package api

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	glob "github.com/bmatcuk/doublestar/v4"
	"github.com/gorilla/mux"

	"zotregistry.io/zot/pkg/api/config"
	"zotregistry.io/zot/pkg/api/constants"
	"zotregistry.io/zot/pkg/common"
	"zotregistry.io/zot/pkg/log"
	localCtx "zotregistry.io/zot/pkg/requestcontext"
)

const (
	// method actions.
	Create = "create"
	Read   = "read"
	Update = "update"
	Delete = "delete"
	// behaviour actions.
	DetectManifestCollision = "detectManifestCollision"
)

// AccessController authorizes users to act on resources.
type AccessController struct {
	Config *config.AccessControlConfig
	Log    log.Logger
}

func NewAccessController(config *config.Config) *AccessController {
	return &AccessController{
		Config: config.HTTP.AccessControl,
		Log:    log.NewLogger(config.Log.Level, config.Log.Output),
	}
}

// getGlobPatterns gets glob patterns from authz config on which <username> has <action> perms.
// used to filter /v2/_catalog repositories based on user rights.
func (ac *AccessController) getGlobPatterns(username string, groups []string, action string) map[string]bool {
	globPatterns := make(map[string]bool)

	for pattern, policyGroup := range ac.Config.Repositories {
		if username == "" {
			// check anonymous policy
			if common.Contains(policyGroup.AnonymousPolicy, action) {
				globPatterns[pattern] = true
			}
		} else {
			// check default policy (authenticated user)
			if common.Contains(policyGroup.DefaultPolicy, action) {
				globPatterns[pattern] = true
			}
		}

		// check user based policy
		for _, p := range policyGroup.Policies {
			if common.Contains(p.Users, username) && common.Contains(p.Actions, action) {
				globPatterns[pattern] = true
			}
		}

		// check group based policy
		for _, group := range groups {
			for _, p := range policyGroup.Policies {
				if common.Contains(p.Groups, group) && common.Contains(p.Actions, action) {
					globPatterns[pattern] = true
				}
			}
		}

		// if not allowed then mark it
		if _, ok := globPatterns[pattern]; !ok {
			globPatterns[pattern] = false
		}
	}

	return globPatterns
}

// can verifies if a user can do action on repository.
func (ac *AccessController) can(ctx context.Context, username, action, repository string) bool {
	can := false

	var longestMatchedPattern string

	for pattern := range ac.Config.Repositories {
		matched, err := glob.Match(pattern, repository)
		if err == nil {
			if matched && len(pattern) > len(longestMatchedPattern) {
				longestMatchedPattern = pattern
			}
		}
	}

	acCtx, err := localCtx.GetAccessControlContext(ctx)
	if err != nil {
		return false
	}

	userGroups := acCtx.Groups

	// check matched repo based policy
	pg, ok := ac.Config.Repositories[longestMatchedPattern]
	if ok {
		can = ac.isPermitted(userGroups, username, action, pg)
	}

	// check admins based policy
	if !can {
		if ac.isAdmin(username) && common.Contains(ac.Config.AdminPolicy.Actions, action) {
			can = true
		}

		if ac.isAnyGroupInAdminPolicy(userGroups) && common.Contains(ac.Config.AdminPolicy.Actions, action) {
			can = true
		}
	}

	return can
}

// isAdmin .
func (ac *AccessController) isAdmin(username string) bool {
	return common.Contains(ac.Config.AdminPolicy.Users, username)
}

func (ac *AccessController) isAnyGroupInAdminPolicy(userGroups []string) bool {
	for _, group := range userGroups {
		if common.Contains(ac.Config.AdminPolicy.Groups, group) {
			return true
		}
	}

	return false
}

func (ac *AccessController) getUserGroups(username string) []string {
	var groupNames []string

	for groupName, group := range ac.Config.Groups {
		for _, user := range group.Users {
			// find if the user is part of any groups
			if user == username {
				groupNames = append(groupNames, groupName)
			}
		}
	}

	return groupNames
}

// getContext updates an AccessControlContext for a user/anonymous and returns a context.Context containing it.
func (ac *AccessController) getContext(acCtx *localCtx.AccessControlContext, request *http.Request) context.Context {
	readGlobPatterns := ac.getGlobPatterns(acCtx.Username, acCtx.Groups, Read)
	dmcGlobPatterns := ac.getGlobPatterns(acCtx.Username, acCtx.Groups, DetectManifestCollision)

	acCtx.ReadGlobPatterns = readGlobPatterns
	acCtx.DmcGlobPatterns = dmcGlobPatterns

	if ac.isAdmin(acCtx.Username) {
		acCtx.IsAdmin = true
	} else {
		acCtx.IsAdmin = false
	}

	authzCtxKey := localCtx.GetContextKey()
	ctx := context.WithValue(request.Context(), authzCtxKey, *acCtx)

	return ctx
}

// isPermitted returns true if username can do action on a repository policy.
func (ac *AccessController) isPermitted(userGroups []string, username, action string,
	policyGroup config.PolicyGroup,
) bool {
	var result bool

	// check repo/system based policies
	for _, p := range policyGroup.Policies {
		if common.Contains(p.Users, username) && common.Contains(p.Actions, action) {
			result = true

			return result
		}
	}

	if userGroups != nil {
		for _, p := range policyGroup.Policies {
			if common.Contains(p.Actions, action) {
				for _, group := range p.Groups {
					if common.Contains(userGroups, group) {
						result = true

						return result
					}
				}
			}
		}
	}

	// check defaultPolicy
	if !result {
		if common.Contains(policyGroup.DefaultPolicy, action) && username != "" {
			result = true
		}
	}

	// check anonymousPolicy
	if !result {
		if common.Contains(policyGroup.AnonymousPolicy, action) && username == "" {
			result = true
		}
	}

	return result
}

func AuthzHandler(ctlr *Controller) mux.MiddlewareFunc {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
			vars := mux.Vars(request)
			resource := vars["name"]
			reference, ok := vars["reference"]

			if request.Method == http.MethodOptions {
				next.ServeHTTP(response, request)

				return
			}

			// bypass authz for /v2/ route
			if request.RequestURI == "/v2/" {
				next.ServeHTTP(response, request)

				return
			}

			acCtrlr := NewAccessController(ctlr.Config)

			var identity string

			var err error

			// anonymous context
			acCtx := &localCtx.AccessControlContext{}

			// get username from context made in authn.go
			if isAuthnEnabled(ctlr.Config) {
				// get access control context made in authn.go if authn is enabled
				acCtx, err = localCtx.GetAccessControlContext(request.Context())
				if err != nil { // should never happen
					authFail(response, ctlr.Config.HTTP.Realm, ctlr.Config.HTTP.Auth.FailDelay)

					return
				}

				identity = acCtx.Username
			}

			if request.TLS != nil {
				verifiedChains := request.TLS.VerifiedChains
				// still no identity, get it from TLS certs
				if identity == "" && verifiedChains != nil &&
					len(verifiedChains) > 0 && len(verifiedChains[0]) > 0 {
					for _, cert := range request.TLS.PeerCertificates {
						identity = cert.Subject.CommonName
					}

					// if we still don't have an identity
					if identity == "" {
						acCtrlr.Log.Info().Msg("couldn't get identity from TLS certificate")
						authFail(response, ctlr.Config.HTTP.Realm, ctlr.Config.HTTP.Auth.FailDelay)

						return
					}
				}
			}

			ctx := acCtrlr.getContext(acCtx, request)

			/* Notes:
			 	- since we only do READ actions in extensions, we can bypass authz for them
				only need to know the username, whether the user is an admin, or what repos he can read.
				let each extension to apply	authorization on them using localCtx.AccessControlContext{}
			*/
			if isExtensionURI(request.RequestURI) {
				next.ServeHTTP(response, request.WithContext(ctx)) //nolint:contextcheck

				return
			}

			var action string
			if request.Method == http.MethodGet || request.Method == http.MethodHead {
				action = Read
			}

			if request.Method == http.MethodPut || request.Method == http.MethodPatch || request.Method == http.MethodPost {
				// assume user wants to create
				action = Create
				// if we get a reference (tag)
				if ok {
					is := ctlr.StoreController.GetImageStore(resource)
					tags, err := is.GetImageTags(resource)
					// if repo exists and request's tag exists then action is UPDATE
					if err == nil && common.Contains(tags, reference) && reference != "latest" {
						action = Update
					}
				}
			}

			if request.Method == http.MethodDelete {
				action = Delete
			}

			can := acCtrlr.can(ctx, identity, action, resource) //nolint:contextcheck
			if !can {
				authzFail(response, ctlr.Config.HTTP.Realm, ctlr.Config.HTTP.Auth.FailDelay)
			} else {
				next.ServeHTTP(response, request.WithContext(ctx)) //nolint:contextcheck
			}
		})
	}
}

func isExtensionURI(requestURI string) bool {
	return strings.Contains(requestURI, constants.ExtPrefix) ||
		requestURI == fmt.Sprintf("%s%s", constants.RoutePrefix, constants.ExtCatalogPrefix)
}

func authzFail(w http.ResponseWriter, realm string, delay int) {
	time.Sleep(time.Duration(delay) * time.Second)
	w.Header().Set("WWW-Authenticate", realm)
	w.Header().Set("Content-Type", "application/json")
	WriteJSON(w, http.StatusForbidden, NewErrorList(NewError(DENIED)))
}

func anonymousPolicyExists(config *config.AccessControlConfig) bool {
	if config == nil {
		return false
	}

	for _, repository := range config.Repositories {
		if len(repository.AnonymousPolicy) > 0 {
			return true
		}
	}

	return false
}