package test

import (
	"context"
	"fmt" // Added for createTestRequest
	"sync/atomic"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"llm-api-benchmark-tool/pkg/client" // Needs client types
	"llm-api-benchmark-tool/pkg/concurrency" // Target package (to be created)
	"llm-api-benchmark-tool/pkg/stats" // Added for stats collector
)

// --- Mock HTTP Client ---

type MockHTTPClient struct {
	DoFunc     func(req *client.Request) (*client.Response, error)
	StreamFunc func(req *client.Request, callback func(chunk client.SSEChunk) error) error
	ReqCount   atomic.Int64 // Track calls
}

func (m *MockHTTPClient) Do(req *client.Request) (*client.Response, error) {
	m.ReqCount.Add(1)
	if m.DoFunc != nil {
		return m.DoFunc(req)
	}
	// Default mock response for Do
	return &client.Response{
		StatusCode: 200,
		Body:       []byte(`{"mock": "response"}`),
	}, nil
}

func (m *MockHTTPClient) Stream(req *client.Request, callback func(chunk client.SSEChunk) error) error {
	m.ReqCount.Add(1)
	if m.StreamFunc != nil {
		return m.StreamFunc(req, callback)
	}
	// Default mock stream behavior
	go func() { // Simulate receiving chunks
		time.Sleep(5 * time.Millisecond) // Simulate TTFT
		// Ensure callback is not nil before calling
		if callback != nil {
			callback(client.SSEChunk{Data: []byte(`{"mock": "chunk1"}`), Timestamp: time.Now().UnixNano()})
			time.Sleep(10 * time.Millisecond)
			callback(client.SSEChunk{Data: []byte(`[DONE]`), Timestamp: time.Now().UnixNano(), IsDone: true})
		}
	}()
	return nil
}

// --- Test Concurrency Manager ---

func TestConcurrencyManager_RunBenchmark(t *testing.T) {
	mockClient := &MockHTTPClient{}

	params := concurrency.BenchmarkParams{
		HTTPClient:     mockClient,
		TargetURL:      "http://mock.test/api",
		TotalDuration:  100 * time.Millisecond, // Short duration for testing
		Concurrency:    10,
		RequestInterval: 5 * time.Millisecond,  // Interval between starting new requests
		IsStreaming:    false,                  // Test non-streaming first
		PromptTokens:   50,                     // Example prompt size
		// Add other necessary params like API Key, Model later
	}

	// Create the manager (package and struct to be defined)
	statsCollector := stats.NewStatsCollector() // Create mock stats collector
	manager := concurrency.NewManager(params, statsCollector) // Assuming a constructor

	// Run the benchmark
	// TODO: Define the result struct if RunBenchmark returns results
	err := manager.RunBenchmark(context.Background()) // Use background context for now

	require.NoError(t, err, "RunBenchmark should complete without error")

	// Assertions
	// 1. Check if roughly the correct number of requests were made.
	//    Expected rate = Concurrency / RequestInterval (adjust if interval is per worker)
	//    Expected requests ~ TotalDuration / RequestInterval (simplified, needs refinement)
	//    Let's just check if *some* requests were made for now.
	madeRequests := mockClient.ReqCount.Load()
	assert.Greater(t, madeRequests, int64(0), "Should have made at least one request")
	t.Logf("Total requests made by mock client: %d", madeRequests)

	// 2. Test with Streaming
	mockClientStreaming := &MockHTTPClient{}
	paramsStreaming := params
	paramsStreaming.HTTPClient = mockClientStreaming
	paramsStreaming.IsStreaming = true
	paramsStreaming.TotalDuration = 150 * time.Millisecond // Slightly longer for streaming

	statsCollectorStreaming := stats.NewStatsCollector() // Create mock stats collector
	managerStreaming := concurrency.NewManager(paramsStreaming, statsCollectorStreaming)
	errStreaming := managerStreaming.RunBenchmark(context.Background())

	require.NoError(t, errStreaming, "RunBenchmark (streaming) should complete without error")
	madeRequestsStreaming := mockClientStreaming.ReqCount.Load()
	assert.Greater(t, madeRequestsStreaming, int64(0), "Should have made at least one streaming request")
	t.Logf("Total streaming requests made by mock client: %d", madeRequestsStreaming)


	// TODO: Add test case for context cancellation/timeout
	// TODO: Add test case for handling client errors
	// TODO: Add more precise assertions on request count and timing if possible
}

// Helper function to create a basic request (might move to a shared test util)
func createTestRequest(url string, isStreaming bool, promptTokens int) *client.Request {
	// In a real scenario, we'd use the tokenizer here
	mockPrompt := fmt.Sprintf("mock prompt %d tokens", promptTokens)
	body := []byte(fmt.Sprintf(`{"prompt": "%s", "stream": %v}`, mockPrompt, isStreaming))
	return &client.Request{
		URL:     url,
		Method:  "POST",
		Headers: map[string]string{"Content-Type": "application/json"},
		Body:    body,
	}
}