// Shared env-file handling for the installers (Windows and Linux).
package service

import (
	"fmt"
	"os"
	"strings"

	"gpu-turnstile/internal/config"
)

// syncEnvFile ensures the installed env file at path is a current
// installer-written sample. A missing file is created; a file without a
// CFG_VER line (hand-written or from before versioning) is invalid and
// replaced by a fresh sample after a .bak backup; a file written by an
// older version gets newly added settings appended via config.SyncSample.
// logPath activates the LOG_FILE line (Windows); empty leaves it commented.
func syncEnvFile(path, version, logPath string) error {
	data, err := os.ReadFile(path)
	switch {
	case os.IsNotExist(err):
		return writeEnvFile(path, config.SampleEnv(version, logPath))
	case err != nil:
		return fmt.Errorf("read %s: %w", path, err)
	}
	values, perr := config.ParseEnvFile(strings.NewReader(string(data)))
	if perr == nil && values["CFG_VER"] != "" {
		synced, changed := config.SyncSample(string(data), version, logPath)
		if !changed {
			return nil
		}
		return writeEnvFile(path, synced)
	}
	// No readable CFG_VER: the file is invalid — keep a backup and start
	// from a fresh sample.
	if err := os.WriteFile(path+".bak", data, 0o644); err != nil {
		return fmt.Errorf("back up %s: %w", path, err)
	}
	return writeEnvFile(path, config.SampleEnv(version, logPath))
}

func writeEnvFile(path, content string) error {
	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
		return fmt.Errorf("write %s: %w", path, err)
	}
	return nil
}

// configuredValue reads one key from the env file the service will load, so
// the installers can adapt the sandbox to it (ACL grants, unit directives).
// "" when unset or unreadable.
func configuredValue(configPath, key string) string {
	f, err := os.Open(configPath)
	if err != nil {
		return ""
	}
	defer f.Close()
	values, err := config.ParseEnvFile(f)
	if err != nil {
		return ""
	}
	return values[key]
}