ch29.ixx

export module ch29;



import std;



export namespace ch29 {

	namespace exercises {

		namespace ex1 {

			namespace myanswer {

				using namespace std;

				export class NameDB

				{

				public:

					// Reads list of baby names in nameFile to populate the database.

					// Throws invalid_argument if nameFile cannot be opened or read.

					explicit NameDB(const std::string& nameFile);



					// Returns the rank of the name (1st, 2nd, etc).

					// Returns -1 if the name is not found.

					int getNameRank(const std::string& name) const;



					// Returns the number of babies with a given name.

					// Returns -1 if the name is not found.

					int getAbsoluteNumber(const std::string& name) const;



				private:

					std::unordered_map<std::string, int> m_names;

				};

				// Reads the names from the file and populates the database.

				// The database is a map associating names with their frequency.

				NameDB::NameDB(const string& nameFile)

				{

					// Open the file and check for errors.

					ifstream inputFile{ nameFile };

					if (!inputFile) {

						throw invalid_argument{ "Unable to open file" };

					}



					// Read the names one at a time.
					while (!inputFile.eof()) {
						string name;
						getline(inputFile, name);
						m_names[name] += 1;
					}

				}



				// Returns the rank of the name.

				// First looks up the name to obtain the number of babies with that name.

				// Then iterates through all the names, counting all the names with a higher

				// count than the specified name. Returns that count as the rank.

				int NameDB::getNameRank(const string& name) const

				{

					int num{ getAbsoluteNumber(name) };



					// Check if we found the name.

					if (num == -1) {

						return -1;

					}



					// Now count all the names in the map that have?

					// count higher than this one. If no name has a higher count,

					// this name is rank number 1. Every name with a higher count

					// decreases the rank of this name by 1.

					int rank{ 1 };

					for (auto& entry : m_names) {

						if (entry.second > num) {

							++rank;

						}

					}



					return rank;

				}



				// Returns the count associated with the given name.

				int NameDB::getAbsoluteNumber(const string& name) const

				{

					auto res{ m_names.find(name) };

					if (res != end(m_names)) {

						return res->second;

					}



					return -1;

				}



				void test()

				{

					NameDB boys{ "boys_long.txt" };



					println("{}", boys.getNameRank("Daniel"));

					println("{}", boys.getNameRank("Jacob"));

					println("{}", boys.getNameRank("William"));

				}

			}

		}

	}

}