feat: Initial version

main.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+)
+
+func main() {
+	// Verify and parse arguments
+	op := flag.String("op", "sum", "Operation to be executed")
+	column := flag.Int("col", 1, "CSV column on which to execute operation")
+	flag.Parse()
+	if err := run(flag.Args(), *op, *column, os.Stdout); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+func run(filenames []string, op string, column int, out io.Writer) error {
+	var opFunc statsFunc
+	if len(filenames) == 0 {
+		return ErrNoFiles
+	}
+	if column < 1 {
+		return fmt.Errorf("%w: %d", ErrInvalidColumn, column)
+	}
+
+	switch op {
+	case "sum":
+		opFunc = sum
+	case "avg":
+		opFunc = avg
+	default:
+		return fmt.Errorf("%w: %s", ErrInvalidOperation, op)
+	}
+
+	consolidate := make([]float64, 0)
+
+	for _, fname := range filenames {
+		f, err := os.Open(fname)
+		if err != nil {
+			return fmt.Errorf("cannot open file: %w", err)
+		}
+
+		data, err := csv2float(f, column)
+		if err != nil {
+			return err
+		}
+
+		if err := f.Close(); err != nil {
+			return err
+		}
+
+		consolidate = append(consolidate, data...)
+	}
+
+	_, err := fmt.Fprintln(out, opFunc(consolidate))
+	return err
+}