#include <stddef.h>
#include <string.h>

#include "ota_url_policy.h"

#define BANBAN_OTA_LEGACY_URL_PREFIX \
    "http://101.35.224.118:8080/assets/firmware/"
#define BANBAN_OTA_BASE_DOMAIN "talkingq.com"

static int banban_ascii_equal_nocase(const char *left,
                                     const char *right,
                                     size_t length)
{
    size_t i;

    for (i = 0; i < length; ++i) {
        unsigned char a = (unsigned char)left[i];
        unsigned char b = (unsigned char)right[i];

        if (a >= 'A' && a <= 'Z') {
            a = (unsigned char)(a + ('a' - 'A'));
        }
        if (b >= 'A' && b <= 'Z') {
            b = (unsigned char)(b + ('a' - 'A'));
        }
        if (a != b) {
            return 0;
        }
    }

    return 1;
}

static int banban_hostname_is_valid(const char *host, size_t host_length)
{
    size_t i;
    int label_has_character = 0;
    int previous_was_hyphen = 0;

    if (host_length == 0 || host_length > 253) {
        return 0;
    }

    for (i = 0; i < host_length; ++i) {
        unsigned char character = (unsigned char)host[i];

        if ((character >= 'A' && character <= 'Z') ||
            (character >= 'a' && character <= 'z') ||
            (character >= '0' && character <= '9')) {
            label_has_character = 1;
            previous_was_hyphen = 0;
            continue;
        }

        if (character == '-') {
            if (!label_has_character) {
                return 0;
            }
            previous_was_hyphen = 1;
            continue;
        }

        if (character == '.') {
            if (!label_has_character || previous_was_hyphen) {
                return 0;
            }
            label_has_character = 0;
            previous_was_hyphen = 0;
            continue;
        }

        return 0;
    }

    return label_has_character && !previous_was_hyphen;
}

static int banban_host_is_talkingq(const char *host, size_t host_length)
{
    const size_t base_length = sizeof(BANBAN_OTA_BASE_DOMAIN) - 1;

    if (!banban_hostname_is_valid(host, host_length)) {
        return 0;
    }

    if (host_length == base_length) {
        return banban_ascii_equal_nocase(host,
                                         BANBAN_OTA_BASE_DOMAIN,
                                         base_length);
    }

    if (host_length <= base_length + 1 ||
        host[host_length - base_length - 1] != '.') {
        return 0;
    }

    return banban_ascii_equal_nocase(host + host_length - base_length,
                                     BANBAN_OTA_BASE_DOMAIN,
                                     base_length);
}

static int banban_port_is_valid(const char *port, size_t port_length)
{
    size_t i;
    unsigned long value = 0;

    if (port_length == 0 || port_length > 5) {
        return 0;
    }

    for (i = 0; i < port_length; ++i) {
        if (port[i] < '0' || port[i] > '9') {
            return 0;
        }
        value = value * 10 + (unsigned long)(port[i] - '0');
    }

    return value > 0 && value <= 65535;
}

static int banban_path_is_fbf(const char *path)
{
    const char *path_end;
    const char *query;

    if (path == NULL || path[0] != '/' || path[1] == '\0' ||
        strstr(path, "..") != NULL || strchr(path, '\\') != NULL ||
        strchr(path, '#') != NULL) {
        return 0;
    }

    query = strchr(path, '?');
    path_end = query != NULL ? query : path + strlen(path);
    if ((size_t)(path_end - path) < 4) {
        return 0;
    }

    return banban_ascii_equal_nocase(path_end - 4, ".bin", 4);
}

int banban_ota_url_is_allowed(const char *url)
{
    const char *authority;
    const char *path;
    const char *host_end;
    const char *colon;
    const size_t legacy_prefix_length =
        sizeof(BANBAN_OTA_LEGACY_URL_PREFIX) - 1;

    if (url == NULL || url[0] == '\0') {
        return 0;
    }

    if (strncmp(url, BANBAN_OTA_LEGACY_URL_PREFIX,
                legacy_prefix_length) == 0) {
        return banban_path_is_fbf(url + legacy_prefix_length - 1);
    }

    if (strncmp(url, "http://", 7) == 0) {
        authority = url + 7;
    } else if (strncmp(url, "https://", 8) == 0) {
        authority = url + 8;
    } else {
        return 0;
    }

    path = strchr(authority, '/');
    if (path == NULL || path == authority) {
        return 0;
    }

    if (memchr(authority, '@', (size_t)(path - authority)) != NULL) {
        return 0;
    }

    colon = memchr(authority, ':', (size_t)(path - authority));
    host_end = colon != NULL ? colon : path;
    if (!banban_host_is_talkingq(authority,
                                 (size_t)(host_end - authority))) {
        return 0;
    }

    if (colon != NULL &&
        !banban_port_is_valid(colon + 1, (size_t)(path - colon - 1))) {
        return 0;
    }

    return banban_path_is_fbf(path);
}