using System.IO;
using System.Linq;

using SongTidy.Models;
using SongTidy.Services;

namespace SongTidy.Tests;

/// <summary>
/// Contains tests for <see cref="RenameValidator"/>.
/// </summary>
[TestClass]
public sealed class RenameValidatorTests {
    private string _tempDirectory = string.Empty;

    /// <summary>
    /// Creates a unique temporary directory for the current test.
    /// </summary>
    [TestInitialize]
    public void Initialize() {
        _tempDirectory = Path.Combine(Path.GetTempPath(), $"SongTidy Validation {Guid.NewGuid():N}");
        Directory.CreateDirectory(_tempDirectory);
    }

    /// <summary>
    /// Removes the temporary directory created for the current test.
    /// </summary>
    [TestCleanup]
    public void Cleanup() {
        Directory.Delete(_tempDirectory, recursive: true);
    }

    #region Per-entry validation

    /// <summary>
    /// Verifies that empty and whitespace-only titles are rejected.
    /// </summary>
    /// <param name="title">The title to validate.</param>
    [TestMethod]
    [DataRow("")]
    [DataRow("   ")]
    public void ReportsEmptyTitle(string title) {
        string sourcePath = CreateFile("A.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, title));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.EmptyTitle, 1));
    }

    /// <summary>
    /// Verifies that every forbidden file name character is detected in the title.
    /// </summary>
    /// <param name="invalidCharacter">The character to insert into the title.</param>
    [TestMethod]
    [DataRow("\\")]
    [DataRow("/")]
    [DataRow(":")]
    [DataRow("*")]
    [DataRow("?")]
    [DataRow("\"")]
    [DataRow("<")]
    [DataRow(">")]
    [DataRow("|")]
    [DataRow("\t")]
    public void ReportsInvalidCharacterInTitle(string invalidCharacter) {
        string sourcePath = CreateFile("A.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "A" + invalidCharacter + "B"));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.InvalidFieldCharacter, 1));
    }

    /// <summary>
    /// Verifies that invalid characters are detected in the artist and comment fields.
    /// </summary>
    [TestMethod]
    public void ReportsInvalidCharactersInArtistAndComment() {
        string sourcePath = CreateFile("A.mp3");

        RenameValidationResult result = Validate(
            CreateItem(sourcePath, "Title", artist: "A\\B", comment: "C:D"));

        Assert.HasCount(
            2,
            result.Issues.Where(issue => issue.Problem == RenameValidationProblem.InvalidFieldCharacter));
    }

    /// <summary>
    /// Verifies that target names ending with a dot or a space are rejected.
    /// </summary>
    /// <param name="title">The title that produces the invalid target ending.</param>
    [TestMethod]
    [DataRow("Title.")]
    [DataRow("Title ")]
    public void ReportsInvalidTargetEnding(string title) {
        string sourcePath = CreateFile("Source");

        RenameValidationResult result = Validate(CreateItem(sourcePath, title));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.InvalidTargetEnding, 1));
    }

    /// <summary>
    /// Verifies that missing source files are detected.
    /// </summary>
    [TestMethod]
    public void ReportsMissingSourceFile() {
        string sourcePath = Path.Combine(_tempDirectory, "Missing.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "Title"));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.MissingSourceFile, 1));
    }

    #endregion

    #region Source path validation

    /// <summary>
    /// Verifies that duplicate source paths are reported for every affected row.
    /// </summary>
    [TestMethod]
    public void ReportsDuplicateSourcePaths() {
        string sourcePath = CreateFile("Dup.mp3");

        RenameValidationResult result = Validate(
            CreateItem(sourcePath, "One"),
            CreateItem(sourcePath, "Two"));

        Assert.HasCount(
            2,
            result.Issues.Where(issue => issue.Problem == RenameValidationProblem.DuplicateSourcePath));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateSourcePath, 1));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateSourcePath, 2));
    }

    /// <summary>
    /// Verifies that source path comparison is case-sensitive.
    /// </summary>
    [TestMethod]
    public void TreatsSourcePathsAsCaseSensitive() {
        CreateFile("Case.mp3");
        PlanItem first = CreateItem(Path.Combine(_tempDirectory, "Case.mp3"), "One");
        PlanItem second = CreateItem(Path.Combine(_tempDirectory, "case.mp3"), "Two");

        RenameValidationResult result = Validate(first, second);

        Assert.IsFalse(
            result.Issues.Any(issue => issue.Problem == RenameValidationProblem.DuplicateSourcePath));
    }

    #endregion

    #region Target conflict validation

    /// <summary>
    /// Verifies that duplicate target paths are detected case-insensitively.
    /// </summary>
    [TestMethod]
    public void ReportsDuplicateTargetNamesCaseInsensitively() {
        string firstPath = CreateFile("A.mp3");
        string secondPath = CreateFile("B.mp3");

        RenameValidationResult result = Validate(
            CreateItem(firstPath, "Same"),
            CreateItem(secondPath, "same"));

        Assert.HasCount(
            2,
            result.Issues.Where(issue => issue.Problem == RenameValidationProblem.DuplicateTargetName));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateTargetName, 1));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateTargetName, 2));
    }

    /// <summary>
    /// Verifies that equal target names in different directories do not conflict.
    /// </summary>
    [TestMethod]
    public void AllowsSameTargetNameInDifferentDirectories() {
        string firstPath = CreateFile(Path.Combine("dir1", "A.mp3"));
        string secondPath = CreateFile(Path.Combine("dir2", "B.mp3"));

        RenameValidationResult result = Validate(
            CreateItem(firstPath, "Same"),
            CreateItem(secondPath, "Same"));

        Assert.IsTrue(result.IsValid);
    }

    /// <summary>
    /// Verifies that an existing target file is reported as a conflict.
    /// </summary>
    [TestMethod]
    public void ReportsTargetFileConflict() {
        string sourcePath = CreateFile("A.mp3");
        CreateFile("Existing.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "Existing"));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.TargetFileConflict, 1));
    }

    /// <summary>
    /// Verifies that a target equal to the entry's own source is not a conflict.
    /// </summary>
    [TestMethod]
    public void AllowsTargetEqualToOwnSource() {
        string sourcePath = CreateFile("A.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "A"));

        Assert.IsTrue(result.IsValid);
    }

    /// <summary>
    /// Verifies that casing-only changes to the entry's own source are not conflicts.
    /// </summary>
    [TestMethod]
    public void AllowsTargetEqualToOwnSourceIgnoringCase() {
        string sourcePath = CreateFile("A.mp3");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "a"));

        Assert.IsTrue(result.IsValid);
    }

    /// <summary>
    /// Verifies that a renaming chain such as A to B and B to A is blocked.
    /// </summary>
    [TestMethod]
    public void BlocksConflictChain() {
        string aPath = CreateFile("A.mp3");
        string bPath = CreateFile("B.mp3");

        RenameValidationResult result = Validate(
            CreateItem(aPath, "B"),
            CreateItem(bPath, "A"));

        Assert.HasCount(
            2,
            result.Issues.Where(issue => issue.Problem == RenameValidationProblem.TargetFileConflict));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.TargetFileConflict, 1));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.TargetFileConflict, 2));
    }

    /// <summary>
    /// Verifies that the original file extension is preserved when checking conflicts.
    /// </summary>
    [TestMethod]
    public void UsesOriginalExtensionForTargetNames() {
        string sourcePath = CreateFile("Source.flac");
        CreateFile("Title.flac");

        RenameValidationResult result = Validate(CreateItem(sourcePath, "Title"));

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.TargetFileConflict, 1));
    }

    /// <summary>
    /// Verifies that the selected naming format controls the generated target name.
    /// </summary>
    [TestMethod]
    public void UsesSelectedFormatForTargetNames() {
        string sourcePath = CreateFile("A.mp3");
        CreateFile("Title - Artist.mp3");
        PlanItem item = CreateItem(sourcePath, "Title", artist: "Artist");

        RenameValidationResult result = RenameValidator.Validate(
            new[] { item },
            RenameFormat.TitleFirst);

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.TargetFileConflict, 1));
    }

    #endregion

    #region Combined validation

    /// <summary>
    /// Verifies that validation collects problems from multiple rules in one pass.
    /// </summary>
    [TestMethod]
    public void ReportsAllProblemKinds() {
        string sourcePath = CreateFile("A.mp3");
        PlanItem emptyTitle = CreateItem(sourcePath, "");
        PlanItem missingSource = CreateItem(Path.Combine(_tempDirectory, "Missing.mp3"), "Title");
        PlanItem invalidCharacter = CreateItem(sourcePath, "Bad/Title");

        RenameValidationResult result = Validate(emptyTitle, missingSource, invalidCharacter);

        Assert.IsTrue(HasProblem(result, RenameValidationProblem.EmptyTitle, 1));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.MissingSourceFile, 2));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.InvalidFieldCharacter, 3));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateSourcePath, 1));
        Assert.IsTrue(HasProblem(result, RenameValidationProblem.DuplicateSourcePath, 3));
    }

    /// <summary>
    /// Verifies that a clean set of entries produces no issues.
    /// </summary>
    [TestMethod]
    public void ReturnsValidResultForRenameableEntries() {
        string firstPath = CreateFile("A.mp3");
        string secondPath = CreateFile("B.mp3");

        RenameValidationResult result = Validate(
            CreateItem(firstPath, "One"),
            CreateItem(secondPath, "Two"));

        Assert.IsTrue(result.IsValid);
        Assert.HasCount(0, result.Issues);
    }

    #endregion

    /// <summary>
    /// Creates an empty file inside the test directory.
    /// </summary>
    /// <param name="fileName">The relative file name, which may include a subdirectory.</param>
    /// <returns>The full path of the created file.</returns>
    private string CreateFile(string fileName) {
        string path = Path.Combine(_tempDirectory, fileName);
        string directory = Path.GetDirectoryName(path) ?? _tempDirectory;

        Directory.CreateDirectory(directory);
        File.WriteAllText(path, string.Empty);

        return path;
    }

    /// <summary>
    /// Creates a plan item with the supplied field values.
    /// </summary>
    /// <param name="path">The source file path.</param>
    /// <param name="title">The title value.</param>
    /// <param name="artist">The artist value.</param>
    /// <param name="comment">The comment value.</param>
    /// <returns>The created plan item.</returns>
    private static PlanItem CreateItem(string path, string title, string artist = "", string comment = "") {
        return new PlanItem {
            Path = path,
            Artist = artist,
            Title = title,
            Comment = comment,
        };
    }

    /// <summary>
    /// Validates entries with the artist-first format.
    /// </summary>
    /// <param name="items">The entries to validate.</param>
    /// <returns>The validation result.</returns>
    private static RenameValidationResult Validate(params PlanItem[] items) {
        return RenameValidator.Validate(items, RenameFormat.ArtistFirst);
    }

    /// <summary>
    /// Determines whether the result contains a specific problem for a row.
    /// </summary>
    /// <param name="result">The validation result to inspect.</param>
    /// <param name="problem">The problem category to find.</param>
    /// <param name="rowNumber">The one-based row number to match.</param>
    /// <returns><see langword="true"/> when the problem is present.</returns>
    private static bool HasProblem(
        RenameValidationResult result,
        RenameValidationProblem problem,
        int rowNumber) {
        return result.Issues.Any(issue => issue.Problem == problem && issue.RowNumber == rowNumber);
    }
}