#include "asset_source.h"

#include <cstdio>
#include <filesystem>
#include <fstream>

namespace fs = std::filesystem;

namespace mtpack {

bool AssetSource::build(const std::string &assets_root, const std::string &pack_dir,
		const std::string &cache_dir, std::string *err) {
	if (!m_loose.build(assets_root, fmt::AssetResolver::default_priority(), err)) {
		return false;
	}
	if (!pack_dir.empty()) {
		int n = m_packs.scan_dir(pack_dir);
		m_have_packs = n > 0;
		m_cache = !cache_dir.empty()
				? cache_dir
				: (fs::path(pack_dir) / ".mtcache").string();
	}
	return true;
}

bool AssetSource::exists(const std::string &vpath) const {
	if (!m_loose.resolve(vpath).empty()) {
		return true;
	}
	return m_have_packs && m_packs.has(vpath);
}

bool AssetSource::read(const std::string &vpath, std::vector<uint8_t> &out, std::string *err) const {
	std::string lp = m_loose.resolve(vpath);
	if (!lp.empty()) {
		std::ifstream f(lp, std::ios::binary);
		if (f) {
			out.assign((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
			return true;
		}
	}
	if (m_have_packs && m_packs.read(vpath, out, err)) {
		return true;
	}
	if (err && err->empty()) {
		*err = "not found: " + vpath;
	}
	return false;
}

std::string AssetSource::to_path(const std::string &vpath, std::string *err) const {
	std::string lp = m_loose.resolve(vpath);
	if (!lp.empty()) {
		return lp;
	}
	if (!m_have_packs || !m_packs.has(vpath)) {
		if (err) *err = "not found: " + vpath;
		return "";
	}
	// extract to cache/<normalized vpath>, once
	std::string rel = PackMount::norm(vpath);
	fs::path dst = fs::path(m_cache) / rel;
	std::error_code ec;
	if (fs::exists(dst, ec) && fs::file_size(dst, ec) > 0) {
		return dst.string();
	}
	std::vector<uint8_t> bytes;
	if (!m_packs.read(vpath, bytes, err)) {
		return "";
	}
	fs::create_directories(dst.parent_path(), ec);
	std::ofstream o(dst, std::ios::binary | std::ios::trunc);
	if (!o) {
		if (err) *err = "cannot write cache file " + dst.string();
		return "";
	}
	o.write(reinterpret_cast<const char *>(bytes.data()),
			static_cast<std::streamsize>(bytes.size()));
	o.close();
	return dst.string();
}

} // namespace mtpack