using Npgsql;
using Backend.Interface;

namespace Backend.DatabaseHandler;

public sealed class PostgresUserInterestStore : IUserInterestStore
{
	private readonly string _connectionString;

	public PostgresUserInterestStore(IConfiguration configuration)
	{
		_connectionString = configuration.GetConnectionString("MarketDataDb")
			?? throw new InvalidOperationException("Missing connection string: MarketDataDb");
	}

	public async Task<List<string>> FetchAllAsync(string user, string type)
	{
		ValidateUser(user);

		string normalizedType = NormalizeType(type);
		string sql = normalizedType == "symbol"
			? """
			  SELECT symbol
			  FROM user_interest_symbols
			  WHERE username = @user
			  ORDER BY symbol ASC;
			  """
			: """
			  SELECT topic
			  FROM user_interest_topics
			  WHERE username = @user
			  ORDER BY topic ASC;
			  """;

		var results = new List<string>();

		await using var conn = new NpgsqlConnection(_connectionString);
		await conn.OpenAsync();

		await using var cmd = new NpgsqlCommand(sql, conn);
		cmd.Parameters.AddWithValue("user", user.Trim());

		await using var reader = await cmd.ExecuteReaderAsync();
		while (await reader.ReadAsync())
		{
			results.Add(reader.GetString(0));
		}

		return results;
	}

	public async Task<List<string>> FetchAllDistinctValuesAsync(CancellationToken cancellationToken = default)
	{
		const string sql = """
			SELECT symbol AS value FROM user_interest_symbols
			UNION
			SELECT topic AS value FROM user_interest_topics;
			""";

		var results = new List<string>();

		await using var conn = new NpgsqlConnection(_connectionString);
		await conn.OpenAsync(cancellationToken);

		await using var cmd = new NpgsqlCommand(sql, conn);
		await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
		while (await reader.ReadAsync(cancellationToken))
		{
			results.Add(reader.GetString(0));
		}

		return results;
	}

	public async Task<bool> AddAsync(string user, string type, string value)
	{
		ValidateUser(user);
		ValidateValue(value);

		string normalizedType = NormalizeType(type);
		string normalizedValue = normalizedType == "symbol"
			? value.Trim().ToUpperInvariant()
			: value.Trim();

		string sql = normalizedType == "symbol"
			? """
			  INSERT INTO user_interest_symbols (username, symbol)
			  VALUES (@user, @value)
			  ON CONFLICT (username, symbol) DO NOTHING;
			  """
			: """
			  INSERT INTO user_interest_topics (username, topic)
			  VALUES (@user, @value)
			  ON CONFLICT (username, topic) DO NOTHING;
			  """;

		await using var conn = new NpgsqlConnection(_connectionString);
		await conn.OpenAsync();

		await using var cmd = new NpgsqlCommand(sql, conn);
		cmd.Parameters.AddWithValue("user", user.Trim());
		cmd.Parameters.AddWithValue("value", normalizedValue);

		int rows = await cmd.ExecuteNonQueryAsync();
		return rows > 0;
	}

	public async Task<bool> RemoveAsync(string user, string type, string value)
	{
		ValidateUser(user);
		ValidateValue(value);

		string normalizedType = NormalizeType(type);
		string normalizedValue = normalizedType == "symbol"
			? value.Trim().ToUpperInvariant()
			: value.Trim();

		string sql = normalizedType == "symbol"
			? """
			  DELETE FROM user_interest_symbols
			  WHERE username = @user AND symbol = @value;
			  """
			: """
			  DELETE FROM user_interest_topics
			  WHERE username = @user AND topic = @value;
			  """;

		await using var conn = new NpgsqlConnection(_connectionString);
		await conn.OpenAsync();

		await using var cmd = new NpgsqlCommand(sql, conn);
		cmd.Parameters.AddWithValue("user", user.Trim());
		cmd.Parameters.AddWithValue("value", normalizedValue);

		int rows = await cmd.ExecuteNonQueryAsync();
		return rows > 0;
	}

	private static string NormalizeType(string type)
	{
		string normalized = type.Trim().ToLowerInvariant();
		return normalized switch
		{
			"symbol" => "symbol",
			"topic" => "topic",
			_ => throw new ArgumentException("Type must be either 'symbol' or 'topic'.")
		};
	}

	private static void ValidateUser(string user)
	{
		if (string.IsNullOrWhiteSpace(user))
		{
			throw new ArgumentException("User cannot be empty.");
		}
	}

	private static void ValidateValue(string value)
	{
		if (string.IsNullOrWhiteSpace(value))
		{
			throw new ArgumentException("Value cannot be empty.");
		}
	}
}