// Copyright (c) .NET Foundation. 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 System.Text.RegularExpressions;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

namespace Microsoft.AspNetCore.Razor.Tasks
{
    public class ApplyCssScopes : Task
    {
        [Required]
        public ITaskItem[] RazorComponents { get; set; }

        [Required]
        public ITaskItem[] ScopedCss { get; set; }

        [Output]
        public ITaskItem[] RazorComponentsWithScopes { get; set; }

        public override bool Execute()
        {
            var razorComponentsWithScopes = new List<ITaskItem>();
            var unmatchedScopedCss = new List<ITaskItem>(ScopedCss);
            var scopedCssByComponent = new Dictionary<string, IList<ITaskItem>>();

            for (var i = 0; i < RazorComponents.Length; i++)
            {
                var componentCandidate = RazorComponents[i];
                var j = 0;
                while (j < unmatchedScopedCss.Count)
                {
                    var scopedCssCandidate = unmatchedScopedCss[j];
                    var explicitRazorcomponent = scopedCssCandidate.GetMetadata("RazorComponent");
                    var razorComponent = !string.IsNullOrWhiteSpace(explicitRazorcomponent) ?
                        explicitRazorcomponent :
                        Regex.Replace(scopedCssCandidate.ItemSpec, "(.*)\\.razor\\.css$", "$1.razor", RegexOptions.IgnoreCase);

                    if (string.Equals(componentCandidate.ItemSpec, razorComponent, StringComparison.OrdinalIgnoreCase))
                    {
                        unmatchedScopedCss.RemoveAt(j);
                        if (!scopedCssByComponent.TryGetValue(componentCandidate.ItemSpec, out var existing))
                        {
                            scopedCssByComponent[componentCandidate.ItemSpec] = new List<ITaskItem>() { scopedCssCandidate };
                            var item = new TaskItem(componentCandidate);
                            item.SetMetadata("CssScope", scopedCssCandidate.GetMetadata("CssScope"));
                            razorComponentsWithScopes.Add(item);
                        }
                        else
                        {
                            existing.Add(scopedCssCandidate);
                        }
                    }
                    else
                    {
                        j++;
                    }
                }
            }

            foreach (var kvp in scopedCssByComponent)
            {
                var component = kvp.Key;
                var scopeFiles = kvp.Value;

                if (scopeFiles.Count > 1)
                {
                    Log.LogError(null, "BLAZOR101", "", component, 0, 0, 0, 0, $"More than one scoped css files were found for the razor component '{component}'. " +
                        $"Each razor component must have at most a single associated scoped css file." +
                        Environment.NewLine +
                        string.Join(Environment.NewLine, scopeFiles.Select(f => f.ItemSpec)));
                }
            }

            // We don't want to allow scoped css files without a matching component. Our convention is very specific in its requirements
            // so failing to have a matching component very likely means an error.
            // When the matching component was specified explicitly, failing to find a matching component is an error.
            // This simplifies a few things like being able to assume that the presence of a .razor.css file or a ScopedCssInput item will result in a bundle being produced,
            // that the contents of the bundle are independent of the existence of a component and that users will be able to catch errors at compile
            // time instead of wondering why their component doesn't have a scope applied to it.
            // In the rare case that a .razor file exists on the user project, has an associated .razor.css file and the user decides to exclude it as a RazorComponent they
            // can update the Content item for the .razor.css file with Scoped=false and we will not consider it.
            foreach (var unmatched in unmatchedScopedCss)
            {
                Log.LogError(null, "BLAZOR102", "", unmatched.ItemSpec, 0, 0, 0, 0, $"The scoped css file '{unmatched.ItemSpec}' was defined but no associated razor component was found for it.");
            }

            RazorComponentsWithScopes = razorComponentsWithScopes.ToArray();

            return !Log.HasLoggedErrors;
        }
    }
}