package httpx_test

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"git.codelab.vc/pkg/httpx"
	"git.codelab.vc/pkg/httpx/balancer"
	"git.codelab.vc/pkg/httpx/middleware"
	"git.codelab.vc/pkg/httpx/retry"
)

func TestClient_Get(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			t.Errorf("expected GET, got %s", r.Method)
		}
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, "hello")
	}))
	defer srv.Close()

	client := httpx.New()
	resp, err := client.Get(context.Background(), srv.URL+"/test")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	body, err := resp.String()
	if err != nil {
		t.Fatalf("reading body: %v", err)
	}
	if body != "hello" {
		t.Errorf("expected body %q, got %q", "hello", body)
	}
	if resp.StatusCode != http.StatusOK {
		t.Errorf("expected status 200, got %d", resp.StatusCode)
	}
}

func TestClient_Post(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			t.Errorf("expected POST, got %s", r.Method)
		}
		b, _ := io.ReadAll(r.Body)
		if string(b) != "request-body" {
			t.Errorf("expected body %q, got %q", "request-body", string(b))
		}
		w.WriteHeader(http.StatusCreated)
		fmt.Fprint(w, "created")
	}))
	defer srv.Close()

	client := httpx.New()
	resp, err := client.Post(context.Background(), srv.URL+"/items", strings.NewReader("request-body"))
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	if resp.StatusCode != http.StatusCreated {
		t.Errorf("expected status 201, got %d", resp.StatusCode)
	}
	body, err := resp.String()
	if err != nil {
		t.Fatalf("reading body: %v", err)
	}
	if body != "created" {
		t.Errorf("expected body %q, got %q", "created", body)
	}
}

func TestClient_BaseURL(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/users" {
			t.Errorf("expected path /api/v1/users, got %s", r.URL.Path)
		}
		w.WriteHeader(http.StatusOK)
	}))
	defer srv.Close()

	client := httpx.New(httpx.WithBaseURL(srv.URL + "/api/v1"))

	// Use a relative path (no scheme/host).
	resp, err := client.Get(context.Background(), "/users")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.StatusCode != http.StatusOK {
		t.Errorf("expected status 200, got %d", resp.StatusCode)
	}
}

func TestClient_WithMiddleware(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		val := r.Header.Get("X-Custom-Header")
		if val != "test-value" {
			t.Errorf("expected header X-Custom-Header=%q, got %q", "test-value", val)
		}
		w.WriteHeader(http.StatusOK)
	}))
	defer srv.Close()

	addHeader := func(next http.RoundTripper) http.RoundTripper {
		return middleware.RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
			req = req.Clone(req.Context())
			req.Header.Set("X-Custom-Header", "test-value")
			return next.RoundTrip(req)
		})
	}

	client := httpx.New(httpx.WithMiddleware(addHeader))

	resp, err := client.Get(context.Background(), srv.URL+"/test")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if resp.StatusCode != http.StatusOK {
		t.Errorf("expected status 200, got %d", resp.StatusCode)
	}
}

func TestClient_RetryIntegration(t *testing.T) {
	var calls atomic.Int32

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		n := calls.Add(1)
		if n <= 2 {
			w.WriteHeader(http.StatusServiceUnavailable)
			return
		}
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, "success")
	}))
	defer srv.Close()

	client := httpx.New(
		httpx.WithRetry(
			retry.WithMaxAttempts(3),
			retry.WithBackoff(retry.ConstantBackoff(1*time.Millisecond)),
		),
	)

	resp, err := client.Get(context.Background(), srv.URL+"/flaky")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

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

	body, err := resp.String()
	if err != nil {
		t.Fatalf("reading body: %v", err)
	}
	if body != "success" {
		t.Errorf("expected body %q, got %q", "success", body)
	}

	if got := calls.Load(); got != 3 {
		t.Errorf("expected 3 total requests, got %d", got)
	}
}

func TestClient_BalancerIntegration(t *testing.T) {
	var hits1, hits2 atomic.Int32

	srv1 := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hits1.Add(1)
		fmt.Fprint(w, "server1")
	}))
	defer srv1.Close()

	srv2 := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hits2.Add(1)
		fmt.Fprint(w, "server2")
	}))
	defer srv2.Close()

	client := httpx.New(
		httpx.WithEndpoints(
			balancer.Endpoint{URL: srv1.URL},
			balancer.Endpoint{URL: srv2.URL},
		),
	)

	const totalRequests = 6
	for i := range totalRequests {
		resp, err := client.Get(context.Background(), fmt.Sprintf("/item/%d", i))
		if err != nil {
			t.Fatalf("request %d: unexpected error: %v", i, err)
		}
		resp.Close()
	}

	h1 := hits1.Load()
	h2 := hits2.Load()

	if h1+h2 != totalRequests {
		t.Errorf("expected %d total hits, got %d", totalRequests, h1+h2)
	}
	if h1 == 0 || h2 == 0 {
		t.Errorf("expected requests distributed across both servers, got server1=%d server2=%d", h1, h2)
	}
}

func TestClient_ErrorMapper(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusNotFound)
		fmt.Fprint(w, "not found")
	}))
	defer srv.Close()

	mapper := func(resp *http.Response) error {
		if resp.StatusCode >= 400 {
			return fmt.Errorf("HTTP %d", resp.StatusCode)
		}
		return nil
	}

	client := httpx.New(httpx.WithErrorMapper(mapper))

	resp, err := client.Get(context.Background(), srv.URL+"/missing")
	if err == nil {
		t.Fatal("expected error, got nil")
	}

	// The response should still be returned alongside the error.
	if resp == nil {
		t.Fatal("expected non-nil response even on mapped error")
	}
	if resp.StatusCode != http.StatusNotFound {
		t.Errorf("expected status 404, got %d", resp.StatusCode)
	}

	// Verify the error message contains the status code.
	if !strings.Contains(err.Error(), "404") {
		t.Errorf("expected error to contain 404, got: %v", err)
	}
}

func TestClient_JSON(t *testing.T) {
	type reqPayload struct {
		Name string `json:"name"`
		Age  int    `json:"age"`
	}
	type respPayload struct {
		ID   int    `json:"id"`
		Name string `json:"name"`
	}

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if ct := r.Header.Get("Content-Type"); ct != "application/json" {
			t.Errorf("expected Content-Type application/json, got %q", ct)
		}

		var p reqPayload
		if err := json.NewDecoder(r.Body).Decode(&p); err != nil {
			t.Errorf("decoding request body: %v", err)
			w.WriteHeader(http.StatusBadRequest)
			return
		}
		if p.Name != "Alice" || p.Age != 30 {
			t.Errorf("unexpected payload: %+v", p)
		}

		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(respPayload{ID: 1, Name: p.Name})
	}))
	defer srv.Close()

	client := httpx.New()

	req, err := httpx.NewJSONRequest(context.Background(), http.MethodPost, srv.URL+"/users", reqPayload{
		Name: "Alice",
		Age:  30,
	})
	if err != nil {
		t.Fatalf("creating JSON request: %v", err)
	}

	resp, err := client.Do(context.Background(), req)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	var result respPayload
	if err := resp.JSON(&result); err != nil {
		t.Fatalf("decoding JSON response: %v", err)
	}
	if result.ID != 1 {
		t.Errorf("expected ID 1, got %d", result.ID)
	}
	if result.Name != "Alice" {
		t.Errorf("expected Name %q, got %q", "Alice", result.Name)
	}
}

// Ensure slog import is used (referenced in imports for completeness with the spec).
var _ = slog.Default