package server

import (
	"errors"
	"net/http"
	"sort"
	"strings"
	"time"

	"cc.tiredsysadmin.keeporg/internal/secret"
	"cc.tiredsysadmin.keeporg/internal/store"
)

var errForbidden = errors.New("forbidden")

// deny maps a domain error onto a response.
func deny(w http.ResponseWriter, err error) {
	switch {
	case err == nil:
		return
	case errors.Is(err, errForbidden):
		fail(w, http.StatusForbidden, "forbidden", "you do not administer that object")
	default:
		fail(w, http.StatusBadRequest, "bad_request", err.Error())
	}
}

// ---- databases ----

func (s *Server) handleCreateDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Name          string         `json:"name"`
		OwnerGroupID  string         `json:"owner_group_id"`
		MergeStrategy store.Strategy `json:"merge_strategy"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out dbView
	err := s.st.Update(func(st *store.State) error {
		if strings.TrimSpace(req.Name) == "" {
			return errors.New("name is required")
		}
		if st.Groups[req.OwnerGroupID] == nil {
			return errors.New("unknown owner group")
		}
		if !st.IsGroupAdmin(u.ID, req.OwnerGroupID) {
			return errForbidden
		}
		strategy := req.MergeStrategy
		if strategy == "" {
			strategy = store.StrategyServerWins
		}
		if !strategy.Valid() {
			return errors.New("unknown merge strategy")
		}
		db := &store.Database{ID: secret.ID(), Name: strings.TrimSpace(req.Name),
			OwnerGroupID: req.OwnerGroupID, MergeStrategy: strategy, UpdatedAt: time.Now()}
		st.Databases[db.ID] = db
		out = toView(db, store.PermAdmin)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.notifyList(out.ID)
	writeJSON(w, http.StatusCreated, out)
}

func (s *Server) handlePatchDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	id := r.PathValue("id")
	var req struct {
		Name          *string         `json:"name"`
		MergeStrategy *store.Strategy `json:"merge_strategy"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out dbView
	err := s.st.Update(func(st *store.State) error {
		db := st.Databases[id]
		if db == nil {
			return errors.New("no such database")
		}
		if st.DatabasePerm(u.ID, id) != store.PermAdmin {
			return errForbidden
		}
		if req.Name != nil {
			if strings.TrimSpace(*req.Name) == "" {
				return errors.New("name may not be empty")
			}
			db.Name = strings.TrimSpace(*req.Name)
		}
		if req.MergeStrategy != nil {
			if !req.MergeStrategy.Valid() {
				return errors.New("unknown merge strategy")
			}
			if req.MergeStrategy.NeedsKey() && db.WrappedKey == "" {
				return errors.New("merging needs the vault password: store it with " +
					"`keeporg db -id <id> -store-password` first")
			}
			db.MergeStrategy = *req.MergeStrategy
		}
		out = toView(db, store.PermAdmin)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.notifyList(id)
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) handleDeleteDatabase(w http.ResponseWriter, r *http.Request, u *store.User) {
	id := r.PathValue("id")
	var watchers []string
	err := s.st.Update(func(st *store.State) error {
		if st.Databases[id] == nil {
			return errors.New("no such database")
		}
		if st.DatabasePerm(u.ID, id) != store.PermAdmin {
			return errForbidden
		}
		watchers = st.Watchers(id)
		delete(st.Databases, id)
		st.Grants = filterGrants(st.Grants, func(g store.Grant) bool { return g.DatabaseID != id })
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	if err := s.blobs.Forget(id); err != nil {
		s.log.Printf("delete blobs for %s: %v", id, err)
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: id})
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// ---- groups and membership ----

type groupView struct {
	ID       string `json:"id"`
	Name     string `json:"name"`
	ParentID string `json:"parent_id,omitempty"`
	Admin    bool   `json:"admin"`
	Members  int    `json:"members"`
}

func (s *Server) handleListGroups(w http.ResponseWriter, r *http.Request, u *store.User) {
	out := []groupView{}
	s.st.Read(func(st *store.State) {
		counts := map[string]int{}
		for _, m := range st.Memberships {
			counts[m.GroupID]++
		}
		reach := st.EffectiveGroups(u.ID)
		for id, g := range st.Groups {
			admin := st.IsGroupAdmin(u.ID, id)
			visible := admin || reach[id] || u.ServerAdmin
			if !visible {
				// A group below one the user administers is visible too.
				for _, anc := range st.Ancestors(id) {
					if st.IsGroupAdmin(u.ID, anc) {
						visible = true
						break
					}
				}
			}
			if visible {
				out = append(out, groupView{ID: id, Name: g.Name, ParentID: g.ParentID,
					Admin: admin, Members: counts[id]})
			}
		}
	})
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	writeJSON(w, http.StatusOK, map[string]any{"groups": out})
}

func (s *Server) handleCreateGroup(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		Name     string `json:"name"`
		ParentID string `json:"parent_id"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var out groupView
	err := s.st.Update(func(st *store.State) error {
		if strings.TrimSpace(req.Name) == "" {
			return errors.New("name is required")
		}
		if req.ParentID == "" {
			if !u.ServerAdmin {
				return errForbidden
			}
		} else {
			if st.Groups[req.ParentID] == nil {
				return errors.New("unknown parent group")
			}
			if !st.IsGroupAdmin(u.ID, req.ParentID) {
				return errForbidden
			}
		}
		g := &store.Group{ID: secret.ID(), Name: strings.TrimSpace(req.Name),
			ParentID: req.ParentID, CreatedAt: time.Now()}
		st.Groups[g.ID] = g
		out = groupView{ID: g.ID, Name: g.Name, ParentID: g.ParentID, Admin: true}
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, out)
}

func (s *Server) handleDeleteGroup(w http.ResponseWriter, r *http.Request, u *store.User) {
	id := r.PathValue("id")
	err := s.st.Update(func(st *store.State) error {
		g := st.Groups[id]
		if g == nil {
			return errors.New("no such group")
		}
		if !st.IsGroupAdmin(u.ID, id) {
			return errForbidden
		}
		if len(st.Descendants(id)) > 1 {
			return errors.New("the group still has child groups")
		}
		for _, db := range st.Databases {
			if db.OwnerGroupID == id {
				return errors.New("the group still owns databases")
			}
		}
		for _, m := range st.Memberships {
			if m.GroupID == id {
				return errors.New("the group still has members")
			}
		}
		delete(st.Groups, id)
		st.Grants = filterGrants(st.Grants, func(gr store.Grant) bool { return gr.GroupID != id })
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

func (s *Server) handleSetMember(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID := r.PathValue("id")
	var req struct {
		Username string     `json:"username"`
		UserID   string     `json:"user_id"`
		Role     store.Role `json:"role"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	err := s.st.Update(func(st *store.State) error {
		if st.Groups[groupID] == nil {
			return errors.New("no such group")
		}
		if !st.IsGroupAdmin(u.ID, groupID) {
			return errForbidden
		}
		target := st.Users[req.UserID]
		if target == nil && req.Username != "" {
			target = st.UserByName(req.Username)
		}
		if target == nil {
			return errors.New("no such user")
		}
		role := req.Role
		if role == "" {
			role = store.RoleMember
		}
		if !role.Valid() {
			return errors.New("role must be member or admin")
		}
		for i := range st.Memberships {
			if st.Memberships[i].UserID == target.ID && st.Memberships[i].GroupID == groupID {
				st.Memberships[i].Role = role
				return nil
			}
		}
		st.Memberships = append(st.Memberships, store.Membership{UserID: target.ID, GroupID: groupID, Role: role})
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleRemoveMember(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID, userRef := r.PathValue("id"), r.PathValue("user")
	err := s.st.Update(func(st *store.State) error {
		if st.Groups[groupID] == nil {
			return errors.New("no such group")
		}
		if !st.IsGroupAdmin(u.ID, groupID) {
			return errForbidden
		}
		target := st.Users[userRef]
		if target == nil {
			target = st.UserByName(userRef)
		}
		if target == nil {
			return errors.New("no such user")
		}
		out := st.Memberships[:0]
		for _, m := range st.Memberships {
			if m.UserID == target.ID && m.GroupID == groupID {
				continue
			}
			out = append(out, m)
		}
		st.Memberships = out
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "removed"})
}

// ---- grants ----

func (s *Server) handleSetGrant(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		GroupID    string     `json:"group_id"`
		DatabaseID string     `json:"database_id"`
		Perm       store.Perm `json:"perm"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	var watchers []string
	err := s.st.Update(func(st *store.State) error {
		if st.Databases[req.DatabaseID] == nil {
			return errors.New("no such database")
		}
		if st.Groups[req.GroupID] == nil {
			return errors.New("no such group")
		}
		if st.DatabasePerm(u.ID, req.DatabaseID) != store.PermAdmin {
			return errForbidden
		}
		if !req.Perm.Valid() {
			return errors.New("perm must be read, write or admin")
		}
		for i := range st.Grants {
			if st.Grants[i].GroupID == req.GroupID && st.Grants[i].DatabaseID == req.DatabaseID {
				st.Grants[i].Perm = req.Perm
				watchers = st.Watchers(req.DatabaseID)
				return nil
			}
		}
		st.Grants = append(st.Grants, store.Grant{GroupID: req.GroupID,
			DatabaseID: req.DatabaseID, Perm: req.Perm})
		watchers = st.Watchers(req.DatabaseID)
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: req.DatabaseID})
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleDeleteGrant(w http.ResponseWriter, r *http.Request, u *store.User) {
	groupID := r.URL.Query().Get("group_id")
	dbID := r.URL.Query().Get("database_id")
	var watchers []string
	err := s.st.Update(func(st *store.State) error {
		if st.Databases[dbID] == nil {
			return errors.New("no such database")
		}
		if st.DatabasePerm(u.ID, dbID) != store.PermAdmin {
			return errForbidden
		}
		watchers = st.Watchers(dbID)
		st.Grants = filterGrants(st.Grants, func(g store.Grant) bool {
			return g.GroupID != groupID || g.DatabaseID != dbID
		})
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: dbID})
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// ---- invites ----

func (s *Server) handleCreateInvite(w http.ResponseWriter, r *http.Request, u *store.User) {
	var req struct {
		GroupID  string     `json:"group_id"`
		Role     store.Role `json:"role"`
		TTLHours int        `json:"ttl_hours"`
		MaxUses  int        `json:"max_uses"`
	}
	if !readJSON(w, r, &req) {
		return
	}
	inv := &store.Invite{Token: secret.Token(), GroupID: req.GroupID, Role: req.Role,
		CreatedBy: u.ID, CreatedAt: time.Now(), MaxUses: req.MaxUses}
	if inv.Role == "" {
		inv.Role = store.RoleMember
	}
	if req.TTLHours <= 0 {
		req.TTLHours = 168
	}
	if inv.MaxUses == 0 {
		inv.MaxUses = 1
	}
	inv.ExpiresAt = time.Now().Add(time.Duration(req.TTLHours) * time.Hour)
	err := s.st.Update(func(st *store.State) error {
		if inv.GroupID == "" {
			if !u.ServerAdmin {
				return errors.New("group_id is required")
			}
		} else {
			if st.Groups[inv.GroupID] == nil {
				return errors.New("unknown group")
			}
			if !st.IsGroupAdmin(u.ID, inv.GroupID) {
				return errForbidden
			}
		}
		if !inv.Role.Valid() {
			return errors.New("role must be member or admin")
		}
		st.Invites[inv.Token] = inv
		return nil
	})
	if err != nil {
		deny(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, map[string]any{
		"token":      inv.Token,
		"url":        s.cfg.ExternalURL + "/invite/" + inv.Token,
		"expires_at": inv.ExpiresAt,
		"max_uses":   inv.MaxUses,
		"group_id":   inv.GroupID,
		"role":       inv.Role,
	})
}

func (s *Server) handleListInvites(w http.ResponseWriter, r *http.Request, u *store.User) {
	type inviteView struct {
		Token     string     `json:"token"`
		URL       string     `json:"url"`
		GroupID   string     `json:"group_id,omitempty"`
		Role      store.Role `json:"role"`
		Uses      int        `json:"uses"`
		MaxUses   int        `json:"max_uses"`
		ExpiresAt time.Time  `json:"expires_at"`
	}
	out := []inviteView{}
	s.st.Read(func(st *store.State) {
		for _, inv := range st.Invites {
			if !u.ServerAdmin && inv.CreatedBy != u.ID &&
				!(inv.GroupID != "" && st.IsGroupAdmin(u.ID, inv.GroupID)) {
				continue
			}
			out = append(out, inviteView{Token: inv.Token, URL: s.cfg.ExternalURL + "/invite/" + inv.Token,
				GroupID: inv.GroupID, Role: inv.Role, Uses: inv.Uses, MaxUses: inv.MaxUses,
				ExpiresAt: inv.ExpiresAt})
		}
	})
	sort.Slice(out, func(i, j int) bool { return out[i].ExpiresAt.Before(out[j].ExpiresAt) })
	writeJSON(w, http.StatusOK, map[string]any{"invites": out})
}

// ---- users ----

func (s *Server) handleListUsers(w http.ResponseWriter, r *http.Request, u *store.User) {
	out := []userView{}
	s.st.Read(func(st *store.State) {
		for id, target := range st.Users {
			if u.ServerAdmin || id == u.ID || s.sharesAdministeredGroup(st, u.ID, id) {
				out = append(out, view(target))
			}
		}
	})
	sort.Slice(out, func(i, j int) bool { return out[i].Username < out[j].Username })
	writeJSON(w, http.StatusOK, map[string]any{"users": out})
}

// sharesAdministeredGroup reports whether admin administers any group the
// target belongs to, which is what makes the target visible to them.
func (s *Server) sharesAdministeredGroup(st *store.State, adminID, targetID string) bool {
	for _, m := range st.Memberships {
		if m.UserID == targetID && st.IsGroupAdmin(adminID, m.GroupID) {
			return true
		}
	}
	return false
}

// notifyList tells everyone with access that the database list changed.
func (s *Server) notifyList(dbID string) {
	var watchers []string
	s.st.Read(func(st *store.State) { watchers = st.Watchers(dbID) })
	s.hub.Publish(watchers, Event{Type: EventChanged, DatabaseID: dbID})
}

func filterGrants(in []store.Grant, keep func(store.Grant) bool) []store.Grant {
	out := in[:0]
	for _, g := range in {
		if keep(g) {
			out = append(out, g)
		}
	}
	return out
}