package math

import "math"

type Point struct {
	X, Y float64
}

// ShoelaceArea calculates the area of a polygon using the Shoelace formula.
// It takes a slice of Point structs representing the vertices of the polygon.
// If the number of vertices is less than 3, it returns 0.0 indicating that it is not a valid polygon.
func ShoelaceArea(polygon []Point) float64 {
	if len(polygon) < 3 {
		return 0.0 // Not a polygon
	}

	var area float64 = 0.0
	j := len(polygon) - 1 // The last vertex is the 'previous' one to the first

	for i := 0; i < len(polygon); i++ {
		area += (polygon[j].X + polygon[i].X) * (polygon[j].Y - polygon[i].Y)
		j = i // j is previous vertex to i
	}

	return 0.5 * math.Abs(area)
}

// floodFill performs a flood fill algorithm on the given matrix starting from the specified row and column.
// It replaces all occurrences of the previous color with the new color.
// The height and width parameters define the dimensions of the matrix.
func floodFill(matrix Matrix[int64], row int, col int, prevColor int64, newColor int64, height int, width int) {
	if row < 0 || row >= height || col < 0 || col >= width {
		return
	}

	if matrix[row][col] != prevColor {
		return
	}

	if matrix[row][col] == newColor {
		return
	}

	matrix[row][col] = newColor

	floodFill(matrix, row+1, col, prevColor, newColor, height, width)
	floodFill(matrix, row-1, col, prevColor, newColor, height, width)
	floodFill(matrix, row, col+1, prevColor, newColor, height, width)
	floodFill(matrix, row, col-1, prevColor, newColor, height, width)
}