"""
Point.cobra

This sample library class demonstrates numerous Cobra features including
unit tests, contracts, properties, overrides, etc. in fairly small,
easy-to-understand classes.

You can run the test cases for this (and also test compile) like so:

cobra -test Point.cobra

Or build this into a Point.dll libary like so:

cobra -t:lib -c Point.cobra

Upon final delivery, you may wish to turn on optimizations while removing
asserts, contracts and unit tests. You can do these individually or
all in one fell swoop with the -turbo option:

cobra -t:lib -turbo -c Point.cobra

See cobra -h for more information.
"""

class Point
    """
    An immutable point in 2D space with integer coordinates.
    
    Because points are immutable they can be put in sets and used as keys in dictionaries.
    """

    test

        p1 = Point(1, 2)
        assert p1.x == 1 and p1.y == 2
        assert p1.isPositive and not p1.isZero
        assert p1.toString == 'Point(1, 2)'

        p2 = p1.movedBy(3, 4)
        assert p2.x == 4 and p2.y == 6
        assert p1 <> p2
        
        p3 = Point(1, 2)
        assert p1 == p3

        assert Point.zero.isZero

        points = {p1, p2, p3}  # a Set
        # but p1 and p3 are not unique so:
        assert points.count == 2
        assert p1 in points and p2 in points and p3 in points

    shared

        var _zero = Point(0, 0)
    
        get zero as Point
            """
            Returns the zero point, (0, 0).
            This is cached and slightly faster than creating a new point every time.
            """
            return _zero
    
    cue init(x as int, y as int)
        ensure .x == x and .y == y
        _x, _y = x, y
    
    get x from var as int
    
    get y from var as int
    
    get isPositive as bool
        return .x > 0 and .y > 0

    get isZero as bool
        return .x == 0 and .y == 0

    def movedBy(dx as int, dy as int) as Point
        ensure result.x == .x+dx and result.y == .y+dy
        return Point(_x+dx, _y+dy)

    def toString as String is override
        return '[.typeOf.name]([.x], [.y])'

    def equals(other as Object?) as bool is override
        if this is other, return true
        if other inherits Point
            return .x == other.x and .y == other.y
        else
            return false

    def getHashCode as int is override
        return .x ^ .y