package config

import (
	"fmt"
	"os"
	"regexp"
)

var (
	ValidMethods = []string{"passphrase", "keyfile", "fido2", "tpm2"}
	uuidPattern  = regexp.MustCompile(`^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$`)
)

// Validate checks the config for common issues. Returns a list of errors.
func Validate(cfg *Config) []error {
	var errs []error

	for alias, dev := range cfg.Devices {
		if dev.UUID == "" {
			errs = append(errs, fmt.Errorf("%s: missing uuid", alias))
		} else if !uuidPattern.MatchString(dev.UUID) {
			errs = append(errs, fmt.Errorf("%s: malformed uuid %q", alias, dev.UUID))
		}

		for _, m := range dev.Methods {
			if !isValidMethod(m) {
				errs = append(errs, fmt.Errorf("%s: unknown method %q (valid: %v)", alias, m, ValidMethods))
			}
		}

		hasKeyfileMethod := false
		for _, m := range dev.Methods {
			if m == "keyfile" {
				hasKeyfileMethod = true
				break
			}
		}

		if hasKeyfileMethod && dev.Keyfile == "" {
			errs = append(errs, fmt.Errorf("%s: method 'keyfile' listed but no keyfile path set", alias))
		}

		if dev.Keyfile != "" {
			if _, err := os.Stat(dev.Keyfile); err != nil {
				errs = append(errs, fmt.Errorf("%s: keyfile %q not found (may be on removable media)", alias, dev.Keyfile))
			}
		}
	}

	return errs
}

func isValidMethod(m string) bool {
	for _, v := range ValidMethods {
		if m == v {
			return true
		}
	}
	return false
}