using Microsoft.Extensions.AI;

namespace AnchorCli;

internal sealed class ChatSession
{
    private readonly IChatClient _agent;
    public ContextCompactor Compactor { get; }
    public List<ChatMessage> History { get; }

    public ChatSession(IChatClient innerClient)
    {
        Compactor = new ContextCompactor(innerClient);
        
        var tools = ToolRegistry.GetTools();
        _agent = new ChatClientBuilder(innerClient)
            .UseFunctionInvocation()
            .Build();

        History = new List<ChatMessage>
        {
            new(ChatRole.System, $$"""
                You are anchor, a coding assistant that edits files using the Hashline technique.

                ## Reading files
                When you read a file, lines are returned in the format: lineNumber:hash|content
                The "lineNumber:hash|" prefix is METADATA for anchoring — it is NOT part of the file.

                ## Editing files
                To edit, reference anchors as "lineNumber:hash" in startAnchor/endAnchor parameters.
                The newLines/initialLines parameter must contain RAW SOURCE CODE ONLY.
                ❌ WRONG: ["5:a3|    public void Foo()"]
                ✅ RIGHT: ["    public void Foo()"]
                Never include the "lineNumber:hash|" prefix in content you write — it will corrupt the file.

                ## Workflow
                1. Always read a file before editing it.
                2. After a mutation, verify the returned fingerprint.
                3. Edit from bottom to top so line numbers don't shift.
                4. If an anchor fails validation, re-read the file to get fresh anchors.

                Keep responses concise. You have access to the current working directory.
                You are running on: {{System.Runtime.InteropServices.RuntimeInformation.OSDescription}}
            """)
        };
    }

    public async IAsyncEnumerable<ChatResponseUpdate> GetStreamingResponseAsync(
        [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken = default)
    {
        var options = new ChatOptions { Tools = ToolRegistry.GetTools() };
        var stream = _agent.GetStreamingResponseAsync(History, options, cancellationToken);
        
        await foreach (var update in stream.WithCancellation(cancellationToken))
        {
            yield return update;
        }
    }
}