package llm

import (
	"context"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"

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

func mockServer(t *testing.T, response string) *httptest.Server {
	t.Helper()
	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		assert.Equal(t, "/chat/completions", r.URL.Path)
		assert.Equal(t, "application/json", r.Header.Get("Content-Type"))
		w.Header().Set("Content-Type", "application/json")
		_ = json.NewEncoder(w).Encode(map[string]any{
			"choices": []map[string]any{
				{"message": map[string]any{"role": "assistant", "content": response}},
			},
		})
	}))
}

func TestClient_Complete(t *testing.T) {
	srv := mockServer(t, "hello world")
	defer srv.Close()

	c := New(srv.URL, "", "test-model", 10*time.Second)
	got, err := c.Complete(context.Background(), "you are helpful", "say hello")
	require.NoError(t, err)
	assert.Equal(t, "hello world", got)
}

func TestClient_ReturnsErrorOnNon200(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		http.Error(w, "overloaded", http.StatusServiceUnavailable)
	}))
	defer srv.Close()

	c := New(srv.URL, "", "test-model", 10*time.Second)
	_, err := c.Complete(context.Background(), "sys", "user")
	assert.Error(t, err)
}

func TestClient_SendsAuthHeader(t *testing.T) {
	var gotAuth string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotAuth = r.Header.Get("Authorization")
		_ = json.NewEncoder(w).Encode(map[string]any{
			"choices": []map[string]any{{"message": map[string]any{"content": "ok"}}},
		})
	}))
	defer srv.Close()

	c := New(srv.URL, "my-key", "test-model", 10*time.Second)
	_, err := c.Complete(context.Background(), "sys", "user")
	require.NoError(t, err)
	assert.Equal(t, "Bearer my-key", gotAuth)
}

func TestClient_Retries429(t *testing.T) {
	calls := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		calls++
		if calls == 1 {
			w.Header().Set("Retry-After", "0")
			w.WriteHeader(http.StatusTooManyRequests)
			return
		}
		_ = json.NewEncoder(w).Encode(map[string]any{
			"choices": []map[string]any{{"message": map[string]any{"content": "retried"}}},
		})
	}))
	defer srv.Close()

	c := New(srv.URL, "", "test-model", 10*time.Second)
	got, err := c.Complete(context.Background(), "sys", "user")
	require.NoError(t, err)
	assert.Equal(t, "retried", got)
	assert.Equal(t, 2, calls)
}