package database_test

import (
	"context"
	"path/filepath"
	"strings"
	"testing"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"gorm.io/gorm"
	"sneak.berlin/go/webhooker/internal/database"
)

// livePragma reads a pragma off a live handle. Reading the DSN back
// would prove only that the string was built; these tests assert that
// SQLite actually applied it.
func livePragma(t *testing.T, db *gorm.DB, name string) string {
	t.Helper()

	var v string

	row := db.Raw("pragma " + name).Row()
	require.NoError(t, row.Scan(&v))

	return v
}

func TestSQLiteDSNCarriesTheDurabilitySettings(t *testing.T) {
	t.Parallel()

	dsn := database.SQLiteDSN(
		"/var/lib/webhooker/webhooker.db",
		database.SQLiteModeCreate,
	)

	assert.Contains(t, dsn, "journal_mode%28WAL%29")
	assert.Contains(t, dsn, "busy_timeout%2810000%29")
	assert.Contains(t, dsn, "_txlock=immediate")
	assert.Contains(t, dsn, "mode=rwc")

	// busy_timeout must come first. The driver runs these in order on
	// every new connection, and PRAGMA journal_mode takes a lock — a
	// connection opened while the database is busy would fail on that
	// pragma, with no busy handler yet installed to wait it out.
	assert.Less(
		t,
		strings.Index(dsn, "busy_timeout"),
		strings.Index(dsn, "journal_mode"),
		"busy_timeout must be applied before journal_mode",
	)

	// cache=shared turns an in-process conflict into SQLITE_LOCKED,
	// which the busy handler does not retry. It must never come back.
	// See https://git.eeqj.de/sneak/webhooker/issues/256.
	assert.NotContains(t, strings.ToLower(dsn), "cache=shared")
}

// TestPerWebhookDBAppliesPragmasOnALiveHandle is the check the issue
// asks for by name: the settings are confirmed by querying the running
// database, not by inspecting the connection string.
func TestPerWebhookDBAppliesPragmasOnALiveHandle(t *testing.T) {
	t.Parallel()

	mgr, lc := setupTestWebhookDBManager(t)
	ctx := context.Background()
	require.NoError(t, lc.Start(ctx))

	defer func() { require.NoError(t, lc.Stop(ctx)) }()

	webhookID := uuid.New().String()

	db, err := mgr.GetDB(webhookID)
	require.NoError(t, err)

	assert.Equal(
		t, "wal",
		strings.ToLower(livePragma(t, db, "journal_mode")),
	)
	assert.Equal(
		t, "10000", livePragma(t, db, "busy_timeout"),
	)
}

func TestMainDBAppliesPragmasOnALiveHandle(t *testing.T) {
	t.Parallel()

	ctx := context.Background()
	dir := t.TempDir()

	sqlDB, err := database.OpenSQLite(
		filepath.Join(dir, database.MainDBFileName),
		database.SQLiteModeCreate,
	)
	require.NoError(t, err)

	defer func() { require.NoError(t, sqlDB.Close()) }()

	var journal string

	require.NoError(t, sqlDB.
		QueryRowContext(ctx, "pragma journal_mode").
		Scan(&journal))
	assert.Equal(t, "wal", strings.ToLower(journal))

	var busy string

	require.NoError(t, sqlDB.
		QueryRowContext(ctx, "pragma busy_timeout").
		Scan(&busy))
	assert.Equal(t, "10000", busy)
}

// TestConcurrentReaderDoesNotBlockWrites is the unit-scale form of the
// reproduction in
// https://git.eeqj.de/sneak/webhooker/issues/256: an operator's
// long-held read of their own data used to make every concurrent write
// fail. Under WAL the reader takes a snapshot and the writes proceed.
func TestConcurrentReaderDoesNotBlockWrites(t *testing.T) {
	t.Parallel()

	mgr, lc := setupTestWebhookDBManager(t)
	ctx := context.Background()
	require.NoError(t, lc.Start(ctx))

	defer func() { require.NoError(t, lc.Stop(ctx)) }()

	webhookID := uuid.New().String()

	db, err := mgr.GetDB(webhookID)
	require.NoError(t, err)

	// A second handle on the same file, holding a read transaction
	// open across every write below — what `sqlite3 <db> .dump` is.
	readerSQL, err := database.OpenSQLite(
		mgr.DBPath(webhookID), database.SQLiteModeExisting,
	)
	require.NoError(t, err)

	defer func() { require.NoError(t, readerSQL.Close()) }()

	readerConn, err := readerSQL.Conn(ctx)
	require.NoError(t, err)

	defer func() { require.NoError(t, readerConn.Close()) }()

	_, err = readerConn.ExecContext(ctx, "begin deferred")
	require.NoError(t, err)

	_, err = readerConn.ExecContext(
		ctx, "select count(*) from events",
	)
	require.NoError(t, err)

	for range 25 {
		err = db.Transaction(func(tx *gorm.DB) error {
			return tx.Create(&database.Event{
				WebhookID:    webhookID,
				EntrypointID: uuid.New().String(),
				Method:       "POST",
				Body:         "{}",
			}).Error
		})
		require.NoError(t, err)
	}

	_, err = readerConn.ExecContext(ctx, "commit")
	require.NoError(t, err)

	var count int64

	require.NoError(
		t,
		db.Model(&database.Event{}).Count(&count).Error,
	)
	assert.Equal(t, int64(25), count)
}