#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <curl/curl.h>

#include "http.h"
#include "util.h"

#define INIT_PAGE_SIZE 8192
#define MAX_PAGE_SIZE 1048576
#define MEM_INC_FACTOR 2

#define TIMEOUT_MS 10000
#define CONNECT_TIMEOUT_MS 3000

const char *useragents[] = {
    "AvaBot",
    NULL,
};

size_t bufwritecb(const byte *ptr, size_t size, size_t nmemb, writecb_data_t *userdata) {
    for (size_t i = 0; i < userdata->modules->len; i++) {
        if (userdata->modules->data[i]->module.onpagewrite != NULL) {
            int rc;
            rc = userdata->modules->data[i]->module.onpagewrite(
                    userdata->modules->data[i]->module.userdata, userdata->url, ptr, nmemb);
            if (rc != 0)
                error("module %s onpagewrite failed with code %d", userdata->modules->data[i]->name);
        }
    }
    size_t len = nmemb;
    while (userdata->begin + nmemb + 1 > userdata->end) {
        // Buffer is undersized
        size_t buf_len = userdata->end - userdata->base;
        if (buf_len >= MAX_PAGE_SIZE)
            break;
        size_t new_buf_len = buf_len * MEM_INC_FACTOR;
        if (new_buf_len > MAX_PAGE_SIZE)
            new_buf_len = MAX_PAGE_SIZE;
        byte *new_base = xrealloc(userdata->base, new_buf_len);
        userdata->end = new_base + new_buf_len;
        userdata->begin = new_base + (userdata->begin - userdata->base);
        userdata->base = new_base;
    }
    if (userdata->begin + nmemb + 1 > userdata->end)
        // Buffer is still undersized
        len = userdata->end - userdata->begin;
    memcpy(userdata->begin, ptr, len);
    userdata->begin[len] = '\0';
    userdata->begin += len;
    return len;
}

bool is_redirect(int status) {
    return status == 301 || // Moved Permanently
        status == 302 ||    // Found
        status == 307 ||    // Temporary Redirect
        status == 308;      // Permanent Redirect
}

size_t headerwritecb(const char *buffer, size_t _size, size_t nitems, headercb_data_t *userdata) {
    const char content_type_str[] = "content-type:", html_mime_str[] = "text/html", http_str[] = "HTTP/";
    // Parses HTTP status line
    if (nitems < sizeof(http_str) - 1)
        return nitems;
    if (memcmp(buffer, http_str, sizeof(http_str) - 1) == 0) { 
        // Header is an http status line
        userdata->num_requests++;
        const char *status_line = memchr(buffer, ' ', nitems);
        for (; *status_line == ' '; status_line++) {
            // Ensures that status_line...(buffer+nitems) can fit a status code (3 numbers)
            if (status_line > buffer + nitems - 3) {
                userdata->status = 0;
                return CURL_WRITEFUNC_ERROR;
            }
        }
        char code_str[4] = { status_line[0], status_line[1], status_line[2], '\0' };
        userdata->status = atoi(code_str);
        if (userdata->status == 200 || is_redirect(userdata->status))
            return nitems;
        return CURL_WRITEFUNC_ERROR;
    }
    if (userdata->status == 0 || is_redirect(userdata->status))
        return nitems;
    // Parses Content-Type header
    if (userdata->flags & HEADERCB_CONTENT_TYPE_ENCOUNTERED)
        return nitems;
    // We need an extra byte to plop header_val to the byte after the ':'
    if (nitems < sizeof(content_type_str))
        return nitems;
    for (size_t i = 0; i < sizeof(content_type_str)-1; i++)
        if (tolower(buffer[i]) != content_type_str[i])
            return nitems;
    const char *header_val = buffer + sizeof(content_type_str);
    for (; *header_val == ' '; header_val++)
        // Ensures that header_val..(buffer+nitems) can fit "text/html"
        if (header_val > buffer + nitems - sizeof(html_mime_str) + 1)
            return nitems;
    userdata->flags |= HEADERCB_CONTENT_TYPE_ENCOUNTERED;
    if (memcmp(header_val, html_mime_str, sizeof(html_mime_str)-1) != 0)
        return CURL_WRITEFUNC_ERROR;
    userdata->flags |= HEADERCB_VALID_MIME;
    return nitems;
}

void initcbdata(const char *url, moduleentryp_dynarr_t *modules, cbdata_t *data) {
    memset(data, 0, sizeof(cbdata_t));
    data->writecb_data.base = xmalloc(INIT_PAGE_SIZE);
    data->writecb_data.begin = data->writecb_data.base;
    data->writecb_data.end = data->writecb_data.base + INIT_PAGE_SIZE;
    data->writecb_data.url = url;
    data->writecb_data.modules = modules;
}

CURL *makehandle(const char *url, hostentry_t *host_entry, cbdata_t *cbdata, bool wasrequested) {
    CURL *curl_h = curl_easy_init();
    CURLcode easy_res;
    if (curl_h == NULL) {
        error("curl failed to initialize\n");
        return NULL;
    }
    if (/* 1MiB/s max send speed */
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_MAX_SEND_SPEED_LARGE, 1024 * 1024)) != CURLE_OK || 
        /* 1MiB/s max recv speed */
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_MAX_RECV_SPEED_LARGE, 1024 * 1024)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_TIMEOUT_MS, TIMEOUT_MS)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_CONNECTTIMEOUT_MS, CONNECT_TIMEOUT_MS)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_FOLLOWLOCATION, 1)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_MAXREDIRS, 3)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_HTTPHEADER, host_entry->headers)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_PROTOCOLS_STR, "http,https")) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_WRITEFUNCTION, bufwritecb)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_WRITEDATA, &cbdata->writecb_data)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_URL, url) != CURLE_OK)) {
        error("curl setopt failed: %s (code %d)\n", curl_easy_strerror(easy_res), easy_res);
        curl_easy_cleanup(curl_h);
        return NULL;
    }

    if (!wasrequested &&
        ((easy_res = curl_easy_setopt(curl_h, CURLOPT_HEADERFUNCTION, headerwritecb)) != CURLE_OK ||
        (easy_res = curl_easy_setopt(curl_h, CURLOPT_HEADERDATA, &cbdata->headercb_data)) != CURLE_OK)) {
        error("curl setopt failed: %s (code %d)\n", curl_easy_strerror(easy_res), easy_res);
        curl_easy_cleanup(curl_h);
        return NULL;
    }
    return curl_h;
}