package server

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

	"steward/internal/api"
	"steward/internal/auth"
	"steward/internal/config"
	"steward/internal/model"
	"steward/internal/store"
)

func (s *Server) changeOwnPassword(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if p.Token != nil {
		return forbidden("passwords can't be changed with an API token; log in to the web UI")
	}
	if p.User.ID == 0 {
		return badRequest("%s on the local socket isn't a Steward user; use 'steward user update USER --password'", p.Name())
	}
	var in api.PasswordChange
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	u, err := s.store.GetUser(r.Context(), p.User.ID)
	if err != nil {
		return err
	}
	if u.PasswordHash != "" && !auth.CheckPassword(u.PasswordHash, in.Current) {
		s.eng.Audit(r.Context(), p, "user.password", "user "+u.Username, "failure", "wrong current password")
		return &httpError{http.StatusForbidden, "wrong_password", "the current password is wrong"}
	}
	hash, err := auth.HashPassword(in.Password)
	if err != nil {
		return badRequest("%v", err)
	}
	u.PasswordHash = hash
	if err := s.store.UpdateUser(r.Context(), u); err != nil {
		return err
	}
	keep := ""
	if se, ok := r.Context().Value(keySession).(*model.Session); ok {
		keep = se.IDHash
	}
	s.store.DeleteUserSessions(r.Context(), u.ID, keep)
	s.eng.Audit(r.Context(), p, "user.password", "user "+u.Username, "success", "")
	w.WriteHeader(http.StatusNoContent)
	return nil
}

func grantsFrom(strs []string, role string) ([]model.Grant, bool, error) {
	var out []model.Grant
	set := false
	if role != "" {
		gs, ok := auth.Roles[role]
		if !ok {
			return nil, false, badRequest("unknown role %q (use %s)", role, strings.Join(auth.RoleNames(), ", "))
		}
		out = append(out, gs...)
		set = true
	}
	for _, g := range strs {
		gr, err := auth.ParseGrant(g)
		if err != nil {
			return nil, false, badRequest("%v", err)
		}
		out = append(out, gr)
		set = true
	}
	if set && out == nil {
		out = []model.Grant{}
	}
	return out, set, nil
}

func grantStrings(gs []model.Grant) []string {
	out := []string{}
	for _, g := range gs {
		out = append(out, auth.FormatGrant(g))
	}
	return out
}

func presentToken(t *model.Token) api.Token {
	out := api.Token{Token: t, GrantStrings: grantStrings(t.Grants)}
	if t.Grants == nil {
		out.GrantStrings = []string{"(all of the user's)"}
	}
	return out
}

func (s *Server) createTokenFor(w http.ResponseWriter, r *http.Request, p *auth.Principal, u *model.User) error {
	var in api.TokenInput
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	if strings.TrimSpace(in.Name) == "" {
		return badRequest("a token needs a name")
	}
	grants, set, err := grantsFrom(in.Grants, in.Role)
	if err != nil {
		return err
	}
	var exp *time.Time
	switch {
	case in.ExpiresAt != nil:
		if in.ExpiresAt.Before(time.Now()) {
			return badRequest("expires_at is in the past")
		}
		exp = in.ExpiresAt
	case in.ExpiresIn != "":
		d, err := config.ParseDuration(in.ExpiresIn)
		if err != nil || d <= 0 {
			return badRequest("invalid expires_in %q (use e.g. 90d or 720h)", in.ExpiresIn)
		}
		t := time.Now().Add(d)
		exp = &t
	}
	// A restricted token can only make tokens no wider than itself.
	if p.Token != nil && p.Token.Grants != nil {
		if !set {
			grants, set = p.Token.Grants, true
		} else if !auth.Narrower(grants, p.Token.Grants) {
			return forbidden("a restricted token can only create tokens with a subset of its own grants")
		}
	}
	secret, pid, hash := auth.NewToken()
	t := &model.Token{UserID: u.ID, Name: strings.TrimSpace(in.Name), PublicID: pid, SecretHash: hash, ExpiresAt: exp}
	if set {
		t.Grants = grants
	}
	if err := s.store.CreateToken(r.Context(), t); err != nil {
		return err
	}
	t.Username = u.Username
	s.eng.Audit(r.Context(), p, "token.create", "token "+u.Username+"/"+t.Name, "success", strings.Join(grantStrings(t.Grants), " "))
	out := presentToken(t)
	out.Secret = secret
	writeJSON(w, http.StatusCreated, out)
	return nil
}

func (s *Server) createOwnToken(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if p.User.ID == 0 {
		return badRequest("%s on the local socket isn't a Steward user and has no tokens; make the token for a user (steward token create NAME --user admin)", p.Name())
	}
	return s.createTokenFor(w, r, p, p.User)
}

func (s *Server) listTokens(w http.ResponseWriter, r *http.Request, userID int64) error {
	ts, err := s.store.ListTokens(r.Context(), userID)
	if err != nil {
		return err
	}
	out := []api.Token{}
	for _, t := range ts {
		if t.RevokedAt != nil && !queryBool(r, "all") {
			continue
		}
		out = append(out, presentToken(t))
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

func (s *Server) listOwnTokens(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if p.User.ID == 0 {
		writeJSON(w, http.StatusOK, []api.Token{})
		return nil
	}
	return s.listTokens(w, r, p.User.ID)
}

func (s *Server) listAllTokens(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireAdmin(p); err != nil {
		return err
	}
	return s.listTokens(w, r, 0)
}

func (s *Server) revokeToken(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	id, err := pathID(r, "id")
	if err != nil {
		return err
	}
	t, err := s.store.GetToken(r.Context(), id)
	if err != nil || t.UserID != p.User.ID && !p.IsAdmin() {
		return notFound("token %d not found", id)
	}
	if err := s.store.RevokeToken(r.Context(), id); err != nil {
		if errors.Is(err, store.ErrNotFound) {
			return conflict("token %d is already revoked", id)
		}
		return err
	}
	s.eng.Audit(r.Context(), p, "token.revoke", "token "+t.Username+"/"+t.Name, "success", "")
	w.WriteHeader(http.StatusNoContent)
	return nil
}

func presentUser(u *model.User) api.User {
	return api.User{User: u, GrantStrings: grantStrings(u.Grants)}
}

func (s *Server) listUsers(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireAdmin(p); err != nil {
		return err
	}
	us, err := s.store.ListUsers(r.Context())
	if err != nil {
		return err
	}
	out := []api.User{}
	for _, u := range us {
		out = append(out, presentUser(u))
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

// ValidUsername checks a user name.
func ValidUsername(n string) error {
	if len(n) < 1 || len(n) > 64 {
		return badRequest("user names have 1 to 64 characters")
	}
	for _, c := range n {
		if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || strings.ContainsRune("._-@", c)) {
			return badRequest("user names may have letters, digits, '.', '_', '-' and '@'")
		}
	}
	return nil
}

func applyUserInput(u *model.User, in *api.UserInput) error {
	role := ""
	if in.Role != nil {
		role = *in.Role
	}
	var strs []string
	if in.Grants != nil {
		strs = *in.Grants
	}
	grants, set, err := grantsFrom(strs, role)
	if err != nil {
		return err
	}
	if set || in.Grants != nil {
		if grants == nil {
			grants = []model.Grant{}
		}
		u.Grants = grants
	}
	if in.Admin != nil {
		u.Admin = *in.Admin
	}
	if in.Disabled != nil {
		u.Disabled = *in.Disabled
	}
	if in.Comment != nil {
		u.Comment = *in.Comment
	}
	if in.Password != nil {
		if *in.Password == "" {
			u.PasswordHash = "" // tokens only
		} else {
			h, err := auth.HashPassword(*in.Password)
			if err != nil {
				return badRequest("%v", err)
			}
			u.PasswordHash = h
		}
	}
	return nil
}

func (s *Server) createUser(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireAdmin(p); err != nil {
		return err
	}
	var in api.UserInput
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	if in.Username == nil {
		return badRequest("a user needs a username")
	}
	u := &model.User{Username: strings.TrimSpace(*in.Username)}
	if err := ValidUsername(u.Username); err != nil {
		return err
	}
	if err := applyUserInput(u, &in); err != nil {
		return err
	}
	if err := s.store.CreateUser(r.Context(), u); err != nil {
		if errors.Is(err, store.ErrConflict) {
			return conflict("user %s already exists", u.Username)
		}
		return err
	}
	s.eng.Audit(r.Context(), p, "user.create", "user "+u.Username, "success", strings.Join(grantStrings(u.Grants), " "))
	writeJSON(w, http.StatusCreated, presentUser(u))
	return nil
}

func (s *Server) userByPath(r *http.Request) (*model.User, error) {
	id, err := pathID(r, "id")
	if err != nil {
		return nil, err
	}
	u, err := s.store.GetUser(r.Context(), id)
	if errors.Is(err, store.ErrNotFound) {
		return nil, notFound("user %d not found", id)
	}
	return u, err
}

func (s *Server) updateUser(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireAdmin(p); err != nil {
		return err
	}
	u, err := s.userByPath(r)
	if err != nil {
		return err
	}
	var in api.UserInput
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	wasAdmin := u.Admin && !u.Disabled
	if in.Username != nil {
		u.Username = strings.TrimSpace(*in.Username)
		if err := ValidUsername(u.Username); err != nil {
			return err
		}
	}
	if err := applyUserInput(u, &in); err != nil {
		return err
	}
	if wasAdmin && (!u.Admin || u.Disabled) {
		if n, err := s.store.CountAdmins(r.Context()); err == nil && n <= 1 {
			return conflict("%s is the last administrator; make someone else an administrator first", u.Username)
		}
	}
	if err := s.store.UpdateUser(r.Context(), u); err != nil {
		if errors.Is(err, store.ErrConflict) {
			return conflict("user %s already exists", u.Username)
		}
		return err
	}
	if u.Disabled || in.Password != nil {
		s.store.DeleteUserSessions(r.Context(), u.ID, "")
	}
	s.eng.Audit(r.Context(), p, "user.update", "user "+u.Username, "success", strings.Join(grantStrings(u.Grants), " "))
	writeJSON(w, http.StatusOK, presentUser(u))
	return nil
}

func (s *Server) deleteUser(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := requireAdmin(p); err != nil {
		return err
	}
	u, err := s.userByPath(r)
	if err != nil {
		return err
	}
	if u.ID == p.User.ID {
		return conflict("you can't delete yourself")
	}
	if u.Admin && !u.Disabled {
		if n, err := s.store.CountAdmins(r.Context()); err == nil && n <= 1 {
			return conflict("%s is the last administrator", u.Username)
		}
	}
	if err := s.store.DeleteUser(r.Context(), u.ID); err != nil {
		return err
	}
	s.eng.Audit(r.Context(), p, "user.delete", "user "+u.Username, "success", "")
	w.WriteHeader(http.StatusNoContent)
	return nil
}

func (s *Server) listUserTokens(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	u, err := s.userByPath(r)
	if err != nil {
		return err
	}
	if u.ID != p.User.ID && !p.IsAdmin() {
		return forbidden("only administrators can see other users' tokens")
	}
	return s.listTokens(w, r, u.ID)
}

func (s *Server) createUserToken(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	u, err := s.userByPath(r)
	if err != nil {
		return err
	}
	if u.ID != p.User.ID && !p.IsAdmin() {
		return forbidden("only administrators can make tokens for other users")
	}
	return s.createTokenFor(w, r, p, u)
}