#include <assert.h>
#include <ctype.h>
#include <string.h>
#include <time.h>

#include "libcreddy_common.h"

#define ROLE_SEPARATOR " <- "
#define INTERSECTION_SEP " & "
#define SHA1_LENGTH 40

struct _creddy_attribute_t {
    creddy_id_t *issuer;
    char *role;
    int validity;

    char **subject;
    int num_subjects;
    int size_subjects;
    int total_len; // total length of all subject strings

    certificate_t *cert; // NULL until baked
};

static char *_validate_principal(char *keyid);
static void _append(creddy_attribute_t *attr, char *subject);
char *_get_role_encoding(creddy_attribute_t *attr);

// validity is measured in seconds (as of 0.2.0)
int creddy_attribute_create(creddy_attribute_t **ret, creddy_id_t *issuer, char *role, int validity) {
    if (creddy_id_privkey(issuer) == NULL)
        return CREDDY_ATTRIBUTE_ISSUER_NOKEY;
    if (!creddy_clean_name(role))
        return CREDDY_ATTRIBUTE_INVALID_ROLE;
    if (validity < 0)
        return CREDDY_ATTRIBUTE_INVALID_VALIDITY;

    creddy_attribute_t *attr = creddy_xmalloc(sizeof(creddy_attribute_t));
    attr->issuer = creddy_id_dup(issuer);
    attr->role = creddy_xstrdup(role);
    attr->validity = validity;

    attr->num_subjects = 0;
    attr->size_subjects = 4;
    attr->subject = creddy_xmalloc(sizeof(char *) * attr->size_subjects);
    attr->total_len = 0;

    // NULL until baked
    attr->cert = NULL;

    *ret = attr;
    return CREDDY_SUCCESS;
}

int creddy_attribute_principal(creddy_attribute_t *attr, char *keyid) {
    char *copy = _validate_principal(keyid);
    if (copy == NULL)
        return 0;

    _append(attr, copy);
    return 1;
}

int creddy_attribute_role(creddy_attribute_t *attr, char *keyid, char *role) {
    if (!creddy_clean_name(role))
        return 0;

    char *copy = _validate_principal(keyid);
    if (copy == NULL)
        return 0;

    int len = strlen(copy) + strlen(role) + strlen(ROLE_SEPARATOR) + 1;
    copy = creddy_xrealloc(copy, len);
    strcat(copy, ".");
    strcat(copy, role);

    _append(attr, copy);
    return 1;
}

int creddy_attribute_linking_role(creddy_attribute_t *attr, char *keyid, char *role, char *linked) {
    if (!creddy_clean_name(role) || !creddy_clean_name(linked))
        return 0;

    char *copy = _validate_principal(keyid);
    if (copy == NULL)
        return 0;

    int len = strlen(copy) + strlen(role) + strlen(linked) + strlen(ROLE_SEPARATOR) + 2;
    copy = creddy_xrealloc(copy, len);
    strcat(copy, ".");
    strcat(copy, role);
    strcat(copy, ".");
    strcat(copy, linked);

    _append(attr, copy);
    return 1;
}

int creddy_attribute_bake(creddy_attribute_t *attr) {
    if (attr->num_subjects == 0)
        return 0;

    libabac_init();

    char *role_encoding = _get_role_encoding(attr);

    // create attribute cert
    time_t not_before = time(NULL);
    time_t not_after = not_before + attr->validity;
    chunk_t serial = creddy_generate_serial();

    certificate_t *attr_cert = lib->creds->create(lib->creds,
        CRED_CERTIFICATE, CERT_X509_AC,
        BUILD_CERT, creddy_id_cert(attr->issuer),
        BUILD_NOT_BEFORE_TIME, not_before,
        BUILD_NOT_AFTER_TIME, not_after,
        BUILD_SERIAL, serial,
        BUILD_IETF_GROUP_ATTR, role_encoding,
        BUILD_SIGNING_CERT, creddy_id_cert(attr->issuer),
        BUILD_SIGNING_KEY, creddy_id_privkey(attr->issuer),
        BUILD_END
    );
    if (attr_cert == NULL)
        return 0;

    attr->cert = attr_cert;

    free(role_encoding);
    free(serial.ptr);
    return 1;
}

int creddy_attribute_cert_chunk(creddy_attribute_t *attr, abac_chunk_t *chunk) {
    if (attr->cert == NULL)
        return 0;

    chunk_t encoding = attr->cert->get_encoding(attr->cert);
    chunk->ptr = encoding.ptr; chunk->len = encoding.len;
    return 1;
}

int creddy_attribute_baked(creddy_attribute_t *attr) {
    return attr->cert != NULL;
}

// returns 0 if the cert hasn't been baked
int creddy_attribute_write(creddy_attribute_t *attr, FILE *out) {
    assert(attr != NULL);

    if (attr->cert == NULL)
        return 0;

    // write to file
    chunk_t encoding = attr->cert->get_encoding(attr->cert);
    fwrite(encoding.ptr, encoding.len, 1, out);
    free(encoding.ptr);

    return 1;
}

void creddy_attribute_free(creddy_attribute_t *attr) {
    int i;

    if (attr == NULL)
        return;

    creddy_id_free(attr->issuer);
    free(attr->role);
    DESTROY_IF(attr->cert);

    // free all the subjects
    for (i = 0; i < attr->num_subjects; ++i)
        free(attr->subject[i]);
    free(attr->subject);

    free(attr);
}

//
// Helper functions below
//

// validate a princpal's name
// makes sure it's a valid SHA1 identifier
// return values:
//  success: malloc'd copy with all hex digits lowercase
//  fail: NULL
static char *_validate_principal(char *keyid) {
    int i;
    char *copy = NULL;

    if (strlen(keyid) != SHA1_LENGTH)
        return NULL;

    copy = creddy_xstrdup(keyid);
    for (i = 0; i < SHA1_LENGTH; ++i) {
        copy[i] = tolower(copy[i]);
        if (!isxdigit(copy[i]))
            goto error;
    }

    return copy;

error:
    free(copy);
    return NULL;
}

static void _append(creddy_attribute_t *attr, char *subject) {
    // expand the array if necessary
    if (attr->num_subjects == attr->size_subjects) {
        attr->size_subjects *= 2;
        attr->subject = creddy_xrealloc(attr->subject, attr->size_subjects * sizeof(creddy_attribute_t));
    }

    attr->subject[attr->num_subjects++] = subject;
    attr->total_len += strlen(subject);
}

char *_get_role_encoding(creddy_attribute_t *attr) {
    int i, num_subjects;

    num_subjects = attr->num_subjects;

    int len = SHA1_LENGTH + 1 + strlen(attr->role) + strlen(ROLE_SEPARATOR);
    len += attr->total_len + num_subjects * strlen(INTERSECTION_SEP);

    char *encoding = creddy_xmalloc(len);
    sprintf(encoding, "%s.%s" ROLE_SEPARATOR, creddy_id_keyid(attr->issuer), attr->role);

    for (i = 0; i < num_subjects; ++i) {
        strcat(encoding, attr->subject[i]);
        if (i < num_subjects - 1)
            strcat(encoding, INTERSECTION_SEP);
    }

    return encoding;
}