package openai_test

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"

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

	"github.com/veylant/ia-gateway/internal/provider"
	"github.com/veylant/ia-gateway/internal/provider/openai"
)

// newTestAdapter builds an Adapter pointed at the given mock server URL.
func newTestAdapter(serverURL string) *openai.Adapter {
	return openai.New(openai.Config{
		APIKey:         "test-key",
		BaseURL:        serverURL,
		TimeoutSeconds: 5,
		MaxConns:       10,
	})
}

// minimalRequest returns a valid ChatRequest for tests.
func minimalRequest() *provider.ChatRequest {
	return &provider.ChatRequest{
		Model:    "gpt-4o",
		Messages: []provider.Message{{Role: "user", Content: "hello"}},
	}
}

// ─── Send ────────────────────────────────────────────────────────────────────

func TestAdapter_Send_Nominal(t *testing.T) {
	expected := provider.ChatResponse{
		ID:     "chatcmpl-test",
		Object: "chat.completion",
		Model:  "gpt-4o",
		Choices: []provider.Choice{{
			Index:        0,
			Message:      provider.Message{Role: "assistant", Content: "Hello!"},
			FinishReason: "stop",
		}},
		Usage: provider.Usage{PromptTokens: 5, CompletionTokens: 3, TotalTokens: 8},
	}

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		assert.Equal(t, "/chat/completions", r.URL.Path)
		assert.Equal(t, "Bearer test-key", r.Header.Get("Authorization"))
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(expected)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	got, err := adapter.Send(context.Background(), minimalRequest())

	require.NoError(t, err)
	require.NotNil(t, got)
	assert.Equal(t, expected.ID, got.ID)
	assert.Equal(t, "Hello!", got.Choices[0].Message.Content)
}

func TestAdapter_Send_Upstream401_ReturnsAuthError(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusUnauthorized)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	_, err := adapter.Send(context.Background(), minimalRequest())

	require.Error(t, err)
	// The error message must contain "API key".
	assert.Contains(t, err.Error(), "API key")
}

// ─── Stream ──────────────────────────────────────────────────────────────────

func TestAdapter_Stream_Nominal(t *testing.T) {
	// Simulate an OpenAI SSE response with two chunks and the [DONE] sentinel.
	ssePayload := strings.Join([]string{
		`data: {"id":"chatcmpl-1","choices":[{"delta":{"content":"Hel"}}]}`,
		`data: {"id":"chatcmpl-1","choices":[{"delta":{"content":"lo"}}]}`,
		`data: [DONE]`,
		"",
	}, "\n")

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		assert.Equal(t, "/chat/completions", r.URL.Path)
		w.Header().Set("Content-Type", "text/event-stream")
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, ssePayload)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)

	rec := httptest.NewRecorder()
	// Set SSE headers as the proxy handler would.
	rec.Header().Set("Content-Type", "text/event-stream")
	rec.Header().Set("Cache-Control", "no-cache")

	req := minimalRequest()
	req.Stream = true
	err := adapter.Stream(context.Background(), req, rec)

	require.NoError(t, err)
	body := rec.Body.String()
	assert.Contains(t, body, `"Hel"`)
	assert.Contains(t, body, `"lo"`)
	assert.Contains(t, body, "data: [DONE]")
}

// ─── HealthCheck ─────────────────────────────────────────────────────────────

func TestAdapter_HealthCheck_Nominal(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		assert.Equal(t, "/models", r.URL.Path)
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte(`{"data":[]}`))
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	err := adapter.HealthCheck(context.Background())
	require.NoError(t, err)
}

func TestAdapter_Send_Upstream429_ReturnsRateLimit(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusTooManyRequests)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	_, err := adapter.Send(context.Background(), minimalRequest())

	require.Error(t, err)
	assert.Contains(t, err.Error(), "rate limit")
}

func TestAdapter_Send_Upstream400_ReturnsBadRequest(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusBadRequest)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	_, err := adapter.Send(context.Background(), minimalRequest())

	require.Error(t, err)
	assert.Contains(t, err.Error(), "rejected")
}

func TestAdapter_Send_Upstream500_ReturnsUpstreamError(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusInternalServerError)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	_, err := adapter.Send(context.Background(), minimalRequest())

	require.Error(t, err)
	assert.Contains(t, err.Error(), "500")
}

func TestAdapter_Stream_Upstream401_ReturnsError(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusUnauthorized)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	req := minimalRequest()
	req.Stream = true

	rec := httptest.NewRecorder()
	err := adapter.Stream(context.Background(), req, rec)

	require.Error(t, err)
}

func TestAdapter_HealthCheck_FailureReturnsError(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusServiceUnavailable)
	}))
	defer srv.Close()

	adapter := newTestAdapter(srv.URL)
	err := adapter.HealthCheck(context.Background())
	require.Error(t, err)
	assert.Contains(t, err.Error(), "503")
}

// ─── Validate ────────────────────────────────────────────────────────────────

func TestAdapter_Validate_MissingModel(t *testing.T) {
	adapter := newTestAdapter("http://unused")
	err := adapter.Validate(&provider.ChatRequest{
		Messages: []provider.Message{{Role: "user", Content: "hi"}},
	})
	require.Error(t, err)
	assert.Contains(t, err.Error(), "model")
}

func TestAdapter_Validate_EmptyMessages(t *testing.T) {
	adapter := newTestAdapter("http://unused")
	err := adapter.Validate(&provider.ChatRequest{Model: "gpt-4o"})
	require.Error(t, err)
	assert.Contains(t, err.Error(), "messages")
}