#pragma once

#include <functional>
#include <string>
#include <pgsql/libpq-fe.h>
#include <cassert>
#include <QString>

#include <codecvt>
#include <memory>

namespace Pgsql {

	const Oid oid_bool = 16;
	const Oid oid_int2 = 21;
	const Oid oid_int4 = 23;
	const Oid oid_int8 = 20;
	const Oid oid_float4 = 700;
	const Oid oid_float8 = 701;
	const Oid oid_numeric = 1700;
	const Oid oid_oid = 26;


	class Connection;
	/*
	This library has multiple layers.

	Layer 1 delivers lowlevel C++ wrappers for the basic libpq functionality. Adding
	automatic resource management.

	*/

//	class ConnectionParams {
//	public:
//		std::string host;
//		std::string hostaddr;
//		unsigned short port = 5432;
//		std::string dbname;
//		std::string user;
//		std::string password;
//		int connect_timeout = -1; ///< -1 omit (ie uses default)
//		std::string application_name;

//	};

	class ErrorDetails {
	public:
		static ErrorDetails createErrorDetailsFromPGresult(const PGresult *res);

		std::string errorMessage;
		std::string state; ///< PG_DIAG_SQLSTATE Error code as listed in	https://www.postgresql.org/docs/9.5/static/errcodes-appendix.html
		std::string severity;
		std::string messagePrimary;
		std::string messageDetail;
		std::string messageHint;
		int statementPosition; ///< First character is one, measured in characters not bytes!
		int internalPosition;
		std::string internalQuery;
		std::string context;
		std::string schemaName;
		std::string tableName;
		std::string columnName;
		std::string datatypeName;
		std::string constraintName;
		std::string sourceFile;
		std::string sourceLine;
		std::string sourceFunction;
	};

	class Value {
	public:
		Value(const char *val, Oid typ)
			: m_val(val), m_typ(typ)
		{}

		QString asQString() const
		{
			return QString::fromUtf8(m_val);
		}

		operator QString() const
		{
			return QString::fromUtf8(m_val);
		}

		operator std::string() const
		{
			return m_val;
		}

		operator short() const
		{
			return (short)std::atoi(m_val);
		}

		operator int() const
		{
			return std::atoi(m_val);
		}

		operator Oid() const
		{
			return operator int();
		}

		operator __int64() const
		{
			return strtoull(m_val, nullptr, 10);
		}

		operator bool() const
		{
			return strcmp(m_val, "t") == 0;
		}

	private:
		const char *m_val;
		Oid m_typ;

	};


	class Result;

	class Row {
	public:
		Row(const Result &result, int row)
			: m_result(result)
			, m_row(row)
		{}

		bool next();
		bool operator==(const Row& rhs)
		{
			return &m_result == &rhs.m_result
					&& m_row == rhs.m_row;
		}

		Value get(int col) const;
		//Value get(const char *colname) const;
		//bool get(int col, QString &s);
	private:
		const Result& m_result;
		int m_row;
	};

	/** Non-copyable but movable wrapper for a postgresql result. */
	class Result {
	public:
		class const_iterator {
		public:
			const_iterator(const Result &r, int rw)
				: m_row(r, rw)
			{}

			const_iterator operator++()
			{
				const_iterator t(*this);
				m_row.next();
				return t;
			}

			const_iterator& operator++(int)
			{
				m_row.next();
				return *this;
			}

			bool operator==(const const_iterator &rhs)
			{
				return m_row == rhs.m_row;
			}

			bool operator!=(const const_iterator &rhs)
			{
				return !operator==(rhs);
			}

			const Row& operator*()
			{
				return m_row;
			}
			const Row& operator->()
			{
				return m_row;
			}

		private:
			Row m_row;
		};

		Result() = default;
		Result(PGresult *result);
		~Result();

		Result(const Result &rhs) = delete;
		Result& operator=(const Result &rhs) = delete;

		Result(Result &&rhs);
		Result& operator=(Result &&rhs);

		operator bool() const;

		ExecStatusType resultStatus();

		std::string getResStatus();

		/** Use this to retrieve an error code when this is an error result
		 *
		 * The possible code are listed in https://www.postgresql.org/docs/9.5/static/errcodes-appendix.html
		 */
		std::string diagSqlState();
		/** Retrieves all the error fields. */
		ErrorDetails diagDetails();

		const_iterator begin() const
		{
			return const_iterator(*this, 0);
		}

		const_iterator end() const
		{
			return const_iterator(*this, getRows());
		}

		int tuplesAffected() const;
		int getRows() const;
		int getCols() const;

		const char* const getColName(int idx) const;

		const char * getVal(int col, int row) const;
		Value get(int col, int row) const;
		Oid type(int col) const;
		bool null(int col, int row) const;


//		iterator begin();
	private:
		PGresult *result = nullptr;
	};


	class Canceller {
	public:
		Canceller() = default;
		Canceller(PGcancel *c);
		Canceller(const Canceller&) = delete;
		Canceller& operator=(const Canceller&) = delete;
		Canceller(Canceller&& rhs);
		Canceller& operator=(Canceller&& rhs);
		~Canceller();

		bool cancel(std::string *error);
	private:
		PGcancel *m_cancel = nullptr;
	};


	class Connection {
	public:
		Connection();
		~Connection();

		Connection(const Connection &rhs) = delete;
		Connection& operator=(const Connection &rhs) = delete;

		Connection(Connection &&rhs);
		Connection& operator=(Connection &&rhs);

//		void connect(const ConnectionParams &params);
		bool connect(const char *params);
		bool connect(const QString &params)
		{
			return connect(params.toUtf8().data());
		}

		bool connectStart(const char *params);

		bool connectStart(const std::string &params)
		{
			return connectStart(params.c_str());
		}

		bool connectStart(const QString &params)
		{
			return connectStart(params.toUtf8().data());
		}
		bool connectStart(const char * const *keywords,
						  const char * const *values);

		PostgresPollingStatusType connectPoll();
		ConnStatusType status();
		int socket();

		void close();
		Canceller getCancel();

		std::string getErrorMessage() const;

		Result query(const char * command);
		Result query(const QString &command)
		{
			return query(command.toUtf8().data());
		}

		bool sendQuery(const char * query);
		bool sendQuery(const std::string &command)
		{
			return sendQuery(command.c_str());
		}
		bool sendQuery(const QString &command)
		{
			return sendQuery(command.toUtf8().data());
		}

		std::shared_ptr<Result> getResult();

		bool consumeInput();
		bool isBusy();

		void setNoticeReceiver(std::function<void(const PGresult *)> callback);
	private:
		PGconn *conn = nullptr;
		std::function<void(const PGresult *)> notifyReceiver;

		static void notifyReceiveFunc(void *arg, const PGresult *result);
	};




	class Field {
	public:

		std::string getName() const;

	private:
		//Tuples tuples;
		int field;
		//

	};

	class Tuples {
	public:
		int getRowCount() const;
		int getColCount() const;

		Field getField(const std::string &fname);
		Field getField(const int idx);

		class const_iterator {
		public:
            const_iterator& operator++();
		};

		void rewind();


	};

	class OkResult: public Result {
	public:
		/** If the result is a data result then returns an interface for processing this data.

		The returned interface remains valid as long as this OkResult exists.
		*/
		Tuples* hasTuples();
	};

//	class ErrorResult: public Result {
//
//	};

//	class ITransaction {
//	public:
//
//		Canceller Query(std::string query,
//			std::function<void(OkResult)> on_success,
//			std::function<void()> on_cancelled,
//			std::function<void(ErrorResult)> on_error);
//
//		Canceller Query(std::string query,
//			std::function<void(OkResult)> on_success,
//			std::function<void()> on_cancelled,
//			std::function<void(ErrorResult)> on_error);
//
//
//		void Rollback(
//			std::function<void(OkResult)> on_success,
//			std::function<void(ErrorResult)> on_error);
//		void Commit(
//			std::function<void(OkResult)> on_success,
//			std::function<void()> on_cancelled,
//			std::function<void(ErrorResult)> on_error);
//
//	};
}