Fixed sources of your own documents not reacting to a click

app/MindWork AI Studio/Assistants/I18N/allTexts.lua

@@ -5029,6 +5029,30 @@ UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SETTINGS::SETTINGSPANELTRANSCRIPTION::T78
 -- Are you sure you want to delete the transcription provider '{0}'?
 UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SETTINGS::SETTINGSPANELTRANSCRIPTION::T789660305"] = "Are you sure you want to delete the transcription provider '{0}'?"
 
+-- Could not open the file location.
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T1118835751"] = "Could not open the file location."
+
+-- Opens {0}
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T1170655868"] = "Opens {0}"
+
+-- Could not open the file location: {0}
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T1455637941"] = "Could not open the file location: {0}"
+
+-- Show this file in the file manager of your system
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T1587653504"] = "Show this file in the file manager of your system"
+
+-- Opens {0} on page {1}
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T2402202635"] = "Opens {0} on page {1}"
+
+-- Unknown error
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T3461425987"] = "Unknown error"
+
+-- Could not open the document.
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T3570758363"] = "Could not open the document."
+
+-- Could not open the document: {0}
+UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::SOURCESLIST::T945417289"] = "Could not open the document: {0}"
+
 -- Copy {0} to the clipboard
 UI_TEXT_CONTENT["AISTUDIO::COMPONENTS::TEXTINFOLINE::T2206391442"] = "Copy {0} to the clipboard"
 
@@ -12199,6 +12223,9 @@ UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T1238078807"] = "No com
 -- Failed to store the API key due to an API issue.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T1704298921"] = "Failed to store the API key due to an API issue."
 
+-- The runtime document endpoint returned '{0}'.
+UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T1843760475"] = "The runtime document endpoint returned '{0}'."
+
 -- The global shortcut could not be registered because of a desktop integration error.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T2032590244"] = "The global shortcut could not be registered because of a desktop integration error."
 
@@ -12226,6 +12253,9 @@ UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T3351807428"] = "Succes
 -- The desktop service returned an invalid response while registering the global shortcut.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T3369097283"] = "The desktop service returned an invalid response while registering the global shortcut."
 
+-- The runtime document endpoint failed without details.
+UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T353458993"] = "The runtime document endpoint failed without details."
+
 -- AI Studio could not access secure storage because no default collection is configured. Open a compatible password manager, create or select a collection, unlock it, and set it as the default.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T3611400673"] = "AI Studio could not access secure storage because no default collection is configured. Open a compatible password manager, create or select a collection, unlock it, and set it as the default."
 
@@ -12244,6 +12274,9 @@ UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T3929880252"] = "No sav
 -- Failed to get the secret data due to an API issue.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T4007657575"] = "Failed to get the secret data due to an API issue."
 
+-- The runtime document endpoint is not available.
+UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T541638186"] = "The runtime document endpoint is not available."
+
 -- AI Studio could not access secure storage. See the log for technical details.
 UI_TEXT_CONTENT["AISTUDIO::TOOLS::SERVICES::RUSTSERVICE::T624023541"] = "AI Studio could not access secure storage. See the log for technical details."
 

app/MindWork AI Studio/Chat/ContentBlockComponent.razor

@@ -223,7 +223,7 @@
                                 }
                                 @if (textContent.Sources.Count > 0)
                                 {
-                                    <MudMarkdown Value="@textContent.Sources.ToMarkdown()" Props="Markdown.DefaultConfig" Styling="@this.MarkdownStyling" MarkdownPipeline="Markdown.SAFE_MARKDOWN_PIPELINE" />
+                                    <SourcesList Sources="@textContent.Sources"/>
                                 }
                             </div>
                         }

app/MindWork AI Studio/Components/SourcesList.razor

@@ -0,0 +1,37 @@
+@inherits MSGComponentBase
+
+@* The class is what the Markdown renderer wraps its own output in, so the headings and the list
+   keep the look they had while this list was Markdown. *@
+<div class="mud-markdown-body">
+    @foreach (var group in this.groups)
+    {
+        <MudText Typo="Typo.h2">
+            @group.Heading
+        </MudText>
+        <ul>
+            @foreach (var entry in group.Entries)
+            {
+                <li>
+                    @($"[{entry.Number}] ")
+                    @if (entry.Document is { } document)
+                    {
+                        <MudTooltip Text="@this.GetDocumentTooltip(document)" Placement="Placement.Top">
+                            <MudLink Typo="Typo.body1" OnClick="@(() => this.OpenDocument(document))">
+                                @entry.Title
+                            </MudLink>
+                        </MudTooltip>
+                        <MudTooltip Text="@T("Show this file in the file manager of your system")" Placement="Placement.Top">
+                            <MudIconButton Icon="@Icons.Material.Filled.FolderOpen" Size="Size.Small" OnClick="@(() => this.ShowInFileManager(document))"/>
+                        </MudTooltip>
+                    }
+                    else
+                    {
+                        <MudLink Href="@entry.Link" Target="_blank" Typo="Typo.body1">
+                            @entry.Title
+                        </MudLink>
+                    }
+                </li>
+            }
+        </ul>
+    }
+</div>

app/MindWork AI Studio/Components/SourcesList.razor.cs

@@ -0,0 +1,147 @@
+using AIStudio.Tools.Rust;
+using AIStudio.Tools.Services;
+
+using Microsoft.AspNetCore.Components;
+
+namespace AIStudio.Components;
+
+/// <summary>
+/// Shows the sources an answer rests on, grouped and numbered the way the export is.
+/// </summary>
+/// <remarks>
+/// This list used to be Markdown, which read correctly but could not be clicked where it mattered:
+/// a Markdown renderer hands every link to the browser, and the browser refuses a file address on a
+/// page it loaded over http. A source of the user's own documents therefore did nothing at all.
+/// Written out as components, an entry can hand its document to the runtime instead, together with
+/// the page the passage was found on.
+/// </remarks>
+public partial class SourcesList : MSGComponentBase
+{
+    /// <summary>
+    /// The sources to show.
+    /// </summary>
+    [Parameter]
+    public IList<Source> Sources { get; set; } = [];
+
+    [Inject]
+    private RustService RustService { get; init; } = null!;
+
+    [Inject]
+    private ILogger<SourcesList> Logger { get; init; } = null!;
+
+    private readonly List<SourceEntryGroup> groups = [];
+
+    #region Overrides of ComponentBase
+
+    protected override async Task OnParametersSetAsync()
+    {
+        this.RebuildGroups();
+        await base.OnParametersSetAsync();
+    }
+
+    #endregion
+
+    /// <summary>
+    /// Reads the sources once per render instead of once per entry and render.
+    /// </summary>
+    /// <remarks>
+    /// Where a source points is answered by looking at its link, and while an answer streams, this
+    /// runs again for every chunk. The previous Markdown list was rebuilt and parsed just as often,
+    /// so this is the cheaper of the two, but it is still worth doing once for the whole list.
+    /// </remarks>
+    private void RebuildGroups()
+    {
+        this.groups.Clear();
+        foreach (var group in this.Sources.GroupSources())
+        {
+            var entries = new List<SourceEntry>(group.Sources.Count);
+            foreach (var numberedSource in group.Sources)
+            {
+                var document = numberedSource.Source.TryGetDocumentLocation(out var location) ? location : (SourceDocumentLocation?)null;
+                entries.Add(new(numberedSource.Number, numberedSource.Source.Title, numberedSource.Source.URL, document));
+            }
+
+            this.groups.Add(new(group.Heading, entries));
+        }
+    }
+
+    private string GetDocumentTooltip(SourceDocumentLocation document) => document.PageNumber is > 0
+        ? string.Format(T("Opens {0} on page {1}"), document.Path, document.PageNumber)
+        : string.Format(T("Opens {0}"), document.Path);
+
+    /// <summary>
+    /// Opens a document in the program the system uses for it.
+    /// </summary>
+    /// <remarks>
+    /// Whether the program can be sent to a page is the runtime's business, and it says afterwards
+    /// whether it managed to. Nothing is shown about that here: the document is open, and the title
+    /// of the source names the page anyway.
+    /// </remarks>
+    /// <param name="document">The document to open, and the page to show.</param>
+    private async Task OpenDocument(SourceDocumentLocation document)
+    {
+        OpenDocumentResponse response;
+        try
+        {
+            response = await this.RustService.TryOpenDocumentInSystemViewer(document.Path, document.PageNumber);
+        }
+        catch (Exception e)
+        {
+            this.Logger.LogWarning(e, "Could not open a source document.");
+            await this.MessageBus.SendError(new(Icons.Material.Filled.Description, T("Could not open the document.")));
+            return;
+        }
+
+        if (response.Success)
+            return;
+
+        var issue = string.IsNullOrWhiteSpace(response.Issue) ? T("Unknown error") : response.Issue;
+        await this.MessageBus.SendError(new(Icons.Material.Filled.Description, string.Format(T("Could not open the document: {0}"), issue)));
+    }
+
+    /// <summary>
+    /// Opens the file browser of the system and selects the document in it.
+    /// </summary>
+    /// <remarks>
+    /// The second way out of the list: a document which the system opens in the wrong program, or
+    /// which the user wants to move or send on instead of read, is reached from here without being
+    /// opened. This is the same way out the embeddings page offers for a file it could not read.
+    /// </remarks>
+    /// <param name="document">The document to show.</param>
+    private async Task ShowInFileManager(SourceDocumentLocation document)
+    {
+        OpenPathResponse response;
+        try
+        {
+            response = await this.RustService.TryOpenPathInRuntimeFileManager(document.Path);
+        }
+        catch (Exception e)
+        {
+            this.Logger.LogWarning(e, "Could not show a source document in the file manager.");
+            await this.MessageBus.SendError(new(Icons.Material.Filled.FolderOpen, T("Could not open the file location.")));
+            return;
+        }
+
+        if (response.Success)
+            return;
+
+        var issue = string.IsNullOrWhiteSpace(response.Issue) ? T("Unknown error") : response.Issue;
+        await this.MessageBus.SendError(new(Icons.Material.Filled.FolderOpen, string.Format(T("Could not open the file location: {0}"), issue)));
+    }
+
+    /// <summary>
+    /// One group of the list, prepared so that the markup only has to show it.
+    /// </summary>
+    /// <param name="Heading">The heading above the group.</param>
+    /// <param name="Entries">The entries of the group, in the order they are shown.</param>
+    private readonly record struct SourceEntryGroup(string Heading, IReadOnlyList<SourceEntry> Entries);
+
+    /// <summary>
+    /// One entry of the list, prepared so that the markup only has to show it.
+    /// </summary>
+    /// <param name="Number">The number the source is listed under.</param>
+    /// <param name="Title">The title of the source.</param>
+    /// <param name="Link">The address of the source, which a web source is opened by.</param>
+    /// <param name="Document">The document the source names, or null when it names none.</param>
+    private readonly record struct SourceEntry(int Number, string Title, string Link, SourceDocumentLocation? Document);
+}

app/MindWork AI Studio/Tools/NumberedSource.cs

@@ -0,0 +1,13 @@
+namespace AIStudio.Tools;
+
+/// <summary>
+/// A source together with the number it is listed under.
+/// </summary>
+/// <remarks>
+/// The number runs through the whole list rather than starting over per group, because that is how
+/// an answer refers to a source. It is assigned once, where the groups are formed, so the chat and
+/// an exported document cannot end up numbering the same list differently.
+/// </remarks>
+/// <param name="Number">The number this source is listed under, counted from one.</param>
+/// <param name="Source">The source itself.</param>
+public readonly record struct NumberedSource(int Number, Source Source);

app/MindWork AI Studio/Tools/SourceDocumentLocation.cs

@@ -0,0 +1,8 @@
+namespace AIStudio.Tools;
+
+/// <summary>
+/// Where a source points in the file system, and where inside the document it was found.
+/// </summary>
+/// <param name="Path">The document in the file system, spelled the way this system spells a path.</param>
+/// <param name="PageNumber">The page the passage stands on, counted from one, or null when no page is known.</param>
+public readonly record struct SourceDocumentLocation(string Path, int? PageNumber);

app/MindWork AI Studio/Tools/SourceExtensions.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using System.Text;
 using System.Text.RegularExpressions;
 
@@ -79,6 +80,60 @@ public static partial class SourceExtensions
         return c is '-' or '.' or '_' or '~' or ':' or '/' or '?' or '#' or '[' or ']' or '@' or '!' or '$' or '&' or '\'' or '(' or ')' or '*' or '+' or ',' or ';' or '=';
     }
     
+    /// <summary>
+    /// Sorts a list of sources into the groups it is shown in, and numbers them.
+    /// </summary>
+    /// <remarks>
+    /// The order of the groups and the running number are what a reader follows, and they have to
+    /// be the same wherever the list appears: in the chat, in an exported document, and in the
+    /// clipboard. This is why both the chat and the Markdown below ask here instead of sorting the
+    /// list themselves.
+    /// </remarks>
+    /// <param name="sources">The list of sources to sort.</param>
+    /// <returns>The groups which have sources, in the order they are shown; empty when there are none.</returns>
+    public static IReadOnlyList<SourceGroup> GroupSources(this IList<Source> sources)
+    {
+        var llmSources = new List<Source>();
+        var toolSources = new List<Source>();
+        var ragSources = new List<Source>();
+        foreach (var source in sources)
+        {
+            switch (source.Origin)
+            {
+                case SourceOrigin.LLM:
+                    llmSources.Add(source);
+                    break;
+
+                case SourceOrigin.TOOL:
+                    toolSources.Add(source);
+                    break;
+
+                case SourceOrigin.RAG:
+                    ragSources.Add(source);
+                    break;
+            }
+        }
+
+        var groups = new List<SourceGroup>(3);
+        var sourceNum = 0;
+        AddGroup(groups, TB("Sources provided by the AI"), llmSources, ref sourceNum);
+        AddGroup(groups, TB("Sources used by tools"), toolSources, ref sourceNum);
+        AddGroup(groups, TB("Sources provided by the data providers"), ragSources, ref sourceNum);
+        return groups;
+    }
+
+    private static void AddGroup(ICollection<SourceGroup> groups, string heading, IReadOnlyList<Source> sources, ref int sourceNum)
+    {
+        if (sources.Count == 0)
+            return;
+
+        var numberedSources = new List<NumberedSource>(sources.Count);
+        foreach (var source in sources)
+            numberedSources.Add(new(++sourceNum, source));
+
+        groups.Add(new(heading, numberedSources));
+    }
+
     /// <summary>
     /// Converts a list of sources to a markdown-formatted string.
     /// </summary>
@@ -87,65 +142,18 @@ public static partial class SourceExtensions
     public static string ToMarkdown(this IList<Source> sources)
     {
         var sb = new StringBuilder();
-        var ragSources = new List<ISource>();
+        foreach (var group in sources.GroupSources())
-        var toolSources = new List<ISource>();
-        var sourceNum = 0;
-        var addedLLMHeaders = false;
-        foreach (var source in sources)
         {
-            switch (source.Origin)
+            if (sb.Length > 0)
-            {
-                case SourceOrigin.RAG: 
-                    ragSources.Add(source);
-                    break;
-                
-                case SourceOrigin.LLM:
-                    if (!addedLLMHeaders)
-                    {
-                        sb.Append("## ");
-                        sb.AppendLine(TB("Sources provided by the AI"));
-                        addedLLMHeaders = true;
-                    }
-                    
-                    sb.Append($"- [{++sourceNum}] ");
-                    AppendMarkdownLink(sb, source.Title, source.URL);
-                    sb.AppendLine();
-                    break;
-
-                case SourceOrigin.TOOL:
-                    toolSources.Add(source);
-                    break;
-            }
-        }
-
-        if(toolSources.Count > 0)
-        {
-            if(sb.Length > 0)
                 sb.AppendLine();
 
             sb.Append("## ");
-            sb.AppendLine(TB("Sources used by tools"));
+            sb.AppendLine(group.Heading);
 
-            foreach (var source in toolSources)
+            foreach (var numberedSource in group.Sources)
             {
-                sb.Append($"- [{++sourceNum}] ");
+                sb.Append($"- [{numberedSource.Number}] ");
-                AppendMarkdownLink(sb, source.Title, source.URL);
+                AppendMarkdownLink(sb, numberedSource.Source.Title, numberedSource.Source.URL);
-                sb.AppendLine();
-            }
-        }
-
-        if(ragSources.Count > 0)
-        {
-            if(sb.Length > 0)
-                sb.AppendLine();
-
-            sb.Append("## ");
-            sb.AppendLine(TB("Sources provided by the data providers"));
-
-            foreach (var source in ragSources)
-            {
-                sb.Append($"- [{++sourceNum}] ");
-                AppendMarkdownLink(sb, source.Title, source.URL);
                 sb.AppendLine();
             }
         }
@@ -173,6 +181,55 @@ public static partial class SourceExtensions
         return $"# {TB("Sources")}{Environment.NewLine}{Environment.NewLine}{sourcesMarkdown}";
     }
 
+    /// <summary>
+    /// Reads which document a source names, and which page of it.
+    /// </summary>
+    /// <remarks>
+    /// Only a source which names a file has such a location; a web source is opened by the browser
+    /// and never asks. The page rides in the fragment of the link as `page=N`, which is what the PDF
+    /// open parameters call for. A chat written before v26.9.1 carries `chunk=N` instead, which names
+    /// nothing a program could be sent to: such a source keeps its document and loses only the page.
+    /// </remarks>
+    /// <param name="source">The source to read.</param>
+    /// <param name="location">The document and its page, or the default when the source names no file.</param>
+    /// <returns>Whether the source names a file.</returns>
+    public static bool TryGetDocumentLocation(this ISource source, out SourceDocumentLocation location)
+    {
+        location = default;
+        if (string.IsNullOrWhiteSpace(source.URL))
+            return false;
+
+        var cleanedUrl = source.URL.Trim().Replace("\r", string.Empty).Replace("\n", string.Empty);
+        if (!Uri.TryCreate(cleanedUrl, UriKind.Absolute, out var absoluteUri) || !absoluteUri.IsFile)
+            return false;
+
+        //
+        // The link was made from a path of this system, so reading it back gives that path again --
+        // percent-encoded spaces and umlauts included, and with the separators this system uses.
+        //
+        var path = absoluteUri.LocalPath;
+        if (string.IsNullOrWhiteSpace(path))
+            return false;
+
+        location = new(path, ReadPageFromFragment(absoluteUri.Fragment));
+        return true;
+    }
+
+    private static int? ReadPageFromFragment(string fragment)
+    {
+        const string PAGE_PARAMETER = "page=";
+        foreach (var parameter in fragment.TrimStart('#').Split('&', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries))
+        {
+            if (!parameter.StartsWith(PAGE_PARAMETER, StringComparison.OrdinalIgnoreCase))
+                continue;
+
+            if (int.TryParse(parameter.AsSpan(PAGE_PARAMETER.Length), NumberStyles.None, CultureInfo.InvariantCulture, out var pageNumber) && pageNumber > 0)
+                return pageNumber;
+        }
+
+        return null;
+    }
+
     /// <summary>
     /// Merges a list of added sources into an existing list of sources, avoiding duplicates based on normalized URLs.
     /// </summary>

app/MindWork AI Studio/Tools/SourceGroup.cs

@@ -0,0 +1,8 @@
+namespace AIStudio.Tools;
+
+/// <summary>
+/// One group of a source list: a heading and the sources below it.
+/// </summary>
+/// <param name="Heading">The heading above the group.</param>
+/// <param name="Sources">The sources of the group, in the order they are shown.</param>
+public readonly record struct SourceGroup(string Heading, IReadOnlyList<NumberedSource> Sources);

app/Tests/Tools/SourceExtensionsTests.cs

@@ -85,6 +85,134 @@ public sealed class SourceExtensionsTests
         });
     }
 
+    [Test]
+    public void TheGroupingIsWhatTheChatAndTheExportBothRead()
+    {
+        // Mixed on purpose, and with two sources of one origin, so neither the order of the groups
+        // nor the order inside a group can come from the order of the input:
+        IList<Source> sources =
+        [
+            new("Handbook", "https://example.org/handbook", SourceOrigin.RAG),
+            new("Search result", "https://example.org/search", SourceOrigin.TOOL),
+            new("Cited by the model", "https://example.org/cited", SourceOrigin.LLM),
+            new("Second handbook", "https://example.org/handbook-2", SourceOrigin.RAG),
+        ];
+
+        var listed = sources.GroupSources().SelectMany(group => group.Sources).ToList();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(sources.GroupSources(), Has.Count.EqualTo(3), "Each of the three origins has a source, so each of them is a group.");
+            Assert.That(listed.Select(numbered => numbered.Source.Title), Is.EqualTo(new[] { "Cited by the model", "Search result", "Handbook", "Second handbook" }), "What the AI cited comes first, then what the tools read, then what the data providers gave.");
+            Assert.That(listed.Select(numbered => numbered.Number), Is.EqualTo(new[] { 1, 2, 3, 4 }), "The number runs through the whole list instead of starting over per group.");
+        });
+    }
+
+    [Test]
+    public void AnOriginWithoutSourcesIsNoGroup()
+    {
+        IList<Source> sources = [new("Search result", "https://example.org/search", SourceOrigin.TOOL)];
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(sources.GroupSources().Select(group => group.Sources.Count), Is.EqualTo(new[] { 1 }), "An answer which only used a tool gets one group, not three with two of them empty.");
+            Assert.That(new List<Source>().GroupSources(), Is.Empty, "An answer nobody had to look up gets no group at all.");
+        });
+    }
+
+    [Test]
+    public void TheMarkdownListsExactlyWhatTheGroupingSaysItShould()
+    {
+        IList<Source> sources =
+        [
+            new("Handbook (Page 12)", "file:///Users/someone/handbook.pdf#page=12", SourceOrigin.RAG),
+            new("Cited by the model", "https://example.org/cited", SourceOrigin.LLM),
+        ];
+
+        var entries = EntriesOf(sources.ToMarkdown());
+        var listed = sources.GroupSources().SelectMany(group => group.Sources).ToList();
+
+        Assert.That(entries, Has.Count.EqualTo(listed.Count), "Every source the grouping lists is written out, and nothing else is.");
+        for (var index = 0; index < entries.Count; index++)
+            Assert.That(entries[index], Does.StartWith($"- [{listed[index].Number}] ").And.Contains(listed[index].Source.Title), "The Markdown and the chat read the same grouping, so a source cannot be numbered one way here and another way there.");
+    }
+
+    [Test]
+    public void AKnownPageRidesInTheLinkOfASource()
+    {
+        var location = LocationOf("file:///Users/someone/My%20Documents/Gr%C3%B6%C3%9Fere%20%C3%9Cbersicht.pdf#page=12");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(location.Path, Does.EndWith("Größere Übersicht.pdf").And.Contains("My Documents"), "The percent-encoding of the link is undone, so the program is handed the name the file really has.");
+            Assert.That(location.PageNumber, Is.EqualTo(12), "This is the page the passage was found on, and the page the document is opened at.");
+        });
+    }
+
+    [Test]
+    public void APathOfAWindowsMachineComesBackAsOne()
+    {
+        var location = LocationOf("file:///C:/Users/someone/Documents/handbook.pdf#page=3");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(location.Path, Is.EqualTo(@"C:\Users\someone\Documents\handbook.pdf"), "A drive letter and backslashes are what a program on Windows is handed -- and what the link was made from there.");
+            Assert.That(location.PageNumber, Is.EqualTo(3));
+        });
+    }
+
+    [Test]
+    public void AChatFromBeforeThisReleaseKeepsItsDocumentAndLosesOnlyItsPage()
+    {
+        var location = LocationOf("file:///Users/someone/handbook.pdf#chunk=3");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(location.Path, Does.EndWith("handbook.pdf"), "Such a source still names its document, so the click still opens it.");
+            Assert.That(location.PageNumber, Is.Null, "A chunk is not a page: no program can be sent to one, so the document opens on its first page.");
+        });
+    }
+
+    [Test]
+    public void ALinkWithoutAFragmentNamesNoPage()
+    {
+        Assert.That(LocationOf("file:///Users/someone/handbook.pdf").PageNumber, Is.Null);
+    }
+
+    [Test]
+    public void APageWhichIsNoPageIsReadAsNone()
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(LocationOf("file:///Users/someone/handbook.pdf#page=0").PageNumber, Is.Null, "Pages are counted from one, so a zero is not a page.");
+            Assert.That(LocationOf("file:///Users/someone/handbook.pdf#page=-2").PageNumber, Is.Null);
+            Assert.That(LocationOf("file:///Users/someone/handbook.pdf#page=twelve").PageNumber, Is.Null);
+            Assert.That(LocationOf("file:///Users/someone/handbook.pdf#chunk=3&page=12").PageNumber, Is.EqualTo(12), "A link which already carried a fragment gets the page appended with an ampersand, and it is found there too.");
+        });
+    }
+
+    [Test]
+    public void AWebSourceNamesNoDocumentAtAll()
+    {
+        // The fragment reads like a page on purpose: what decides is the scheme, not the fragment.
+        ISource source = new Source("Article", "https://example.org/article#page=12", SourceOrigin.LLM);
+
+        Assert.That(source.TryGetDocumentLocation(out _), Is.False, "A web source is opened by the browser and has no path to hand to a program.");
+    }
+
+    /// <summary>
+    /// Reads where the link of a source points, and fails the test when it points nowhere.
+    /// </summary>
+    /// <param name="url">The link of the source.</param>
+    /// <returns>The document and the page the link names.</returns>
+    private static SourceDocumentLocation LocationOf(string url)
+    {
+        ISource source = new Source("Handbook", url, SourceOrigin.RAG);
+
+        Assert.That(source.TryGetDocumentLocation(out var location), Is.True, "This link names a file, so a location is what it has.");
+        return location;
+    }
+
     /// <summary>
     /// Reads the entries of a source list, without the headings above them.
     /// </summary>