package dbsnap

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"

	"gitea.dooplex.hu/admin/felhom-hub/internal/store"
)

func newStore(t *testing.T) (*store.Store, string) {
	t.Helper()
	p := filepath.Join(t.TempDir(), "hub.db")
	s, err := store.New(p, log.New(io.Discard, "", 0))
	if err != nil {
		t.Fatalf("store.New: %v", err)
	}
	t.Cleanup(func() { s.Close() })
	return s, p
}

func openRO(t *testing.T, p string) *sql.DB {
	t.Helper()
	db, err := sql.Open("sqlite", "file:"+p+"?mode=ro")
	if err != nil {
		t.Fatalf("open %s: %v", p, err)
	}
	t.Cleanup(func() { db.Close() })
	return db
}

// rowCounts returns count(*) of every table.
func rowCounts(t *testing.T, db *sql.DB) map[string]int {
	t.Helper()
	rows, err := db.Query(`SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' ORDER BY name`)
	if err != nil {
		t.Fatalf("list tables: %v", err)
	}
	var names []string
	for rows.Next() {
		var n string
		_ = rows.Scan(&n)
		names = append(names, n)
	}
	rows.Close()
	out := map[string]int{}
	for _, n := range names {
		var c int
		if err := db.QueryRow(fmt.Sprintf(`SELECT count(*) FROM "%s"`, n)).Scan(&c); err != nil {
			t.Fatalf("count %s: %v", n, err)
		}
		out[n] = c
	}
	return out
}

// TestSnapshot_ConsistentWithLiveDBIncludingWAL is the consequence test: the snapshot passes integrity_check and has
// the live database's row count in EVERY table — including rows that so far live only in hub.db-wal. Precondition
// asserted in-test: copying hub.db alone (the naive file backup) LOSES those rows, so this test can tell the two apart.
func TestSnapshot_ConsistentWithLiveDBIncludingWAL(t *testing.T) {
	s, live := newStore(t)
	for i := 0; i < 150; i++ {
		if err := s.UpsertHost(&store.Host{HostID: fmt.Sprintf("h%03d", i), CustomerID: "c1", APIKey: fmt.Sprintf("k%03d", i)}); err != nil {
			t.Fatalf("UpsertHost: %v", err)
		}
	}
	if fi, err := os.Stat(live + "-wal"); err != nil || fi.Size() == 0 {
		t.Fatalf("precondition: want a non-empty WAL, got %v", err)
	}
	// Precondition: a plain copy of hub.db does not hold the WAL rows.
	naive := filepath.Join(t.TempDir(), "naive.db")
	b, _ := os.ReadFile(live)
	_ = os.WriteFile(naive, b, 0o600)
	if c := rowCounts(t, openRO(t, naive))["hosts"]; c == 150 {
		t.Fatalf("precondition: a plain file copy already holds all 150 hosts — the test cannot tell a WAL-blind copy apart")
	}

	dir := filepath.Join(t.TempDir(), "snapshots")
	m := &Maker{Store: s, Dir: dir}
	res, err := m.Make(context.Background())
	if err != nil {
		t.Fatalf("Make: %v", err)
	}
	snap := openRO(t, filepath.Join(dir, res.Name))
	var ic string
	if err := snap.QueryRow(`PRAGMA integrity_check`).Scan(&ic); err != nil || ic != "ok" {
		t.Fatalf("integrity_check = %q, %v", ic, err)
	}
	want, got := rowCounts(t, openRO(t, live)), rowCounts(t, snap)
	if len(want) < 10 || want["hosts"] != 150 {
		t.Fatalf("live counts look wrong: %d tables, hosts=%d", len(want), want["hosts"])
	}
	for tbl, n := range want {
		if got[tbl] != n {
			t.Errorf("table %s: snapshot %d rows, live %d", tbl, got[tbl], n)
		}
	}
	if fi, _ := os.Stat(filepath.Join(dir, res.Name)); fi == nil || fi.Mode().Perm() != 0o600 || res.Bytes != fi.Size() {
		t.Errorf("snapshot file mode/size wrong: %+v res.Bytes=%d", fi, res.Bytes)
	}
	if _, err := os.Stat(filepath.Join(dir, res.Name+".tmp")); !os.IsNotExist(err) {
		t.Errorf("the .tmp file is left behind")
	}
}

// TestSnapshot_KeepsNewestTwo pins Keep: three runs leave the two newest.
func TestSnapshot_KeepsNewestTwo(t *testing.T) {
	s, _ := newStore(t)
	dir := filepath.Join(t.TempDir(), "snapshots")
	base := time.Date(2026, 10, 5, 0, 0, 0, 0, time.UTC)
	i := 0
	m := &Maker{Store: s, Dir: dir, Now: func() time.Time { i++; return base.Add(time.Duration(i) * 24 * time.Hour) }}
	for k := 0; k < 3; k++ {
		if _, err := m.Make(context.Background()); err != nil {
			t.Fatalf("Make %d: %v", k, err)
		}
	}
	got := List(dir)
	want := []string{"hub-20261007T000000Z.db", "hub-20261008T000000Z.db"}
	if strings.Join(got, ",") != strings.Join(want, ",") {
		t.Fatalf("kept %v, want %v", got, want)
	}
}

type blockingStore struct {
	in, release chan struct{}
	once        *sync.Once
}

func (b blockingStore) SnapshotInto(ctx context.Context, path string) error {
	b.once.Do(func() { close(b.in) })
	<-b.release
	return os.WriteFile(path, []byte("x"), 0o600)
}

// TestSnapshot_NeverTwoAtOnce: a second Make while the first runs returns ErrBusy and writes nothing.
func TestSnapshot_NeverTwoAtOnce(t *testing.T) {
	bs := blockingStore{in: make(chan struct{}), release: make(chan struct{}), once: &sync.Once{}}
	dir := t.TempDir()
	m := &Maker{Store: bs, Dir: dir}
	done := make(chan error, 1)
	go func() { _, err := m.Make(context.Background()); done <- err }()
	<-bs.in
	second := make(chan error, 1)
	go func() { _, err := m.Make(context.Background()); second <- err }()
	select {
	case err := <-second:
		if !errors.Is(err, ErrBusy) {
			t.Fatalf("second Make = %v, want ErrBusy", err)
		}
	case <-time.After(2 * time.Second):
		close(bs.release)
		t.Fatalf("second Make did not return ErrBusy at once: it ran alongside the first")
	}
	close(bs.release)
	if err := <-done; err != nil {
		t.Fatalf("first Make: %v", err)
	}
	if n := len(List(dir)); n != 1 {
		t.Fatalf("%d snapshots, want 1", n)
	}
	m.Now = func() time.Time { return time.Now().Add(time.Hour) } // a distinct name
	if _, err := m.Make(context.Background()); err != nil {
		t.Fatalf("Make after the first ended: %v", err)
	}
}

type failStore struct{}

func (failStore) SnapshotInto(ctx context.Context, path string) error {
	_ = os.WriteFile(path, []byte("half"), 0o600)
	return errors.New("disk full")
}

// TestSnapshot_FailureLeavesNoFile: a failed VACUUM INTO leaves neither a snapshot nor a .tmp for DooPlex to pick up.
func TestSnapshot_FailureLeavesNoFile(t *testing.T) {
	dir := t.TempDir()
	if _, err := (&Maker{Store: failStore{}, Dir: dir}).Make(context.Background()); err == nil {
		t.Fatal("Make succeeded over a failing store")
	}
	if e, _ := os.ReadDir(dir); len(e) != 0 {
		t.Fatalf("left %d file(s) behind", len(e))
	}
}

func TestNeedsCatchUp(t *testing.T) {
	dir := t.TempDir()
	now := time.Date(2026, 10, 5, 12, 0, 0, 0, time.UTC)
	if !NeedsCatchUp(dir, now, 24*time.Hour) {
		t.Error("empty dir: want catch-up")
	}
	_ = os.WriteFile(filepath.Join(dir, "hub-20261005T000000Z.db"), nil, 0o600)
	if NeedsCatchUp(dir, now, 24*time.Hour) {
		t.Error("12 h old: want no catch-up")
	}
	if !NeedsCatchUp(dir, now.Add(13*time.Hour), 24*time.Hour) {
		t.Error("25 h old: want catch-up")
	}
}