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

using System;
using System.Collections.Generic;
using Microsoft.Build.Collections;
using Microsoft.Build.Construction;

namespace Microsoft.Build.Evaluation
{
    /// <summary>
    /// Implementation of a metadata table for use by the evaluator.
    /// Accumulates ProjectMetadataElement objects and their evaluated value,
    /// overwriting any previous metadata with that name.
    /// </summary>
    internal class EvaluatorMetadataTable : IMetadataTable
    {
        /// <summary>
        /// The actual metadata dictionary.
        /// </summary>
        private Dictionary<string, string>? _metadata;

        /// <summary>
        /// The type of item the metadata should be considered to apply to.
        /// </summary>
        private string _implicitItemType;

        /// <summary>
        /// The expected number of metadata entries in this table.
        /// </summary>
        private readonly int _capacity;

        /// <summary>
        /// Creates a new table using the specified item type.
        /// </summary>
        public EvaluatorMetadataTable(string implicitItemType, int capacity = 0)
        {
            _implicitItemType = implicitItemType;
            _capacity = capacity;
        }

        /// <summary>
        /// Retrieves any value we have in our metadata table for the metadata name specified,
        /// whatever the item type.
        /// If no value is available, returns empty string.
        /// </summary>
        public string GetEscapedValue(string name)
        {
            return GetEscapedValue(null, name);
        }

        /// <summary>
        /// Retrieves any value we have in our metadata table for the metadata name and item type specified.
        /// If no value is available, returns empty string.
        /// </summary>
        public string GetEscapedValue(string? itemType, string name)
        {
            return GetEscapedValueIfPresent(itemType, name) ?? String.Empty;
        }

        /// <summary>
        /// Retrieves any value we have in our metadata table for the metadata name and item type specified.
        /// If no value is available, returns null.
        /// </summary>
        public string? GetEscapedValueIfPresent(string? itemType, string name)
        {
            if (_metadata == null)
            {
                return null;
            }

            string? value = null;

            if (itemType == null || String.Equals(_implicitItemType, itemType, StringComparison.OrdinalIgnoreCase))
            {
                if (_metadata.TryGetValue(name, out string? evaluatedValueEscaped))
                {
                    value = evaluatedValueEscaped;
                }
            }

            return value;
        }

        /// <summary>
        /// Adds a metadata entry to the table
        /// </summary>
        internal void SetValue(ProjectMetadataElement xml, string evaluatedValueEscaped)
        {
            if (_metadata == null)
            {
                _metadata = new Dictionary<string, string>(_capacity, MSBuildNameIgnoreCaseComparer.Default);
            }

            _metadata[xml.Name] = evaluatedValueEscaped;
        }
    }
}