feat: better structured internal

cmd/lambda/lambda.go

@@ -7,35 +7,37 @@ import (
 	"time"
 
 	"git.maximhutz.com/max/lambda/internal/cli"
+	"git.maximhutz.com/max/lambda/internal/config"
 	"git.maximhutz.com/max/lambda/pkg/lambda"
 	"git.maximhutz.com/max/lambda/pkg/parser"
 	"git.maximhutz.com/max/lambda/pkg/tokenizer"
 )
 
+// Run main application.
 func main() {
-
-	options, err := cli.ParseOptions(os.Args[1:])
+	options, err := config.FromArgs()
 	cli.HandleError(err)
 
-	logger := cli.GetLogger(*options)
+	logger := options.GetLogger()
 	logger.Info("Using program arguments.", "args", os.Args)
 	logger.Info("Parsed CLI options.", "options", options)
 
-	if options.Input == "-" {
-		options.Input, err = cli.ReadInput()
-		cli.HandleError(err)
-	}
+	input, err := options.Source.Pull()
+	cli.HandleError(err)
 
-	tokens, fails := tokenizer.GetTokens([]rune(options.Input))
+	// Parse tokens.
+	tokens, fails := tokenizer.GetTokens([]rune(input))
 	if len(fails) > 0 {
 		cli.HandleError(errors.Join(fails...))
 	}
 	logger.Info("Parsed tokens.", "tokens", tokens)
 
+	// Turn tokens into syntax tree.
 	expression, err := parser.GetTree(tokens)
 	cli.HandleError(err)
 	logger.Info("Parsed syntax tree.", "tree", lambda.Stringify(expression))
 
+	// Reduce expression.
 	start := time.Now()
 
 	if options.Explanation {