// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Collections.Immutable;
using System.Globalization;
using System.Runtime.Serialization;
using Microsoft.CodeAnalysis.PooledObjects;
 
namespace Microsoft.CodeAnalysis.TaskList
{
    internal enum TaskListItemPriority
    {
        Low,
        Medium,
        High,
    }
 
    /// <summary>
    /// Description of a TODO comment type to find in a user's comments.
    /// </summary>
    [DataContract]
    internal readonly struct TaskListItemDescriptor
    {
        [DataMember(Order = 0)]
        public string Text { get; }
        [DataMember(Order = 1)]
        public TaskListItemPriority Priority { get; }
 
        public TaskListItemDescriptor(string text, TaskListItemPriority priority)
        {
            Text = text;
            Priority = priority;
        }
 
        public static ImmutableArray<TaskListItemDescriptor> Parse(ImmutableArray<string> items)
        {
            using var _ = ArrayBuilder<TaskListItemDescriptor>.GetInstance(out var result);
 
            foreach (var item in items)
            {
                if (item.Split(':') is [var token, var priorityString] &&
                    !string.IsNullOrWhiteSpace(token) &&
                    int.TryParse(priorityString, NumberStyles.None, CultureInfo.InvariantCulture, out var encoded))
                {
                    // From:
                    // https://devdiv.visualstudio.com/DevDiv/_git/VS?path=/src/env/ErrorList/Pkg/Shims/TaskListOptions.cs&version=GBmain&line=133&lineEnd=134&lineStartColumn=1&lineEndColumn=98&lineStyle=plain&_a=contents
#if false
                    // I've no idea why the strange conversion (legacy mapping from __VSERRORCATEGORY?).
                    private static int EncodedValueFromPriority(CommentTaskPriority p) { return 3 - (int)p; }
                    private static CommentTaskPriority PriorityFromEncodedValue(int v) { return (CommentTaskPriority)(3 - v); }
#endif
                    // In other words, the actual VS enum here goes from high-to-low priority, but the values are
                    // encoded low-to-high. So we undo this conversion to map from the encoded priority values to what
                    // they represent.
                    var priority = encoded switch
                    {
                        1 => TaskListItemPriority.Low,
                        2 => TaskListItemPriority.Medium,
                        3 => TaskListItemPriority.High,
                        _ => TaskListItemPriority.Medium,
                    };
                    result.Add(new TaskListItemDescriptor(token, priority));
                }
            }
 
            return result.ToImmutable();
        }
    }
}