namespace Uwaa.HTTP;

/// <summary>
/// Helper methods for HTTP.
/// </summary>
public static class HttpHelpers
{
    /// <summary>
    /// Parses an array of MIME types from an Accept field.
    /// </summary>
    public static MIMEType[] ParseAccept(string accept)
    {
        int count = 1;
        for (int i = 0; i < accept.Length; i++)
            if (accept[i] == ',')
                count++;

        MIMEType[] result = new MIMEType[count];
        int resultIndex = 0;
        int splStart = 0;
        int splEnd = 0;
        void flush()
        {
            try
            {
                result[resultIndex++] = new MIMEType(accept.AsSpan(splStart..(splEnd + 1)));
            }
            catch (FormatException e)
            {
                throw new HttpException(e.Message, e);
            }
        }
        for (int i = 0; i < accept.Length; i++)
        {
            switch (accept[i])
            {
                case ';':
                    flush();

                    //Another stupid idea by the W3C. Not interested in implementing it - skip!!!
                    while (i < accept.Length && accept[i] != ',')
                        i++;
                    splStart = i + 1;
                    continue;

                case ',':
                    flush();
                    splStart = i + 1;
                    continue;

                case ' ':
                    if (splEnd <= splStart)
                        splStart = i + 1; //Trim start
                    continue; //Trim end

                default:
                    splEnd = i;
                    continue;
            }
        }
        if (splStart < splEnd)
            flush(); //Flush remaining

        return result;
    }
}