package directory

import (
	"context"
	"fmt"
	"time"

	"github.com/netkingdom/flex-auth/pkg/api"
)

// GraphClient is the Microsoft Graph group lookup boundary.
type GraphClient interface {
	GetMemberGroups(context.Context, string) ([]ExternalGroup, OverageMetadata, error)
}

// SCIMClient is the SCIM group lookup boundary.
type SCIMClient interface {
	GroupsForUser(context.Context, string) ([]ExternalGroup, error)
}

// LDAPClient is the LDAP/AD group lookup boundary.
type LDAPClient interface {
	GroupsForDN(context.Context, string) ([]ExternalGroup, error)
}

// KeycloakClient is the Keycloak admin API group lookup boundary.
type KeycloakClient interface {
	GroupsForUser(context.Context, string) ([]ExternalGroup, error)
}

// ExternalGroup is a provider-native group normalized enough for flex-auth.
type ExternalGroup struct {
	ID          string
	DisplayName string
	Descriptor  *api.CaringAccessDescriptor
	Metadata    map[string]any
}

// GraphResolver resolves Microsoft Graph groups, including token overage.
type GraphResolver struct {
	Client               GraphClient
	OrganizationRelation api.OrganizationRelation
	MaxAge               time.Duration
}

func (r GraphResolver) ResolveGroups(ctx context.Context, request ResolveRequest) (ResolveResult, error) {
	if r.Client == nil {
		return ResolveResult{}, fmt.Errorf("graph client is required")
	}
	now := resolveNow(request)
	groups, overage, err := r.Client.GetMemberGroups(ctx, request.Subject.ID)
	if err != nil {
		return ResolveResult{}, err
	}
	if tokenIndicatesGraphOverage(request.Claims) {
		overage.Detected = true
		if overage.Claim == "" {
			overage.Claim = "_claim_names.groups"
		}
	}
	return ResolveResult{
		Subject:   request.Subject,
		Source:    SourceGraph,
		Groups:    grantsFromExternalGroups(SourceGraph, groups, r.OrganizationRelation, "_claim_names.groups"),
		Freshness: freshness(SourceGraph, now, r.MaxAge),
		Overage:   overage,
	}, nil
}

// SCIMResolver resolves provisioned SCIM groups.
type SCIMResolver struct {
	Client               SCIMClient
	OrganizationRelation api.OrganizationRelation
	MaxAge               time.Duration
}

func (r SCIMResolver) ResolveGroups(ctx context.Context, request ResolveRequest) (ResolveResult, error) {
	if r.Client == nil {
		return ResolveResult{}, fmt.Errorf("scim client is required")
	}
	groups, err := r.Client.GroupsForUser(ctx, request.Subject.ID)
	if err != nil {
		return ResolveResult{}, err
	}
	return ResolveResult{
		Subject:   request.Subject,
		Source:    SourceSCIM,
		Groups:    grantsFromExternalGroups(SourceSCIM, groups, r.OrganizationRelation, "groups"),
		Freshness: freshness(SourceSCIM, resolveNow(request), r.MaxAge),
	}, nil
}

// LDAPResolver resolves LDAP/AD group memberships.
type LDAPResolver struct {
	Client               LDAPClient
	OrganizationRelation api.OrganizationRelation
	MaxAge               time.Duration
}

func (r LDAPResolver) ResolveGroups(ctx context.Context, request ResolveRequest) (ResolveResult, error) {
	if r.Client == nil {
		return ResolveResult{}, fmt.Errorf("ldap client is required")
	}
	dn := stringClaim(request.Claims, "distinguished_name")
	if dn == "" {
		dn = request.Subject.ID
	}
	groups, err := r.Client.GroupsForDN(ctx, dn)
	if err != nil {
		return ResolveResult{}, err
	}
	return ResolveResult{
		Subject:   request.Subject,
		Source:    SourceLDAP,
		Groups:    grantsFromExternalGroups(SourceLDAP, groups, r.OrganizationRelation, "memberOf"),
		Freshness: freshness(SourceLDAP, resolveNow(request), r.MaxAge),
	}, nil
}

// KeycloakResolver resolves groups through the Keycloak admin API.
type KeycloakResolver struct {
	Client               KeycloakClient
	OrganizationRelation api.OrganizationRelation
	MaxAge               time.Duration
}

func (r KeycloakResolver) ResolveGroups(ctx context.Context, request ResolveRequest) (ResolveResult, error) {
	if r.Client == nil {
		return ResolveResult{}, fmt.Errorf("keycloak client is required")
	}
	groups, err := r.Client.GroupsForUser(ctx, request.Subject.ID)
	if err != nil {
		return ResolveResult{}, err
	}
	return ResolveResult{
		Subject:   request.Subject,
		Source:    SourceKeycloak,
		Groups:    grantsFromExternalGroups(SourceKeycloak, groups, r.OrganizationRelation, "groups"),
		Freshness: freshness(SourceKeycloak, resolveNow(request), r.MaxAge),
	}, nil
}

func grantsFromExternalGroups(source Source, groups []ExternalGroup, relation api.OrganizationRelation, claim string) []GroupGrant {
	grants := make([]GroupGrant, 0, len(groups))
	for _, group := range groups {
		grants = append(grants, GroupGrant{
			ID:                   group.ID,
			DisplayName:          group.DisplayName,
			Source:               source,
			OrganizationRelation: relation,
			SubjectType:          api.SubjectTypeGroup,
			Claim:                claim,
			Descriptor:           group.Descriptor,
			Metadata:             copyMap(group.Metadata),
		})
	}
	return grants
}

func freshness(source Source, now time.Time, maxAge time.Duration) Freshness {
	out := Freshness{Source: source, RetrievedAt: now}
	if maxAge > 0 {
		out.MaxAge = maxAge.String()
		out.ExpiresAt = now.Add(maxAge)
		out.Stale = now.After(out.ExpiresAt)
	}
	return out
}

func resolveNow(request ResolveRequest) time.Time {
	if !request.Now.IsZero() {
		return request.Now
	}
	return time.Now().UTC()
}

func tokenIndicatesGraphOverage(claims map[string]any) bool {
	if value, ok := claims["hasgroups"].(bool); ok && value {
		return true
	}
	claimNames, ok := claims["_claim_names"].(map[string]any)
	if !ok {
		return false
	}
	_, ok = claimNames["groups"]
	return ok
}

func stringClaim(claims map[string]any, key string) string {
	value, _ := claims[key].(string)
	return value
}

func copyMap(in map[string]any) map[string]any {
	out := make(map[string]any, len(in))
	for key, value := range in {
		out[key] = value
	}
	return out
}