package metrics

import (
	"context"
	"strings"
	"testing"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/testutil"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestPoolCollector(t *testing.T) {
	// The pool connects lazily, so no database is needed to read its statistics.
	pool, err := pgxpool.New(context.Background(), "postgres://user:pass@127.0.0.1:1/music?pool_max_conns=7")
	require.NoError(t, err)
	t.Cleanup(pool.Close)

	registry := prometheus.NewRegistry()
	registry.MustRegister(NewPoolCollector(pool))

	assert.Equal(t, 11, testutil.CollectAndCount(registry))
	require.NoError(t, testutil.GatherAndCompare(registry, strings.NewReader(`
# HELP musicserver_db_pool_max_conns Most connections the pool opens.
# TYPE musicserver_db_pool_max_conns gauge
musicserver_db_pool_max_conns 7
# HELP musicserver_db_pool_acquired_conns Connections in use.
# TYPE musicserver_db_pool_acquired_conns gauge
musicserver_db_pool_acquired_conns 0
`), "musicserver_db_pool_max_conns", "musicserver_db_pool_acquired_conns"))
}