#pragma once

// Copyright (C) Force67 2019

#include <cstdint>
#include <algorithm>
#include <string>
#include <memory>
#include <vector>

namespace utl
{
#ifdef _WIN32
	using native_handle = void*;
#else
	using native_handle = int;
#endif

	enum class fileMode
	{
		read,
		write,
		append,
		create,
		trunc
	};

	enum class seekMode : uint32_t
	{
		seek_set,
		seek_cur,
		seek_end,
	};

	class fileBase
	{
	public:

		virtual ~fileBase() = default;

		virtual void Close() {};
		virtual bool IsOpen() { return true; }
		virtual uint64_t Read(void*, size_t) = 0;
		virtual uint64_t Write(const void*, size_t) = 0;
		virtual uint64_t Seek(int64_t, seekMode) = 0;
		virtual uint64_t Tell() = 0;
		virtual uint64_t GetSize() = 0;
		virtual native_handle GetNativeHandle() = 0;
	};

	class File
	{
		std::unique_ptr<fileBase> file{};

	public:

		File() = default;
		File(const std::string&, fileMode mode = fileMode::read);
		File(const void*, size_t);
		File(std::unique_ptr<fileBase>&&);
		~File();

		// move
		File(File& rhs) :
			file(rhs.GetBase())
		{}

		void Close() {
			if (file)
			    file.reset();
		}

		void Reset(std::unique_ptr<fileBase>&& ptr) {
			file = std::move(ptr);
		}

		inline std::unique_ptr<fileBase> GetBase() {
			return std::move(file);
		}

		inline uint64_t Read(void* ptr, size_t size) { return file->Read(ptr, size); }
		inline uint64_t Write(const void* ptr, size_t size) { return file->Write(ptr, size); }
		inline uint64_t Seek(uint64_t ofs, seekMode mods) { return file->Seek(ofs, mods); }
		inline uint64_t GetSize() { return file->GetSize(); }
		inline uint64_t Tell() { return file->Tell(); }
		inline native_handle GetNativeHandle() { return file->GetNativeHandle(); }
		inline bool IsOpen() { return file->IsOpen(); }
		inline bool Exists() { return file.get(); }

		// POD to std::vector
		template<typename T>
		std::enable_if_t<std::is_pod<T>::value && !std::is_pointer<T>::value, bool> Read(std::vector<T>& vec, std::size_t size)
		{
			vec.resize(size);
			return this->Read(vec.data(), sizeof(T) * size) == sizeof(T) * size;
		}

		// Read POD std::vector, size must be set by resize() method
		template<typename T>
		std::enable_if_t<std::is_pod<T>::value && !std::is_pointer<T>::value, bool> Read(std::vector<T>& vec)
		{
			return this->Read(vec.data(), sizeof(T) * vec.size()) == sizeof(T) * vec.size();
		}

		// Read POD, sizeof(T) is used
		template<typename T>
		std::enable_if_t<std::is_pod<T>::value && !std::is_pointer<T>::value, bool> Read(T& data)
		{
			return Read(&data, sizeof(T)) == sizeof(T);
		}

		// Write POD unconditionally
		template<typename T>
		std::enable_if_t<std::is_pod<T>::value && !std::is_pointer<T>::value, const File&> Write(const T& data)
		{
			Write(std::addressof(data), sizeof(T));
			return *this;
		}

		// Write POD std::vector unconditionally
		template<typename T>
		std::enable_if_t<std::is_pod<T>::value && !std::is_pointer<T>::value, const File&> Write(const std::vector<T>& vec)
		{
			/*if (*/Write(vec.data(), vec.size() * sizeof(T));// != vec.size() * sizeof(T);//) //xfail();
			return *this;
		}
	};

	using FileHandle = std::shared_ptr<File>;

	template <typename T>
	struct ContainerStream final : fileBase
	{
		// T can be a reference, but this is not recommended
		using value_type = typename std::remove_reference_t<T>::value_type;

		T obj;
		uint64_t pos;

		ContainerStream(T&& obj)
			: obj(std::forward<T>(obj))
			, pos(0)
		{
		}

		~ContainerStream() override
		{
		}

		uint64_t Read(void* buffer, uint64_t size) override
		{
			const uint64_t end = obj.size();

			if (pos < end)
			{
				// Get readable size
				if (const uint64_t max = std::min<uint64_t>(size, end - pos))
				{
					std::copy(obj.cbegin() + pos, obj.cbegin() + pos + max, static_cast<value_type*>(buffer));
					pos = pos + max;
					return max;
				}
			}

			return 0;
		}

		uint64_t Write(const void* buffer, uint64_t size) override
		{
			const uint64_t old_size = obj.size();

			if (old_size + size < old_size)
			{
				//fmt::raw_error("fs::container_stream<>::write(): overflow");
			}

			if (pos > old_size)
			{
				// Fill gap if necessary (default-initialized)
				obj.resize(pos);
			}

			const auto src = static_cast<const value_type*>(buffer);

			// Overwrite existing part
			const uint64_t overlap = std::min<uint64_t>(obj.size() - pos, size);
			std::copy(src, src + overlap, obj.begin() + pos);

			// Append new data
			obj.insert(obj.end(), src + overlap, src + size);
			pos += size;

			return size;
		}

		uint64_t Seek(int64_t offset, seekMode whence) override
		{
			const int64_t new_pos =
				whence == seekMode::seek_set ? offset :
				whence == seekMode::seek_cur ? offset + pos :
				whence == seekMode::seek_end ? offset + GetSize() : (0);

			if (new_pos < 0)
			{
				//fs::g_tls_error = fs::error::inval;
				return -1;
			}

			pos = new_pos;
			return pos;
		}

		uint64_t GetSize() override {
			return obj.size();
		}

		native_handle GetNativeHandle() override {
			return nullptr;
		}

		uint64_t Tell() override {
			return pos;
		}
	};

	template <typename T>
	File make_stream(T&& container = T{})
	{
		File result(std::make_unique<ContainerStream<T>>(std::forward<T>(container)));
		return result;
	}
}