/***********************************************
 *  CS2510 Spring 2011 
 *  Lecture #10
 *  Function-Classes/Objects (1)
 ***********************************************/

import tester.*;

// Represents a Student
class Student{
    String name;
    double gpa;
    boolean graduating;
    
    Student(String name, double gpa, boolean graduating) {
        this.name = name;
        this.gpa = gpa;
        this.graduating = graduating;
    }
}

// Represents a List of Students
interface ILoS{
    // Insert the given Student into this sorted list with the given IComp
    public ILoS insertByComp(Student s, IComp decider);
    // Sort this list by the given IComp
    public ILoS sortByComp(IComp decider);
}

// Represents an empty list of Students
class MtLoS implements ILoS{
    MtLoS(){ }
    
    // Insert the given Student into this sorted list by the given IComp
    public ILoS insertByComp(Student s, IComp decider){
        return new ConsLoS(s, this);
    }    
    // Sort this list by the given IComp
    public ILoS sortByComp(IComp decider){
        return this;
    }
}

// An interface for comparing Students
interface IComp{
    // Decide which Student should go "first"
    public boolean lessThan(Student s1, Student s2);
}

// Function-Class for comparing Students by GPA
class ByGPA implements IComp{
    // Decide which goes first, by GPA
    public boolean lessThan(Student s1, Student s2){
        return s1.gpa > s2.gpa;
    }
}

// Function-Class for comparing Students by Name
class ByName implements IComp{
    // Decide which goes first, by Name
    public boolean lessThan(Student s1, Student s2){
        return s1.name.compareTo(s2.name) < 0;
    }
}

// Represents a non-empty list of Students
class ConsLoS implements ILoS{
    Student first;
    ILoS rest;
    
    ConsLoS(Student first, ILoS rest) {
        this.first = first;
        this.rest = rest;
    }
    
    /** Template
     *    Fields:
     *      ... this.first ... -- Student
     *      ... this.rest ...  -- ILoS
     *      
     *    Methods:
     *      ... this.insert(Student) ... -- ILoS
     *      ... this.sort() ...          -- ILoS
     *      
     *    Method of Fields:
     *      ... this.rest.insertByComp(Student,IComp) ... -- ILoS
     *      ... this.rest.sort(IComp) ...                 -- ILoS
     */
    
    // Insert the given Student into this sorted list by the given IComp
    public ILoS insertByComp(Student s, IComp decider){
        if(decider.lessThan(s, this.first)){
            return new ConsLoS(s, this);
        }else{
            return new ConsLoS(this.first,
                    this.rest.insertByComp(s, decider));
        }
    }
    // Sort this list by the given IComp
    public ILoS sortByComp(IComp decider){
        return this.rest.sortByComp(decider)
                 .insertByComp(this.first, decider);
    }
}

// Examples and Tests for this Lecture...
class LectureExamples{
    // Important students...
    Student kev = new Student("Kevin", 490, true);
    Student spenc = new Student("Spencer", 500, false);
    Student gina = new Student("Gina", 500, false);
    
    // Some function-objects
    IComp bygpa = new ByGPA();
    IComp byname = new ByName();
    
    // test the method lessThan in classes ByGPA and ByName
    boolean testLessThan(Tester t){
    	    return
    	    t.checkExpect(this.bygpa.lessThan(this.gina, this.kev), false) &&
    	    t.checkExpect(this.bygpa.lessThan(this.kev, this.spenc), true) &&
    	    t.checkExpect(this.bygpa.lessThan(this.kev, this.kev), false) &&
    	    t.checkExpect(this.byname.lessThan(this.spenc, this.kev), false) &&
    	    t.checkExpect(this.byname.lessThan(this.gina, this.kev), true) &&
    	    t.checkExpect(this.byname.lessThan(this.spenc, this.spenc), false);
    }  
    
    // Some example Lists
    ILoS mt = new MtLoS();
    ILoS los = new ConsLoS(this.spenc, this.mt);
    ILoS los2 = new ConsLoS(this.kev, this.los);
    ILoS sortedGPA = new ConsLoS(this.spenc, new ConsLoS(this.kev, this.mt));
    ILoS sortedName = new ConsLoS(this.kev, new ConsLoS(this.spenc, this.mt));
    
    boolean testInsert(Tester t){
        return (t.checkExpect(this.mt.insertByComp(this.kev, this.bygpa),
                              new ConsLoS(this.kev, this.mt)) &&
                t.checkExpect(this.los.insertByComp(this.kev, this.bygpa),
                              this.sortedGPA) &&
                t.checkExpect(this.mt.insertByComp(this.kev, this.byname),
                              new ConsLoS(this.kev, this.mt)) &&
                t.checkExpect(this.los.insertByComp(this.kev, this.byname),
                              this.sortedName));
    }
    boolean testSort(Tester t){
        return (t.checkExpect(this.mt.sortByComp(this.bygpa), this.mt) &&
                t.checkExpect(this.los.sortByComp(this.bygpa), this.los) &&
                t.checkExpect(this.los2.sortByComp(this.bygpa), this.sortedGPA) &&
                t.checkExpect(this.mt.sortByComp(this.byname), this.mt) &&
                t.checkExpect(this.los.sortByComp(this.byname), this.los) &&
                t.checkExpect(this.los2.sortByComp(this.byname), this.sortedName));
    }
}