package store

import (
	"context"
	"errors"
	"io"
	"net"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/alicebob/miniredis/v2"
	"github.com/redis/go-redis/v9"

	"migadu_counters/internal/config"
)

func newMini(t *testing.T) *miniredis.Miniredis {
	t.Helper()
	m := miniredis.RunT(t)
	return m
}

// testStore wires a Store to two separate miniredis instances so tests can
// prove which side (write master vs read replica) a method talks to.
func testStore(t *testing.T) (*Store, *miniredis.Miniredis, *miniredis.Miniredis) {
	t.Helper()
	w, r := newMini(t), newMini(t)
	s := NewWithClients(
		redis.NewClient(&redis.Options{Addr: w.Addr()}),
		[]*redis.Client{redis.NewClient(&redis.Options{Addr: r.Addr()})},
	)
	t.Cleanup(func() { s.Close() })
	return s, w, r
}

func TestKey(t *testing.T) {
	tests := []struct {
		level, id, date, flow, want string
	}{
		{"A", "x@example.com", "2026-10-13", "i", "cnt/A/x@example.com/d/2026-10-13/i"},
		{"D", "example.com", "2026-10-13", "o", "cnt/D/example.com/d/2026-10-13/o"},
		{"O", "1234", "2026-01-01", "i", "cnt/O/1234/d/2026-01-01/i"},
	}
	for _, tt := range tests {
		if got := Key(tt.level, tt.id, tt.date, tt.flow); got != tt.want {
			t.Errorf("Key(%s,%s,%s,%s) = %q, want %q", tt.level, tt.id, tt.date, tt.flow, got, tt.want)
		}
	}
}

// The day stamp is always the UTC calendar day, matching migadu_web's
// Date.utc_today() — never the server's local day.
func TestDayKey_UTC(t *testing.T) {
	cest := time.FixedZone("CEST", 2*3600)
	tests := []struct {
		in   time.Time
		want string
	}{
		{time.Date(2026, 10, 13, 23, 59, 0, 0, cest), "2026-10-13"},  // 21:59 UTC
		{time.Date(2026, 10, 14, 1, 30, 0, 0, cest), "2026-10-13"},   // 23:30 UTC the day before
		{time.Date(2026, 10, 14, 2, 0, 0, 0, cest), "2026-10-14"},    // 00:00 UTC
		{time.Date(2026, 3, 5, 12, 0, 0, 0, time.UTC), "2026-03-05"}, // zero padded
	}
	for _, tt := range tests {
		if got := DayKey(tt.in); got != tt.want {
			t.Errorf("DayKey(%v) = %q, want %q", tt.in, got, tt.want)
		}
	}
}

func TestIncr(t *testing.T) {
	s, w, _ := testStore(t)
	ctx := context.Background()
	keys := []string{"cnt/A/x@example.com/d/2026-10-13/o", "cnt/O/1234/d/2026-10-13/o"}

	got, err := s.Incr(ctx, keys)
	if err != nil {
		t.Fatalf("Incr: %v", err)
	}
	if len(got) != 2 || got[0].Count != 1 || got[1].Count != 1 || got[0].Err != nil || got[1].Err != nil {
		t.Fatalf("first Incr = %+v, want counts [1 1]", got)
	}
	got, err = s.Incr(ctx, keys)
	if err != nil || got[0].Count != 2 || got[1].Count != 2 {
		t.Fatalf("second Incr = %+v, %v; want [2 2]", got, err)
	}
	for _, k := range keys {
		if v, _ := w.Get(k); v != "2" {
			t.Errorf("stored %s = %q, want \"2\"", k, v)
		}
		if ttl := w.TTL(k); ttl <= 30*24*time.Hour || ttl > TTL {
			t.Errorf("TTL(%s) = %v, want (30d, 31d]", k, ttl)
		}
	}
	if got, err := s.Incr(ctx, nil); err != nil || len(got) != 0 {
		t.Errorf("Incr(no keys) = %v, %v; want empty, nil", got, err)
	}
}

// One key holding a non-number fails its own INCR inside EXEC; the other
// keys are still incremented and their counts reported (review #4).
func TestIncr_PartialFailure(t *testing.T) {
	s, w, _ := testStore(t)
	w.Set("bad", "garbage")
	got, err := s.Incr(context.Background(), []string{"k1", "bad", "k3"})
	if err != nil {
		t.Fatalf("a per-key failure must not fail the whole Incr: %v", err)
	}
	if got[0].Count != 1 || got[0].Err != nil || got[2].Count != 1 || got[2].Err != nil {
		t.Errorf("good keys = %+v %+v, want count 1 without error", got[0], got[2])
	}
	if got[1].Err == nil || !strings.Contains(got[1].Err.Error(), "not an integer") {
		t.Errorf("bad key err = %v, want the INCR error", got[1].Err)
	}
	if v, _ := w.Get("bad"); v != "garbage" {
		t.Errorf("bad key = %q, must be untouched", v)
	}
	if ttl := w.TTL("k1"); ttl <= 30*24*time.Hour {
		t.Errorf("TTL(k1) = %v, EXPIRE should still have run", ttl)
	}
}

// GetMaster reads from the write side (used after a lost reply, when the
// replica may not have the increment yet).
func TestGetMaster(t *testing.T) {
	s, w, r := testStore(t)
	w.Set("k", "19")
	r.Set("k", "3")
	got, err := s.GetMaster(context.Background(), []string{"k", "missing"})
	if err != nil || len(got) != 2 || got[0] != 19 || got[1] != 0 {
		t.Errorf("GetMaster = %v, %v; want [19 0] from the master", got, err)
	}
}

// OutcomeUnknown tells whether a failed Incr may still have been applied: a
// refused connection never reached Redis, a timeout or reset after the write
// might have.
func TestOutcomeUnknown(t *testing.T) {
	s, w, _ := testStore(t)
	w.Close()
	_, err := s.Incr(context.Background(), []string{"k"})
	if err == nil {
		t.Fatal("expected an error with the write side down")
	}
	if OutcomeUnknown(err) {
		t.Errorf("connection refused must be a known failure, got unknown: %v", err)
	}
	if OutcomeUnknown(nil) || OutcomeUnknown(context.Canceled) {
		t.Error("nil / canceled are not unknown outcomes")
	}
	for _, e := range []error{context.DeadlineExceeded, io.EOF, &net.OpError{Op: "read", Err: timeoutErr{}}, errors.New("i/o timeout")} {
		if !OutcomeUnknown(e) {
			t.Errorf("%v should be an unknown outcome", e)
		}
	}
}

type timeoutErr struct{}

func (timeoutErr) Error() string   { return "i/o timeout" }
func (timeoutErr) Timeout() bool   { return true }
func (timeoutErr) Temporary() bool { return true }

// Fifty concurrent increments of one key must end at exactly 50 — the
// pipeline relies on INCRBY being atomic, not on read-then-write.
func TestIncr_Concurrent(t *testing.T) {
	s, w, _ := testStore(t)
	var wg sync.WaitGroup
	for i := 0; i < 50; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			if _, err := s.Incr(context.Background(), []string{"k"}); err != nil {
				t.Error(err)
			}
		}()
	}
	wg.Wait()
	if v, _ := w.Get("k"); v != "50" {
		t.Errorf("k = %q, want 50", v)
	}
}

// Get reads from the replica side: a key present only on the write instance
// is invisible, a key present on the read instance is returned, missing = 0.
func TestGet_UsesReadSide(t *testing.T) {
	s, w, r := testStore(t)
	w.Set("only-on-write", "9")
	r.Set("on-read", "5")
	got, err := s.Get(context.Background(), []string{"on-read", "only-on-write", "missing"})
	if err != nil {
		t.Fatal(err)
	}
	if len(got) != 3 || got[0] != 5 || got[1] != 0 || got[2] != 0 {
		t.Errorf("Get = %v, want [5 0 0]", got)
	}
	if got, err := s.Get(context.Background(), nil); err != nil || len(got) != 0 {
		t.Errorf("Get(no keys) = %v, %v", got, err)
	}
}

func TestGet_RoundRobinReaders(t *testing.T) {
	w, r1, r2 := newMini(t), newMini(t), newMini(t)
	r1.Set("k", "1")
	r2.Set("k", "2")
	s := NewWithClients(redis.NewClient(&redis.Options{Addr: w.Addr()}), []*redis.Client{
		redis.NewClient(&redis.Options{Addr: r1.Addr()}),
		redis.NewClient(&redis.Options{Addr: r2.Addr()}),
	})
	defer s.Close()
	seen := map[int64]int{}
	for i := 0; i < 4; i++ {
		got, err := s.Get(context.Background(), []string{"k"})
		if err != nil {
			t.Fatal(err)
		}
		seen[got[0]]++
	}
	if seen[1] != 2 || seen[2] != 2 {
		t.Errorf("reads not alternated between replicas: %v", seen)
	}
}

func TestErrors_RedisDown(t *testing.T) {
	s, w, r := testStore(t)
	ctx := context.Background()
	if err := s.Ping(ctx); err != nil {
		t.Fatalf("Ping before close: %v", err)
	}
	w.Close()
	if _, err := s.Incr(ctx, []string{"k"}); err == nil {
		t.Error("Incr with write side down should fail")
	}
	if err := s.Ping(ctx); err == nil {
		t.Error("Ping with write side down should fail")
	}
	r.Close()
	if _, err := s.Get(ctx, []string{"k"}); err == nil {
		t.Error("Get with read side down should fail")
	}
}

func TestNew_Static(t *testing.T) {
	w, r := newMini(t), newMini(t)
	s, err := New(config.RedisConfig{WriteAddr: w.Addr(), ReadAddrs: []string{r.Addr()}, PoolSize: 2, TimeoutMS: 200})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	defer s.Close()
	ctx := context.Background()
	if err := s.Ping(ctx); err != nil {
		t.Fatalf("Ping: %v", err)
	}
	if _, err := s.Incr(ctx, []string{"k"}); err != nil {
		t.Fatal(err)
	}
	if v, _ := w.Get("k"); v != "1" {
		t.Errorf("write went to %q, want the write_addr instance", v)
	}
	r.Set("k", "7")
	if got, _ := s.Get(ctx, []string{"k"}); got[0] != 7 {
		t.Errorf("Get = %v, want 7 from read_addrs", got)
	}
}

func TestNew_StaticDefaultsReadToWrite(t *testing.T) {
	w := newMini(t)
	s, err := New(config.RedisConfig{WriteAddr: w.Addr(), PoolSize: 1, TimeoutMS: 200})
	if err != nil {
		t.Fatal(err)
	}
	defer s.Close()
	w.Set("k", "3")
	if got, err := s.Get(context.Background(), []string{"k"}); err != nil || got[0] != 3 {
		t.Errorf("Get = %v, %v; want 3 from the write instance", got, err)
	}
}

func TestNew_RejectsNonZeroDB(t *testing.T) {
	if _, err := New(config.RedisConfig{WriteAddr: "127.0.0.1:6379", DB: 1, PoolSize: 1, TimeoutMS: 100}); err == nil {
		t.Error("New with db=1 should fail: migadu_web reads DB 0")
	}
}

// Sentinel mode constructs lazily; an unreachable sentinel surfaces on the
// first command, bounded by the configured timeout.
func TestNew_SentinelUnreachable(t *testing.T) {
	s, err := New(config.RedisConfig{MasterName: "mymaster", Sentinels: []string{"127.0.0.1:1"}, PoolSize: 1, TimeoutMS: 200})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	defer s.Close()
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
	start := time.Now()
	if err := s.Ping(ctx); err == nil {
		t.Error("Ping against an unreachable sentinel should fail")
	}
	if time.Since(start) > 2500*time.Millisecond {
		t.Errorf("Ping took %v, should fail fast", time.Since(start))
	}
}

func TestClose(t *testing.T) {
	s, _, _ := testStore(t)
	if err := s.Close(); err != nil {
		t.Fatalf("Close: %v", err)
	}
	if err := s.Ping(context.Background()); err == nil {
		t.Error("Ping after Close should fail")
	}
}