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package calculator
import (
"fmt"
"regexp"
"strconv"
"strings"
)
func Parse(input string) (string, error) {
input = strings.ToLower(strings.TrimSpace(input))
input = strings.ReplaceAll(input, "what is ", "")
input = strings.TrimSpace(input)
if result, ok := parseXPercentOfY(input); ok {
return result, nil
}
if result, ok := parseXIsWhatPercentOfY(input); ok {
return result, nil
}
if result, ok := parseXIsYPercentOfWhat(input); ok {
return result, nil
}
return "", fmt.Errorf("unable to parse input. See usage for examples")
}
func parseXPercentOfY(input string) (string, bool) {
re := regexp.MustCompile(`^(\d+(?:\.\d+)?)\s*%\s*(?:of\s+)?(\d+(?:\.\d+)?)$`)
matches := re.FindStringSubmatch(input)
if matches == nil {
return "", false
}
percent, _ := strconv.ParseFloat(matches[1], 64)
base, _ := strconv.ParseFloat(matches[2], 64)
result := (percent / 100.0) * base
return fmt.Sprintf("%.2f%% of %.2f = %.2f", percent, base, result), true
}
func parseXIsWhatPercentOfY(input string) (string, bool) {
re := regexp.MustCompile(`^(\d+(?:\.\d+)?)\s+is\s+what\s*%\s*(?:of\s+)?(\d+(?:\.\d+)?)$`)
matches := re.FindStringSubmatch(input)
if matches == nil {
return "", false
}
part, _ := strconv.ParseFloat(matches[1], 64)
whole, _ := strconv.ParseFloat(matches[2], 64)
if whole == 0 {
return "", false
}
percent := (part / whole) * 100.0
return fmt.Sprintf("%.2f is %.2f%% of %.2f", part, percent, whole), true
}
func parseXIsYPercentOfWhat(input string) (string, bool) {
re := regexp.MustCompile(`^(\d+(?:\.\d+)?)\s+is\s+(\d+(?:\.\d+)?)\s*%\s*(?:of\s+)?what$`)
matches := re.FindStringSubmatch(input)
if matches == nil {
return "", false
}
part, _ := strconv.ParseFloat(matches[1], 64)
percent, _ := strconv.ParseFloat(matches[2], 64)
if percent == 0 {
return "", false
}
whole := (part / percent) * 100.0
return fmt.Sprintf("%.2f is %.2f%% of %.2f", part, percent, whole), true
}
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