package db_test

import (
	"database/sql"
	"fmt"
	"net/url"
	"os"
	"strings"
	"sync"
	"testing"

	"git.ryuvia.com/niklas/terdut-server/internal/db"

	_ "github.com/jackc/pgx/v5/stdlib"
)

// TERDUT_TEST_DSN must point at a database the test role may create schemas
// in; see internal/api/testdb_test.go for the fuller rationale this mirrors.
// An unset DSN fails rather than skips, deliberately.
const testDSNEnv = "TERDUT_TEST_DSN"

// TestMigrate_ConcurrentCallersDoNotRace reproduces two replicas starting at
// once against a brand-new, unmigrated schema: both call db.Migrate at the
// same time. Before migrationLockKey, the loser could crash on a
// duplicate-key insert into schema_migrations, or contend with the winner's
// uncommitted DDL; with the advisory lock, one blocks until the other
// finishes and both return cleanly.
func TestMigrate_ConcurrentCallersDoNotRace(t *testing.T) {
	dsn := os.Getenv(testDSNEnv)
	if dsn == "" {
		t.Fatalf("%s is not set: these tests need Postgres.\n"+
			"Run `make test-db` for a local one, then\n"+
			"  export %s=postgres://terdut:terdut@localhost:5432/terdut_test?sslmode=disable",
			testDSNEnv, testDSNEnv)
	}

	schema := fmt.Sprintf("migrate_race_%d", os.Getpid())
	admin, err := sql.Open("pgx", dsn)
	if err != nil {
		t.Fatalf("connect to %s: %v", testDSNEnv, err)
	}
	defer admin.Close()
	if _, err := admin.Exec("CREATE SCHEMA " + schema); err != nil {
		t.Fatalf("create schema %s: %v", schema, err)
	}
	t.Cleanup(func() {
		cleanup, err := sql.Open("pgx", dsn)
		if err != nil {
			return
		}
		defer cleanup.Close()
		if _, err := cleanup.Exec("DROP SCHEMA " + schema + " CASCADE"); err != nil {
			t.Logf("drop schema %s: %v", schema, err)
		}
	})

	scoped := withSearchPath(dsn, schema)

	const callers = 2
	errs := make([]error, callers)
	var wg sync.WaitGroup
	for i := range callers {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			database, err := db.Open(scoped)
			if err != nil {
				errs[i] = fmt.Errorf("open: %w", err)
				return
			}
			defer database.Close()
			errs[i] = db.Migrate(database)
		}(i)
	}
	wg.Wait()

	for i, err := range errs {
		if err != nil {
			t.Fatalf("Migrate #%d: %v", i, err)
		}
	}

	entries, err := os.ReadDir("migrations")
	if err != nil {
		t.Fatalf("read migrations dir: %v", err)
	}
	var want int
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
			want++
		}
	}

	check, err := sql.Open("pgx", scoped)
	if err != nil {
		t.Fatalf("connect for verification: %v", err)
	}
	defer check.Close()

	var got int
	if err := check.QueryRow("SELECT COUNT(*) FROM schema_migrations").Scan(&got); err != nil {
		t.Fatalf("count schema_migrations: %v", err)
	}
	if got != want {
		t.Fatalf("schema_migrations has %d row(s) after two concurrent Migrate calls, want %d (one per migration file, no duplicates)", got, want)
	}
}

// withSearchPath pins a DSN to one schema. Copied from
// internal/api/testdb_test.go rather than shared: that helper lives in the
// api_test package, a separate compiled package this one cannot import.
func withSearchPath(dsn, schema string) string {
	opt := "-csearch_path=" + schema

	if strings.HasPrefix(dsn, "postgres://") || strings.HasPrefix(dsn, "postgresql://") {
		u, err := url.Parse(dsn)
		if err == nil {
			q := u.Query()
			q.Set("options", opt)
			u.RawQuery = q.Encode()
			return u.String()
		}
	}
	return dsn + " options='" + opt + "'"
}