package config

import (
	"errors"
	"regexp"
	"strings"
)

// Shell is the public presentation configuration, independent of deployment topology and auth.
type Shell struct {
	Mode          string `yaml:"mode" json:"mode"`
	DefaultLocale string `yaml:"defaultLocale" json:"defaultLocale"`
	Adapter       string `yaml:"adapter,omitempty" json:"adapter,omitempty"`
}

// NormalizeDefaults resolves omitted installation settings before projecting them to the browser.
func (s *Shell) NormalizeDefaults() error {
	if s.Mode == "" {
		s.Mode = "embedded"
	}
	if s.DefaultLocale == "" {
		s.DefaultLocale = "en"
	}
	if s.Mode != "embedded" && s.Mode != "full" {
		return errors.New("shell.mode must be full or embedded")
	}
	if !wellFormedLocale(s.DefaultLocale) {
		return errors.New("shell.defaultLocale must be a well-formed BCP47 language tag")
	}
	if s.Adapter != "" && s.Adapter != "omics-portal" {
		return errors.New("shell.adapter must be omics-portal")
	}
	if s.Mode == "full" {
		s.Adapter = ""
		return nil
	}
	if s.Adapter == "" {
		s.Adapter = "omics-portal"
	}
	return nil
}

// RFC 5646 section 2.1 grammar. Capture variants and extensions to reject duplicates.
// Validate syntax without consulting a language registry or the frontend's available catalogs.
var localePattern = regexp.MustCompile(`^(?:` +
	`(?:[a-z]{2,3}(?:-[a-z]{3}){0,3}|[a-z]{4}|[a-z]{5,8})` + // language / extlang
	`(?:-[a-z]{4})?(?:-(?:[a-z]{2}|[0-9]{3}))?` + // script / region
	`((?:-(?:[a-z0-9]{5,8}|[0-9][a-z0-9]{3}))*)` + // variants
	`((?:-[0-9a-wy-z](?:-[a-z0-9]{2,8})+)*)` + // extensions
	`(?:-x(?:-[a-z0-9]{1,8})+)?` + // private use after a language
	`|x(?:-[a-z0-9]{1,8})+)$`) // private use alone

func wellFormedLocale(locale string) bool {
	// BCP47 is ASCII. Check before case folding, which could otherwise map Unicode to ASCII.
	for _, character := range locale {
		if character > 127 {
			return false
		}
	}
	tag := strings.ToLower(locale)
	// These grandfathered irregular tags do not match the normal language-tag grammar.
	switch tag {
	case "en-gb-oed", "i-ami", "i-bnn", "i-default", "i-enochian", "i-hak", "i-klingon",
		"i-lux", "i-mingo", "i-navajo", "i-pwn", "i-tao", "i-tay", "i-tsu",
		"sgn-be-fr", "sgn-be-nl", "sgn-ch-de":
		return true
	}
	parts := localePattern.FindStringSubmatch(tag)
	if parts == nil {
		return false
	}
	variants := make(map[string]bool)
	for _, variant := range strings.Split(strings.TrimPrefix(parts[1], "-"), "-") {
		if variants[variant] {
			return false
		}
		variants[variant] = true
	}
	singletons := make(map[string]bool)
	for _, subtag := range strings.Split(parts[2], "-") {
		if len(subtag) != 1 {
			continue
		}
		if singletons[subtag] {
			return false
		}
		singletons[subtag] = true
	}
	return true
}