#include "Scraping.h"
#include <curl/curl.h>
#include <libxml/HTMLparser.h>
#include <libxml/xpath.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

typedef struct {
  char *memory;
  size_t size;
} MemoryBuffer;

static size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb,
                                  void *userp) {
  size_t realsize = size * nmemb;
  MemoryBuffer *mem = (MemoryBuffer *)userp;

  char *ptr = (char *)realloc(mem->memory, mem->size + realsize + 1);
  if (ptr == NULL) {
    LOG_ERROR("Not enough memory (realloc returned NULL)");
    return 0;
  }

  mem->memory = ptr;
  memcpy(&(mem->memory[mem->size]), contents, realsize);
  mem->size += realsize;
  mem->memory[mem->size] = 0;

  return realsize;
}

static const char *get_random_user_agent() {
  static const char *agents[] = {
      "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, "
      "like Gecko) Chrome/120.0.0.0 Safari/537.36",
      "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 "
      "(KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36",
      "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like "
      "Gecko) "
      "Chrome/120.0.0.0 Safari/537.36",
      "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 "
      "Firefox/121.0",
      "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 "
      "(KHTML, like Gecko) Version/17.2 Safari/605.1.15"};
  return agents[rand() % 5];
}

static int parse_ddg_lite(const char *engine_name, xmlDocPtr doc,
                          SearchResult **out_results, int max_results) {
  LOG_DEBUG("[%s] Starting XPath parsing...", engine_name);
  int found_count = 0;
  xmlXPathContextPtr xpathCtx = xmlXPathNewContext(doc);
  if (!xpathCtx) {
    LOG_ERROR("[%s] Could not create XPath context", engine_name);
    return 0;
  }

  const char *link_xpath = "//a[@class='result-link']";
  xmlXPathObjectPtr xpathObj =
      xmlXPathEvalExpression((xmlChar *)link_xpath, xpathCtx);

  if (!xpathObj || !xpathObj->nodesetval || xpathObj->nodesetval->nodeNr == 0) {
    LOG_WARN("[%s] No results found with XPath: %s", engine_name, link_xpath);
    if (xpathObj) xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  int num_links = xpathObj->nodesetval->nodeNr;
  LOG_INFO("[%s] XPath matched %d potential result links", engine_name,
           num_links);

  int actual_alloc = (num_links < max_results) ? num_links : max_results;
  *out_results = (SearchResult *)calloc(actual_alloc, sizeof(SearchResult));
  if (!*out_results) {
    LOG_ERROR("[%s] Failed to allocate memory for results", engine_name);
    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  for (int i = 0; i < num_links && found_count < max_results; i++) {
    xmlNodePtr linkNode = xpathObj->nodesetval->nodeTab[i];
    char *title = (char *)xmlNodeGetContent(linkNode);
    char *url = (char *)xmlGetProp(linkNode, (xmlChar *)"href");
    char *snippet_text = NULL;

    xmlNodePtr current = linkNode->parent;
    while (current && xmlStrcasecmp(current->name, (const xmlChar *)"tr") != 0)
      current = current->parent;

    if (current && current->next) {
      xmlNodePtr snippetRow = current->next;
      while (snippetRow &&
             xmlStrcasecmp(snippetRow->name, (const xmlChar *)"tr") != 0)
        snippetRow = snippetRow->next;
      if (snippetRow) {
        xmlXPathContextPtr subCtx = xmlXPathNewContext(doc);
        if (subCtx) {
          subCtx->node = snippetRow;
          xmlXPathObjectPtr sObj = xmlXPathEvalExpression(
              (xmlChar *)".//td[@class='result-snippet']", subCtx);
          if (sObj && sObj->nodesetval && sObj->nodesetval->nodeNr > 0) {
            snippet_text =
                (char *)xmlNodeGetContent(sObj->nodesetval->nodeTab[0]);
          }
          if (sObj) xmlXPathFreeObject(sObj);
          xmlXPathFreeContext(subCtx);
        }
      }
    }

    (*out_results)[found_count].url = strdup(url ? url : "");
    (*out_results)[found_count].title = strdup(title ? title : "No Title");
    (*out_results)[found_count].snippet =
        strdup(snippet_text ? snippet_text : "");

    LOG_DEBUG("[%s] Parsed Result %d: %s", engine_name, found_count + 1,
              (*out_results)[found_count].title);
    found_count++;

    if (title) xmlFree(title);
    if (url) xmlFree(url);
    if (snippet_text) xmlFree(snippet_text);
  }

  xmlXPathFreeObject(xpathObj);
  xmlXPathFreeContext(xpathCtx);
  return found_count;
}

static int parse_startpage(const char *engine_name, xmlDocPtr doc,
                           SearchResult **out_results, int max_results) {
  LOG_DEBUG("[%s] Starting XPath parsing...", engine_name);
  int found_count = 0;
  xmlXPathContextPtr xpathCtx = xmlXPathNewContext(doc);
  if (!xpathCtx) {
    LOG_ERROR("[%s] Could not create XPath context", engine_name);
    return 0;
  }

  const char *container_xpath = "//div[contains(@class, 'result')]";
  xmlXPathObjectPtr xpathObj =
      xmlXPathEvalExpression((xmlChar *)container_xpath, xpathCtx);

  if (!xpathObj || !xpathObj->nodesetval || xpathObj->nodesetval->nodeNr == 0) {
    LOG_WARN("[%s] No result containers found with XPath: %s", engine_name,
             container_xpath);
    if (xpathObj) xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  int num_results = xpathObj->nodesetval->nodeNr;
  LOG_INFO("[%s] Found %d result containers", engine_name, num_results);

  int actual_alloc = (num_results < max_results) ? num_results : max_results;
  *out_results = (SearchResult *)calloc(actual_alloc, sizeof(SearchResult));
  if (!*out_results) {
    LOG_ERROR("[%s] Failed to allocate memory for results", engine_name);
    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  for (int i = 0; i < num_results && found_count < max_results; i++) {
    xmlNodePtr resultNode = xpathObj->nodesetval->nodeTab[i];
    xmlXPathContextPtr resCtx = xmlXPathNewContext(doc);
    if (!resCtx) {
      LOG_ERROR("[%s] Failed to create result context for item %d", engine_name,
                i);
      continue;
    }
    resCtx->node = resultNode;

    xmlXPathObjectPtr linkObj = xmlXPathEvalExpression(
        (xmlChar *)".//a[contains(@class, 'result-link')]", resCtx);
    char *url =
        (linkObj && linkObj->nodesetval && linkObj->nodesetval->nodeNr > 0)
            ? (char *)xmlGetProp(linkObj->nodesetval->nodeTab[0],
                                 (xmlChar *)"href")
            : NULL;

    xmlXPathObjectPtr titleObj = xmlXPathEvalExpression(
        (xmlChar *)".//h2[contains(@class, 'wgl-title')]", resCtx);
    char *title =
        (titleObj && titleObj->nodesetval && titleObj->nodesetval->nodeNr > 0)
            ? (char *)xmlNodeGetContent(titleObj->nodesetval->nodeTab[0])
            : NULL;

    xmlXPathObjectPtr snippetObj = xmlXPathEvalExpression(
        (xmlChar *)".//p[contains(@class, 'description')]", resCtx);
    char *snippet_text =
        (snippetObj && snippetObj->nodesetval &&
         snippetObj->nodesetval->nodeNr > 0)
            ? (char *)xmlNodeGetContent(snippetObj->nodesetval->nodeTab[0])
            : NULL;

    if (url && title) {
      (*out_results)[found_count].url = strdup(url);
      (*out_results)[found_count].title = strdup(title);
      (*out_results)[found_count].snippet =
          strdup(snippet_text ? snippet_text : "");
      LOG_DEBUG("[%s] Parsed Result %d: %s", engine_name, found_count + 1,
                title);
      found_count++;
    } else {
      LOG_WARN("[%s] Container %d missed URL or Title. URL: %s, Title: %s",
               engine_name, i, url ? "Yes" : "No", title ? "Yes" : "No");
    }

    if (title) xmlFree(title);
    if (url) xmlFree(url);
    if (snippet_text) xmlFree(snippet_text);
    if (linkObj) xmlXPathFreeObject(linkObj);
    if (titleObj) xmlXPathFreeObject(titleObj);
    if (snippetObj) xmlXPathFreeObject(snippetObj);
    xmlXPathFreeContext(resCtx);
  }

  xmlXPathFreeObject(xpathObj);
  xmlXPathFreeContext(xpathCtx);
  return found_count;
}

static int parse_yahoo(const char *engine_name, xmlDocPtr doc,
                       SearchResult **out_results, int max_results) {
  LOG_DEBUG("[%s] Starting XPath parsing...", engine_name);
  int found_count = 0;
  xmlXPathContextPtr xpathCtx = xmlXPathNewContext(doc);
  if (!xpathCtx) {
    LOG_ERROR("[%s] Could not create XPath context", engine_name);
    return 0;
  }

  const char *container_xpath = "//div[contains(@class, 'algo-sr')]";
  xmlXPathObjectPtr xpathObj =
      xmlXPathEvalExpression((xmlChar *)container_xpath, xpathCtx);

  if (!xpathObj || !xpathObj->nodesetval || xpathObj->nodesetval->nodeNr == 0) {
    LOG_WARN("[%s] No result containers found with XPath: %s", engine_name,
             container_xpath);
    if (xpathObj) xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  int num_results = xpathObj->nodesetval->nodeNr;
  LOG_INFO("[%s] Found %d result containers", engine_name, num_results);

  int actual_alloc = (num_results < max_results) ? num_results : max_results;
  *out_results = (SearchResult *)calloc(actual_alloc, sizeof(SearchResult));
  if (!*out_results) {
    LOG_ERROR("[%s] Failed to allocate memory for results", engine_name);
    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    return 0;
  }

  for (int i = 0; i < num_results && found_count < max_results; i++) {
    xmlNodePtr resultNode = xpathObj->nodesetval->nodeTab[i];
    xmlXPathContextPtr resCtx = xmlXPathNewContext(doc);
    if (!resCtx) {
      LOG_ERROR("[%s] Failed to create result context for item %d", engine_name,
                i);
      continue;
    }
    resCtx->node = resultNode;

    xmlXPathObjectPtr linkObj = xmlXPathEvalExpression(
        (xmlChar *)".//div[contains(@class, 'compTitle')]//a[@target='_blank']",
        resCtx);
    char *url =
        (linkObj && linkObj->nodesetval && linkObj->nodesetval->nodeNr > 0)
            ? (char *)xmlGetProp(linkObj->nodesetval->nodeTab[0],
                                 (xmlChar *)"href")
            : NULL;

    xmlXPathObjectPtr titleObj = xmlXPathEvalExpression(
        (xmlChar *)".//h3[contains(@class, 'title')]", resCtx);
    char *title =
        (titleObj && titleObj->nodesetval && titleObj->nodesetval->nodeNr > 0)
            ? (char *)xmlNodeGetContent(titleObj->nodesetval->nodeTab[0])
            : NULL;

    xmlXPathObjectPtr snippetObj = xmlXPathEvalExpression(
        (xmlChar *)".//div[contains(@class, 'compText')]//p", resCtx);
    char *snippet_text =
        (snippetObj && snippetObj->nodesetval &&
         snippetObj->nodesetval->nodeNr > 0)
            ? (char *)xmlNodeGetContent(snippetObj->nodesetval->nodeTab[0])
            : NULL;

    if (!url || !title) {
      LOG_DEBUG("[%s] Container %d debug - URL: %s, Title: %s", engine_name, i,
                url ? url : "(null)", title ? title : "(null)");
    }

    if (url && title) {
      (*out_results)[found_count].url = strdup(url);
      (*out_results)[found_count].title = strdup(title);
      (*out_results)[found_count].snippet =
          strdup(snippet_text ? snippet_text : "");
      LOG_DEBUG("[%s] Parsed Result %d: %s", engine_name, found_count + 1,
                title);
      found_count++;
    } else {
      LOG_WARN("[%s] Container %d missed URL or Title. URL: %s, Title: %s",
               engine_name, i, url ? "Yes" : "No", title ? "Yes" : "No");
    }

    if (title) xmlFree(title);
    if (url) xmlFree(url);
    if (snippet_text) xmlFree(snippet_text);
    if (linkObj) xmlXPathFreeObject(linkObj);
    if (titleObj) xmlXPathFreeObject(titleObj);
    if (snippetObj) xmlXPathFreeObject(snippetObj);
    xmlXPathFreeContext(resCtx);
  }

  xmlXPathFreeObject(xpathObj);
  xmlXPathFreeContext(xpathCtx);
  return found_count;
}

const SearchEngine ENGINE_REGISTRY[] = {
    {.name = "DuckDuckGo Lite",
     .base_url = "https://lite.duckduckgo.com/lite/?q=",
     .host_header = "lite.duckduckgo.com",
     .referer = "https://lite.duckduckgo.com/",
     .parser = parse_ddg_lite},
    {.name = "Startpage",
     .base_url = "https://www.startpage.com/sp/search?q=",
     .host_header = "www.startpage.com",
     .referer = "https://www.startpage.com/",
     .parser = parse_startpage},
    {.name = "Yahoo",
     .base_url = "https://search.yahoo.com/search?p=",
     .host_header = "search.yahoo.com",
     .referer = "https://search.yahoo.com/",
     .parser = parse_yahoo}};

const int ENGINE_COUNT = sizeof(ENGINE_REGISTRY) / sizeof(SearchEngine);

int scrape_engine(const SearchEngine *engine, const char *query,
                  SearchResult **out_results, int max_results) {
  CURL *curl;
  MemoryBuffer chunk = {.memory = (char *)malloc(1), .size = 0};
  int results_count = 0;

  LOG_INFO("--- Starting scrape for engine: %s ---", engine->name);
  LOG_INFO("[%s] Query: '%s'", engine->name, query);

  if (!chunk.memory) {
    LOG_ERROR("Initial memory allocation failed");
    return -1;
  }

  curl = curl_easy_init();

  if (curl && query) {
    char full_url[1024];
    char *encoded_query = curl_easy_escape(curl, query, 0);
    if (!encoded_query) {
      LOG_ERROR("[%s] Failed to encode query", engine->name);
      curl_easy_cleanup(curl);
      free(chunk.memory);
      return -1;
    }
    snprintf(full_url, sizeof(full_url), "%s%s", engine->base_url,
             encoded_query);
    curl_free(encoded_query);

    LOG_DEBUG("[%s] Requesting URL: %s", engine->name, full_url);

    struct curl_slist *headers = NULL;
    char host_buf[256], ref_buf[256];
    snprintf(host_buf, sizeof(host_buf), "Host: %s", engine->host_header);
    snprintf(ref_buf, sizeof(ref_buf), "Referer: %s", engine->referer);

    headers = curl_slist_append(headers, host_buf);
    headers = curl_slist_append(headers, ref_buf);
    headers = curl_slist_append(headers,
                                "Accept: "
                                "text/html,application/xhtml+xml,application/"
                                "xml;q=0.9,image/avif,image/webp,*/*;q=0.8");
    headers = curl_slist_append(headers, "Accept-Language: en-US,en;q=0.5");
    headers = curl_slist_append(headers, "DNT: 1");
    headers = curl_slist_append(headers, "Upgrade-Insecure-Requests: 1");
    headers = curl_slist_append(headers, "Sec-Fetch-Dest: document");
    headers = curl_slist_append(headers, "Sec-Fetch-Mode: navigate");
    headers = curl_slist_append(headers, "Sec-Fetch-Site: same-origin");
    headers = curl_slist_append(headers, "Connection: keep-alive");

    curl_easy_setopt(curl, CURLOPT_URL, full_url);
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);

    const char *ua = get_random_user_agent();
    LOG_DEBUG("[%s] Using User-Agent: %s", engine->name, ua);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, ua);

    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 15L);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);

    curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "");

    LOG_DEBUG("[%s] Waiting for rate-limit jitter...", engine->name);
    usleep(500000 + (rand() % 1000000));

    CURLcode res = curl_easy_perform(curl);

    if (res != CURLE_OK) {
      LOG_ERROR("[%s] libcurl error: %s", engine->name,
                curl_easy_strerror(res));
    } else {
      long response_code;
      curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response_code);
      LOG_INFO("[%s] HTTP Response Code: %ld", engine->name, response_code);

      if (chunk.size > 0) {
        xmlDocPtr doc = htmlReadMemory(
            chunk.memory, chunk.size, NULL, NULL,
            HTML_PARSE_RECOVER | HTML_PARSE_NOERROR | HTML_PARSE_NOWARNING);
        if (doc) {
          results_count =
              engine->parser(engine->name, doc, out_results, max_results);
          xmlFreeDoc(doc);
        }
      }
    }

    if (results_count <= 0) {
      LOG_WARN("[%s] No results found. Generating skeleton fallback.",
               engine->name);
      *out_results = (SearchResult *)malloc(sizeof(SearchResult));
      if (*out_results) {
        char fallback_msg[512];
        snprintf(fallback_msg, sizeof(fallback_msg),
                 "Search %s manually for '%s'", engine->name, query);

        (*out_results)[0].title = strdup(fallback_msg);
        (*out_results)[0].url = strdup(full_url);
        (*out_results)[0].snippet = strdup(
            "Automated results were blocked by a Captcha or anti-bot "
            "challenge. Click the link above to perform the search "
            "manually in your browser.");
        results_count = 1;
      }
    }

    curl_slist_free_all(headers);
    curl_easy_cleanup(curl);
  } else {
    if (curl) {
      curl_easy_cleanup(curl);
    }
  }

  free(chunk.memory);

  return results_count;
}