#include "maze32_provisioning_protocol.h"

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

static const char *skip_space(const char *cursor, const char *end)
{
    while (cursor < end && isspace((unsigned char)*cursor)) {
        ++cursor;
    }
    return cursor;
}

static int parse_json_string(const char **cursor_pointer,
                             const char *end,
                             char *output,
                             size_t capacity)
{
    const char *cursor = *cursor_pointer;
    size_t length = 0U;
    if (cursor >= end || *cursor++ != '"') {
        return 0;
    }
    while (cursor < end && *cursor != '"') {
        unsigned char value = (unsigned char)*cursor++;
        if (value == '\\') {
            if (cursor >= end) {
                return 0;
            }
            char escaped = *cursor++;
            if (escaped == '"' || escaped == '\\' || escaped == '/') {
                value = (unsigned char)escaped;
            } else if (escaped == 'b') {
                value = '\b';
            } else if (escaped == 'f') {
                value = '\f';
            } else if (escaped == 'n') {
                value = '\n';
            } else if (escaped == 'r') {
                value = '\r';
            } else if (escaped == 't') {
                value = '\t';
            } else {
                return 0;
            }
        }
        if (value < 0x20U || length + 1U >= capacity) {
            return 0;
        }
        output[length++] = (char)value;
    }
    if (cursor >= end || *cursor++ != '"') {
        return 0;
    }
    output[length] = '\0';
    *cursor_pointer = cursor;
    return 1;
}

int maze32_provisioning_parse_credentials(const char *body,
                                           size_t length,
                                           maze32_wifi_credentials_t *credentials)
{
    if (body == NULL || credentials == NULL) {
        return 0;
    }
    const char *cursor = body;
    const char *end = body + length;
    int have_ssid = 0;
    int have_password = 0;
    memset(credentials, 0, sizeof(*credentials));
    cursor = skip_space(cursor, end);
    if (cursor >= end || *cursor++ != '{') {
        return 0;
    }
    for (int field_index = 0; field_index < 2; ++field_index) {
        char key[12];
        char value[MAZE32_WIFI_PASSWORD_MAX_BYTES + 1U];
        cursor = skip_space(cursor, end);
        if (!parse_json_string(&cursor, end, key, sizeof(key))) {
            return 0;
        }
        cursor = skip_space(cursor, end);
        if (cursor >= end || *cursor++ != ':') {
            return 0;
        }
        cursor = skip_space(cursor, end);
        if (!parse_json_string(&cursor, end, value, sizeof(value))) {
            return 0;
        }
        if (strcmp(key, "ssid") == 0 && !have_ssid &&
            strlen(value) <= MAZE32_WIFI_SSID_MAX_BYTES) {
            memcpy(credentials->ssid, value, strlen(value) + 1U);
            have_ssid = 1;
        } else if (strcmp(key, "password") == 0 && !have_password) {
            memcpy(credentials->password, value, strlen(value) + 1U);
            have_password = 1;
        } else {
            return 0;
        }
        cursor = skip_space(cursor, end);
        if (field_index == 0 && (cursor >= end || *cursor++ != ',')) {
            return 0;
        }
    }
    cursor = skip_space(cursor, end);
    if (cursor >= end || *cursor++ != '}') {
        return 0;
    }
    cursor = skip_space(cursor, end);
    return cursor == end && have_ssid && have_password &&
           maze32_wifi_credentials_validate(credentials) == MAZE32_WIFI_CONFIG_VALID;
}