using System.Text.Json;
using ClawdDotNet.Core.Api.Models;
using Shouldly;

namespace ClawdDotNet.Core.Tests.Api;

public sealed class ChatMessageSerializationTests
{
    private static string Serialize(ChatMessage m) => JsonSerializer.Serialize(m);
    private static ChatMessage Deserialize(string json) => JsonSerializer.Deserialize<ChatMessage>(json)!;

    // ═══════════════════════════════════════════════════════════
    //  Standard format
    // ═══════════════════════════════════════════════════════════

    [Fact]
    public void Without_breakpoint_the_content_stays_a_plain_string()
    {
        var json = Serialize(ChatMessage.User("Hallo"));

        json.ShouldBe("""{"role":"user","content":"Hallo"}""");
    }

    [Fact]
    public void Null_values_are_omitted()
    {
        var json = Serialize(ChatMessage.Assistant("Antwort"));

        json.ShouldNotContain("tool_calls");
        json.ShouldNotContain("tool_call_id");
    }

    [Fact]
    public void Tool_answer_carries_its_ToolCallId()
    {
        var json = Serialize(ChatMessage.ToolResponse("call_42", "Ergebnis"));

        json.ShouldBe("""{"role":"tool","content":"Ergebnis","tool_call_id":"call_42"}""");
    }

    [Fact]
    public void AssistantWithToolCalls_serialises_the_calls()
    {
        var msg = ChatMessage.AssistantWithToolCalls([
            new ToolCall { Id = "c1", Function = new ToolCallFunction { Name = "FileRW", Arguments = "{}" } }
        ]);

        var json = Serialize(msg);

        json.ShouldContain("tool_calls");
        json.ShouldContain("FileRW");
        json.ShouldNotContain("\"content\"", Case.Sensitive);
    }

    // ═══════════════════════════════════════════════════════════
    //  Cache-Breakpoint
    // ═══════════════════════════════════════════════════════════

    [Fact]
    public void With_breakpoint_the_content_becomes_a_block_with_cache_control()
    {
        var msg = ChatMessage.System("Du bist ein Agent.");
        msg.CacheBreakpoint = true;

        var json = Serialize(msg);

        json.ShouldBe(
            """{"role":"system","content":[{"type":"text","text":"Du bist ein Agent.","cache_control":{"type":"ephemeral"}}]}""");
    }

    [Fact]
    public void The_breakpoint_itself_is_not_serialised_as_a_field()
    {
        var msg = ChatMessage.User("Text");
        msg.CacheBreakpoint = true;

        Serialize(msg).ShouldNotContain("CacheBreakpoint", Case.Insensitive);
    }

    // ═══════════════════════════════════════════════════════════
    //  Deserialization: both formats
    // ═══════════════════════════════════════════════════════════

    [Fact]
    public void Content_as_string_is_read()
    {
        var msg = Deserialize("""{"role":"assistant","content":"Antwort"}""");

        msg.Role.ShouldBe("assistant");
        msg.Content.ShouldBe("Antwort");
    }

    [Fact]
    public void Content_as_block_array_is_read()
    {
        // This is what a persisted context written with a breakpoint looks like.
        var msg = Deserialize(
            """{"role":"system","content":[{"type":"text","text":"Prompt","cache_control":{"type":"ephemeral"}}]}""");

        msg.Content.ShouldBe("Prompt");
    }

    [Fact]
    public void Several_text_blocks_are_merged()
    {
        var msg = Deserialize(
            """{"role":"user","content":[{"type":"text","text":"Teil A"},{"type":"text","text":" Teil B"}]}""");

        msg.Content.ShouldBe("Teil A Teil B");
    }

    [Fact]
    public void Missing_content_becomes_null()
    {
        var msg = Deserialize("""{"role":"assistant","tool_calls":[]}""");

        msg.Content.ShouldBeNull();
    }

    [Fact]
    public void Unknown_fields_do_no_harm()
    {
        var msg = Deserialize("""{"role":"user","content":"Text","reasoning":"…","annotations":[1,2]}""");

        msg.Content.ShouldBe("Text");
    }

    [Fact]
    public void RoundTrip_keeps_all_fields()
    {
        var original = ChatMessage.ToolResponse("call_7", "Das Ergebnis");

        var restored = Deserialize(Serialize(original));

        restored.Role.ShouldBe("tool");
        restored.Content.ShouldBe("Das Ergebnis");
        restored.ToolCallId.ShouldBe("call_7");
    }

    [Fact]
    public void RoundTrip_keeps_umlauts_and_emoji()
    {
        var original = ChatMessage.User("Grüße aus München 🦀 — größer & schöner");

        var restored = Deserialize(Serialize(original));

        restored.Content.ShouldBe("Grüße aus München 🦀 — größer & schöner");
    }
}