package middleware

import (
	"net/http"
	"net/url"
	"strconv"
	"strings"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
	"go.uber.org/zap"
)

const wildcardPlaceholder = "<wildcard>"

type VHSSettings interface {
	Domains() []string
	GlobalVHS() bool
	VHSHeader() string
	ServernameHeader() string
	VHSNamespacesEnabled() map[string]bool
}

func PrepareAddressStyle(settings VHSSettings, log *zap.Logger) Func {
	return func(h http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ctx := r.Context()
			reqInfo := GetReqInfo(ctx)
			reqLogger := reqLogOrDefault(ctx, log)
			headerVHSEnabled := r.Header.Get(settings.VHSHeader())

			if isVHSAddress(headerVHSEnabled, settings.GlobalVHS(), settings.VHSNamespacesEnabled(), reqInfo.Namespace) {
				prepareVHSAddress(reqInfo, r, settings)
			} else {
				preparePathStyleAddress(reqInfo, r, reqLogger)
			}

			h.ServeHTTP(w, r)
		})
	}
}

func isVHSAddress(headerVHSEnabled string, enabledFlag bool, vhsNamespaces map[string]bool, namespace string) bool {
	if result, err := strconv.ParseBool(headerVHSEnabled); err == nil {
		return result
	}

	result := enabledFlag
	if v, ok := vhsNamespaces[namespace]; ok {
		result = v
	}

	return result
}

func prepareVHSAddress(reqInfo *ReqInfo, r *http.Request, settings VHSSettings) {
	reqInfo.RequestVHSEnabled = true
	bktName, match := checkDomain(r.Host, getDomains(r, settings))
	if match {
		if bktName == "" {
			reqInfo.RequestType = noneType
		} else {
			if objName := strings.TrimPrefix(r.URL.Path, "/"); objName != "" {
				reqInfo.RequestType = objectType
				reqInfo.ObjectName = objName
				reqInfo.BucketName = bktName
			} else {
				reqInfo.RequestType = bucketType
				reqInfo.BucketName = bktName
			}
		}
	} else {
		parts := strings.Split(r.Host, ".")
		reqInfo.BucketName = parts[0]

		if objName := strings.TrimPrefix(r.URL.Path, "/"); objName != "" {
			reqInfo.RequestType = objectType
			reqInfo.ObjectName = objName
		} else {
			reqInfo.RequestType = bucketType
		}
	}
}

func getDomains(r *http.Request, settings VHSSettings) []string {
	if headerServername := r.Header.Get(settings.ServernameHeader()); headerServername != "" {
		return []string{headerServername}
	}

	return settings.Domains()
}

func preparePathStyleAddress(reqInfo *ReqInfo, r *http.Request, reqLogger *zap.Logger) {
	bktObj := strings.TrimPrefix(r.URL.Path, "/")
	if bktObj == "" {
		reqInfo.RequestType = noneType
	} else if ind := strings.IndexByte(bktObj, '/'); ind != -1 && bktObj[ind+1:] != "" {
		reqInfo.RequestType = objectType
		reqInfo.BucketName = bktObj[:ind]
		reqInfo.ObjectName = bktObj[ind+1:]

		if r.URL.RawPath != "" {
			// we have to do this because of
			// https://github.com/go-chi/chi/issues/641
			// https://github.com/go-chi/chi/issues/642
			if obj, err := url.PathUnescape(reqInfo.ObjectName); err != nil {
				reqLogger.Warn(logs.FailedToUnescapeObjectName, zap.Error(err))
			} else {
				reqInfo.ObjectName = obj
			}
		}
	} else {
		reqInfo.RequestType = bucketType
		reqInfo.BucketName = strings.TrimSuffix(bktObj, "/")
	}
}

func checkDomain(host string, domains []string) (bktName string, match bool) {
	partsHost := strings.Split(host, ".")
	for _, pattern := range domains {
		partsPattern := strings.Split(pattern, ".")
		bktName, match = compareMatch(partsHost, partsPattern)
		if match {
			break
		}
	}
	return
}

func compareMatch(host, pattern []string) (bktName string, match bool) {
	if len(host) < len(pattern) {
		return "", false
	}

	i, j := len(host)-1, len(pattern)-1
	for j >= 0 && (pattern[j] == wildcardPlaceholder || host[i] == pattern[j]) {
		i--
		j--
	}

	switch {
	case i == -1:
		return "", true
	case i == 0 && (j != 0 || host[i] == pattern[j]):
		return host[0], true
	default:
		return "", false
	}
}