// Solution for project 1
// COSC 071 Fall 2002
// Clay Shields

// This program estimates the concentration of pseudo-nitzschia australis(PNA)
// given average water temperature, average light, concentration of
// nitrate nutrients, and water salinity.

#include <iostream>
#include <math.h>

int main () {

    /////////////////////////////////////
    // First, declare necessary variables
    
    // A constant to hold the max concentration of PNA
    const int maxPNA = 2100;
    
    // Variables to take input
    int Lumens;
    float Temp;
    float Salinity;
    float Nitrates;
    
    // Variables that will determine the proportion of max
    // for each factor. These will range between 0 and 1.
     
    float pctLumens;
    float pctTemp;
    float pctSalinity;
    float pctNitrates;
    
    // The amount of PNA we have
    float totalPNA;
    
    // Some constants to hold the cutoffs of different max and min values
    // that determine cutoffs for the things that have min and max
    // specifically light, salinity, and temperature.
    const float minLumens = 600;
    const float maxLumens = 1350;	
    const float minSalinity = 32;
    const float maxSalinity = 37;
    const float minNitrates =  0;
    const float maxNitrates = 25;
    const float minTemp = 10;
    const float maxTemp = 22; 
    
    // gonna need to use pi for the temperature approximation
    const float pi = 3.1415; // close enough
    
    
    ////////////////////////////////////////////
    // Print out a little message that says what the
    // program does
    
    cout << "This program will provide an estimate of the concentration " << endl;
    cout << "of pseudo-nitzschia australis in Monterey Bay given:" << endl;
    cout << "  the average light (in lumens);" << endl;
    cout << "  the average water temperature (in degrees Centigrade);" << endl;
    cout << "  the water salinity (in ppm);" << endl;
    cout << "  and the concentration of nutrients (in mg/m^3)." << endl;
    cout << "Output is in mg/m^3" << endl << endl;
    
    
    ////////////////////////////////////////////
    // Next, get the initial input from the user
    cout << "Please enter the average amount of light in lumens: ";
    cin >> Lumens;
    cout << "Please enter the average water temperature in degrees C: ";
    cin >> Temp;
    cout << "Please enter the water salinity in ppm: ";
    cin >> Salinity;
    cout << "Please enter the nutrients in mg/m^3: ";
    cin >> Nitrates;
    

    ///////////////////////////////////////////
    // Now, determine the proportion of max for each of
    // of the factors
    
    // Temp 
    // Temp is pretty non-linear, and can be approximated by a
    // parabola or by the sin () function. This uses the sine function
    // by converting the point on the range between minTemp and
    // maxTemp to the proportional range between 0 and pi/2.  Do this
    // conversion by figuring out what percent of the way between
    // minTemp and maxTemp Temp is; then multiply this by pi to get
    // the equivalent point on that range. Call sin() on that result
    
    if (Temp < minTemp)
	pctTemp = 0;
    else if (Temp > maxTemp)
	pctTemp = 0;
	else {
	    float pctPi = (Temp - minTemp) / (maxTemp - minTemp);
	    pctTemp = sin(pctPi * pi);
	}
	
    // Lumens

    if (Lumens < minLumens)
	pctLumens = 0;
    else if (Lumens >= maxLumens)
	    pctLumens = 1;
	else 
	    pctLumens = (Lumens - minLumens) / (maxLumens - minLumens);
        
    // Salinity

    if (Salinity > maxSalinity)
	pctSalinity = 0;
    else if (Salinity <= minSalinity)
	    pctSalinity = 1;
	else 
	    pctSalinity = (maxSalinity - Salinity) / (maxSalinity - minSalinity);    
    
    // Nitrates

    if (Nitrates < minNitrates)
	pctNitrates = 0;
    else if (Nitrates >= maxNitrates)
	    pctNitrates = 1;
	else 
	    pctNitrates = (Nitrates - minNitrates) / (maxNitrates - minNitrates);

    ///////////////////////////////////////////    
    // Now go ahead and compute the amount of PNA
    
    totalPNA = maxPNA * pctTemp * pctSalinity * pctLumens * pctNitrates;
    
    
    ///////////////////////////////////////////
    // Output the answer
    
    cout << endl << 
      "The estimated amount of pseudo-nitzschia australis (in mg/m^3) is: " 
	 << totalPNA << endl;


    ///////////////////////////////////////////
    // Done

    return 0;
}