// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;

namespace System.Diagnostics.Eventing.Reader
{
    /// <summary>
    /// Event Metadata
    /// </summary>
    public sealed class EventMetadata
    {
        private readonly byte _channelId;
        private readonly byte _level;
        private readonly short _opcode;
        private readonly int _task;
        private readonly long _keywords;
        private readonly ProviderMetadata _pmReference;

        internal EventMetadata(uint id, byte version, byte channelId,
                 byte level, byte opcode, short task, long keywords,
                 string? template, string? description, ProviderMetadata pmReference)
        {
            Id = id;
            Version = version;
            _channelId = channelId;
            _level = level;
            _opcode = opcode;
            _task = task;
            _keywords = keywords;
            Template = template;
            Description = description;
            _pmReference = pmReference;
        }

        //
        // Max value will be UINT32.MaxValue - it is a long because this property
        // is really a UINT32.  The legacy API allows event message ids to be declared
        // as UINT32 and these event/messages may be migrated into a Provider's
        // manifest as UINT32.  Note that EventRecord ids are
        // still declared as int, because those ids max value is UINT16.MaxValue
        // and rest of the bits of the legacy event id would be stored in
        // Qualifiers property.
        //
        public long Id { get; }

        public byte Version { get; }

        public EventLogLink LogLink
        {
            get
            {
                return new EventLogLink((uint)_channelId, _pmReference);
            }
        }

        public EventLevel Level
        {
            get
            {
                return new EventLevel(_level, _pmReference);
            }
        }

        public EventOpcode Opcode
        {
            get
            {
                return new EventOpcode(_opcode, _pmReference);
            }
        }

        public EventTask Task
        {
            get
            {
                return new EventTask(_task, _pmReference);
            }
        }

        public IEnumerable<EventKeyword> Keywords
        {
            get
            {
                List<EventKeyword> list = new List<EventKeyword>();

                ulong theKeywords = unchecked((ulong)_keywords);
                ulong mask = 0x8000000000000000;

                // For every bit
                // for (int i = 0; i < 64 && theKeywords != 0; i++)
                for (int i = 0; i < 64; i++)
                {
                    // If this bit is set
                    if ((theKeywords & mask) > 0)
                    {
                        // The mask is the keyword we will be searching for.
                        list.Add(new EventKeyword(unchecked((long)mask), _pmReference));
                        // theKeywords = theKeywords - mask;
                    }
                    // Modify the mask to check next bit.
                    mask >>= 1;
                }

                return list;
            }
        }

        public string? Template { get; }

        public string? Description { get; }
    }
}