package site

import (
	"errors"
	"net/url"
	"regexp"
	"strings"
	"unicode/utf8"
)

var (
	ErrSiteNotFound    = errors.New("site not found")
	ErrSiteKeyTaken    = errors.New("a site with that key already exists")
	ErrSiteHasArticles = errors.New("the site still has articles")
	ErrDefaultSite     = errors.New("the default site cannot be deleted")
	ErrKeyImmutable    = errors.New("the key of a site cannot be changed")
	ErrInvalidSiteURL  = errors.New("invalid site url")
	ErrInvalidLocale   = errors.New("invalid locale")
	ErrUseSetDefault   = errors.New("the default flag is changed through the default route")
	ErrInvalidReassign = errors.New("invalid reassign destination")
)

const (
	RobotsIndex   = "index"
	RobotsNoIndex = "noindex"

	DefaultName = "Default"
	DefaultKey  = "default"

	MinNameRunes = 1
	MaxNameRunes = 100

	MinKeyRunes = 2
	MaxKeyRunes = 32
)

var keyPattern = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)
var localePattern = regexp.MustCompile(`^[a-z]{2,3}(-[A-Za-z0-9]{2,8})*$`)

var loopbackHosts = []string{"localhost", "127.0.0.1", "::1"}

type Site struct {
	ID                   uint32  `json:"id"`
	Name                 string  `json:"name"`
	Key                  string  `json:"key"`
	BaseURL              string  `json:"base_url"`
	DefaultSocialImageID *uint32 `json:"default_social_image_id"`
	DefaultRobots        string  `json:"default_robots"`
	Locale               *string `json:"locale"`
	IsDefault            bool    `json:"is_default"`
	ArticleCount         int     `json:"article_count"`
}

type Nullable[T any] struct {
	Set   bool
	Value *T
}

type Patch struct {
	Name                 *string
	Key                  *string
	BaseURL              *string
	DefaultRobots        *string
	Locale               Nullable[string]
	DefaultSocialImageID Nullable[uint32]
	IsDefault            *bool
}

func IsValidKey(key string) bool {
	length := utf8.RuneCountInString(key)
	return length >= MinKeyRunes && length <= MaxKeyRunes && keyPattern.MatchString(key)
}

func IsValidName(name string) bool {
	length := utf8.RuneCountInString(name)
	return length >= MinNameRunes && length <= MaxNameRunes
}

func NormalizeLocale(locale *string) (*string, error) {
	if locale == nil || *locale == "" {
		return nil, nil
	}
	if !localePattern.MatchString(*locale) {
		return nil, ErrInvalidLocale
	}
	return locale, nil
}

func isLoopback(hostname string) bool {
	for _, loopback := range loopbackHosts {
		if hostname == loopback {
			return true
		}
	}
	return false
}

type origin struct {
	scheme   string
	host     string
	hostname string
	parsed   *url.URL
}

func parseOrigin(raw string) (origin, error) {
	parsed, err := url.Parse(strings.TrimSpace(raw))
	if err != nil || parsed.Host == "" || parsed.Hostname() == "" {
		return origin{}, ErrInvalidSiteURL
	}
	scheme := strings.ToLower(parsed.Scheme)
	if scheme != "http" && scheme != "https" {
		return origin{}, ErrInvalidSiteURL
	}
	return origin{scheme: scheme, host: strings.ToLower(parsed.Host), hostname: strings.ToLower(parsed.Hostname()), parsed: parsed}, nil
}

func NormalizeBaseURL(raw string) (string, error) {
	found, err := parseOrigin(raw)
	if err != nil {
		return "", err
	}
	parsed := found.parsed
	if parsed.User != nil || parsed.RawQuery != "" || parsed.ForceQuery || parsed.Fragment != "" || (parsed.Path != "" && parsed.Path != "/") {
		return "", ErrInvalidSiteURL
	}
	if found.scheme == "http" && !isLoopback(found.hostname) {
		return "", ErrInvalidSiteURL
	}
	return found.scheme + "://" + found.host, nil
}

func SeedBaseURL(publicURL string) (string, error) {
	found, err := parseOrigin(publicURL)
	if err != nil {
		return "", err
	}
	scheme := found.scheme
	if scheme == "http" && !isLoopback(found.hostname) {
		scheme = "https"
	}
	return scheme + "://" + found.host, nil
}