// 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.

#nullable disable

using System.Collections.Generic;
using Microsoft.CodeAnalysis.Completion;
using Microsoft.CodeAnalysis.EmbeddedLanguages.RegularExpressions;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.Features.EmbeddedLanguages.RegularExpressions.LanguageServices;

internal sealed partial class RegexEmbeddedCompletionProvider
{
    private readonly struct EmbeddedCompletionContext
    {
        private readonly RegexEmbeddedLanguage _language;
        private readonly CompletionContext _context;
        private readonly HashSet<string> _names = [];

        public readonly RegexTree Tree;
        public readonly SyntaxToken StringToken;
        public readonly int Position;
        public readonly CompletionTrigger Trigger;
        public readonly List<RegexItem> Items = [];

        public EmbeddedCompletionContext(
            RegexEmbeddedLanguage language,
            CompletionContext context,
            RegexTree tree,
            SyntaxToken stringToken)
        {
            _language = language;
            _context = context;
            Tree = tree;
            StringToken = stringToken;
            Position = _context.Position;
            Trigger = _context.Trigger;
        }

        public void AddIfMissing(
            string displayText, string suffix, string description,
            RegexNode parentOpt, int? positionOffset = null, string insertionText = null)
        {
            var replacementStart = parentOpt != null
                ? parentOpt.GetSpan().Start
                : Position;

            var replacementSpan = TextSpan.FromBounds(replacementStart, Position);
            var newPosition = replacementStart + positionOffset;

            insertionText ??= displayText;
            var escapedInsertionText = _language.EscapeText(insertionText, StringToken);

            if (escapedInsertionText != insertionText)
            {
                newPosition += escapedInsertionText.Length - insertionText.Length;
            }

            AddIfMissing(new RegexItem(
                displayText, suffix, description,
                CompletionChange.Create(
                    new TextChange(replacementSpan, escapedInsertionText),
                    newPosition)));
        }

        public void AddIfMissing(RegexItem item)
        {
            if (_names.Add(item.DisplayText))
            {
                Items.Add(item);
            }
        }
    }
}