#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ldap.h>

#define LDAP_URI "ldap://ldap.technikum-wien.at:389"
#define SEARCHBASE "dc=technikum-wien,dc=at"
#define SCOPE LDAP_SCOPE_SUBTREE
#define FILTER "(uid=if17b*)"

static int ldapTryLoginIntern(char* user, char* password)
{
    LDAP *ld; // LDAP resource handle

    BerValue *servercredp;
    BerValue cred;
    cred.bv_val = password;
    cred.bv_len = strlen(password);
    int rc = 0;

    int ldapversion = LDAP_VERSION3;

    /* setup LDAP connection */
    if(ldap_initialize(&ld, LDAP_URI) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_init failed");
        return 0;
    }

    if((rc = ldap_set_option(ld, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_set_option(PROTOCOL_VERSION): %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    if((rc = ldap_start_tls_s(ld, NULL, NULL)) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_start_tls_s(): %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    rc = ldap_sasl_bind_s(ld, user, LDAP_SASL_SIMPLE, &cred, NULL, NULL, &servercredp);

    if(rc != LDAP_SUCCESS)
    {
        return 0;
    }
    ldap_unbind_ext_s(ld, NULL, NULL);
    return 1;
}

int ldapTryLogin(char* user, char* password)
{
    LDAP *ld; // LDAP resource handle
    LDAPMessage *result, *e; // LDAP result handle
    BerElement *ber; // array of attributes
    char *attribute;
    BerValue **vals;

    BerValue *servercredp;
    BerValue cred;
    cred.bv_val = "";
    cred.bv_len = 0;
    int i, rc = 0;

    const char *attribs[] = {"uid", "cn", NULL}; /* attribute array for search */

    int ldapversion = LDAP_VERSION3;

    /* setup LDAP connection */
    if(ldap_initialize(&ld, LDAP_URI) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_init failed");
        return 0;
    }

    if((rc = ldap_set_option(ld, LDAP_OPT_PROTOCOL_VERSION, &ldapversion)) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_set_option(PROTOCOL_VERSION): %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    if((rc = ldap_start_tls_s(ld, NULL, NULL)) != LDAP_SUCCESS)
    {
        fprintf(stderr, "ldap_start_tls_s(): %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    // anonymous bind
    rc = ldap_sasl_bind_s(ld, "", LDAP_SASL_SIMPLE, &cred, NULL, NULL, &servercredp);

    if(rc != LDAP_SUCCESS)
    {
        fprintf(stderr, "LDAP bind error: %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    /* perform ldap search */
    rc = ldap_search_ext_s(ld, SEARCHBASE, SCOPE, FILTER, (char **) attribs, 0, NULL, NULL, NULL, 500, &result);

    if(rc != LDAP_SUCCESS)
    {
        fprintf(stderr, "LDAP search error: %s\n", ldap_err2string(rc));
        ldap_unbind_ext_s(ld, NULL, NULL);
        return 0;
    }

    char buffer[1024];
    buffer[0] = '\0';
    for(e = ldap_first_entry(ld, result); e != NULL; e = ldap_next_entry(ld, e))
    {
        for(attribute = ldap_first_attribute(ld, e, &ber); attribute != NULL; attribute = ldap_next_attribute(ld, e, ber))
        {
            if((vals = ldap_get_values_len(ld, e, attribute)) != NULL)
            {
                for(i = 0; i < ldap_count_values_len(vals); i++)
                {
                    if(strcmp(attribute, "uid") == 0 && strcmp(vals[i]->bv_val, user) == 0)
                    {
                        strncpy(buffer, ldap_get_dn(ld, e), 1023);
                    }
                }
                ldap_value_free_len(vals);
            }
            // free memory used to store the attribute
            ldap_memfree(attribute);
        }
        // free memory used to store the value structure
        if(ber != NULL)
        {
            ber_free(ber, 0);
        }
    }
    
    /* free memory used for result */
    ldap_msgfree(result);
    printf("LDAP search suceeded\n");
    ldap_unbind_ext_s(ld, NULL, NULL);
    
    if(strlen(buffer) == 0)
    {
        return 0;
    }
    return ldapTryLoginIntern(buffer, password);
}