// Parameters holds the names and values of all parsed parameters. If a
+	// value is non-nil, it can be safely type asserted into whatever type
+	// was requested.
+	Parameters map[string] any
+}
+
+// Load loads and parses the files /etc/<name>/<name>.conf and
+// <home>/.config/<name>/<name>.conf.
+func (config *Config) Load (name string) (err error) {
+	if config.LegalParameters == nil {
+		config.LegalParameters = make(map[string] Type)
+	}
+	
+	if config.Parameters == nil {
+		config.Parameters = make(map[string] any)
+	}
+
+	config.loadFile("/etc/" + name + "/" + name + ".conf")
+	var homeDirectory string
+	homeDirectory, err = os.UserHomeDir()
+	if err != nil { return }
+	config.loadFile(filepath.Join(homeDirectory, "/.config/" + name + "/" + name + ".conf"))
+	return
+}
+
+func (config *Config) loadFile (path string) {
+	file, err := os.Open(path)
+	if err != nil { return }
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		
+		if len(line) == 0 {
+			continue
+		}
+
+		if line[0] == '#' {
+			continue
+		}
+	
+		key, value, found := strings.Cut(scanner.Text(), ":")
+		if !found {
+			println (
+				"config: error in file", path +
+				": key-value separator missing")
+			println(scanner.Text())
+			continue
+		}
+		key   = strings.TrimSpace(key)
+		value = strings.TrimSpace(value)
+
+		what, isKnown := config.LegalParameters[key]
+		if !isKnown {
+			println (
+				"config: error in file", path +
+				": unknown parameter")
+			println(scanner.Text())
+			continue
+		}
+
+		switch what {
+		case TypeString:
+			config.Parameters[key] = value
+			
+		case TypeColor:
+			var valueColor color.Color
+			valueColor, err = parseColor(value)
+			if err != nil {
+				println (
+					"config: error in file", path +
+					":", err)
+				println(scanner.Text())
+				continue
+			}
+			config.Parameters[key] = valueColor
+		
+		case TypeInteger:
+			var valueInt int
+			valueInt, err = strconv.Atoi(value)
+			if err != nil {
+				println (
+					"config: error in file", path +
+					": malformed integer literal")
+				println(scanner.Text())
+				continue
+			}
+			config.Parameters[key] = valueInt
+			
+		case TypeFloat:
+			var valueFloat float64
+			valueFloat, err = strconv.ParseFloat(value, 64)
+			if err != nil {
+				println (
+					"config: error in file", path +
+					": malformed float literal")
+				println(scanner.Text())
+				continue
+			}
+			config.Parameters[key] = valueFloat
+			
+		case TypeBoolean:
+			value = strings.ToLower(value)
+			truthy :=
+				value == "true" ||
+				value == "yes"  ||
+				value == "on"   ||
+				value == "1"
+			config.Parameters[key] = truthy
+		}
+	}
+
+	return
+}
+
+func parseColor (value string) (valueColor color.Color, err error) {
+	if value[0] == '#' {
+		if len(value) != 7  {
+			err = errors.New("wrong length color literal")
+			return
+		}
+
+		var colorInt uint64
+		colorInt, err = strconv.ParseUint(value[1:7], 16, 24)
+		if err != nil  {
+			err = errors.New("malformed color literal")
+			return
+		}
+
+		valueColor = color.RGBA {
+			R: uint8(colorInt >> 16),
+			G: uint8(colorInt >> 8),
+			B: uint8(colorInt),
+			A: 0xFF,
+		}
+	} else {
+		err = errors.New("malformed color literal")
+		return
+	}
+
+	return
+}