package api

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

	"github.com/loyaly/behavision-server/internal/auth"
)

// Adding people to a company: invitations, registration, and the team list.
//
// Registration is by INVITATION, and that is the same decision handlers_admin.go
// records for creating a company: an endpoint a stranger can call to create an
// account is a far larger thing to secure than one reachable only through
// somebody who already has one. What was missing was not the openness - it was
// that a tenant could not add a SECOND person at all except by somebody with a
// shell on the server running `provision user`. A shop with an owner and four
// staff either shared one password between five people or raised a ticket per
// person, and a phone app for shop-floor staff could not exist while there was
// only ever one account to sign in as.
//
// So: a manager mints a code, hands it over, and the holder chooses their own
// password. The code carries the address and the role; the request carries only
// the password and a name. That split is load-bearing and is why this is not
// simply "create a user with these fields" - see handleRegister.

const (
	// Long enough to reach somebody who is not at work today, short enough that
	// a code left in a chat thread is worthless before anyone scrolls back to
	// it. An expired invitation costs one click to reissue.
	invitationTTL = 7 * 24 * time.Hour
	maxInvitation = 30 * 24 * time.Hour
)

// handleInvite mints one invitation.
//
// Manager and above. Not staff: the holder of a code gets an account inside
// this company, so it is a credential, not a convenience.
func (s *Server) handleInvite(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Your account cannot invite people to this company.")
		return
	}

	var body struct {
		Email    string `json:"email"`
		FullName string `json:"full_name"`
		Role     string `json:"role"`
		Days     int    `json:"expires_in_days"`
	}
	if err := decode(w, r, &body); err != nil {
		badRequest(w, err.Error())
		return
	}
	email := auth.NormalizeEmail(body.Email)
	if email == "" || !strings.Contains(email, "@") {
		badRequest(w, "an email address is required - it is what they will sign in with")
		return
	}
	role := strings.ToLower(trim(body.Role))
	if role == "" {
		role = "staff"
	}
	// 'admin' is absent on purpose. A platform administrator is defined by
	// having no company at all, so an invitation could never mint a real one -
	// what it could do is create the tenant-scoped row with role='admin' that
	// adminOnly exists to reject, and a role nothing can use is a trap rather
	// than a feature.
	switch role {
	case "owner", "manager", "staff":
	default:
		badRequest(w, "role must be owner, manager or staff")
		return
	}
	// Only an owner may create another owner. A manager promoting somebody past
	// themselves is an escalation, and it is the one shape of this endpoint
	// that would matter if a manager account were ever taken over.
	if role == "owner" && p.Role != "owner" && p.Role != "admin" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Only an owner can invite another owner.")
		return
	}

	ttl := invitationTTL
	if body.Days > 0 {
		ttl = time.Duration(body.Days) * 24 * time.Hour
		if ttl > maxInvitation {
			ttl = maxInvitation
		}
	}

	code, err := auth.NewEnrolmentCode()
	if err != nil {
		s.serverError(w, "mint invitation", err)
		return
	}
	inv, err := s.Store.CreateInvitation(r.Context(), NewInvitation{
		ClientID:  p.ClientID,
		Email:     email,
		FullName:  clip(trim(body.FullName), 200),
		Role:      role,
		CodeHash:  auth.HashToken(auth.NormalizeCode(code)),
		InvitedBy: p.UserID,
		ExpiresAt: s.now().Add(ttl),
	})
	if err != nil {
		s.serverError(w, "create invitation", err)
		return
	}
	// The plaintext exists here and in this response, and nowhere else. Like
	// every other secret this system mints, it is shown once: one a support
	// engineer can look up later is one anybody with support access can redeem.
	inv.Code = code

	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "team.invite", Entity: "invitation", EntityID: inv.ID,
		Detail: map[string]any{"email": email, "role": role},
	})
	writeJSON(w, http.StatusCreated, inv)
}

func (s *Server) handleInvitations(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Your account cannot see this company's invitations.")
		return
	}
	rows, err := s.Store.PendingInvitations(r.Context(), p.ClientID)
	if err != nil {
		s.serverError(w, "list invitations", err)
		return
	}
	if rows == nil {
		rows = []Invitation{}
	}
	writeJSON(w, http.StatusOK, rows)
}

func (s *Server) handleRevokeInvitation(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Your account cannot withdraw invitations.")
		return
	}
	id := r.PathValue("id")
	if !looksLikeUUID(id) {
		writeErr(w, http.StatusNotFound, "not_found", "No such invitation.")
		return
	}
	if err := s.Store.RevokeInvitation(r.Context(), p.ClientID, id); err != nil {
		// Already used or already withdrawn. Reported rather than swallowed:
		// "I cancelled it" and "somebody had already joined with it" need
		// opposite next steps from whoever pressed the button.
		writeErr(w, http.StatusNotFound, "not_found",
			"That invitation is no longer pending.")
		return
	}
	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "team.invite.revoke", Entity: "invitation", EntityID: id,
	})
	w.WriteHeader(http.StatusNoContent)
}

// handleInvitationPreview lets a client show what a code is for before asking
// somebody to choose a password.
//
// Unauthenticated, because the holder has no account yet - that is the whole
// point - and it discloses only what the code itself already asserts: the
// company, the address it was issued for, and the role. Unknown, expired, spent
// and revoked are one identical answer, exactly as enrolment already does:
// telling them apart only helps somebody guessing codes, and the holder's next
// step is the same in all four cases.
func (s *Server) handleInvitationPreview(w http.ResponseWriter, r *http.Request) {
	code := auth.NormalizeCode(r.URL.Query().Get("code"))
	if code == "" {
		badRequest(w, "a code is required")
		return
	}
	prev, err := s.Store.InvitationByCode(r.Context(), auth.HashToken(code))
	if err != nil {
		writeErr(w, http.StatusNotFound, "invalid_code",
			"That invitation code is not valid. Ask for a new one.")
		return
	}
	writeJSON(w, http.StatusOK, prev)
}

// handleRegister turns a code into an account and signs the person in.
//
// Unauthenticated for the same reason `POST /api/agent/enrol` is: whoever is
// doing this has no account yet, and requiring one first would mean shipping a
// password to everybody who needs one.
//
// The email and the role come from the INVITATION, never from this body. A code
// forwarded to a colleague must not become an account for them, and a staff
// invitation must not be redeemed as an owner - which is exactly what a
// caller-supplied role would allow. The only things the request decides are the
// password and the display name.
//
// It returns a Session, identical in shape to login. A new member's next screen
// is the app, not a sign-in form they have to fill in with the password they
// chose four seconds ago.
func (s *Server) handleRegister(w http.ResponseWriter, r *http.Request) {
	var body struct {
		Code     string `json:"code"`
		FullName string `json:"full_name"`
		Password string `json:"password"`
		Device   string `json:"device"`
	}
	if err := decode(w, r, &body); err != nil {
		badRequest(w, err.Error())
		return
	}
	code := auth.NormalizeCode(body.Code)
	if code == "" {
		badRequest(w, "an invitation code is required")
		return
	}

	// Throttled on the code, by IP. Redeeming is the one unauthenticated write
	// in this package that creates a row, so an unbounded one is a way to grind
	// through the code space and to fill a table while doing it.
	_, perIP := s.throttles()
	ipKey := clientIP(r)
	if !perIP.Allow(ipKey) {
		writeErr(w, http.StatusTooManyRequests, "too_many_attempts",
			"Too many attempts. Wait a few minutes and try again.")
		return
	}

	if err := auth.CheckPasswordPolicy(body.Password); err != nil {
		badRequest(w, err.Error())
		return
	}
	hash, err := auth.HashPassword(body.Password)
	if err != nil {
		s.serverError(w, "hash password", err)
		return
	}

	rec, err := s.Store.RedeemInvitation(r.Context(), auth.HashToken(code),
		clip(trim(body.FullName), 200), hash)
	if err != nil {
		perIP.Fail(ipKey)
		if msg, ok := conflictMessage(err); ok {
			// The address already has an account somewhere on the platform.
			// Worth saying plainly: the fix is to sign in, not to try again.
			writeErr(w, http.StatusConflict, "conflict", msg)
			return
		}
		writeErr(w, http.StatusNotFound, "invalid_code",
			"That invitation code is not valid. Ask for a new one.")
		return
	}
	perIP.Reset(ipKey)

	sess, err := s.mint(r, rec, body.Device)
	if err != nil {
		// The account exists and the invitation is spent. Say so rather than
		// implying nothing happened - the recovery is to sign in, and telling
		// them to redeem again would fail forever.
		s.logf("ERROR register: created %s but could not start a session: %v", rec.ID, err)
		writeErr(w, http.StatusInternalServerError, "server_error",
			"Your account was created but we could not sign you in. Please sign in.")
		return
	}
	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: rec.ClientID, ActorID: rec.ID, ActorKind: "user",
		Action: "team.register", Entity: "user", EntityID: rec.ID,
		Detail: map[string]any{"role": rec.Role, "device": trim(body.Device)},
	})
	s.logf("registered %s (%s) into client %s", rec.Email, rec.Role, rec.ClientID)
	writeJSON(w, http.StatusCreated, sess)
}

func (s *Server) handleTeam(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"This account does not belong to a company.")
		return
	}
	rows, err := s.Store.Team(r.Context(), p.ClientID)
	if err != nil {
		s.serverError(w, "list team", err)
		return
	}
	if rows == nil {
		rows = []TeamMember{}
	}
	writeJSON(w, http.StatusOK, rows)
}

// handleUpdateTeamMember changes a role, or turns an account off.
//
// Deactivating is the "they have left" button, and the store revokes their
// sessions in the same transaction: an access token lives twelve hours, so
// without that, removing somebody's access would remove it sometime tomorrow.
func (s *Server) handleUpdateTeamMember(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Your account cannot change who works here.")
		return
	}
	id := r.PathValue("id")
	if !looksLikeUUID(id) {
		writeErr(w, http.StatusNotFound, "not_found", "No such team member.")
		return
	}

	var up TeamUpdate
	if err := decode(w, r, &up); err != nil {
		badRequest(w, err.Error())
		return
	}
	if up.Role == nil && up.Active == nil {
		badRequest(w, "nothing to change - send a role, an active flag, or both")
		return
	}
	if up.Role != nil {
		role := strings.ToLower(trim(*up.Role))
		switch role {
		case "owner", "manager", "staff":
		default:
			badRequest(w, "role must be owner, manager or staff")
			return
		}
		if role == "owner" && p.Role != "owner" && p.Role != "admin" {
			writeErr(w, http.StatusForbidden, "forbidden",
				"Only an owner can make somebody else an owner.")
			return
		}
		up.Role = &role
	}

	// The company must keep an owner. Losing the last one leaves a tenant
	// nobody can administer, and the only way back is a shell on the server -
	// which is the thing this whole surface exists to stop needing.
	demoting := up.Role != nil && *up.Role != "owner"
	disabling := up.Active != nil && !*up.Active
	if demoting || disabling {
		if last, err := s.lastOwner(r, id); err != nil {
			s.serverError(w, "count owners", err)
			return
		} else if last {
			writeErr(w, http.StatusConflict, "last_owner",
				"This is the company's only owner. Make somebody else an owner first.")
			return
		}
	}

	m, err := s.Store.UpdateTeamMember(r.Context(), p.ClientID, id, up)
	if err != nil {
		writeErr(w, http.StatusNotFound, "not_found", "No such team member.")
		return
	}
	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "team.update", Entity: "user", EntityID: id,
		Detail: map[string]any{"role": m.Role, "active": m.Active},
	})
	writeJSON(w, http.StatusOK, m)
}

// lastOwner reports whether the named member is the only active owner left.
func (s *Server) lastOwner(r *http.Request, userID string) (bool, error) {
	p := PrincipalFrom(r.Context())
	rows, err := s.Store.Team(r.Context(), p.ClientID)
	if err != nil {
		return false, err
	}
	owners, isOwner := 0, false
	for _, m := range rows {
		if m.Role == "owner" && m.Active {
			owners++
			if m.ID == userID {
				isOwner = true
			}
		}
	}
	return isOwner && owners == 1, nil
}

// handleCreateMember is a manager creating a salesperson's login directly and
// handing it over - the path for somebody being set up before their first
// shift, without a phone in hand.
//
// Same rules as an invitation for who may create whom: manager and above, and
// only an owner mints an owner. Same rule as the platform admin creating a
// merchant for the password: generated unless given, returned exactly once.
func (s *Server) handleCreateMember(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Only a manager or owner can add team members.")
		return
	}

	var in NewMemberInput
	if err := decode(w, r, &in); err != nil {
		badRequest(w, err.Error())
		return
	}
	in.Email = auth.NormalizeEmail(in.Email)
	if in.Email == "" || !strings.Contains(in.Email, "@") {
		badRequest(w, "an email address is required - it is what they will sign in with")
		return
	}
	in.FullName = clip(trim(in.FullName), 200)
	in.Role = strings.ToLower(trim(in.Role))
	if in.Role == "" {
		in.Role = "staff"
	}
	switch in.Role {
	case "owner", "manager", "staff":
	default:
		badRequest(w, "role must be owner, manager or staff")
		return
	}
	if in.Role == "owner" && p.Role != "owner" && p.Role != "admin" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Only an owner can create another owner.")
		return
	}

	password := in.Password
	if password == "" {
		generated, err := auth.RandomPassword()
		if err != nil {
			s.serverError(w, "generate password", err)
			return
		}
		password = generated
	}
	hash, err := auth.HashPassword(password)
	if err != nil {
		// The policy message ("at least 8 characters") is written for the
		// person who typed it, so it goes out as-is.
		badRequest(w, err.Error())
		return
	}

	m, err := s.Store.CreateMember(r.Context(), p.ClientID, in, hash)
	if err != nil {
		if msg, ok := conflictMessage(err); ok {
			writeErr(w, http.StatusConflict, "conflict", msg)
			return
		}
		s.serverError(w, "create member", err)
		return
	}

	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "team.create", Entity: "user", EntityID: m.ID,
		Detail: map[string]any{"email": m.Email, "role": m.Role},
	})
	// The plaintext exists here and in this response, and nowhere else.
	writeJSON(w, http.StatusCreated, NewMemberResult{TeamMember: m, Password: password})
}

// handleResetPassword is a manager resetting a member's password: the
// salesperson forgot it, or lost the phone it was on. Returns the new one
// once, and signs the member out everywhere - see the store for why those are
// one operation.
//
// Deliberately not self-service and not "send an email": a shop-floor account
// often has no mailbox anyone checks, and the person who can vouch for the
// salesperson standing in front of them is their manager.
func (s *Server) handleResetPassword(w http.ResponseWriter, r *http.Request) {
	p := PrincipalFrom(r.Context())
	if !p.CanManageSites() || p.ClientID == "" {
		writeErr(w, http.StatusForbidden, "forbidden",
			"Only a manager or owner can reset a team member's password.")
		return
	}
	userID := r.PathValue("id")

	var in PasswordReset
	if err := decodeOptional(w, r, &in); err != nil {
		badRequest(w, err.Error())
		return
	}
	password := in.Password
	if password == "" {
		generated, err := auth.RandomPassword()
		if err != nil {
			s.serverError(w, "generate password", err)
			return
		}
		password = generated
	}
	hash, err := auth.HashPassword(password)
	if err != nil {
		badRequest(w, err.Error())
		return
	}

	m, err := s.Store.ResetMemberPassword(r.Context(), p.ClientID, userID, hash)
	if err != nil {
		// A user id from another tenant matches nothing, so it reads as 404 -
		// a tenant user has no business learning the id was real.
		writeErr(w, http.StatusNotFound, "not_found", "No such team member.")
		return
	}

	s.Store.Audit(r.Context(), AuditEntry{
		ClientID: p.ClientID, ActorID: p.UserID, ActorKind: "user",
		Action: "team.reset_password", Entity: "user", EntityID: m.ID,
		Detail: map[string]any{"email": m.Email},
	})
	writeJSON(w, http.StatusOK, PasswordReset{Password: password})
}