// Package testenv keeps tests that run commands in a sandbox out of the
// user's home.
package testenv

import (
	"os"
	"path/filepath"
	"strings"

	"blinker/internal/policy"
)

// LeaveHome drops the paths in the user's home from every environment
// variable, and the variables left empty, so a test's sandbox, given a
// home of its own, resolves no path in the real one: the policies name
// paths through $XDG_CONFIG_HOME, $CARGO_HOME, $PATH and the like.
func LeaveHome() error {
	home, err := os.UserHomeDir()
	if err != nil {
		return err
	}
	for _, kv := range os.Environ() {
		name, value, _ := strings.Cut(kv, "=")
		var keep []string
		for _, p := range filepath.SplitList(value) {
			if !policy.Under(p, home) {
				keep = append(keep, p)
			}
		}
		switch kept := strings.Join(keep, string(os.PathListSeparator)); {
		case kept == value:
		case kept == "":
			err = os.Unsetenv(name)
		default:
			err = os.Setenv(name, kept)
		}
		if err != nil {
			return err
		}
	}
	return nil
}