// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Framework.Internal;

namespace Microsoft.AspNet.Mvc.ModelBinding.Internal
{
    public static class DictionaryHelper
    {
        public static IEnumerable<KeyValuePair<string, TValue>> FindKeysWithPrefix<TValue>(
                [NotNull] IDictionary<string, TValue> dictionary,
                [NotNull] string prefix)
        {
            TValue exactMatchValue;
            if (dictionary.TryGetValue(prefix, out exactMatchValue))
            {
                yield return new KeyValuePair<string, TValue>(prefix, exactMatchValue);
            }

            foreach (var entry in dictionary)
            {
                var key = entry.Key;

                if (key.Length <= prefix.Length)
                {
                    continue;
                }

                if (key.StartsWith("[", StringComparison.OrdinalIgnoreCase))
                {
                    key = key.Substring(key.IndexOf('.') + 1);
                    if (string.Equals(prefix, key, StringComparison.Ordinal))
                    {
                        yield return entry;
                        continue;
                    }
                }

                if (!key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
                {
                    continue;
                }

                // Everything is prefixed by the empty string
                if (prefix.Length == 0)
                {
                    yield return entry;
                }
                else
                {
                    var charAfterPrefix = key[prefix.Length];
                    switch (charAfterPrefix)
                    {
                        case '[':
                        case '.':
                            yield return entry;
                            break;
                    }
                }
            }
        }
    }
}