package api

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

func TestParseRateLimit(t *testing.T) {
	tests := []struct {
		in     string
		limit  int
		window time.Duration
	}{
		{"", defaultRateLimitCount, defaultRateLimitWindow},
		{"30/1h", 30, time.Hour},
		{"10/10m", 10, 10 * time.Minute},
		{"5 / 30s", 5, 30 * time.Second},
		{"bogus", defaultRateLimitCount, defaultRateLimitWindow},
		{"0/1h", defaultRateLimitCount, defaultRateLimitWindow},
		{"-3/1h", defaultRateLimitCount, defaultRateLimitWindow},
		{"10/-1h", defaultRateLimitCount, defaultRateLimitWindow},
		{"10/soon", defaultRateLimitCount, defaultRateLimitWindow},
		{"/1h", defaultRateLimitCount, defaultRateLimitWindow},
	}
	for _, tc := range tests {
		limit, window := parseRateLimit(tc.in)
		if limit != tc.limit || window != tc.window {
			t.Errorf("parseRateLimit(%q) = %d, %s; want %d, %s",
				tc.in, limit, window, tc.limit, tc.window)
		}
	}
}

func TestNewHandlerReadsRateLimitEnv(t *testing.T) {
	t.Setenv("EXPLOREDNS_RATE_LIMIT", "5/10m")
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	h := newHandler(ctx)
	if h.limiter.limit != 5 || h.limiter.window != 10*time.Minute {
		t.Fatalf("limiter = %d/%s, want 5/10m", h.limiter.limit, h.limiter.window)
	}
}

// postTraverse sends POST /api/traverse with an empty JSON body so requests
// that pass the rate limiter fail validation (400) instead of spawning a
// real traversal. remoteAddr and headers shape the client identity.
func postTraverse(t *testing.T, h *Handler, remoteAddr string, headers map[string]string) *httptest.ResponseRecorder {
	t.Helper()
	req := httptest.NewRequest(http.MethodPost, "/api/traverse", strings.NewReader(`{}`))
	req.RemoteAddr = remoteAddr
	for k, v := range headers {
		req.Header.Set(k, v)
	}
	rec := httptest.NewRecorder()
	h.mux.ServeHTTP(rec, req)
	return rec
}

func TestRateLimit_OverLimitReturns429(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	h := newHandler(ctx)
	h.limiter = newRateLimiter(2, time.Hour)

	hdr := map[string]string{"X-Forwarded-For": "203.0.113.9"}
	for i := 0; i < 2; i++ {
		if rec := postTraverse(t, h, "10.0.0.1:1234", hdr); rec.Code != http.StatusBadRequest {
			t.Fatalf("request %d: want 400 (under limit), got %d: %s", i, rec.Code, rec.Body.String())
		}
	}
	rec := postTraverse(t, h, "10.0.0.1:1234", hdr)
	if rec.Code != http.StatusTooManyRequests {
		t.Fatalf("want 429 over limit, got %d: %s", rec.Code, rec.Body.String())
	}
	if body := rec.Body.String(); !strings.Contains(body, "2 requests per 1h0m0s") {
		t.Fatalf("429 body should name the limit, got %s", body)
	}

	// A distinct client IP has its own bucket and is unaffected.
	other := map[string]string{"X-Forwarded-For": "203.0.113.10"}
	if rec := postTraverse(t, h, "10.0.0.1:1234", other); rec.Code != http.StatusBadRequest {
		t.Fatalf("distinct IP: want 400, got %d: %s", rec.Code, rec.Body.String())
	}
}

func TestRateLimit_RefillsContinuously(t *testing.T) {
	rl := newRateLimiter(2, time.Second)
	now := time.Now()
	rl.now = func() time.Time { return now }

	if !rl.allow("a") || !rl.allow("a") {
		t.Fatal("first two requests should be allowed")
	}
	if rl.allow("a") {
		t.Fatal("third request should be denied")
	}
	// Half a window refills half the bucket: one token.
	now = now.Add(500 * time.Millisecond)
	if !rl.allow("a") {
		t.Fatal("request after refill should be allowed")
	}
	if rl.allow("a") {
		t.Fatal("bucket should hold only the refilled token")
	}
}

func TestRateLimit_SweepDropsIdleBuckets(t *testing.T) {
	rl := newRateLimiter(1, time.Minute)
	now := time.Now()
	rl.now = func() time.Time { return now }

	rl.allow("stale")
	now = now.Add(2 * time.Minute)
	rl.allow("fresh")
	rl.sweep()

	rl.mu.Lock()
	defer rl.mu.Unlock()
	if _, ok := rl.buckets["stale"]; ok {
		t.Fatal("idle bucket should have been swept")
	}
	if _, ok := rl.buckets["fresh"]; !ok {
		t.Fatal("active bucket should survive the sweep")
	}
}

func TestRateLimit_LocalhostExempt(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	h := newHandler(ctx)
	h.limiter = newRateLimiter(1, time.Hour)

	for _, addr := range []string{"127.0.0.1:5555", "[::1]:5555"} {
		for i := 0; i < 3; i++ {
			rec := postTraverse(t, h, addr, nil)
			if rec.Code != http.StatusBadRequest {
				t.Fatalf("%s request %d: localhost should be exempt, got %d: %s",
					addr, i, rec.Code, rec.Body.String())
			}
		}
	}
}

// TestRateLimit_ProxiedLocalhostNotExempt verifies that a request arriving
// from a local proxy (RemoteAddr loopback) is still limited by the real
// client IP carried in Fly-Client-IP / X-Forwarded-For.
func TestRateLimit_ProxiedLocalhostNotExempt(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	h := newHandler(ctx)
	h.limiter = newRateLimiter(1, time.Hour)

	hdr := map[string]string{"Fly-Client-IP": "198.51.100.4"}
	if rec := postTraverse(t, h, "127.0.0.1:5555", hdr); rec.Code != http.StatusBadRequest {
		t.Fatalf("first proxied request: want 400, got %d", rec.Code)
	}
	if rec := postTraverse(t, h, "127.0.0.1:5555", hdr); rec.Code != http.StatusTooManyRequests {
		t.Fatalf("second proxied request: want 429, got %d", rec.Code)
	}
	// The same proxy forwarding a different client is unaffected.
	other := map[string]string{"Fly-Client-IP": "198.51.100.5"}
	if rec := postTraverse(t, h, "127.0.0.1:5555", other); rec.Code != http.StatusBadRequest {
		t.Fatalf("other client via proxy: want 400, got %d", rec.Code)
	}
}