// Helene Martin, CSE 142
// This structured program computes one person's body mass index and 
// displays their weight status.

// goal: demonstrate good decomposition and use of returns.
// See chapter 4 case study for more details.
// In particular, the "procedural design heuristics" section is excellent (p283)

import java.util.*;  // for Scanner

public class BMICalculator {
	public static void main(String[] args) {
		Scanner console = new Scanner(System.in);
		printIntroduction();

		double bmi1 = getBMI(console);
		double bmi2 = getBMI(console);
		
		String status1 = getStatus(bmi1);
		String status2 = getStatus(bmi2);

		reportResults(1, bmi1, status1);
		reportResults(2, bmi2, status2);
		
		System.out.println("Difference = " + round(Math.abs(bmi1 - bmi2), 2));
	}
	
	// Prints an introduction for the program.
	public static void printIntroduction() {
		System.out.println("This program reads in data for two people and");
		System.out.println("computes their body mass index (BMI)");
		System.out.println();	
	}
	
	// Prompts for height and weight; calculates and returns 
	// body mass index.	
	public static double getBMI(Scanner console) {
		System.out.println("Enter next person's information:");
		System.out.print("height (in inches)? ");
		double height = console.nextDouble();
		
 		System.out.print("weight (in pounds)? ");		
		double weight = console.nextDouble();
		System.out.println();		
			
		return bmiFor(weight, height);
	}
	
	// Calculates and returns body mass index based on weight and height
	public static double bmiFor(double weight, double height) {
		return weight / Math.pow(height, 2) * 703;
	}
		
	// Calculates and returns the bmi class based on a 
	// chart published by the Centers for Disease Control and Prevention
	public static String getStatus(double bmi) {
		if (bmi < 18.5) {
			return "underweight";
		} else if (bmi < 25) {
			return "normal";
		} else if (bmi < 30) {
			return "overweight";
		} else {
			return "obese";
		}	
	}
	
	// Prints bmi and bmi status for a person.
	public static void reportResults(int person, double bmi, String status) {
		System.out.println("Person " + person + " BMI = " + round(bmi, 2));
		System.out.println(status);	
	}
	
	// Rounds a value to a given number of digits.
	public static double round(double value, int digits) {
		return Math.round(value * Math.pow(10, digits)) / Math.pow(10, digits);
	}
}