package parser

import (
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
)

const DefaultFile = "input"

func ParseFile(input *string) ([]int, error) {
	if input == nil {

		file := DefaultFile

		if len(os.Args) == 2 {
			file = os.Args[1]
		}

		inputFile, err := os.Open(file)
		if err != nil {
			return nil, fmt.Errorf("could not parse input file: %v", err)
		}

		fileData, err := io.ReadAll(inputFile)
		if err != nil {
			return nil, fmt.Errorf("could not read input file: %v", err)
		}

		fileStr := strings.TrimSpace(string(fileData))
		input = &fileStr
	}

	strNums := strings.Split(*input, ",")
	opcodes := make([]int, len(strNums))

	for i, v := range strNums {
		num, err := strconv.Atoi(v)
		if err != nil {
			fmt.Fprintf(os.Stderr, "WARNING: error parsing int from input, substring was %v", v)
		}
		opcodes[i] = num
	}

	return opcodes, nil
}