// 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;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Editor.OptionsExtensionMethods;
 
namespace Microsoft.CodeAnalysis.Text.Shared.Extensions;
 
internal static class ITextSnapshotLineExtensions
{
    /// <summary>
    /// Returns the first non-whitespace position on the given line, or null if 
    /// the line is empty or contains only whitespace.
    /// </summary>
    public static int? GetFirstNonWhitespacePosition(this ITextSnapshotLine line)
    {
        var firstNonWhitespaceOffset = line.GetFirstNonWhitespaceOffset();
 
        return firstNonWhitespaceOffset.HasValue
            ? firstNonWhitespaceOffset + line.Start
            : null;
    }
 
    /// <summary>
    /// Returns the first non-whitespace position on the given line as an offset
    /// from the start of the line, or null if the line is empty or contains only
    /// whitespace.
    /// </summary>
    public static int? GetFirstNonWhitespaceOffset(this ITextSnapshotLine line)
    {
        Contract.ThrowIfNull(line);
 
        var snapshot = line.Snapshot;
        for (var i = 0; i < line.Length; i++)
        {
            if (!char.IsWhiteSpace(snapshot[line.Start + i]))
            {
                return i;
            }
        }
 
        return null;
    }
 
    /// <summary>
    /// Returns the last non-whitespace position on the given line, or null if 
    /// the line is empty or contains only whitespace.
    /// </summary>
    public static int? GetLastNonWhitespacePosition(this ITextSnapshotLine line)
        => line.AsTextLine().GetLastNonWhitespacePosition();
 
    /// <summary>
    /// Determines whether the specified line is empty or contains whitespace only.
    /// </summary>
    public static bool IsEmptyOrWhitespace(this ITextSnapshotLine line, int startIndex = 0, int endIndex = -1)
    {
        Contract.ThrowIfNull(line, "line");
        Contract.ThrowIfFalse(startIndex >= 0);
 
        if (endIndex == -1)
        {
            endIndex = line.Length;
        }
 
        var snapshot = line.Snapshot;
        for (var i = startIndex; i < endIndex; i++)
        {
            if (!char.IsWhiteSpace(snapshot[line.Start + i]))
            {
                return false;
            }
        }
 
        return true;
    }
 
    public static ITextSnapshotLine? GetPreviousMatchingLine(this ITextSnapshotLine line, Func<ITextSnapshotLine, bool> predicate)
    {
        Contract.ThrowIfNull(line, @"line");
        Contract.ThrowIfNull(predicate, @"tree");
 
        if (line.LineNumber <= 0)
        {
            return null;
        }
 
        var snapshot = line.Snapshot;
        for (var lineNumber = line.LineNumber - 1; lineNumber >= 0; lineNumber--)
        {
            var currentLine = snapshot.GetLineFromLineNumber(lineNumber);
            if (!predicate(currentLine))
            {
                continue;
            }
 
            return currentLine;
        }
 
        return null;
    }
 
    public static int GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(this ITextSnapshotLine line, IEditorOptions editorOptions)
        => line.GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(editorOptions.GetTabSize());
 
    public static int GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(this ITextSnapshotLine line, int tabSize)
        => line.GetText().GetColumnOfFirstNonWhitespaceCharacterOrEndOfLine(tabSize);
 
    public static int GetColumnFromLineOffset(this ITextSnapshotLine line, int lineOffset, IEditorOptions editorOptions)
        => line.GetText().GetColumnFromLineOffset(lineOffset, editorOptions.GetTabSize());
 
    public static int GetLineOffsetFromColumn(this ITextSnapshotLine line, int column, IEditorOptions editorOptions)
        => line.GetText().GetLineOffsetFromColumn(column, editorOptions.GetTabSize());
 
    /// <summary>
    /// Checks if the given line at the given snapshot index starts with the provided value.
    /// </summary>
    public static bool StartsWith(this ITextSnapshotLine line, int index, string value, bool ignoreCase)
    {
        var snapshot = line.Snapshot;
        if (index + value.Length > snapshot.Length)
            return false;
 
        for (var i = 0; i < value.Length; i++)
        {
            var snapshotIndex = index + i;
            var actualCharacter = snapshot[snapshotIndex];
            var expectedCharacter = value[i];
 
            if (ignoreCase)
            {
                actualCharacter = char.ToLowerInvariant(actualCharacter);
                expectedCharacter = char.ToLowerInvariant(expectedCharacter);
            }
 
            if (actualCharacter != expectedCharacter)
                return false;
        }
 
        return true;
    }
 
    public static bool Contains(this ITextSnapshotLine line, int index, string value, bool ignoreCase)
    {
        var snapshot = line.Snapshot;
        for (var i = index; i < line.End; i++)
        {
            if (i + value.Length > snapshot.Length)
                return false;
 
            if (line.StartsWith(i, value, ignoreCase))
                return true;
        }
 
        return false;
    }
}