import { Test, TestingModule } from "@nestjs/testing";
import { MatrixStreamingService } from "./matrix-streaming.service";
import { MatrixService } from "./matrix.service";
import { vi, describe, it, expect, beforeEach, afterEach } from "vitest";
import type { StreamResponseOptions } from "./matrix-streaming.service";

// Mock matrix-bot-sdk to prevent native module loading
vi.mock("matrix-bot-sdk", () => {
  return {
    MatrixClient: class MockMatrixClient {},
    SimpleFsStorageProvider: class MockStorageProvider {
      constructor(_filename: string) {
        // No-op for testing
      }
    },
    AutojoinRoomsMixin: {
      setupOnClient: vi.fn(),
    },
  };
});

// Mock MatrixClient
const mockClient = {
  sendMessage: vi.fn().mockResolvedValue("$initial-event-id"),
  sendEvent: vi.fn().mockResolvedValue("$edit-event-id"),
  setTyping: vi.fn().mockResolvedValue(undefined),
};

// Mock MatrixService
const mockMatrixService = {
  isConnected: vi.fn().mockReturnValue(true),
  getClient: vi.fn().mockReturnValue(mockClient),
};

/**
 * Helper: create an async iterable from an array of strings with optional delays
 */
async function* createTokenStream(
  tokens: string[],
  delayMs = 0
): AsyncGenerator<string, void, undefined> {
  for (const token of tokens) {
    if (delayMs > 0) {
      await new Promise((resolve) => setTimeout(resolve, delayMs));
    }
    yield token;
  }
}

/**
 * Helper: create a token stream that throws an error mid-stream
 */
async function* createErrorStream(
  tokens: string[],
  errorAfter: number
): AsyncGenerator<string, void, undefined> {
  let count = 0;
  for (const token of tokens) {
    if (count >= errorAfter) {
      throw new Error("LLM provider connection lost");
    }
    yield token;
    count++;
  }
}

describe("MatrixStreamingService", () => {
  let service: MatrixStreamingService;

  beforeEach(async () => {
    vi.useFakeTimers({ shouldAdvanceTime: true });

    const module: TestingModule = await Test.createTestingModule({
      providers: [
        MatrixStreamingService,
        {
          provide: MatrixService,
          useValue: mockMatrixService,
        },
      ],
    }).compile();

    service = module.get<MatrixStreamingService>(MatrixStreamingService);

    // Clear all mocks
    vi.clearAllMocks();

    // Re-apply default mock returns after clearing
    mockMatrixService.isConnected.mockReturnValue(true);
    mockMatrixService.getClient.mockReturnValue(mockClient);
    mockClient.sendMessage.mockResolvedValue("$initial-event-id");
    mockClient.sendEvent.mockResolvedValue("$edit-event-id");
    mockClient.setTyping.mockResolvedValue(undefined);
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  describe("editMessage", () => {
    it("should send a m.replace event to edit an existing message", async () => {
      await service.editMessage("!room:example.com", "$original-event-id", "Updated content");

      expect(mockClient.sendEvent).toHaveBeenCalledWith("!room:example.com", "m.room.message", {
        "m.new_content": {
          msgtype: "m.text",
          body: "Updated content",
        },
        "m.relates_to": {
          rel_type: "m.replace",
          event_id: "$original-event-id",
        },
        // Fallback for clients that don't support edits
        msgtype: "m.text",
        body: "* Updated content",
      });
    });

    it("should throw error when client is not connected", async () => {
      mockMatrixService.isConnected.mockReturnValue(false);

      await expect(
        service.editMessage("!room:example.com", "$event-id", "content")
      ).rejects.toThrow("Matrix client is not connected");
    });

    it("should throw error when client is null", async () => {
      mockMatrixService.getClient.mockReturnValue(null);

      await expect(
        service.editMessage("!room:example.com", "$event-id", "content")
      ).rejects.toThrow("Matrix client is not connected");
    });
  });

  describe("setTypingIndicator", () => {
    it("should call client.setTyping with true and timeout", async () => {
      await service.setTypingIndicator("!room:example.com", true);

      expect(mockClient.setTyping).toHaveBeenCalledWith("!room:example.com", true, 30000);
    });

    it("should call client.setTyping with false to clear indicator", async () => {
      await service.setTypingIndicator("!room:example.com", false);

      expect(mockClient.setTyping).toHaveBeenCalledWith("!room:example.com", false, undefined);
    });

    it("should throw error when client is not connected", async () => {
      mockMatrixService.isConnected.mockReturnValue(false);

      await expect(service.setTypingIndicator("!room:example.com", true)).rejects.toThrow(
        "Matrix client is not connected"
      );
    });
  });

  describe("sendStreamingMessage", () => {
    it("should send an initial message and return the event ID", async () => {
      const eventId = await service.sendStreamingMessage("!room:example.com", "Thinking...");

      expect(eventId).toBe("$initial-event-id");
      expect(mockClient.sendMessage).toHaveBeenCalledWith("!room:example.com", {
        msgtype: "m.text",
        body: "Thinking...",
      });
    });

    it("should send a thread message when threadId is provided", async () => {
      const eventId = await service.sendStreamingMessage(
        "!room:example.com",
        "Thinking...",
        "$thread-root-id"
      );

      expect(eventId).toBe("$initial-event-id");
      expect(mockClient.sendMessage).toHaveBeenCalledWith("!room:example.com", {
        msgtype: "m.text",
        body: "Thinking...",
        "m.relates_to": {
          rel_type: "m.thread",
          event_id: "$thread-root-id",
          is_falling_back: true,
          "m.in_reply_to": {
            event_id: "$thread-root-id",
          },
        },
      });
    });

    it("should throw error when client is not connected", async () => {
      mockMatrixService.isConnected.mockReturnValue(false);

      await expect(service.sendStreamingMessage("!room:example.com", "Test")).rejects.toThrow(
        "Matrix client is not connected"
      );
    });
  });

  describe("streamResponse", () => {
    it("should send initial 'Thinking...' message and start typing indicator", async () => {
      vi.useRealTimers();

      const tokens = ["Hello", " world"];
      const stream = createTokenStream(tokens);

      await service.streamResponse("!room:example.com", stream);

      // Should have sent initial message
      expect(mockClient.sendMessage).toHaveBeenCalledWith(
        "!room:example.com",
        expect.objectContaining({
          msgtype: "m.text",
          body: "Thinking...",
        })
      );

      // Should have started typing indicator
      expect(mockClient.setTyping).toHaveBeenCalledWith("!room:example.com", true, 30000);
    });

    it("should use custom initial message when provided", async () => {
      vi.useRealTimers();

      const tokens = ["Hi"];
      const stream = createTokenStream(tokens);

      const options: StreamResponseOptions = { initialMessage: "Processing..." };
      await service.streamResponse("!room:example.com", stream, options);

      expect(mockClient.sendMessage).toHaveBeenCalledWith(
        "!room:example.com",
        expect.objectContaining({
          body: "Processing...",
        })
      );
    });

    it("should edit message with accumulated tokens on completion", async () => {
      vi.useRealTimers();

      const tokens = ["Hello", " ", "world", "!"];
      const stream = createTokenStream(tokens);

      await service.streamResponse("!room:example.com", stream);

      // The final edit should contain the full accumulated text
      const sendEventCalls = mockClient.sendEvent.mock.calls;
      const lastEditCall = sendEventCalls[sendEventCalls.length - 1];

      expect(lastEditCall).toBeDefined();
      // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
      expect(lastEditCall[2]["m.new_content"].body).toBe("Hello world!");
    });

    it("should clear typing indicator on completion", async () => {
      vi.useRealTimers();

      const tokens = ["Done"];
      const stream = createTokenStream(tokens);

      await service.streamResponse("!room:example.com", stream);

      // Last setTyping call should be false
      const typingCalls = mockClient.setTyping.mock.calls;
      const lastTypingCall = typingCalls[typingCalls.length - 1];

      expect(lastTypingCall).toEqual(["!room:example.com", false, undefined]);
    });

    it("should rate-limit edits to at most one every 500ms", async () => {
      vi.useRealTimers();

      // Send tokens with small delays - all within one 500ms window
      const tokens = ["a", "b", "c", "d", "e"];
      const stream = createTokenStream(tokens, 50); // 50ms between tokens = 250ms total

      await service.streamResponse("!room:example.com", stream);

      // With 250ms total streaming time (5 tokens * 50ms), all tokens arrive
      // within one 500ms window. We expect at most 1 intermediate edit + 1 final edit,
      // or just the final edit. The key point is that there should NOT be 5 separate edits.
      const editCalls = mockClient.sendEvent.mock.calls.filter(
        (call) => call[1] === "m.room.message"
      );

      // Should have fewer edits than tokens (rate limiting in effect)
      expect(editCalls.length).toBeLessThanOrEqual(2);
      // Should have at least the final edit
      expect(editCalls.length).toBeGreaterThanOrEqual(1);
    });

    it("should handle errors gracefully and edit message with error notice", async () => {
      vi.useRealTimers();

      const stream = createErrorStream(["Hello", " ", "world"], 2);

      await service.streamResponse("!room:example.com", stream);

      // Should edit message with error content
      const sendEventCalls = mockClient.sendEvent.mock.calls;
      const lastEditCall = sendEventCalls[sendEventCalls.length - 1];

      expect(lastEditCall).toBeDefined();
      // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
      const finalBody = lastEditCall[2]["m.new_content"].body as string;
      expect(finalBody).toContain("error");

      // Should clear typing on error
      const typingCalls = mockClient.setTyping.mock.calls;
      const lastTypingCall = typingCalls[typingCalls.length - 1];
      expect(lastTypingCall).toEqual(["!room:example.com", false, undefined]);
    });

    it("should include token usage in final message when provided", async () => {
      vi.useRealTimers();

      const tokens = ["Hello"];
      const stream = createTokenStream(tokens);

      const options: StreamResponseOptions = {
        showTokenUsage: true,
        tokenUsage: { prompt: 10, completion: 5, total: 15 },
      };

      await service.streamResponse("!room:example.com", stream, options);

      const sendEventCalls = mockClient.sendEvent.mock.calls;
      const lastEditCall = sendEventCalls[sendEventCalls.length - 1];

      expect(lastEditCall).toBeDefined();
      // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
      const finalBody = lastEditCall[2]["m.new_content"].body as string;
      expect(finalBody).toContain("15");
    });

    it("should throw error when client is not connected", async () => {
      mockMatrixService.isConnected.mockReturnValue(false);

      const stream = createTokenStream(["test"]);

      await expect(service.streamResponse("!room:example.com", stream)).rejects.toThrow(
        "Matrix client is not connected"
      );
    });

    it("should handle empty token stream", async () => {
      vi.useRealTimers();

      const stream = createTokenStream([]);

      await service.streamResponse("!room:example.com", stream);

      // Should still send initial message
      expect(mockClient.sendMessage).toHaveBeenCalled();

      // Should edit with empty/no-content message
      const sendEventCalls = mockClient.sendEvent.mock.calls;
      expect(sendEventCalls.length).toBeGreaterThanOrEqual(1);

      // Should clear typing
      const typingCalls = mockClient.setTyping.mock.calls;
      const lastTypingCall = typingCalls[typingCalls.length - 1];
      expect(lastTypingCall).toEqual(["!room:example.com", false, undefined]);
    });

    it("should support thread context in streamResponse", async () => {
      vi.useRealTimers();

      const tokens = ["Reply"];
      const stream = createTokenStream(tokens);

      const options: StreamResponseOptions = { threadId: "$thread-root" };
      await service.streamResponse("!room:example.com", stream, options);

      // Initial message should include thread relation
      expect(mockClient.sendMessage).toHaveBeenCalledWith(
        "!room:example.com",
        expect.objectContaining({
          "m.relates_to": expect.objectContaining({
            rel_type: "m.thread",
            event_id: "$thread-root",
          }),
        })
      );
    });

    it("should perform multiple edits for long-running streams", async () => {
      vi.useRealTimers();

      // Create tokens with 200ms delays - total ~2000ms, should get multiple edit windows
      const tokens = Array.from({ length: 10 }, (_, i) => `token${String(i)} `);
      const stream = createTokenStream(tokens, 200);

      await service.streamResponse("!room:example.com", stream);

      // With 10 tokens at 200ms each = 2000ms total, at 500ms intervals
      // we expect roughly 3-4 intermediate edits + 1 final = 4-5 total
      const editCalls = mockClient.sendEvent.mock.calls.filter(
        (call) => call[1] === "m.room.message"
      );

      // Should have multiple edits (at least 2) but far fewer than 10
      expect(editCalls.length).toBeGreaterThanOrEqual(2);
      expect(editCalls.length).toBeLessThanOrEqual(8);
    });
  });
});