#ifndef POM_HPP_
#define POM_HPP_

#include <exception>
#include <cstdint>
#include <string_view>
#include <memory>
#include <optional>

namespace pom {

class Error: public std::exception {
public:
	~Error();
	std::string_view file() const noexcept;
	uint64_t line() const noexcept;
	std::string_view message() const noexcept;
	const Error *next() const noexcept;
	std::string_view to_string() noexcept;
	/// You should only call this on the first error in an error list.
	/// (This can't be enforced with constness because it needs to
	/// override `std::exception::what`.)
	virtual const char *what() const noexcept override;
private:
	friend class Configuration;
	friend class Parser;
	Error() = delete;
	Error(void *C_error);
	Error(const void *C_error);
	void *C;
	bool m_is_original;
	std::unique_ptr<const Error> m_next;
};

class Allocator {
public:
	virtual ~Allocator() = 0;
	virtual void *calloc(size_t, size_t) = 0;
	virtual void *realloc(void *, size_t) = 0;
	virtual void free(void *) = 0;
};

class Settings {
public:
	Settings();
	/// Set allocator.
	void set_allocator(std::shared_ptr<Allocator> allocator) {
		m_allocator = allocator;
	}
	void set_error_language(std::string_view lang);
private:
	void to_C(void *C) const;
	friend class Configuration;
	char m_error_lang[16] = {};
	std::shared_ptr<Allocator> m_allocator;
	uint32_t version = 1; // future-proofing
};

class Reader {
public:
	virtual size_t read(char *buf, size_t count) = 0;
};

class Configuration {
public:
	Configuration();
	~Configuration();
	std::optional<std::string_view> get(std::string_view key) const;
	std::string_view get_or_default(std::string_view key, std::string_view dflt) const;
	Configuration section(std::string_view name) const;
	void merge(const Configuration &other);
	static Configuration load(std::string_view filename, Reader &source, const Settings *settings = nullptr);
	static Configuration load(std::string_view filename, std::istream &stream, const Settings *settings = nullptr);
	static Configuration load(std::string_view path, const Settings *settings = nullptr);
	static Configuration load(std::string_view filename, std::string_view string, const Settings *settings = nullptr);
private:
	explicit Configuration(void *c);
	void *C;
};




} // namespace pom

#endif // POM_HPP_