namespace EMQual;

public static class QualData
{
    /// <summary>
    ///     Executes the <see cref="QualData"/> program.
    /// </summary>
    public static void Run()
    {
        var matches = ReadMatchesFromFile("Data/matches.csv");
        PrintMatches(matches);
        Console.WriteLine();

        var countryNames = ExtractUniqueCountryNames(matches);
        var selCountry = AskForCountry(countryNames);
        var countryMatches = FilterMatchesByCountry(matches, selCountry);
        PrintMatches(countryMatches);
    }

    /// <summary>
    ///     Reads match information from a CSV file at the provided location.
    ///     If the file does not exist or does not contain relevant or some
    ///     corrupted data an empty array is returned.
    /// </summary>
    /// <param name="filePath">The relative path to the CSV file</param>
    /// <returns>An array containing parsed match data records</returns>
    public static Match[] ReadMatchesFromFile(string filePath)
    {
        if (!File.Exists(filePath))
        {
            return Array.Empty<Match>();
        }

        string[] lines = File.ReadAllLines(filePath);
        lines = lines.Skip(1).ToArray();
        if (lines.Length == 0)
        {
            return Array.Empty<Match>();
        }
        
        int index = 0;
        Match[] matches = new Match[lines.Length];
        foreach(var line in lines)
        {
            if (TryParseMatch(line, out Match? match))
            {
                matches[index++] = match!;
            }
            else
            {
                return Array.Empty<Match>();
            }
        }
        
        return matches;
        
        //again, would be much easier with a list
        /*var matches = new List<Match>();
        foreach (var line in lines)
        {
            if (TryParseMatch(line, out Match? match))
            {
                matches.Add(match!);
            }
            else
            {
                return Array.Empty<Match>();
            }
        }
        return matches.ToArray();*/
    }

    /// <summary>
    ///     Attempts to parse a line with semicolon separated data for a match.
    /// </summary>
    /// <param name="line">Line to parse</param>
    /// <param name="match">Parsed match object; null if parsing fails</param>
    /// <returns>True if the line could be parsed successfully; false otherwise</returns>
    public static bool TryParseMatch(string line, out Match? match)
    {
        match = null;
        
        string[] parts = line.Split(';');
        if (parts.Length != 4)
        {
            return false;
        }

        foreach (var part in parts)
        {
            if (part.Length == 0)
            {
                return false;
            }
        }

        int[] goals = new int[2];
        if (!int.TryParse(parts[2], out goals[0]) || !int.TryParse(parts[3], out goals[1]))
        {
            return false;
        }
        if(goals[0] < 0 || goals[1] < 0)
        {
            return false;
        }
        
        match = new Match(new TeamResult(parts[0], goals[0]), new TeamResult(parts[1], goals[1]));
        return true;
    }

    /// <summary>
    ///     Determines if the supplied string is contained in the provided array of strings.
    ///     Case is ignored.
    /// </summary>
    /// <param name="value">Value to check for</param>
    /// <param name="possibleValues">Array of values to check in</param>
    /// <returns>True if the value is found; false otherwise</returns>
    public static bool IsContained(string value, string[] possibleValues)
    {
        foreach (var possibleValue in possibleValues)
        {
            if (string.Equals(possibleValue, value, StringComparison.InvariantCultureIgnoreCase))
            {
                return true;
            }
        }

        return false;
    }

    /// <summary>
    ///     Returns an array containing the names of all countries which have participated
    ///     in at least one match exactly one time.
    /// </summary>
    /// <param name="matches">Array of all matches played</param>
    /// <returns>An array of unique country names</returns>
    public static string[] ExtractUniqueCountryNames(Match[] matches)
    {
        int uniqueCount = 0;
        string[] tempCountryNames = new string[matches.Length * 2];
        foreach (var match in matches)
        {
            TeamResult homeTeam = match.HomeTeam;
            TeamResult guestTeam = match.GuestTeam;
            if (!IsContained(homeTeam.TeamName, tempCountryNames))
            {
                tempCountryNames[uniqueCount++] = homeTeam.TeamName;
            }
            if (!IsContained(guestTeam.TeamName, tempCountryNames))
            {
                tempCountryNames[uniqueCount++] = guestTeam.TeamName;
            }
        }
        
        string[] countryNames = new string[uniqueCount];
        
        for (int i = 0; i < uniqueCount; i++)
        {
            countryNames[i] = tempCountryNames[i];
        }
        
        return countryNames;
        
        //Would be much easier with a list, but unfortunately the task requires an array
        /*string[] countryNames = [];
        foreach (var match in matches)
        {
            TeamResult homeTeam = match.HomeTeam;
            TeamResult guestTeam = match.GuestTeam;
            if (!IsContained(homeTeam.TeamName, countryNames))
            {
                countryNames = countryNames.Append(homeTeam.TeamName).ToArray();
            }
            if (!IsContained(guestTeam.TeamName, countryNames))
            {
                countryNames = countryNames.Append(guestTeam.TeamName).ToArray();
            }
        }

        return countryNames;*/
    }

    /// <summary>
    ///     Returns a new array of matches, based on the supplied full collection, but
    ///     with filtered to only contain matches the provided country participated in.
    /// </summary>
    /// <param name="allMatches">Array of all matches played</param>
    /// <param name="countryName">Name of the country to filter for</param>
    /// <returns>Array of matches in which the supplied country participated</returns>
    public static Match[] FilterMatchesByCountry(Match[] allMatches, string countryName)
    {
        int count = 0;
        foreach (var match in allMatches)
        {
            if (IsCountryMatch(match, countryName))
            {
                count++;
            }
        }
        
        Match[] filteredMatches = new Match[count];
        
        int index = 0;
        for (int i = 0; i < allMatches.Length; i++)
        {
            if (IsCountryMatch(allMatches[i], countryName))
            {
                filteredMatches[index++] = allMatches[i];
            }
        }

        return filteredMatches;
        
        //Mister Haslinger, please allow me to use lists
        /*Match[] filteredMatches = [];
        foreach (var match in allMatches)
        {
            if (IsCountryMatch(match, countryName))
            {
                filteredMatches = filteredMatches.Append(match).ToArray();
            }
                
        }

        return filteredMatches;*/
    }

    /// <summary>
    ///     Determines if the supplied match is one the provided country participated in.
    /// </summary>
    /// <param name="match">Match to check</param>
    /// <param name="countryName">Country for which to check</param>
    /// <returns>True if the country participated in the match; false otherwise</returns>
    public static bool IsCountryMatch(Match match, string countryName)
    {
        TeamResult homeTeam = match.HomeTeam;
        TeamResult guestTeam = match.GuestTeam;
        return homeTeam.TeamName == countryName || guestTeam.TeamName == countryName;
    }

    /// <summary>
    ///     Prints the matches to the terminal.
    /// </summary>
    /// <param name="matches">Array of matches to print</param>
    private static void PrintMatches(Match[] matches)
    {
        Console.WriteLine($"{"Home",-15}  {"Guest",-20}");
        for(int i = 0; i < 39; i++)
        {
            Console.Write("=");
        }
        Console.WriteLine();
        foreach (var match in matches)
        {
            TeamResult homeTeam = match.HomeTeam;
            TeamResult guestTeam = match.GuestTeam;
            Console.WriteLine($"{homeTeam.TeamName,-14} | {guestTeam.TeamName, -15} => {homeTeam.Goals}:{guestTeam.Goals}");
        }
    }

    /// <summary>
    ///     Asks the user to enter a country to filter for.
    ///     The user can only enter one of the existing countries. Case is not relevant.
    ///     If the user enters something invalid the input request is retried until the user gets it right.
    /// </summary>
    /// <param name="possibleCountries">Array containing the names of possible countries to pick from</param>
    /// <returns>The name of the country the user selected</returns>
    private static string AskForCountry(string[] possibleCountries)
    {
        string country;
        bool isContained;
        do
        {
            Console.Write("Enter the name of a country to filter: ");
            country = Console.ReadLine()!;
            isContained = IsContained(country, possibleCountries);
            if (!isContained)
            {
                Console.WriteLine("Invalid input, try again...");
            }
        } while (!isContained);
        
        return country;
    }
}