package proxy

import (
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"sort"
	"strings"
	"testing"
	"time"

	"github.com/Riotpiaole/homelab-frontend/internal/config"
)

// ModelListResponse represents the response shape for GET /v1/models
type ModelListResponse struct {
	Object string       `json:"object"`
	Data   []ModelEntry `json:"data"`
}

// ModelEntry represents a single model in the list
type ModelEntry struct {
	ID      string `json:"id"`
	Object  string `json:"object"`
	OwnedBy string `json:"owned_by"`
	Created int64  `json:"created"`
}

// TestModelsEndpointReturns200 verifies GET /v1/models returns 200
func TestModelsEndpointReturns200(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		t.Errorf("expected 200, got %d", resp.StatusCode)
	}
}

// TestModelsEndpointContentType verifies correct content type
func TestModelsEndpointContentType(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	ct := resp.Header.Get("Content-Type")
	if !strings.Contains(ct, "application/json") {
		t.Errorf("expected content-type application/json, got %s", ct)
	}
}

// TestModelsEndpointResponseShape verifies correct JSON structure
func TestModelsEndpointResponseShape(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	var result ModelListResponse
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		t.Fatalf("failed to decode response: %v", err)
	}

	if result.Object != "list" {
		t.Errorf("expected object='list', got %q", result.Object)
	}

	if len(result.Data) != 1 {
		t.Errorf("expected 1 model, got %d", len(result.Data))
	}

	model := result.Data[0]
	if model.ID != "reasoning" {
		t.Errorf("expected id='reasoning', got %q", model.ID)
	}

	if model.Object != "model" {
		t.Errorf("expected object='model', got %q", model.Object)
	}
}

// TestModelsEndpointEnumeratesAllModels verifies all models are listed
func TestModelsEndpointEnumeratesAllModels(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
			"ornith:35b": {
				Name:    "ornith:35b",
				Address: "localhost:9000",
			},
			"qwen2.5:3b-instruct": {
				Name:    "qwen2.5:3b-instruct",
				Address: "localhost:9000",
			},
			"nomic-ai/nomic-embed-text-v2-moe": {
				Name:    "nomic-ai/nomic-embed-text-v2-moe",
				Address: "localhost:9000",
			},
			"BAAI/bge-reranker-base": {
				Name:    "BAAI/bge-reranker-base",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	var result ModelListResponse
	json.NewDecoder(resp.Body).Decode(&result)

	if len(result.Data) != 5 {
		t.Errorf("expected 5 models, got %d", len(result.Data))
	}

	// Collect actual model IDs
	modelIDs := make(map[string]bool)
	for _, model := range result.Data {
		modelIDs[model.ID] = true
	}

	// Verify all expected models are present
	expectedModels := []string{
		"reasoning",
		"ornith:35b",
		"qwen2.5:3b-instruct",
		"nomic-ai/nomic-embed-text-v2-moe",
		"BAAI/bge-reranker-base",
	}

	for _, expected := range expectedModels {
		if !modelIDs[expected] {
			t.Errorf("expected model %q in response", expected)
		}
	}
}

// TestModelsEndpointHasRequiredFields verifies all required fields are present
func TestModelsEndpointHasRequiredFields(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	var result ModelListResponse
	json.NewDecoder(resp.Body).Decode(&result)

	model := result.Data[0]
	if model.ID == "" {
		t.Errorf("expected id field")
	}

	if model.Object == "" {
		t.Errorf("expected object field")
	}

	if model.OwnedBy == "" {
		t.Errorf("expected owned_by field")
	}

	if model.Created == 0 {
		t.Errorf("expected created field (unix timestamp)")
	}
}

// TestModelsEndpointNoUpstreamContact verifies endpoint doesn't contact upstream
func TestModelsEndpointNoUpstreamContact(t *testing.T) {
	upstreamCalled := false
	upstreamServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		upstreamCalled = true
		w.WriteHeader(http.StatusOK)
	}))
	defer upstreamServer.Close()

	upstreamAddr := strings.TrimPrefix(upstreamServer.URL, "http://")

	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: upstreamAddr,
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	_, _ = http.Get(server.URL + "/v1/models")

	if upstreamCalled {
		t.Errorf("upstream should not be called for /v1/models endpoint")
	}
}

// TestModelsEndpointDerivedFromConfig verifies models come from config, not hardcoded
func TestModelsEndpointDerivedFromConfig(t *testing.T) {
	// Create config with specific models
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"custom-model-1": {
				Name:    "custom-model-1",
				Address: "localhost:9000",
			},
			"custom-model-2": {
				Name:    "custom-model-2",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	defer resp.Body.Close()

	var result ModelListResponse
	json.NewDecoder(resp.Body).Decode(&result)

	// Verify only the configured models are returned
	if len(result.Data) != 2 {
		t.Errorf("expected 2 models from config, got %d", len(result.Data))
	}

	modelIDs := make([]string, len(result.Data))
	for i, model := range result.Data {
		modelIDs[i] = model.ID
	}
	sort.Strings(modelIDs)

	expected := []string{"custom-model-1", "custom-model-2"}
	if !equal(modelIDs, expected) {
		t.Errorf("expected models %v, got %v", expected, modelIDs)
	}
}

// TestModelsEndpointConsistentWithDispatch verifies advertised models can dispatch
func TestModelsEndpointConsistentWithDispatch(t *testing.T) {
	upstreamServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
	}))
	defer upstreamServer.Close()

	upstreamAddr := strings.TrimPrefix(upstreamServer.URL, "http://")

	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: upstreamAddr,
			},
			"ornith:35b": {
				Name:    "ornith:35b",
				Address: upstreamAddr,
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	// Get list of models
	resp, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	var result ModelListResponse
	json.NewDecoder(resp.Body).Decode(&result)
	resp.Body.Close()

	// Try to dispatch to each advertised model
	for _, model := range result.Data {
		dispatchResp, err := http.Post(
			server.URL+"/v1/chat/completions",
			"application/json",
			strings.NewReader(`{"model":"`+model.ID+`","messages":[]}`),
		)
		if err != nil {
			t.Fatalf("request failed: %v", err)
		}
		defer dispatchResp.Body.Close()

		// Should not return 400 (unknown model error)
		if dispatchResp.StatusCode == http.StatusBadRequest {
			body, _ := io.ReadAll(dispatchResp.Body)
			if strings.Contains(string(body), "unknown model") {
				t.Errorf("model %q advertised in /v1/models but not accepted for dispatch", model.ID)
			}
		}
	}
}

// TestModelsEndpointResponseIsConsistent verifies response is consistent across calls
func TestModelsEndpointResponseIsConsistent(t *testing.T) {
	cfg := &config.Config{
		Models: map[string]*config.ModelUpstream{
			"reasoning": {
				Name:    "reasoning",
				Address: "localhost:9000",
			},
			"ornith:35b": {
				Name:    "ornith:35b",
				Address: "localhost:9000",
			},
		},
		Routes: make(map[string]*config.Route),
	}

	handler := New(cfg)
	defer handler.Close()

	server := httptest.NewServer(handler)
	defer server.Close()

	// Call endpoint twice
	resp1, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	var result1 ModelListResponse
	json.NewDecoder(resp1.Body).Decode(&result1)
	resp1.Body.Close()

	time.Sleep(10 * time.Millisecond)

	resp2, err := http.Get(server.URL + "/v1/models")
	if err != nil {
		t.Fatalf("request failed: %v", err)
	}
	var result2 ModelListResponse
	json.NewDecoder(resp2.Body).Decode(&result2)
	resp2.Body.Close()

	// Verify both responses have same models
	if len(result1.Data) != len(result2.Data) {
		t.Errorf("response length inconsistent: %d vs %d", len(result1.Data), len(result2.Data))
	}

	ids1 := make([]string, len(result1.Data))
	ids2 := make([]string, len(result2.Data))

	for i, m := range result1.Data {
		ids1[i] = m.ID
	}
	for i, m := range result2.Data {
		ids2[i] = m.ID
	}

	sort.Strings(ids1)
	sort.Strings(ids2)

	if !equal(ids1, ids2) {
		t.Errorf("responses differ: %v vs %v", ids1, ids2)
	}
}

// Helper function to compare string slices
func equal(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}