package redis

import (
	"context"
	"io"
	"math"
	"net"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/redis/go-redis/v9/internal/proto"
	"github.com/redis/go-redis/v9/maintnotifications"
	"github.com/redis/go-redis/v9/push"
)

// fakeConn is a no-I/O net.Conn: the min-idle connection is created in the pool
// but never initialized (initConn is deferred to first checkout), so its
// Read/Write are never exercised. Close bumps a counter.
type fakeConn struct{ closed *int64 }

func (f *fakeConn) Read([]byte) (int, error)         { return 0, io.EOF }
func (f *fakeConn) Write(b []byte) (int, error)      { return len(b), nil }
func (f *fakeConn) Close() error                     { atomic.AddInt64(f.closed, 1); return nil }
func (f *fakeConn) LocalAddr() net.Addr              { return fakeAddr{} }
func (f *fakeConn) RemoteAddr() net.Addr             { return fakeAddr{} }
func (f *fakeConn) SetDeadline(time.Time) error      { return nil }
func (f *fakeConn) SetReadDeadline(time.Time) error  { return nil }
func (f *fakeConn) SetWriteDeadline(time.Time) error { return nil }

type fakeAddr struct{}

func (fakeAddr) Network() string { return "fake" }
func (fakeAddr) String() string  { return "fake" }

// panicOnRegisterProcessor is a push.NotificationProcessor whose RegisterHandler
// panics — modelling a custom processor that rejects handler registration. With
// MaintNotificationsConfig in ModeEnabled, NewClient registers maintenance
// handlers (after the pools are created) and this panic propagates out.
//
// RegisterHandler first waits for dialed, which the test's dialer closes on its
// first call. The min-idle dial runs in a pool goroutine; without this wait the
// deferred Close in NewClient can win the race, the pool's dialConn sees the
// closed pool and never calls the dialer, and the test observes opened=0 — a
// legal outcome for the client, but not the leak scenario this test pins.
type panicOnRegisterProcessor struct{ dialed <-chan struct{} }

func (panicOnRegisterProcessor) GetHandler(string) push.NotificationHandler { return nil }
func (panicOnRegisterProcessor) ProcessPendingNotifications(context.Context, push.NotificationHandlerContext, *proto.Reader) error {
	return nil
}

func (p panicOnRegisterProcessor) RegisterHandler(string, push.NotificationHandler, bool) error {
	select {
	case <-p.dialed:
	case <-time.After(5 * time.Second):
		// Fall through and panic anyway; the caller's poll reports opened=0.
	}
	panic("push processor rejects handler registration")
}
func (panicOnRegisterProcessor) UnregisterHandler(string) error { return nil }

// TestNewClientPanicClosesPartialClient pins that when a NewClient construction
// step panics AFTER the connection pools are created, the partial client is
// closed on the way out so the pools (and their connections) do not leak. The
// panic still propagates to the caller; here it is recovered.
func TestNewClientPanicClosesPartialClient(t *testing.T) {
	var opened, closed int64
	var dialedOnce sync.Once
	dialed := make(chan struct{})
	dialer := func(context.Context, string, string) (net.Conn, error) {
		atomic.AddInt64(&opened, 1)
		dialedOnce.Do(func() { close(dialed) })
		return &fakeConn{closed: &closed}, nil
	}

	func() {
		defer func() {
			if recover() == nil {
				t.Fatal("NewClient did not panic; the trigger no longer fires")
			}
		}()
		NewClient(&Options{
			Addr:                      "localhost:6379", // never contacted (fake dialer)
			Protocol:                  3,
			PoolSize:                  1,
			MinIdleConns:              1,
			Dialer:                    dialer,
			MaintNotificationsConfig:  &maintnotifications.Config{Mode: maintnotifications.ModeEnabled},
			PushNotificationProcessor: panicOnRegisterProcessor{dialed: dialed},
		})
	}()

	// The dialer has run at least once by the time the panic fires (see
	// panicOnRegisterProcessor). The dialed connection is closed either by the
	// pool's Close (if it was registered in time) or by addIdleConn when it
	// finds the pool already closed, so poll until every dialed conn is closed.
	deadline := time.Now().Add(2 * time.Second)
	for {
		o := atomic.LoadInt64(&opened)
		if o >= 1 && atomic.LoadInt64(&closed) == o {
			return
		}
		if time.Now().After(deadline) {
			t.Fatalf("partial client leaked its pool after NewClient panicked: opened=%d closed=%d", o, atomic.LoadInt64(&closed))
		}
		time.Sleep(time.Millisecond)
	}
}

// TestNewClientPanicCleanupSurvivesNilPool pins that the panic-cleanup defer
// does not itself panic when a pool constructor fails. newConnPool returns a
// nil pool plus an error for an out-of-range PoolSize; the pool field must stay
// nil (not a typed-nil pool.Pooler) so closeResources skips it and the ORIGINAL
// construction error surfaces to the caller, not a nil-deref from the cleanup.
func TestNewClientPanicCleanupSurvivesNilPool(t *testing.T) {
	var recovered any
	func() {
		defer func() { recovered = recover() }()
		// PoolSize overflows int32 -> newConnPool returns (nil, err) -> NewClient
		// panics at pool creation, before the field is assigned.
		NewClient(&Options{PoolSize: math.MaxInt32 + 1})
	}()
	if recovered == nil {
		t.Fatal("expected NewClient to panic on an out-of-range PoolSize")
	}
	err, ok := recovered.(error)
	if !ok || !strings.Contains(err.Error(), "failed to create connection pool") {
		t.Fatalf("cleanup replaced the construction panic (typed-nil pool nil-deref?): recovered=%v (%T)", recovered, recovered)
	}
}

// TestNewFailoverClientPanicClosesPartialClient pins that NewFailoverClient, like
// NewClient, tears down a partially-built client when a construction step panics
// AFTER the main and pub/sub pools are created. An out-of-range PipelinePoolSize
// makes buildPipelinePool fail at that point; the deferred cleanup must Close the
// partial client (so its pools/dialing goroutines do not leak) without itself
// nil-derefing, and the original construction error must still surface. MinIdleConns
// is 0 so the panic precedes any dialing and the sentinel addrs are never contacted.
func TestNewFailoverClientPanicClosesPartialClient(t *testing.T) {
	var recovered any
	func() {
		defer func() { recovered = recover() }()
		NewFailoverClient(&FailoverOptions{
			MasterName:       "mymaster",
			SentinelAddrs:    []string{"127.0.0.1:26379"}, // never contacted: panic precedes dialing
			PipelinePoolSize: math.MaxInt32 + 1,           // overflows int32 in buildPipelinePool
			MinIdleConns:     0,
		})
	}()
	if recovered == nil {
		t.Fatal("expected NewFailoverClient to panic on an out-of-range PipelinePoolSize")
	}
	err, ok := recovered.(error)
	if !ok || !strings.Contains(err.Error(), "failed to create pipeline connection pool") {
		t.Fatalf("cleanup replaced the construction panic (partial failover Close nil-deref?): recovered=%v (%T)", recovered, recovered)
	}
}

// TestNewFailoverClientPanicCleanupSurvivesNilPool is the NewFailoverClient twin
// of TestNewClientPanicCleanupSurvivesNilPool, pinning the specific bug where the
// failover constructor assigned newConnPool's typed-nil straight into the
// pool.Pooler field. An out-of-range PoolSize makes newConnPool return (nil, err),
// so the field must stay a plain nil (not a typed-nil interface) — otherwise
// closeResources' `connPool != nil` guard passes and the panic-cleanup defer
// nil-derefs inside ConnPool.Close, replacing the intended "failed to create
// connection pool" panic. MinIdleConns is 0 and the sentinel addrs are never
// contacted: the panic precedes any dialing.
func TestNewFailoverClientPanicCleanupSurvivesNilPool(t *testing.T) {
	var recovered any
	func() {
		defer func() { recovered = recover() }()
		NewFailoverClient(&FailoverOptions{
			MasterName:    "mymaster",
			SentinelAddrs: []string{"127.0.0.1:26379"}, // never contacted: panic precedes dialing
			PoolSize:      math.MaxInt32 + 1,           // overflows int32 in newConnPool
			MinIdleConns:  0,
		})
	}()
	if recovered == nil {
		t.Fatal("expected NewFailoverClient to panic on an out-of-range PoolSize")
	}
	err, ok := recovered.(error)
	if !ok || !strings.Contains(err.Error(), "failed to create connection pool") {
		t.Fatalf("cleanup replaced the construction panic (typed-nil connPool nil-deref?): recovered=%v (%T)", recovered, recovered)
	}
}