// codepage_test — mt_codepage against Microsoft's WindowsBestFit source tables, plus spot checks of the
// characters each shipped 40250 locale needs.
//
// Argument: the directory holding bestfit<cp>.txt (script/gen_codepage_tables.py downloads them to
// build/bestfit). Without it only the spot checks run and the test exits 77 (ctest SKIP), unless
// MT_ASSETS_STRICT=1.
#include "codepage.h"

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <map>
#include <sstream>
#include <string>
#include <vector>

static int g_failures = 0;
#define CHECK(cond)                                                                    \
	do {                                                                               \
		if (!(cond)) {                                                                 \
			std::fprintf(stderr, "%s:%d: CHECK(%s)\n", __FILE__, __LINE__, #cond);     \
			++g_failures;                                                              \
		}                                                                              \
	} while (0)

static std::u32string dec(unsigned cp, const char* bytes, bool* ok = nullptr)
{
	std::u32string out;
	const bool r = mt_codepage::decode(cp, reinterpret_cast<const unsigned char*>(bytes), std::strlen(bytes), out);
	if (ok) *ok = r;
	return out;
}

static std::string enc(unsigned cp, std::u32string in, bool best_fit = false, bool* used_default = nullptr)
{
	std::string out;
	bool used = false;
	mt_codepage::encode(cp, in, out, best_fit, &used);
	if (used_default) *used_default = used;
	return out;
}

static void spot_checks()
{
	// zh (936): "中文" D6D0 CEC4, and the Windows-only single byte 0x80 = euro.
	CHECK(dec(936, "\xd6\xd0\xce\xc4") == U"中文");
	CHECK(enc(936, U"中文") == "\xd6\xd0\xce\xc4");
	CHECK(dec(936, "\x80") == U"€");
	// GBK extension beyond GB2312 (U+4E02 = 81 40), both directions.
	CHECK(dec(936, "\x81\x40") == U"丂");
	CHECK(enc(936, U"丂") == "\x81\x40");
	// A lead byte with nothing after it is one default char and reports failure.
	bool ok = true;
	CHECK(dec(936, "a\xd6", &ok) == U"a?" && !ok);
	// An unmapped pair is consumed whole (932 uses U+30FB as its default).
	CHECK(dec(932, "\x85\x40") == U"・");
	CHECK(dec(932, "\x82\xa0") == U"あ");

	// The shipped European locales.
	CHECK(dec(1252, "\x80\xe9") == U"€é");         // en/de/fr/...: euro, é
	CHECK(dec(1252, "\x81") == U"\u0081");                   // undefined byte keeps its value, as Windows
	CHECK(dec(1250, "\xb9\xb3\x9c") == U"ąłś"); // pl/cz/hu/ro: ą ł ś
	CHECK(dec(1251, "\xc6\xe8") == U"Жи");         // ru: Жи
	CHECK(dec(1253, "\xd9\xe1") == U"Ωα");         // gr: Ωα
	CHECK(dec(1254, "\xf0\xfe\xdd") == U"ğşİ"); // tr: ğ ş İ
	CHECK(enc(1250, U"ąłś") == "\xb9\xb3\x9c");
	CHECK(enc(1251, U"Жи") == "\xc6\xe8");
	CHECK(enc(1253, U"Ωα") == "\xd9\xe1");
	CHECK(enc(1254, U"ğşİ") == "\xf0\xfe\xdd");

	// Best fit only when WC_NO_BEST_FIT_CHARS is absent: 1252 has no "Ā", its best fit is "A".
	bool used = false;
	CHECK(enc(1252, U"Ā", true, &used) == "A" && !used);
	CHECK(enc(1252, U"Ā", false, &used) == "?" && used);
	// Unmapped either way; beyond the BMP too.
	CHECK(enc(1251, U"中", true, &used) == "?" && used);
	CHECK(enc(936, U"\U0001F600", true, &used) == "?" && used);

	CHECK(mt_codepage::is_lead_byte(936, 0x81) && !mt_codepage::is_lead_byte(936, 0x80));
	CHECK(mt_codepage::is_lead_byte(932, 0xe0) && !mt_codepage::is_lead_byte(932, 0xa1));
	CHECK(!mt_codepage::is_lead_byte(1250, 0xb9));
	CHECK(!mt_codepage::supported(65001) && !mt_codepage::supported(437));
}

struct SourceTable {
	unsigned mb_default = 0x3f;
	std::map<unsigned, unsigned> decode;  // bytes (pair = lead << 8 | trail) -> wc
	std::map<unsigned, unsigned> wctable;
	std::vector<std::pair<unsigned, unsigned>> leads;
};

static bool load(const std::string& path, SourceTable& t)
{
	std::ifstream in(path, std::ios::binary);
	if (!in) return false;
	std::string raw, section;
	unsigned lead = 0;
	while (std::getline(in, raw)) {
		std::string line = raw.substr(0, raw.find(';'));
		std::istringstream words(line);
		std::string head;
		if (!(words >> head)) continue;
		if (head == "CPINFO") {
			std::string size, byte_default, wc_default;
			words >> size >> byte_default >> wc_default;
			t.mb_default = unsigned(std::stoul(wc_default, nullptr, 16));
			continue;
		}
		if (head == "MBTABLE" || head == "WCTABLE" || head == "DBCSRANGE") { section = head; continue; }
		if (head == "DBCSTABLE") {
			section = head;
			lead = unsigned(std::stoul(raw.substr(raw.find("0x", raw.find("LeadByte"))), nullptr, 16));
			continue;
		}
		if (head == "ENDCODEPAGE") break;
		if (head.rfind("0x", 0) != 0) continue;
		std::string second;
		words >> second;
		const unsigned a = unsigned(std::stoul(head, nullptr, 16));
		const unsigned b = unsigned(std::stoul(second, nullptr, 16));
		if (raw.find("Lead Byte Range") != std::string::npos) t.leads.push_back({a, b});
		else if (section == "MBTABLE") t.decode[a] = b;
		else if (section == "DBCSTABLE") t.decode[lead << 8 | a] = b;
		else if (section == "WCTABLE") t.wctable[a] = b;
	}
	return !t.decode.empty() && !t.wctable.empty();
}

static std::string bytes_of(unsigned mb)
{
	return mb > 0xff ? std::string{char(mb >> 8), char(mb & 0xff)} : std::string(1, char(mb));
}

// Every byte / pair the source defines decodes to it, every other one to the default char; every
// WCTABLE entry encodes to it with best fit, and without best fit only when it round-trips.
static int against_source(const std::string& dir)
{
	const unsigned cps[] = {874, 932, 936, 949, 950, 1250, 1251, 1252, 1253, 1254, 1255, 1256, 1257, 1258};
	int loaded = 0;
	for (unsigned cp : cps) {
		SourceTable t;
		if (!load(dir + "/bestfit" + std::to_string(cp) + ".txt", t)) continue;
		++loaded;
		const int before = g_failures;
		auto is_lead = [&](unsigned b) {
			for (auto& r : t.leads) if (b >= r.first && b <= r.second) return true;
			return false;
		};
		for (unsigned b = 0; b < 256; ++b) {
			CHECK(mt_codepage::is_lead_byte(cp, (unsigned char)b) == is_lead(b));
			if (is_lead(b)) {
				for (unsigned trail = 1; trail < 256; ++trail) {
					const unsigned char pair[2] = {(unsigned char)b, (unsigned char)trail};
					std::u32string out;
					const bool ok = mt_codepage::decode(cp, pair, 2, out);
					auto it = t.decode.find(b << 8 | trail);
					const unsigned want = it == t.decode.end() ? t.mb_default : it->second;
					if (out.size() != 1 || out[0] != want || ok != (it != t.decode.end())) {
						std::fprintf(stderr, "cp%u %02x%02x -> %x, want %x\n", cp, b, trail,
							out.empty() ? 0 : unsigned(out[0]), want);
						++g_failures;
					}
				}
			} else if (b != 0) {
				const unsigned char one[1] = {(unsigned char)b};
				std::u32string out;
				const bool ok = mt_codepage::decode(cp, one, 1, out);
				auto it = t.decode.find(b);
				const unsigned want = it == t.decode.end() ? t.mb_default : it->second;
				if (out.size() != 1 || out[0] != want || ok != (it != t.decode.end())) {
					std::fprintf(stderr, "cp%u %02x -> %x, want %x\n", cp, b, out.empty() ? 0 : unsigned(out[0]), want);
					++g_failures;
				}
			}
		}
		for (unsigned wc = 1; wc < 0x10000; ++wc) {
			if (wc >= 0xd800 && wc <= 0xdfff) continue;
			auto it = t.wctable.find(wc);
			bool used = false;
			const std::string fit = enc(cp, std::u32string(1, char32_t(wc)), true, &used);
			const std::string want_fit = it == t.wctable.end() ? "?" : bytes_of(it->second);
			const bool exact = it != t.wctable.end() && t.decode.count(it->second) && t.decode[it->second] == wc;
			const std::string strict = enc(cp, std::u32string(1, char32_t(wc)), false);
			const std::string want_strict = exact ? bytes_of(it->second) : "?";
			if (fit != want_fit || used != (it == t.wctable.end()) || strict != want_strict) {
				std::fprintf(stderr, "cp%u U+%04X -> best fit %zu bytes / strict %zu bytes, mismatch\n", cp, wc,
					fit.size(), strict.size());
				++g_failures;
			}
		}
		std::printf("cp%u: %zu byte sequences, %zu WCTABLE entries: %s\n", cp, t.decode.size(), t.wctable.size(),
			g_failures == before ? "ok" : "FAIL");
	}
	return loaded;
}

int main(int argc, char** argv)
{
	spot_checks();
	const char* strict = std::getenv("MT_ASSETS_STRICT");
	const bool is_strict = strict && std::string(strict) == "1";
	const int loaded = argc > 1 ? against_source(argv[1]) : 0;
	if (g_failures) {
		std::fprintf(stderr, "%d failure(s)\n", g_failures);
		return 1;
	}
	if (loaded < 14) {
		std::printf("bestfit sources: %d of 14 found (run script/gen_codepage_tables.py)\n", loaded);
		return is_strict ? 1 : 77;
	}
	std::printf("ok\n");
	return 0;
}