package api

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

	"github.com/danielgtaylor/huma/v2"

	"github.com/v10networks/nmon/internal/store"
)

// GroupSummary is a group in a list.
type GroupSummary struct {
	GroupView
	MemberCount int  `json:"member_count" doc:"Interfaces in the group now."`
	AlertDown   bool `json:"alert_down" doc:"Member ports alert on interface_down while they are members."`
}

// GroupList is every group, by name.
type GroupList struct {
	Items []GroupSummary `json:"items"`
}

// GroupMemberIface names a member interface and its device.
type GroupMemberIface struct {
	ID      string    `json:"id"`
	IfName  string    `json:"ifname"`
	IfAlias string    `json:"ifalias"`
	Device  DeviceRef `json:"device"`
}

// GroupMemberView is one membership: an interface in force for [effective_from, effective_to).
type GroupMemberView struct {
	Interface     GroupMemberIface `json:"interface"`
	Direction     string           `json:"direction" enum:"toward,away" doc:"toward: the port's in is traffic toward the group's subject; away: it is traffic away, so in and out swap in the sum."` //nolint:lll // struct tag text is the OpenAPI doc; cannot wrap
	EffectiveFrom time.Time        `json:"effective_from"`
	EffectiveTo   *time.Time       `json:"effective_to" nullable:"true" doc:"Null while the membership is open."`
}

// GroupFlag is a warning about a group's membership.
type GroupFlag struct {
	Kind string `json:"kind" enum:"both_ends_of_link" doc:"both_ends_of_link: the group holds both ends of one link and would count it twice."`
	A    string `json:"a" doc:"First interface id."`
	B    string `json:"b" doc:"Second interface id."`
}

// GroupDetail is a group with its membership history.
type GroupDetail struct {
	GroupSummary
	Members []GroupMemberView `json:"members" doc:"Every membership, past and present, ordered by interface and start."`
	Flags   []GroupFlag       `json:"flags"`
}

// GroupBody is the body of POST and PUT /groups.
type GroupBody struct {
	Name string `json:"name" minLength:"1" maxLength:"100"`
	Kind string `json:"kind" enum:"site,customer,role,custom" default:"custom"`
	// AlertDown is a pointer so a PUT that omits it leaves the flag alone.
	AlertDown *bool `json:"alert_down,omitempty" doc:"Opt member ports into interface_down alerts. Omitted: off on create, kept on update."`
}

// GroupMemberBody is the body of POST /groups/{id}/members.
type GroupMemberBody struct {
	InterfaceID   string     `json:"interface_id" minLength:"1"`
	Direction     string     `json:"direction" enum:"toward,away"`
	EffectiveFrom *time.Time `json:"effective_from,omitempty" doc:"Default now. A past date applies the membership to history."`
}

func (s *server) registerGroups(api huma.API) {
	tags := []string{"groups"}
	huma.Register(api, huma.Operation{
		OperationID: "list-groups", Method: http.MethodGet, Path: "/api/v1/groups", Tags: tags,
		Summary: "List groups",
	}, s.listGroups)
	huma.Register(api, huma.Operation{
		OperationID: "create-group", Method: http.MethodPost, Path: "/api/v1/groups", Tags: tags, DefaultStatus: http.StatusCreated,
		Summary: "Create a group", Errors: []int{http.StatusConflict, http.StatusUnprocessableEntity},
	}, s.createGroup)
	huma.Register(api, huma.Operation{
		OperationID: "get-group", Method: http.MethodGet, Path: "/api/v1/groups/{id}", Tags: tags,
		Summary: "A group with its membership history and warnings", Errors: []int{http.StatusNotFound},
	}, s.getGroup)
	huma.Register(api, huma.Operation{
		OperationID: "update-group", Method: http.MethodPut, Path: "/api/v1/groups/{id}", Tags: tags,
		Summary: "Rename a group or change its kind", Errors: []int{http.StatusNotFound, http.StatusConflict, http.StatusUnprocessableEntity},
	}, s.updateGroup)
	huma.Register(api, huma.Operation{
		OperationID: "delete-group", Method: http.MethodDelete, Path: "/api/v1/groups/{id}", Tags: tags, DefaultStatus: http.StatusNoContent,
		Summary:     "Delete a group and its membership history",
		Description: "A group named by a maintenance window cannot be deleted.", Errors: []int{http.StatusNotFound, http.StatusConflict},
	}, s.deleteGroup)
	huma.Register(api, huma.Operation{
		OperationID: "add-group-member", Method: http.MethodPost, Path: "/api/v1/groups/{id}/members", Tags: tags,
		Summary: "Add an interface to a group", DefaultStatus: http.StatusCreated,
		Description: "Opens a membership at effective_from (default now). A port that changes direction is ended and added again, " +
			"so the history of the sums never changes.",
		Errors: []int{http.StatusNotFound, http.StatusConflict, http.StatusUnprocessableEntity},
	}, s.addGroupMember)
	huma.Register(api, huma.Operation{
		OperationID: "end-group-member", Method: http.MethodDelete, Path: "/api/v1/groups/{id}/members", Tags: tags,
		Summary: "End an interface's open membership", DefaultStatus: http.StatusNoContent,
		Errors: []int{http.StatusNotFound, http.StatusUnprocessableEntity},
	}, s.endGroupMember)
}

func summaryOf(now time.Time, g store.Group, members []store.GroupMember) GroupSummary {
	n := 0
	for _, m := range members {
		if m.GroupID == g.ID && m.Covers(now) {
			n++
		}
	}
	gv := GroupView{ID: strconv.FormatInt(g.ID, 10), Name: g.Name, Kind: g.Kind}
	return GroupSummary{GroupView: gv, MemberCount: n, AlertDown: g.AlertDown}
}

func (s *server) listGroups(ctx context.Context, _ *struct{}) (*struct{ Body GroupList }, error) {
	gs, err := s.Store.ListGroups(ctx)
	if err != nil {
		return nil, s.storeErr(err)
	}
	members, err := s.Store.GroupMembers(ctx, 0, time.Time{}, time.Time{})
	if err != nil {
		return nil, s.storeErr(err)
	}
	out := GroupList{Items: make([]GroupSummary, 0, len(gs))}
	for _, g := range gs {
		out.Items = append(out.Items, summaryOf(s.Clock.Now(), g, members))
	}
	return &struct{ Body GroupList }{out}, nil
}

// groupBody validates name and kind.
func groupBody(b GroupBody) (store.Group, error) {
	g := store.Group{Name: strings.TrimSpace(b.Name), Kind: b.Kind}
	if g.Kind == "" {
		g.Kind = store.GroupCustom
	}
	if g.Name == "" {
		return g, huma.Error422UnprocessableEntity("name must not be empty")
	}
	g.AlertDown = b.AlertDown != nil && *b.AlertDown
	return g, nil
}

func (s *server) createGroup(ctx context.Context, in *struct{ Body GroupBody }) (*struct{ Body GroupSummary }, error) {
	g, err := groupBody(in.Body)
	if err != nil {
		return nil, err
	}
	err = s.Store.WithTx(ctx, func(tx store.Store) error {
		if err := tx.CreateGroup(ctx, &g); err != nil {
			return err
		}
		return tx.AppendAudit(ctx, actorOf(ctx), "group.create", "group:"+strconv.FormatInt(g.ID, 10), nil, in.Body)
	})
	if err != nil {
		return nil, s.storeErr(err)
	}
	s.alertDownChanged()
	return &struct{ Body GroupSummary }{summaryOf(s.Clock.Now(), g, nil)}, nil
}

func (s *server) getGroup(ctx context.Context, in *struct {
	ID string `path:"id" doc:"Group id."`
}) (*struct{ Body GroupDetail }, error) {
	id, err := idParam(in.ID)
	if err != nil {
		return nil, err
	}
	ref, err := s.Store.GetGroup(ctx, id)
	if err != nil {
		return nil, s.storeErr(err)
	}
	members, err := s.Store.GroupMembers(ctx, id, time.Time{}, time.Time{})
	if err != nil {
		return nil, s.storeErr(err)
	}
	g := store.Group{ID: ref.ID, Name: ref.Name, Kind: ref.Kind, AlertDown: ref.AlertDown}
	d := GroupDetail{GroupSummary: summaryOf(s.Clock.Now(), g, members),
		Members: make([]GroupMemberView, 0, len(members)), Flags: []GroupFlag{}}
	for _, m := range members {
		d.Members = append(d.Members, s.memberView(ctx, m))
	}
	d.Flags = s.groupFlags(ctx, id)
	return &struct{ Body GroupDetail }{d}, nil
}

func (s *server) memberView(ctx context.Context, m store.GroupMember) GroupMemberView {
	v := GroupMemberView{
		Interface: GroupMemberIface{ID: m.InterfaceID}, Direction: m.Direction, EffectiveFrom: m.EffectiveFrom.UTC(),
		EffectiveTo: utcp(m.EffectiveTo),
	}
	if i, err := s.Store.GetInterface(ctx, m.InterfaceID); err == nil {
		v.Interface.IfName, v.Interface.IfAlias = i.IfName, i.IfAlias
		if d, err := s.Store.GetDeviceByID(ctx, i.DeviceID); err == nil {
			v.Interface.Device = DeviceRef{Slug: d.Slug, Name: d.Name}
		}
	}
	return v
}

// groupFlags are the membership warnings; without the traffic service there are none to show.
func (s *server) groupFlags(ctx context.Context, id int64) []GroupFlag {
	out := []GroupFlag{}
	if s.Groups == nil {
		return out
	}
	fs, err := s.Groups.Flags(ctx, id)
	if err != nil {
		s.Logger.Warn("group flags", "group", id, "err", err)
		return out
	}
	for _, f := range fs {
		out = append(out, GroupFlag{Kind: f.Kind, A: f.A, B: f.B})
	}
	return out
}

func (s *server) updateGroup(ctx context.Context, in *struct {
	ID   string `path:"id" doc:"Group id."`
	Body GroupBody
}) (*struct{ Body GroupSummary }, error) {
	id, err := idParam(in.ID)
	if err != nil {
		return nil, err
	}
	g, err := groupBody(in.Body)
	if err != nil {
		return nil, err
	}
	g.ID = id
	if in.Body.AlertDown == nil {
		cur, err := s.Store.GetGroup(ctx, id)
		if err != nil {
			return nil, s.storeErr(err)
		}
		g.AlertDown = cur.AlertDown
	}
	err = s.Store.WithTx(ctx, func(tx store.Store) error {
		if err := tx.UpdateGroup(ctx, g); err != nil {
			return err
		}
		return tx.AppendAudit(ctx, actorOf(ctx), "group.update", "group:"+in.ID, nil, in.Body)
	})
	if err != nil {
		return nil, s.storeErr(err)
	}
	s.alertDownChanged()
	members, err := s.Store.GroupMembers(ctx, id, time.Time{}, time.Time{})
	if err != nil {
		return nil, s.storeErr(err)
	}
	return &struct{ Body GroupSummary }{summaryOf(s.Clock.Now(), g, members)}, nil
}

func (s *server) deleteGroup(ctx context.Context, in *struct {
	ID string `path:"id" doc:"Group id."`
}) (*struct{}, error) {
	id, err := idParam(in.ID)
	if err != nil {
		return nil, err
	}
	err = s.Store.WithTx(ctx, func(tx store.Store) error {
		if err := tx.DeleteGroup(ctx, id); err != nil {
			return err
		}
		return tx.AppendAudit(ctx, actorOf(ctx), "group.delete", "group:"+in.ID, nil, nil)
	})
	if err != nil {
		return nil, s.storeErr(err)
	}
	s.alertDownChanged()
	return &struct{}{}, nil
}

func (s *server) addGroupMember(ctx context.Context, in *struct {
	ID   string `path:"id" doc:"Group id."`
	Body GroupMemberBody
}) (*struct{ Body GroupMemberView }, error) {
	id, err := idParam(in.ID)
	if err != nil {
		return nil, err
	}
	m := store.GroupMember{GroupID: id, InterfaceID: in.Body.InterfaceID, Direction: in.Body.Direction}
	if in.Body.EffectiveFrom != nil {
		m.EffectiveFrom = in.Body.EffectiveFrom.UTC()
	} else {
		m.EffectiveFrom = s.Clock.Now().UTC()
	}
	err = s.Store.WithTx(ctx, func(tx store.Store) error {
		if _, err := tx.GetGroup(ctx, id); err != nil {
			return err
		}
		if err := tx.AddGroupMember(ctx, m); err != nil {
			return err
		}
		return tx.AppendAudit(ctx, actorOf(ctx), "group.member.add", "group:"+in.ID, nil, in.Body)
	})
	if err != nil {
		return nil, s.storeErr(err)
	}
	s.alertDownChanged()
	return &struct{ Body GroupMemberView }{s.memberView(ctx, m)}, nil
}

func (s *server) endGroupMember(ctx context.Context, in *struct {
	ID          string    `path:"id" doc:"Group id."`
	InterfaceID string    `query:"interface_id" required:"true" doc:"Interface whose open membership ends."`
	At          time.Time `query:"at" doc:"End instant, RFC 3339. Default now."`
}) (*struct{}, error) {
	id, err := idParam(in.ID)
	if err != nil {
		return nil, err
	}
	at := in.At.UTC()
	if in.At.IsZero() {
		at = time.Time{}
	}
	err = s.Store.WithTx(ctx, func(tx store.Store) error {
		if err := tx.EndGroupMember(ctx, id, in.InterfaceID, at); err != nil {
			return err
		}
		return tx.AppendAudit(ctx, actorOf(ctx), "group.member.end", "group:"+in.ID, nil, map[string]string{"interface_id": in.InterfaceID})
	})
	if err != nil {
		return nil, s.storeErr(err)
	}
	s.alertDownChanged()
	return &struct{}{}, nil
}