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

typedef struct list_entry list_entry_t;

struct list_entry {
	void *key;
	void *value;
	list_entry_t *next;
};

typedef struct{
	list_entry_t *list;
	int (*cmp)(const void *, const void *); /*Comparison function */
} list_head_t;

list_head_t *list_init(int (*cmp)(const void *, const void *)){
	assert(cmp!=NULL);

	//Create the head
	list_head_t *newList;

	//Allocate the list	
	newList = (list_head_t *) malloc(sizeof(list_head_t));
	if (newList == NULL) {
		fprintf(stderr, "Cannot allocate list head\n");
		exit(EXIT_FAILURE);
	}
	
	//Assign comparison function
	newList->cmp=cmp;

	//Return the list head
	return newList;
}

list_entry_t *list_insert(list_head_t *head, void *key, void *value)
{
	assert(head!=NULL&&key!=NULL);

	//Create the list entry
	list_entry_t *entry;
	
	//Allocate the list entry
	entry = (list_entry_t *) malloc(sizeof(list_entry_t));
	if(entry == NULL) {
		return NULL;
	}
	
	//Assign values
	entry->key=key;
	entry->value=value;
	entry->next=head->list;

	//Move the head pointer
	head->list=entry;
	return entry;
}

list_entry_t *list_search_entry(list_head_t *head, void *key)
{
	assert(head!=NULL&&key!=NULL);

	//Create a list entry to store temp values in
	list_entry_t* test;

	//Start with first element after head
	test=head->list;

	//Loop until end of list
	while(test!=NULL){
		//If key matches, return value
		if(head->cmp(key,test->key)==0)
			return test;
		test=test->next;
	}
	return NULL;
}

void *list_search(list_head_t *head, void *key)
{
	assert(head!=NULL&&key!=NULL);

	//Create a list entry to store temp values in
	list_entry_t* test;

	//Start with first element after head
	test=head->list;

	//Loop until end of list
	while(test!=NULL){
		//If key matches, return value
		if(head->cmp(key,test->key)==0)
			return test->value;
		test=test->next;
	}
	return NULL;
}