// 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.txt file in the project root for more information.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Microsoft.Build.Framework;
using Microsoft.Build.Tasks.SourceControl;

namespace Microsoft.SourceLink.AzureRepos.Git
{
    public sealed class GetSourceLinkUrl : GetSourceLinkUrlGitTask
    {
        private const string UrlMapEnvironmentVariableName = "BUILD_REPOSITORY_URL_MAP";

        protected override string HostsItemGroupName => "SourceLinkAzureReposGitHost";
        protected override string ProviderDisplayName => "AzureRepos.Git";

        protected override Uri GetDefaultContentUriFromHostUri(string authority, Uri gitUri)
        {
            var gitHost = gitUri.GetHost();
            return AzureDevOpsUrlParser.IsVisualStudioHostedServer(gitHost) ?
                new Uri($"{gitUri.Scheme}://{gitHost[..gitHost.IndexOf('.')]}.{authority}", UriKind.Absolute) :
                new Uri($"{gitUri.Scheme}://{authority}", UriKind.Absolute);
        }

        // Repository URL already contains account in case of VS host. Don't add it like we do when the content URL is inferred from host name.
        protected override Uri GetDefaultContentUriFromRepositoryUri(Uri repositoryUri)
            => new Uri($"{repositoryUri.Scheme}://{repositoryUri.GetAuthority()}", UriKind.Absolute);

        protected override string? BuildSourceLinkUrl(Uri contentUri, Uri gitUri, string relativeUrl, string revisionId, ITaskItem? hostItem)
        {
            // Azure DevOps does not support optional ".git" suffix in repository URLs and adding it may result in 404.
            // Unlike other providers (GitHub, GitLab, etc.), relativeUrl may include the ".git" suffix,
            // so use gitUri.GetPath() here instead.
            if (!AzureDevOpsUrlParser.TryParseHostedHttp(gitUri.GetHost(), gitUri.GetPath(), out var projectPath, out var repositoryName))
            {
                Log.LogError(CommonResources.ValueOfWithIdentityIsInvalid, Names.SourceRoot.RepositoryUrlFullName, SourceRoot!.ItemSpec, gitUri);
                return null;
            }

            return
                UriUtilities.Combine(
                UriUtilities.Combine(contentUri.ToString(), projectPath), $"_apis/git/repositories/{repositoryName}/items") +
                $"?api-version=1.0&versionType=commit&version={revisionId}&path=/*";
        }

        // TODO: confirm design and test https://github.com/dotnet/sourcelink/issues/2
        private Dictionary<Uri, Uri>? TryGetEnvironmentUriMap()
        {
            var urlSeparators = new[] { Path.PathSeparator };
            Dictionary<Uri, Uri>? map = null;

            bool parse(string urls)
            {
                var items = urls.Split(urlSeparators, StringSplitOptions.None);
                if (items.Length % 2 != 0)
                {
                    return false;
                }

                for (var i = 0; i < items.Length; i += 2)
                {
                    var originalUrl = items[i];
                    var mappedUrl = items[i + 1];

                    if (!Uri.TryCreate(originalUrl, UriKind.Absolute, out var originalUri) || originalUri.Query != "")
                    {
                        return false;
                    }

                    if (!Uri.TryCreate(mappedUrl, UriKind.Absolute, out var mappedUri) || mappedUri.Query != "")
                    {
                        return false;
                    }

                    if (map == null)
                    {
                        map = new Dictionary<Uri, Uri>();
                    }

                    map[originalUri] = mappedUri;
                }

                return true;
            }

            IEnumerable<KeyValuePair<string, string>> enumerateVariables()
            {
                var i = 0;
                while (true)
                {
                    var name = UrlMapEnvironmentVariableName + (i == 0 ? "" : i.ToString());
                    var value = Environment.GetEnvironmentVariable(name);
                    if (string.IsNullOrEmpty(value))
                    {
                        yield break;
                    }

                    yield return new KeyValuePair<string, string>(name, value);
                    i++;
                }
            }

            foreach (var variable in enumerateVariables())
            {
                if (!parse(variable.Value))
                {
                    Log.LogError(Resources.EnvironmentVariableIsNotAlistOfUrlPairs, variable.Key, variable.Value);
                    return null;
                }
            }

            return map;
        }
    }
}