// 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 file in the project root for more information.

using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Indentation;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.SplitStringLiteral;

internal abstract partial class StringSplitter(
    ParsedDocument document, int position,
    in IndentationOptions indentationOptions,
    CancellationToken cancellationToken)
{
    protected readonly SyntaxAnnotation RightNodeAnnotation = new();

    protected readonly ParsedDocument Document = document;
    protected readonly int CursorPosition = position;
    protected readonly IndentationOptions IndentationOptions = indentationOptions;
    protected readonly CancellationToken CancellationToken = cancellationToken;
    protected readonly SyntaxToken PlusNewLineToken = SyntaxFactory.Token(
            leading: default,
            SyntaxKind.PlusToken,
            [SyntaxFactory.EndOfLine(
                indentationOptions.FormattingOptions.NewLine)]);

    protected int TabSize => IndentationOptions.FormattingOptions.TabSize;
    protected bool UseTabs => IndentationOptions.FormattingOptions.UseTabs;

    public static StringSplitter? TryCreate(
        ParsedDocument document, int position,
        in IndentationOptions indentationOptions,
        CancellationToken cancellationToken)
    {
        var token = document.Root.FindToken(position);

        if (token.Kind() is SyntaxKind.StringLiteralToken or SyntaxKind.Utf8StringLiteralToken)
        {
            return new SimpleStringSplitter(
                document, position, token, indentationOptions, cancellationToken);
        }

        var interpolatedStringExpression = TryGetInterpolatedStringExpression(token, position);
        if (interpolatedStringExpression != null)
        {
            return new InterpolatedStringSplitter(
                document, position, interpolatedStringExpression, indentationOptions, cancellationToken);
        }

        return null;
    }

    private static InterpolatedStringExpressionSyntax? TryGetInterpolatedStringExpression(
        SyntaxToken token, int position)
    {
        if (token.Kind() is SyntaxKind.InterpolatedStringTextToken or SyntaxKind.InterpolatedStringEndToken ||
            IsInterpolationOpenBrace(token, position))
        {
            return token.GetAncestor<InterpolatedStringExpressionSyntax>();
        }

        return null;
    }

    private static bool IsInterpolationOpenBrace(SyntaxToken token, int position)
    {
        return token.Kind() == SyntaxKind.OpenBraceToken &&
            token.Parent.IsKind(SyntaxKind.Interpolation) &&
            position == token.SpanStart;
    }

    protected abstract int StringOpenQuoteLength();

    protected abstract bool CheckToken();

    protected abstract SyntaxNode GetNodeToReplace();

    protected abstract BinaryExpressionSyntax CreateSplitString();

    public bool TrySplit([NotNullWhen(true)] out SyntaxNode? newRoot, out int newPosition)
    {
        var nodeToReplace = GetNodeToReplace();

        if (CursorPosition <= nodeToReplace.SpanStart || CursorPosition >= nodeToReplace.Span.End)
        {
            newRoot = null;
            newPosition = 0;
            return false;
        }

        if (!CheckToken())
        {
            newRoot = null;
            newPosition = 0;
            return false;
        }

        (newRoot, newPosition) = SplitString();
        return true;
    }

    private (SyntaxNode root, int caretPosition) SplitString()
    {
        var splitString = CreateSplitString();

        var nodeToReplace = GetNodeToReplace();
        var newRoot = Document.Root.ReplaceNode(nodeToReplace, splitString);
        var rightExpression = newRoot.GetAnnotatedNodes(RightNodeAnnotation).Single();

        var indentString = GetIndentString(newRoot);
        var newRightExpression = rightExpression.WithLeadingTrivia(SyntaxFactory.ElasticWhitespace(indentString));
        var newRoot2 = newRoot.ReplaceNode(rightExpression, newRightExpression);

        return (newRoot2, rightExpression.Span.Start + indentString.Length + StringOpenQuoteLength());
    }

    private string GetIndentString(SyntaxNode newRoot)
    {
        var indentationService = Document.LanguageServices.GetRequiredService<IIndentationService>();
        var originalLineNumber = Document.Text.Lines.GetLineFromPosition(CursorPosition).LineNumber;

        var newDocument = Document.WithChangedRoot(newRoot, CancellationToken);
        var desiredIndentation = indentationService.GetIndentation(
            newDocument, originalLineNumber + 1, IndentationOptions, CancellationToken);

        var newSourceText = newDocument.Text;
        var baseLine = newSourceText.Lines.GetLineFromPosition(desiredIndentation.BasePosition);

        var baseOffsetInLineInPositions = desiredIndentation.BasePosition - baseLine.Start;
        var baseOffsetInLineInColumns = baseLine.GetColumnFromLineOffset(baseOffsetInLineInPositions, TabSize);

        var indent = baseOffsetInLineInColumns + desiredIndentation.Offset;
        var indentString = indent.CreateIndentationString(UseTabs, TabSize);
        return indentString;
    }
}