computational-geometry-in-c/include/vertex.h

#ifndef _CGC_VERTEX_H
#define _CGC_VERTEX_H

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

struct Vertex {
    int number;
    int coordinates[2];
    bool ear;
    struct Vertex *next;
    struct Vertex *prev;
};

/**
 * Initializes a new vertex struct.
 * @param number The number of the vertex for identification.
 * @param x X coordinate.
 * @param y Y coordinate.
 * @return An initialized Vertex struct.
 */
struct Vertex *new_vertex(int number, int x, int y);

/**
 * Adds a vertex to a parent vertex under the assumption the parent vertex
 * is the LAST vertex in the list. The reason this is necessary is because
 * the list of vertices is circular, and as such the last element points
 * back to the head of the list. The list will be modified in place.
 *
 * @param head The head of the polygon's vertex list.
 * @param parent The parent vertex to add the new one to.
 * @param child  The child vertex.
 */
void add_vertex(struct Vertex *head, struct Vertex *parent,
                struct Vertex *child);

/**
 * Frees a single vertex. This does not free it's next and previous pointers.
 * @param vertex The vertex to free.
 */
void free_vertex(struct Vertex *vertex);

/**
 * Frees an entire polygon given it's head (first) vertex.
 * @param head The start of the counter-clockwise ordered polygon.
 */
void free_polygon(struct Vertex **head);

/**
 * Pretty prints a vertex.
 * @param vertex The vertex.
 */
void print_vertex(const struct Vertex *vertex);

/**
 * Pretty prints a polygon.
 * @param head The first point in the polygon.
 */
void print_polygon(const struct Vertex *head);

/**
 * Traverses the polygon represented by the starting point `head` and
 * sets the ear parameter correctly.
 *
 * @param head
 */
void init_ear(struct Vertex *head);

/**
 * Counts the number of vertices in a polygon.
 * @param head The start vertex of the polygon.
 * @return The count of vertices.
 */
int vertex_count(const struct Vertex *head);

#endif // _CGC_VERTEX_H