#include <algorithm>
#include <windows.h>
#include <wininet.h>
#include <libxml/HTMLparser.h>
#include <libxml/HTMLtree.h>
#include <libxml/xpath.h>

#include "data.h"

struct InternetFile
{
	InternetFile(const wchar_t* url);
	~InternetFile();
	DWORD Read(void* buf, DWORD cb);
	HINTERNET hi;
	HINTERNET hiUrl;
};

InternetFile::InternetFile(const wchar_t* url)
{
	hi = InternetOpen(L"Episode Browser",
	    INTERNET_OPEN_TYPE_DIRECT, nullptr, nullptr,
	    /*INTERNET_FLAG_ASYNC*/0);
	if (!hi)
		throw Win32Error{};

	hiUrl = InternetOpenUrl(hi, url,
	    nullptr, 0, INTERNET_FLAG_NO_UI, 0);
	if (!hiUrl) {
		InternetCloseHandle(hi);
		throw Win32Error{};
	}
}

InternetFile::~InternetFile()
{
	InternetCloseHandle(hiUrl);
	InternetCloseHandle(hi);
}

DWORD InternetFile::Read(void* buf, DWORD cb)
{
	DWORD cbRead;
	if (InternetReadFile(hiUrl, buf, cb, &cbRead))
		return cbRead;
	else
		throw Win32Error{};
}

template <auto F, typename T>
struct XmlPtr
{
	XmlPtr(T v) : v(v)
	{
		if (!v)
			throw std::runtime_error(xmlGetLastError()->message);
	}
	~XmlPtr() { F(v); }
	operator T() { return v; }
	T operator ->() { return v; }
private:
	T v;
};

using HtmlParserCtxtPtr = XmlPtr<xmlFreeParserCtxt, htmlParserCtxtPtr>;
using HtmlDocPtr = XmlPtr<xmlFreeDoc, htmlDocPtr>;
using XmlXPathContextPtr = XmlPtr<xmlXPathFreeContext, xmlXPathContextPtr>;
using XmlXPathObjectPtr = XmlPtr<xmlXPathFreeObject, xmlXPathObjectPtr>;
static inline void XmlFree(void* p) { xmlFree(p); }
using XmlCharPtr = XmlPtr<XmlFree, xmlChar*>;

template <size_t N>
bool WcharsFromXmlchars(wchar_t (&dst)[N], XmlCharPtr utf8)
{
	/* Truncate if source is larger than destination. */
	int lenUtf8 = xmlStrlen(utf8);
	utf8[std::min(N, static_cast<size_t>(lenUtf8))] = 0;

	/* Convert internal representation from UTF-8 to Latin-1,
	 * which seems to actually convert the string to proper UTF-8
	 * (???). */
	unsigned char lat1[N];
	int lenLat1 = N-1;
	if (UTF8Toisolat1(lat1, &lenLat1, utf8, &lenUtf8) <= 0)
		return false;
	lat1[lenLat1] = 0;

	/* Write wide string to destination, if it fits. */
	char* const src = reinterpret_cast<char*>(lat1);
	const int cchNarrow = lenLat1+1;
	const int cchWide = MultiByteToWideChar(CP_UTF8, 0, src, cchNarrow, nullptr, 0);
	if (static_cast<size_t>(cchWide) > N)
		return false;
	return MultiByteToWideChar(CP_UTF8, 0, src, cchNarrow, dst, cchWide);
}

void FetchData(bool* bDone)
{
	LIBXML_TEST_VERSION;

	InternetFile inf{L"https://www.detectiveconanworld.com/wiki/Anime"};
	//InternetFile inf{L"file://C:/Users/John/Desktop/dcw.html"};
	char buf[1024];

	HtmlParserCtxtPtr ctxt = htmlCreatePushParserCtxt(nullptr, nullptr,
	    buf, sizeof(buf), "https://www.detectiveconanworld.com/wiki/Anime",
	    XML_CHAR_ENCODING_UTF8);

	htmlCtxtUseOptions(ctxt, HTML_PARSE_RECOVER|HTML_PARSE_NOERROR|HTML_PARSE_NOWARNING);

	while (const DWORD cbRead = inf.Read(&buf, sizeof(buf))) {
		if (!htmlParseChunk(ctxt, buf, cbRead, 0))
			throw std::runtime_error(xmlGetLastError()->message);
	}
	htmlParseChunk(ctxt, buf, 0, 1); /* Stop parsing. */

	/* Find table rows containing episode data. */
	HtmlDocPtr doc = ctxt->myDoc;
	XmlXPathContextPtr xpathCtx = xmlXPathNewContext(doc);
	XmlXPathObjectPtr xpathObj = xmlXPathEvalExpression(
	    reinterpret_cast<const xmlChar*>("//tr[./td[1] != '' and ./td[3][@style='background:#f2fde9;']]"),
	    xpathCtx);
	xmlNodeSetPtr nodes = xpathObj->nodesetval;
	int cNodes = nodes? nodes->nodeNr: 0;

	printf("%d nodes\n", cNodes);
	for (int i = 0; i < cNodes; i++) {
		extern FileView<ElvDataA> g_fvElv;
		extern FileView<DlvDataA> g_fvDlv;

		const xmlNodePtr node = nodes->nodeTab[i];
		if (xmlChildElementCount(node) != 8)
			throw std::runtime_error("unexpected remote data format");

		ElvDataA& e = g_fvElv.At(i);
		DlvDataA& d = g_fvDlv.At(i);

		/* Get cells. */
		const xmlNodePtr nodeEp = xmlFirstElementChild(node);
		const xmlNodePtr nodeTitle = xmlNextElementSibling(xmlNextElementSibling(nodeEp));
		const xmlNodePtr nodeDate = xmlNextElementSibling(nodeTitle);
		const xmlNodePtr nodeSource = xmlNextElementSibling(
		    xmlNextElementSibling(xmlNextElementSibling(nodeDate)));
		const xmlNodePtr nodeHint = xmlNextElementSibling(nodeSource);

		WcharsFromXmlchars(e.siEp, xmlNodeGetContent(nodeEp));
		e.siEp[wcscspn(e.siEp, L"W")] = 0; /* Remove WPS suffix. */
		WcharsFromXmlchars(e.title, xmlNodeGetContent(nodeTitle));
		WcharsFromXmlchars(d.date, xmlNodeGetContent(nodeDate));
		WcharsFromXmlchars(d.source, xmlNodeGetContent(nodeSource));
		WcharsFromXmlchars(d.hint, xmlNodeGetContent(nodeHint));

		/* Get wiki URL. */
		const xmlNodePtr nodeLink = xmlFirstElementChild(nodeTitle);
		if (nodeLink)
			WcharsFromXmlchars(d.wiki, xmlGetProp(nodeLink, (const xmlChar*)"href"));
	}

	*bDone = true;
}