//nolint:testpackage // exercises unexported read-only open internals
package database

import (
	"context"
	"database/sql"
	"errors"
	"path/filepath"
	"testing"
)

// genuineSnapshotDB writes a real snapshot database (the full schema
// applied) to a fresh file and returns its path.
func genuineSnapshotDB(t *testing.T) string {
	t.Helper()

	path := filepath.Join(t.TempDir(), "snapshot.db")

	db, err := New(context.Background(), path)
	if err != nil {
		t.Fatalf("creating snapshot database: %v", err)
	}

	err = db.Close()
	if err != nil {
		t.Fatalf("closing snapshot database: %v", err)
	}

	return path
}

// forgedDB creates an empty database file and runs the given statements
// against it read-write, so a test can plant schema objects the real
// schema never defines.
func forgedDB(t *testing.T, stmts ...string) string {
	t.Helper()

	path := filepath.Join(t.TempDir(), "forged.db")

	db, err := sql.Open("sqlite", path)
	if err != nil {
		t.Fatalf("opening forged database: %v", err)
	}

	for _, stmt := range stmts {
		_, err = db.ExecContext(context.Background(), stmt)
		if err != nil {
			t.Fatalf("executing %q: %v", stmt, err)
		}
	}

	err = db.Close()
	if err != nil {
		t.Fatalf("closing forged database: %v", err)
	}

	return path
}

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

	db, err := OpenReadOnly(context.Background(), genuineSnapshotDB(t))
	if err != nil {
		t.Fatalf("OpenReadOnly refused a genuine snapshot database: %v", err)
	}

	t.Cleanup(func() { _ = db.Close() })
}

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

	db, err := OpenReadOnly(context.Background(), genuineSnapshotDB(t))
	if err != nil {
		t.Fatalf("OpenReadOnly: %v", err)
	}

	t.Cleanup(func() { _ = db.Close() })

	// A schema write depends on no table columns, so the only reason it
	// can fail is that the database is open read-only.
	_, err = db.Conn().ExecContext(context.Background(),
		"CREATE TABLE probe_readonly (x)")
	if err == nil {
		t.Fatal("expected a write to a read-only snapshot database to fail")
	}
}

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

	path := forgedDB(t, "CREATE VIEW files AS SELECT 1 AS path")

	_, err := OpenReadOnly(context.Background(), path)
	if !errors.Is(err, errUntrustedSnapshotSchema) {
		t.Fatalf("expected a view named files to be refused, got %v", err)
	}
}

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

	path := forgedDB(t,
		"CREATE TABLE files (path TEXT)",
		"CREATE TRIGGER t AFTER INSERT ON files BEGIN SELECT 1; END")

	_, err := OpenReadOnly(context.Background(), path)
	if !errors.Is(err, errUntrustedSnapshotSchema) {
		t.Fatalf("expected a trigger to be refused, got %v", err)
	}
}

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

	// Only one of the expected tables is present.
	path := forgedDB(t, "CREATE TABLE files (path TEXT)")

	_, err := OpenReadOnly(context.Background(), path)
	if !errors.Is(err, errUntrustedSnapshotSchema) {
		t.Fatalf("expected a missing expected table to be refused, got %v", err)
	}
}

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

	cases := []struct {
		sql  string
		want bool
	}{
		{"CREATE VIRTUAL TABLE t USING fts5(x)", true},
		{"  create virtual table t using fts5(x)", true},
		{"CREATE TABLE t (x)", false},
		{"CREATE VIEW t AS SELECT 1", false},
		{"", false},
	}

	for _, c := range cases {
		if got := isVirtualTableSQL(c.sql); got != c.want {
			t.Errorf("isVirtualTableSQL(%q) = %v, want %v", c.sql, got, c.want)
		}
	}
}