/* abac_verifier.c */
#include <assert.h>

#include "libabac_common.h"
#include "abac.h"

#include "abac_list.h"
#include "uthash.h"
#include "abac_util.h"

typedef struct _abac_id_cert_t {
    char *keyid; // using cert's keyid
    abac_id_t *cert;

    UT_hash_handle hh;
} abac_id_cert_t;

struct _abac_credential_t {
    abac_role_t *head;
    abac_role_t *tail;
    abac_id_t *issuer; /* Acme of Acme.customer <- Coyote */
    abac_attribute_t *cert;

    int refcount;
};

/* hash table of all the principal id credentials */
abac_id_cert_t *id_certs = NULL;

/***********************************************************************/
// convert a chunk to a lowercase binary string
// malloc's the string
static char *_chunk_to_string(abac_chunk_t chunk) {
    int i;

    char *ret = abac_xmalloc(chunk.len * 2 + 1);

    for (i = 0; i < chunk.len; ++i)
        sprintf(ret + 2 * i, "%02x", chunk.ptr[i]);

    return ret;
}

// verify that cert was issued by issuer
// cert and issuer can be the same, in which case the self-sig is validated
static int _verify_cert(abac_id_t *cert) {

    assert(cert); 
    if(!abac_id_still_valid(cert))
        return 0;
    return 1;
}

/**
 * Init the verifier subsystem.
 */
void abac_verifier_init(void) {
    init_openssl();
    init_xmlsec();
}

/**
 * Uninitialize the system, free up any allocated memory.
 */
void abac_verifier_deinit(void) {
    abac_id_cert_t *id;

    while ((id = id_certs) != NULL) {
        HASH_DEL(id_certs, id);

        free(id->keyid);
        abac_id_free(id->cert);
        free(id);
    }
    deinit_xmlsec();
    deinit_openssl();
}

/**
 * Load an ID certificate.
 */
static int _load_id(abac_id_t *cert) {
    abac_id_cert_t *id_cert = NULL;
    char *keyid = NULL;
    int ret;

    assert(cert);

    // get the key ID
    keyid = abac_id_keyid(cert);

    // if we already have this cert 'error' with success
    HASH_FIND_STR(id_certs, keyid, id_cert);
    if (id_cert != NULL) {
        ret = ABAC_CERT_SUCCESS;
        goto error;
    }

    ret = abac_id_still_valid(cert);
    if (!ret) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // success, add the key to the map of certificates
    id_cert = abac_xmalloc(sizeof(abac_id_cert_t));
    id_cert->keyid = abac_xstrdup(keyid);
    id_cert->cert = cert;
    HASH_ADD_KEYPTR(hh, id_certs, id_cert->keyid, strlen(id_cert->keyid), id_cert);

    return ABAC_CERT_SUCCESS;

error:
    if (keyid != NULL) free(keyid);
    return ret;
}

abac_id_t *abac_verifier_lookup_id(char *keyid)
{
    abac_id_cert_t *id_cert;
    HASH_FIND_STR(id_certs, keyid, id_cert);
    if(id_cert == NULL) return NULL;
    return id_cert->cert;
}

/**
 * Load an ID cert from a file.
 */
int abac_verifier_load_id_file(char *filename) {
    // load the cert
    abac_id_t *cert = abac_id_from_file(filename);

    if (cert == NULL)
        return ABAC_CERT_INVALID;

    return _load_id(cert);
}

/**
 * Load an ID cert from a chunk.
 */
int abac_verifier_load_id_chunk(abac_chunk_t chunk) {

    // load the cert
    abac_id_t *cert= abac_id_from_chunk(chunk);

    if (cert == NULL)
        return ABAC_CERT_INVALID;
    return _load_id(cert);
}

/**
 * Load an attribute cert.
 * Returns true only if the certificate is valid and is issued by the proper
 * authority.
 */
static int _load_attribute_cert(abac_attribute_t *cert, abac_credential_t **cred_ret) {
    abac_role_t *head_role = NULL;
    abac_role_t *tail_role = NULL;
    abac_id_cert_t *issuer=NULL;
    int ret;

    char *attr_string=abac_attribute_role_string(cert);

    if(attr_string == NULL) {
       ret = ABAC_CERT_INVALID;
       goto error;
    }

    // split into head/tail parts
    char *head_tail[2];
    abac_split(attr_string, "<-", head_tail, &ret);
    if (ret != 2) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // must be a role
    head_role = abac_role_from_string(head_tail[0]);
    if (head_role == NULL) goto error;
    if (!abac_role_is_role(head_role)) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    // make sure the tail's valid too
    tail_role = abac_role_from_string(head_tail[1]);
    if (tail_role == NULL) {
        ret = ABAC_CERT_INVALID;
        goto error;
    }

    char *principal = abac_role_principal(head_role);
    HASH_FIND_STR(id_certs, principal, issuer);
    if (issuer == NULL) {
        ret = ABAC_CERT_MISSING_ISSUER;
        goto error;
    }

    // check if issuer is still valid
    if (!abac_id_still_valid(issuer->cert)) {
        ret = ABAC_CERT_INVALID_ISSUER;
        goto error;
    }

    // make sure principal match up with keyid
    if(!abac_id_has_keyid(issuer->cert,principal)) {
        ret = ABAC_CERT_BAD_PRINCIPAL;
        goto error;
    }
    
    // at this point we know we have a good attribute cert
    abac_credential_t *cred = abac_xmalloc(sizeof(abac_credential_t));
    cred->head = head_role;
    cred->tail = tail_role;
    cred->cert = cert;
    /* acme's cert */
    cred->issuer = abac_id_dup(issuer->cert);
    cred->refcount = 1;
    *cred_ret = cred;

    return ABAC_CERT_SUCCESS;

error:
    if (head_role != NULL) abac_role_free(head_role);
    if (tail_role != NULL) abac_role_free(tail_role);

    return ret;
}

static int _load_attribute_certs(abac_list_t *attr_list, abac_list_t *cred_list) {

    int sz=abac_list_size(attr_list);
    abac_credential_t *cred_ret=NULL;
    abac_attribute_t *attr;
    if(sz) { 
        abac_list_foreach(attr_list, attr,
            int ret=_load_attribute_cert(attr, &cred_ret);
            if(ret==ABAC_CERT_SUCCESS) {
                abac_list_add(cred_list, cred_ret);
            }
        );
    }
    return sz;
}

/**
 * Load an attribute cert from a file.
 */
int abac_verifier_load_attribute_cert_file(char *filename, abac_list_t *cred_list) {

    // load the cert
    abac_list_t *attr_list = abac_attribute_certs_from_file(filename);

    if (abac_list_size(attr_list) == 0)
        return ABAC_CERT_INVALID;

    int ret=_load_attribute_certs(attr_list, cred_list);

    if(ret) return ABAC_CERT_SUCCESS;
        return ABAC_CERT_INVALID;
}

/**
 * Load an attribute cert from a chunk.
 */
int abac_verifier_load_attribute_cert_chunk(abac_chunk_t chunk, abac_list_t *cred_list) {

    // load the cert
    abac_list_t *attr_list = abac_attribute_certs_from_chunk(chunk);

    if (abac_list_size(attr_list) == 0)
        return ABAC_CERT_INVALID;
    return _load_attribute_certs(attr_list,cred_list);
}

/**
 * Return the head role.
 */
abac_role_t *abac_credential_head(abac_credential_t *cred) {
    return cred->head;
}

/**
 * Return the tail role.
 */
abac_role_t *abac_credential_tail(abac_credential_t *cred) {
    return cred->tail;
}

/**
 * Return the xml chunk of the attribute cert.
 */
abac_chunk_t abac_credential_attribute_cert(abac_credential_t *cred) {
    assert(cred); assert(cred->cert);
    return abac_attribute_cert(cred->cert);
}

/**
 * Return the chunk of the issuer cert.
 */
abac_chunk_t abac_credential_issuer_cert(abac_credential_t *cred) {
    assert(cred); assert(cred->issuer);
    abac_chunk_t ret= abac_id_in_PEM(cred->issuer);
    return ret;
}

/**
 * Increase the ref count of a credential.
 */
abac_credential_t *abac_credential_dup(abac_credential_t *cred) {
    assert(cred != NULL);

    ++cred->refcount;
    return cred;
}

/**
 * Decrease the reference count of a credential, freeing it when it reaches 0.
 */
void abac_credential_free(abac_credential_t *cred) {
    if (cred == NULL)
        return;

    --cred->refcount;
    if (cred->refcount > 0)
        return;

    abac_role_free(cred->head);
    abac_role_free(cred->tail);
    abac_attribute_free(cred->cert);
    abac_id_free(cred->issuer);

    free(cred);
}