package github

import (
	"context"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"
)

func TestNewClient_DefaultBaseURL(t *testing.T) {
	c := NewClient("test-token", "")
	if c.baseURL != "https://api.github.com" {
		t.Errorf("expected default base URL, got %q", c.baseURL)
	}
}

func TestNewClient_CustomBaseURL(t *testing.T) {
	c := NewClient("test-token", "https://github.concur.com/api/v3")
	if c.baseURL != "https://github.concur.com/api/v3" {
		t.Errorf("expected custom base URL, got %q", c.baseURL)
	}
}

func TestNewClient_TrimsTrailingSlash(t *testing.T) {
	c := NewClient("test-token", "https://github.concur.com/api/v3/")
	if c.baseURL != "https://github.concur.com/api/v3" {
		t.Errorf("expected trailing slash trimmed, got %q", c.baseURL)
	}
}

func TestDoRequest_SetsAuthHeader(t *testing.T) {
	var gotAuth string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotAuth = r.Header.Get("Authorization")
		w.WriteHeader(200)
		w.Write([]byte("{}"))
	}))
	defer srv.Close()

	c := NewClient("my-token", srv.URL)
	c.SetHTTPClient(srv.Client())
	_, _ = c.doGet(context.Background(), srv.URL+"/test")

	if gotAuth != "Bearer my-token" {
		t.Errorf("expected Bearer auth, got %q", gotAuth)
	}
}

func TestDoRequest_SetsDefaultAcceptHeader(t *testing.T) {
	var gotAccept string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotAccept = r.Header.Get("Accept")
		w.WriteHeader(200)
		w.Write([]byte("{}"))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	_, _ = c.doGet(context.Background(), srv.URL+"/test")

	if gotAccept != "application/vnd.github+json" {
		t.Errorf("expected default Accept header, got %q", gotAccept)
	}
}

func TestDoRequest_429Retry(t *testing.T) {
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		if attempts == 1 {
			w.WriteHeader(429)
			w.Write([]byte(`{"message":"rate limit"}`))
			return
		}
		w.WriteHeader(200)
		w.Write([]byte(`{"ok":true}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	c.SetRetryBackoff([]time.Duration{10 * time.Millisecond, 10 * time.Millisecond})

	body, err := c.doGet(context.Background(), srv.URL+"/test")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if string(body) != `{"ok":true}` {
		t.Errorf("unexpected body: %s", body)
	}
	if attempts != 2 {
		t.Errorf("expected 2 attempts, got %d", attempts)
	}
}

func TestDoRequest_429ExhaustsRetries(t *testing.T) {
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		w.WriteHeader(429)
		w.Write([]byte(`{"message":"rate limit"}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	c.SetRetryBackoff([]time.Duration{1 * time.Millisecond, 1 * time.Millisecond})

	_, err := c.doGet(context.Background(), srv.URL+"/test")
	if err == nil {
		t.Fatal("expected error after exhausting retries")
	}
	apiErr, ok := err.(*APIError)
	if !ok {
		t.Fatalf("expected *APIError, got %T", err)
	}
	if apiErr.StatusCode != 429 {
		t.Errorf("expected 429, got %d", apiErr.StatusCode)
	}
	if attempts != 3 {
		t.Errorf("expected 3 attempts, got %d", attempts)
	}
}

func TestDoRequest_404NoRetry(t *testing.T) {
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		w.WriteHeader(404)
		w.Write([]byte(`{"message":"not found"}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())

	_, err := c.doGet(context.Background(), srv.URL+"/test")
	if err == nil {
		t.Fatal("expected error for 404")
	}
	if attempts != 1 {
		t.Errorf("expected 1 attempt (no retry on 404), got %d", attempts)
	}
}

func TestDoRequest_401NoRetry(t *testing.T) {
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		w.WriteHeader(401)
		w.Write([]byte(`{"message":"bad credentials"}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())

	_, err := c.doGet(context.Background(), srv.URL+"/test")
	if err == nil {
		t.Fatal("expected error for 401")
	}
	if attempts != 1 {
		t.Errorf("expected 1 attempt (no retry on 401), got %d", attempts)
	}
}

func TestIsNotFound(t *testing.T) {
	err := &APIError{StatusCode: 404, Body: "not found"}
	if !IsNotFound(err) {
		t.Error("expected IsNotFound to return true for 404")
	}
	err2 := &APIError{StatusCode: 500, Body: "server error"}
	if IsNotFound(err2) {
		t.Error("expected IsNotFound to return false for 500")
	}
}

func TestIsUnauthorized(t *testing.T) {
	err := &APIError{StatusCode: 401, Body: "bad credentials"}
	if !IsUnauthorized(err) {
		t.Error("expected IsUnauthorized to return true for 401")
	}
}

func TestDoRequest_429RetryAfterHeader(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping slow retry test in short mode")
	}
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		if attempts == 1 {
			w.Header().Set("Retry-After", "1")
			w.WriteHeader(429)
			w.Write([]byte(`{"message":"rate limit"}`))
			return
		}
		w.WriteHeader(200)
		w.Write([]byte(`{"ok":true}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	// Use short backoff; Retry-After should override
	c.SetRetryBackoff([]time.Duration{1 * time.Millisecond, 1 * time.Millisecond})

	start := time.Now()
	body, err := c.doGet(context.Background(), srv.URL+"/test")
	elapsed := time.Since(start)

	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if string(body) != `{"ok":true}` {
		t.Errorf("unexpected body: %s", body)
	}
	if attempts != 2 {
		t.Errorf("expected 2 attempts, got %d", attempts)
	}
	// Retry-After: 1 means at least 1 second delay
	if elapsed < 900*time.Millisecond {
		t.Errorf("expected ~1s delay from Retry-After, got %v", elapsed)
	}
}

func TestDoRequest_RetryAfterDoesNotMutateBackoff(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping slow retry test in short mode")
	}
	attempts := 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		attempts++
		if attempts == 1 {
			w.Header().Set("Retry-After", "1")
			w.WriteHeader(429)
			w.Write([]byte(`{"message":"rate limit"}`))
			return
		}
		w.WriteHeader(200)
		w.Write([]byte(`{"ok":true}`))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	c.SetRetryBackoff([]time.Duration{1 * time.Millisecond, 1 * time.Millisecond})

	_, err := c.doGet(context.Background(), srv.URL+"/test")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	// Verify the original retryBackoff slice was not mutated
	if c.retryBackoff[0] != 1*time.Millisecond {
		t.Errorf("retryBackoff[0] was mutated: got %v, want 1ms", c.retryBackoff[0])
	}
	if c.retryBackoff[1] != 1*time.Millisecond {
		t.Errorf("retryBackoff[1] was mutated: got %v, want 1ms", c.retryBackoff[1])
	}
}

func TestDoRequest_SetsUserAgentHeader(t *testing.T) {
	var gotUA string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotUA = r.Header.Get("User-Agent")
		w.WriteHeader(200)
		w.Write([]byte("{}"))
	}))
	defer srv.Close()

	c := NewClient("token", srv.URL)
	c.SetHTTPClient(srv.Client())
	_, _ = c.doGet(context.Background(), srv.URL+"/test")

	if gotUA != "review-bot/1.0" {
		t.Errorf("expected User-Agent 'review-bot/1.0', got %q", gotUA)
	}
}

func TestDoRequest_LimitsResponseBody(t *testing.T) {
	// Verify that responses are read through a limit reader.
	// We can't easily test the 10 MiB limit without OOM risk,
	// but we verify the constant is set correctly.
	if maxResponseBytes != 10*1024*1024 {
		t.Errorf("expected maxResponseBytes = 10 MiB, got %d", maxResponseBytes)
	}
}

func TestDoRequest_SkipsAuthWhenTokenEmpty(t *testing.T) {
	var gotAuth string
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		gotAuth = r.Header.Get("Authorization")
		w.WriteHeader(200)
		w.Write([]byte("{}"))
	}))
	defer srv.Close()

	c := NewClient("", srv.URL) // empty token
	c.SetHTTPClient(srv.Client())
	_, _ = c.doGet(context.Background(), srv.URL+"/test")

	if gotAuth != "" {
		t.Errorf("expected no Authorization header with empty token, got %q", gotAuth)
	}
}

func TestNewClient_CheckRedirectStripsAuthOnCrossHost(t *testing.T) {
	// Verify the CheckRedirect function is configured
	c := NewClient("secret-token", "https://api.github.com")
	if c.httpClient.CheckRedirect == nil {
		t.Fatal("expected CheckRedirect to be set")
	}
}