// 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 System.Runtime.Serialization;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.EditAndContinue;

/// <summary>
/// Represents a span of text in a source code file in terms of file name, line number, and offset within line.
/// An alternative for <see cref="FileLinePositionSpan"/> without <see cref="FileLinePositionSpan.HasMappedPath"/> bit.
/// </summary>
/// <remarks>
/// Initializes the <see cref="SourceFileSpan"/> instance.
/// </remarks>
/// <param name="path">The file identifier - typically a relative or absolute path.</param>
/// <param name="span">The span.</param>
/// <exception cref="ArgumentNullException"><paramref name="path"/> is null.</exception>
[DataContract]
internal readonly struct SourceFileSpan(string path, LinePositionSpan span) : IEquatable<SourceFileSpan>
{
    /// <summary>
    /// Path, or null if the span represents an invalid value.
    /// </summary>
    /// <remarks>
    /// Path may be <see cref="string.Empty"/> if not available.
    /// </remarks>
    [DataMember(Order = 0)]
    public string Path { get; } = path ?? throw new ArgumentNullException(nameof(path));

    /// <summary>
    /// Gets the span.
    /// </summary>
    [DataMember(Order = 1)]
    public LinePositionSpan Span { get; } = span;

    public SourceFileSpan WithSpan(LinePositionSpan span)
        => new(Path, span);

    public SourceFileSpan WithPath(string path)
        => new(path, Span);

    /// <summary>
    /// Returns true if the span represents a valid location.
    /// </summary>
    public bool IsValid
        => Path != null; // invalid span can be constructed by new SourceFileSpan()

    /// <summary>
    /// Gets the <see cref="LinePosition"/> of the start of the span.
    /// </summary>
    public LinePosition Start
        => Span.Start;

    /// <summary>
    /// Gets the <see cref="LinePosition"/> of the end of the span.
    /// </summary>
    public LinePosition End
        => Span.End;

    public bool Equals(SourceFileSpan other)
        => Span.Equals(other.Span) && string.Equals(Path, other.Path, StringComparison.Ordinal);

    public override bool Equals(object? other)
        => other is SourceFileSpan span && Equals(span);

    public override int GetHashCode()
        => Hash.Combine(Path, Span.GetHashCode());

    public override string ToString()
        => string.IsNullOrEmpty(Path) ? Span.ToString() : $"{Path}: {Span}";

    public static implicit operator SourceFileSpan(FileLinePositionSpan span)
        => new(span.Path, span.Span);

    public static bool operator ==(SourceFileSpan left, SourceFileSpan right)
        => left.Equals(right);

    public static bool operator !=(SourceFileSpan left, SourceFileSpan right)
        => !(left == right);

    public bool Contains(SourceFileSpan span)
        => Span.Contains(span.Span) && string.Equals(Path, span.Path, StringComparison.Ordinal);
}