Variable handling

Relates to #2

task.go

@@ -43,6 +43,7 @@ type Task struct {
 	Sources   []string
 	Generates []string
 	Dir       string
+	Variables map[string]string
 }
 
 type taskNotFoundError struct {
@@ -101,14 +102,16 @@ func RunTask(name string) error {
 		return nil
 	}
 
+	vars := t.handleVariables()
+
 	for _, d := range t.Deps {
-		if err := RunTask(d); err != nil {
+		if err := RunTask(ReplaceVariables(d, vars)); err != nil {
 			return err
 		}
 	}
 
 	for _, c := range t.Cmds {
-		if err := runCommand(c, t.Dir); err != nil {
+		if err := runCommand(ReplaceVariables(c, vars), ReplaceVariables(t.Dir, vars)); err != nil {
 			return &taskRunError{name, err}
 		}
 	}

variableHandling.go

@@ -0,0 +1,45 @@
+package task
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func (t Task) handleVariables() map[string]string {
+	localVariables := make(map[string]string)
+	for key, value := range t.Variables {
+		localVariables[key] = value
+	}
+	for key, value := range getEnvironmentVariables() {
+		localVariables[key] = value
+	}
+	return localVariables
+}
+
+// ReplaceVariables writes variables into initial string
+func ReplaceVariables(initial string, variables map[string]string) string {
+	replaced := initial
+	for name, val := range variables {
+		replaced = strings.Replace(replaced, fmt.Sprintf("{{%s}}", name), val, -1)
+	}
+	return replaced
+}
+
+// GetEnvironmentVariables returns environment variables as map
+func getEnvironmentVariables() map[string]string {
+	getenvironment := func(data []string, getkeyval func(item string) (key, val string)) map[string]string {
+		items := make(map[string]string)
+		for _, item := range data {
+			key, val := getkeyval(item)
+			items[key] = val
+		}
+		return items
+	}
+	return getenvironment(os.Environ(), func(item string) (key, val string) {
+		splits := strings.Split(item, "=")
+		key = splits[0]
+		val = splits[1]
+		return
+	})
+}