using SongTidy.Services;

namespace SongTidy.Tests;

/// <summary>
/// Contains tests for <see cref="FilenameParser"/>.
/// </summary>
[TestClass]
public sealed class FilenameParserTests {
    #region Successful parsing

    /// <summary>
    /// Verifies the documented example with one English and one Chinese bracket group.
    /// </summary>
    [TestMethod]
    public void ParsesSpecificationExample() {
        AssertParse("A - B (Live - Tokyo)（修正版）", "A", "B", "Live - Tokyo 修正版");
    }

    /// <summary>
    /// Verifies that multiple comment groups are joined with a single half-width space.
    /// </summary>
    [TestMethod]
    public void ParsesMultipleCommentGroups() {
        AssertParse("A - B (Live)（Remix）", "A", "B", "Live Remix");
    }

    /// <summary>
    /// Verifies that Chinese bracket groups are extracted like English bracket groups.
    /// </summary>
    [TestMethod]
    public void ParsesChineseBracketComment() {
        AssertParse("歌手 - 歌名（现场）", "歌手", "歌名", "现场");
    }

    /// <summary>
    /// Verifies that all comment groups are removed from the text used for artist and title.
    /// </summary>
    [TestMethod]
    public void RemovesAllCommentGroupsFromSource() {
        AssertParse("A - B (Live) (Tokyo)", "A", "B", "Live Tokyo");
    }

    /// <summary>
    /// Verifies that nested brackets stay as literal text inside the comment.
    /// </summary>
    [TestMethod]
    public void KeepsNestedBracketsInsideComment() {
        AssertParse("A - B (Live (Tokyo) Mix)", "A", "B", "Live (Tokyo) Mix");
    }

    /// <summary>
    /// Verifies that nested full-width brackets stay as literal text inside an English comment.
    /// </summary>
    [TestMethod]
    public void PreservesFullWidthNestedBrackets() {
        AssertParse("A - B (Live（东京）)", "A", "B", "Live（东京）");
    }

    /// <summary>
    /// Verifies that only the outermost pair of a nested group is treated as the comment.
    /// </summary>
    [TestMethod]
    public void TreatsOnlyOutermostBracketGroupAsComment() {
        AssertParse("A - B ((Live))", "A", "B", "(Live)");
    }

    /// <summary>
    /// Verifies that a comment can be extracted from a name without a hyphen.
    /// </summary>
    [TestMethod]
    public void ParsesCommentWithoutArtistSeparator() {
        AssertParse("Song (Live)", string.Empty, "Song", "Live");
    }

    #endregion

    #region Invalid bracket structures

    /// <summary>
    /// Verifies that an unmatched opening bracket disables comment extraction entirely.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForUnmatchedOpeningBracket() {
        AssertParse("A - B (Live", "A", "B (Live", string.Empty);
    }

    /// <summary>
    /// Verifies that an unmatched closing bracket disables comment extraction entirely.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForUnmatchedClosingBracket() {
        AssertParse("A - B Live)", "A", "B Live)", string.Empty);
    }

    /// <summary>
    /// Verifies that opening and closing brackets of different types cannot pair.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForMismatchedBracketTypes() {
        AssertParse("A - B （Live)", "A", "B （Live)", string.Empty);
    }

    /// <summary>
    /// Verifies that an extra closing bracket after a valid pair disables extraction entirely.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForExtraClosingBracket() {
        AssertParse("A - B (Live))", "A", "B (Live))", string.Empty);
    }

    /// <summary>
    /// Verifies that an extra opening bracket after a valid pair disables extraction entirely.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForExtraOpeningBracket() {
        AssertParse("A - B (Live) (", "A", "B (Live) (", string.Empty);
    }

    /// <summary>
    /// Verifies that an unclosed outer bracket invalidates otherwise complete nested brackets.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForUnclosedOuterBracket() {
        AssertParse("A - B (Live (Tokyo)", "A", "B (Live (Tokyo)", string.Empty);
    }

    /// <summary>
    /// Verifies that crossing bracket groups are treated as an invalid structure.
    /// </summary>
    [TestMethod]
    public void AbandonsExtractionForCrossingBracketGroups() {
        AssertParse("(a（b)）", string.Empty, "(a（b)）", string.Empty);
    }

    #endregion

    #region Hyphen handling

    /// <summary>
    /// Verifies that a single half-width hyphen separates artist from title.
    /// </summary>
    [TestMethod]
    public void SplitsSingleHalfWidthHyphen() {
        AssertParse("A - B", "A", "B", string.Empty);
    }

    /// <summary>
    /// Verifies that multiple half-width hyphens make the whole remaining text the title.
    /// </summary>
    [TestMethod]
    public void TreatsMultipleHyphensAsTitleOnly() {
        AssertParse("A - B - C", string.Empty, "A - B - C", string.Empty);
    }

    /// <summary>
    /// Verifies that hyphens inside a removed comment do not count when applying the multiple-hyphen rule.
    /// </summary>
    [TestMethod]
    public void IgnoresHyphensInsideCommentsWhenSplitting() {
        AssertParse("A - B (Live - Tokyo - Mix)", "A", "B", "Live - Tokyo - Mix");
    }

    /// <summary>
    /// Verifies that a full-width hyphen is not treated as a separator.
    /// </summary>
    [TestMethod]
    public void DoesNotSplitOnFullWidthHyphen() {
        AssertParse("A － B", string.Empty, "A － B", string.Empty);
    }

    /// <summary>
    /// Verifies that an em dash is not treated as a separator.
    /// </summary>
    [TestMethod]
    public void DoesNotSplitOnEmDash() {
        AssertParse("A — B", string.Empty, "A — B", string.Empty);
    }

    /// <summary>
    /// Verifies that a name without a hyphen produces an empty artist and a full title.
    /// </summary>
    [TestMethod]
    public void ReturnsEmptyArtistWhenNoHyphenExists() {
        AssertParse("Song Title", string.Empty, "Song Title", string.Empty);
    }

    /// <summary>
    /// Verifies that an empty input produces three empty fields.
    /// </summary>
    [TestMethod]
    public void ReturnsEmptyFieldsForEmptyInput() {
        AssertParse(string.Empty, string.Empty, string.Empty, string.Empty);
    }

    #endregion

    #region Whitespace handling

    /// <summary>
    /// Verifies that standard whitespace around the artist and title is removed.
    /// </summary>
    [TestMethod]
    public void TrimsStandardWhitespaceAroundArtistAndTitle() {
        AssertParse("  A  -  B  ", "A", "B", string.Empty);
    }

    /// <summary>
    /// Verifies that standard whitespace around extracted comment text is removed.
    /// </summary>
    [TestMethod]
    public void TrimsStandardWhitespaceInsideComments() {
        AssertParse("A - B (  Live  )", "A", "B", "Live");
    }

    /// <summary>
    /// Verifies that full-width spaces inside comment text are preserved.
    /// </summary>
    [TestMethod]
    public void PreservesFullWidthSpacesInsideComments() {
        AssertParse("A - B (\u3000Live\u3000)", "A", "B", "\u3000Live\u3000");
    }

    /// <summary>
    /// Verifies that full-width spaces around artist and title are preserved.
    /// </summary>
    [TestMethod]
    public void PreservesFullWidthSpacesAroundFields() {
        AssertParse("A\u3000-\u3000B", "A\u3000", "\u3000B", string.Empty);
    }

    #endregion

    #region Argument validation

    /// <summary>
    /// Verifies that a null input is rejected.
    /// </summary>
    [TestMethod]
    public void ThrowsForNullInput() {
        Assert.Throws<ArgumentNullException>(() => FilenameParser.Parse(null!));
    }

    #endregion

    /// <summary>
    /// Parses the input and asserts all three resulting fields.
    /// </summary>
    /// <param name="input">The file name to parse.</param>
    /// <param name="expectedArtist">The expected artist value.</param>
    /// <param name="expectedTitle">The expected title value.</param>
    /// <param name="expectedComment">The expected comment value.</param>
    private static void AssertParse(
        string input,
        string expectedArtist,
        string expectedTitle,
        string expectedComment) {
        FilenameParseResult result = FilenameParser.Parse(input);

        Assert.AreEqual(expectedArtist, result.Artist, "Artist mismatch.");
        Assert.AreEqual(expectedTitle, result.Title, "Title mismatch.");
        Assert.AreEqual(expectedComment, result.Comment, "Comment mismatch.");
    }
}