// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Diagnostics;
using System.Net.Mime;
using System.Text.Json.Serialization;
using Microsoft.Shared.Diagnostics;
 
namespace Microsoft.Extensions.AI;
 
/// <summary>
/// Represents a URL, typically to hosted content such as an image, audio, or video.
/// </summary>
/// <remarks>
/// This class is intended for use with HTTP or HTTPS URIs that reference hosted content.
/// For data URIs, use <see cref="DataContent"/> instead.
/// </remarks>
[DebuggerDisplay("{DebuggerDisplay,nq}")]
public class UriContent : AIContent
{
    /// <summary>The default media type for unknown file extensions.</summary>
    private const string DefaultMediaType = "application/octet-stream";
 
    /// <summary>The URI represented.</summary>
    private Uri _uri;
 
    /// <summary>The MIME type of the data at the referenced URI.</summary>
    private string _mediaType;
 
    /// <summary>Initializes a new instance of the <see cref="UriContent"/> class.</summary>
    /// <param name="uri">The URI to the represented content.</param>
    /// <param name="mediaType">
    /// The media type (also known as MIME type) represented by the content. If not provided,
    /// it will be inferred from the file extension of the URI. If it cannot be inferred,
    /// "application/octet-stream" is used.
    /// </param>
    /// <exception cref="ArgumentNullException"><paramref name="uri"/> is <see langword="null"/>.</exception>
    /// <exception cref="ArgumentException"><paramref name="mediaType"/> is an invalid media type.</exception>
    /// <exception cref="UriFormatException"><paramref name="uri"/> is an invalid URL.</exception>
    public UriContent(string uri, string? mediaType = null)
        : this(new Uri(Throw.IfNull(uri)), mediaType)
    {
    }
 
    /// <summary>Initializes a new instance of the <see cref="UriContent"/> class.</summary>
    /// <param name="uri">The URI to the represented content.</param>
    /// <param name="mediaType">
    /// The media type (also known as MIME type) represented by the content. If not provided,
    /// it will be inferred from the file extension of the URI. If it cannot be inferred,
    /// "application/octet-stream" is used.
    /// </param>
    /// <exception cref="ArgumentNullException"><paramref name="uri"/> is <see langword="null"/>.</exception>
    /// <exception cref="ArgumentException"><paramref name="mediaType"/> is an invalid media type.</exception>
    [JsonConstructor]
    public UriContent(Uri uri, string? mediaType = null)
    {
        _uri = Throw.IfNull(uri);
        _mediaType = mediaType is not null
            ? DataUriParser.ThrowIfInvalidMediaType(mediaType)
            : InferMediaType(uri);
    }
 
    /// <summary>Gets or sets the <see cref="Uri"/> for this content.</summary>
    public Uri Uri
    {
        get => _uri;
        set => _uri = Throw.IfNull(value);
    }
 
    /// <summary>Gets or sets the media type (also known as MIME type) for this content.</summary>
    /// <exception cref="ArgumentException"><paramref name="value"/> represents an invalid media type.</exception>
    public string MediaType
    {
        get => _mediaType;
        set => _mediaType = DataUriParser.ThrowIfInvalidMediaType(value);
    }
 
    /// <summary>
    /// Determines whether the <see cref="MediaType"/>'s top-level type matches the specified <paramref name="topLevelType"/>.
    /// </summary>
    /// <param name="topLevelType">The type to compare against <see cref="MediaType"/>.</param>
    /// <returns><see langword="true"/> if the type portion of <see cref="MediaType"/> matches the specified value; otherwise, false.</returns>
    /// <remarks>
    /// A media type is primarily composed of two parts, a "type" and a "subtype", separated by a slash ("/").
    /// The type portion is also referred to as the "top-level type"; for example,
    /// "image/png" has a top-level type of "image". <see cref="HasTopLevelMediaType"/> compares
    /// the specified <paramref name="topLevelType"/> against the type portion of <see cref="MediaType"/>.
    /// </remarks>
    public bool HasTopLevelMediaType(string topLevelType) => DataUriParser.HasTopLevelMediaType(MediaType, topLevelType);
 
    /// <summary>Gets a string representing this instance to display in the debugger.</summary>
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    private string DebuggerDisplay => $"Uri = {_uri}";
 
    /// <summary>Infers the media type from the URI's file extension.</summary>
    private static string InferMediaType(Uri uri)
    {
        string path;
        if (uri.IsAbsoluteUri)
        {
            path = uri.AbsolutePath;
        }
        else
        {
            path = uri.OriginalString;
            int i = path.AsSpan().IndexOfAny('?', '#');
            if (i >= 0)
            {
                path = path.Substring(0, i);
            }
        }
 
        return MediaTypeMap.GetMediaType(path) ?? DefaultMediaType;
    }
}