package middleware

import (
	"context"
	"fmt"
	"hash/crc32"
	"net/http"
	"net/url"
	"path"
	"strconv"
	"strings"

	"github.com/labstack/echo/v4"

	psconfig "prestaproxy/internal/prestashop/config"
	pscookie "prestaproxy/internal/prestashop/cookie"
)

type AnonymousSessionInitializer interface {
	NewAnonymous(ctx context.Context, req *http.Request, cookieName string) (*pscookie.SessionContext, error)
}

type LanguageResolver interface {
	ResolveLanguageID(ctx context.Context, req *http.Request, fallback int64) int64
}

type ProductRouteMatcher interface {
	Owns(path string) bool
}

func Session(cfg psconfig.Config, codec pscookie.Codec, initializer AnonymousSessionInitializer, languageResolver LanguageResolver, matcher ProductRouteMatcher) echo.MiddlewareFunc {
	ownership := cfg.ParseRouteOwnership()

	return func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			ownedRoute := ownsProductRoute(ownership.ProductPrefixes, c.Request().URL.Path, matcher)
			configuredCookieName := cfg.DeriveCookieName(requestCookieHost(c.Request()))
			cookieName, rawCookie := findPrestaShopCookie(c.Request(), configuredCookieName)
			if cookieName == "" {
				cookieName = configuredCookieName
			}

			session, err := codec.Decode(rawCookie)
			if err != nil {
				if ownedRoute {
					return echo.NewHTTPError(http.StatusInternalServerError, "prestashop cookie decode failed")
				}
				SetSession(c, &pscookie.SessionContext{
					CookieName:  cookieName,
					RawCookie:   rawCookie,
					Values:      map[string]string{},
					ParseStatus: pscookie.ParseStatusInvalid,
				})
				return next(c)
			}
			session.CookieName = cookieName
			if ownedRoute && initializer != nil && shouldBootstrapAnonymousSession(rawCookie, session) {
				session, err = initializer.NewAnonymous(c.Request().Context(), c.Request(), cookieName)
				if err != nil {
					return echo.NewHTTPError(http.StatusInternalServerError, fmt.Sprintf("prestashop session bootstrap failed: %v", err))
				}
			}
			if ownedRoute {
				applyRequestLanguage(session, resolveRequestLanguageID(c.Request().Context(), c.Request(), session, languageResolver))
			}
			if ownedRoute && shouldSetSessionCookie(rawCookie, session) {
				encoded, err := codec.Encode(session)
				if err != nil {
					return echo.NewHTTPError(http.StatusInternalServerError, "prestashop cookie encode failed")
				}
				session.RawCookie = encoded
				setPrestaShopCookie(c.Request(), c.Response(), ownership.ProductPrefixes, cookieName, encoded)
			}

			SetSession(c, session)
			return next(c)
		}
	}
}

func resolveRequestLanguageID(ctx context.Context, req *http.Request, session *pscookie.SessionContext, resolver LanguageResolver) int64 {
	if resolver == nil {
		return 0
	}
	return resolver.ResolveLanguageID(ctx, req, sessionLanguageID(session))
}

func findPrestaShopCookie(req *http.Request, configuredName string) (name, value string) {
	cookies := req.Cookies()
	for _, cookie := range cookies {
		if cookie.Name == configuredName {
			return cookie.Name, cookie.Value
		}
	}

	prefix := cookiePrefix(configuredName)
	if prefix == "" {
		return "", ""
	}

	for _, cookie := range cookies {
		if strings.HasPrefix(cookie.Name, prefix) {
			return cookie.Name, cookie.Value
		}
	}

	return "", ""
}

func cookiePrefix(configuredName string) string {
	if configuredName == "" {
		return ""
	}
	if strings.HasPrefix(configuredName, "PrestaShop-") {
		return "PrestaShop-"
	}
	if idx := strings.Index(configuredName, "-"); idx >= 0 {
		return configuredName[:idx+1]
	}
	return ""
}

func shouldBootstrapAnonymousSession(rawCookie string, session *pscookie.SessionContext) bool {
	if session == nil {
		return true
	}
	if rawCookie == "" {
		return true
	}
	if session.IsLoggedIn {
		return false
	}
	return session.GuestID == nil ||
		session.CurrencyID == nil ||
		session.LanguageID == nil ||
		session.Values["id_connections"] == "" ||
		session.Values["iso_code_country"] == ""
}

func shouldSetSessionCookie(rawCookie string, session *pscookie.SessionContext) bool {
	if session == nil {
		return false
	}
	if rawCookie == "" {
		return true
	}
	return rawCookie != session.RawCookie
}

func applyRequestLanguage(session *pscookie.SessionContext, languageID int64) {
	if session == nil || languageID == 0 {
		return
	}
	if current := sessionLanguageID(session); current == languageID {
		return
	}

	if session.Values == nil {
		session.Values = map[string]string{}
	}

	value := strconv.FormatInt(languageID, 10)
	session.LanguageID = int64Ptr(languageID)
	session.Values["id_lang"] = value
	session.Values["id_language"] = value
	session.OrderedKeys = ensureOrderedKey(session.OrderedKeys, "id_lang", 1)
	session.OrderedKeys = ensureOrderedKey(session.OrderedKeys, "id_language", 3)

	if !session.IsLoggedIn {
		if checksum := anonymousSessionChecksum(session, languageID); checksum != "" {
			session.Values["checksum"] = checksum
			session.OrderedKeys = ensureOrderedKey(session.OrderedKeys, "checksum", len(session.OrderedKeys))
		}
	}

	session.Plaintext = ""
	session.RawCookie = ""
}

func sessionLanguageID(session *pscookie.SessionContext) int64 {
	if session == nil || session.LanguageID == nil {
		return 0
	}
	return *session.LanguageID
}

func anonymousSessionChecksum(session *pscookie.SessionContext, languageID int64) string {
	if session == nil || session.Values == nil {
		return ""
	}
	guestID, _ := strconv.ParseInt(session.Values["id_guest"], 10, 64)
	connectionID, _ := strconv.ParseInt(session.Values["id_connections"], 10, 64)
	currencyID, _ := strconv.ParseInt(session.Values["id_currency"], 10, 64)
	shopID, _ := strconv.ParseInt(session.Values["id_shop"], 10, 64)
	if guestID == 0 || connectionID == 0 || currencyID == 0 {
		return ""
	}

	buf := make([]byte, 0, 32)
	for _, value := range []int64{guestID, connectionID, languageID, currencyID, shopID} {
		buf = strconv.AppendInt(buf, value, 10)
		buf = append(buf, '|')
	}
	return strconv.FormatUint(uint64(crc32.ChecksumIEEE(buf)), 10)
}

func ensureOrderedKey(keys []string, key string, index int) []string {
	for i, existing := range keys {
		if existing != key {
			continue
		}
		if i == index || index >= len(keys) {
			return keys
		}
		keys = append(keys[:i], keys[i+1:]...)
		break
	}

	if index < 0 {
		index = 0
	}
	if index >= len(keys) {
		return append(keys, key)
	}

	keys = append(keys, "")
	copy(keys[index+1:], keys[index:])
	keys[index] = key
	return keys
}

func int64Ptr(value int64) *int64 {
	if value == 0 {
		return nil
	}
	v := value
	return &v
}

func setPrestaShopCookie(req *http.Request, res *echo.Response, ownedPrefixes []string, name, value string) {
	http.SetCookie(res.Writer, &http.Cookie{
		Name:     name,
		Value:    value,
		Path:     requestCookiePath(req.URL.Path, ownedPrefixes),
		Domain:   requestCookieDomain(req),
		Secure:   requestCookieSecure(req),
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	})
}

func requestCookiePath(requestPath string, ownedPrefixes []string) string {
	for _, prefix := range ownedPrefixes {
		if prefix == "" || !strings.HasPrefix(requestPath, prefix) {
			continue
		}
		base := path.Clean(strings.TrimSuffix(prefix, "/"))
		if base == "." || base == "/" {
			return "/"
		}
		parent := path.Dir(base)
		if parent == "." {
			return "/"
		}
		if !strings.HasSuffix(parent, "/") {
			parent += "/"
		}
		return parent
	}

	return "/"
}

func requestCookieDomain(req *http.Request) string {
	host := requestCookieHost(req)
	if host == "" {
		return ""
	}
	if parsed, err := url.Parse("http://" + host); err == nil {
		return parsed.Hostname()
	}
	return host
}

func requestCookieHost(req *http.Request) string {
	if req == nil {
		return ""
	}
	host := req.Header.Get("X-Forwarded-Host")
	if host == "" {
		host = req.Host
	}
	if strings.Contains(host, ",") {
		host = strings.TrimSpace(strings.Split(host, ",")[0])
	}
	return host
}

func requestCookieSecure(req *http.Request) bool {
	if req.TLS != nil {
		return true
	}
	if forwarded := req.Header.Get("X-Forwarded-Proto"); forwarded != "" {
		if strings.Contains(forwarded, ",") {
			forwarded = strings.TrimSpace(strings.Split(forwarded, ",")[0])
		}
		return strings.EqualFold(forwarded, "https")
	}
	return false
}

func ownsProductRoute(prefixes []string, path string, matcher ProductRouteMatcher) bool {
	if matcher != nil {
		return matcher.Owns(path)
	}
	for _, prefix := range prefixes {
		if prefix != "" && len(path) >= len(prefix) && path[:len(prefix)] == prefix {
			return true
		}
	}
	return false
}