// Package approvalapi ist die HTTP-Bindung fuer das Freigabe-Postfach
// (APR-01). Die Nutzeridentitaet kommt bis zur Core-JWT-Anbindung
// (Muster aus UX-10/INT-18, hier noch nicht Ticket-Scope) uebergangsweise
// aus dem Header X-User-Id, analog zum DMS-Uebergangsmodus vor UX-10.
package approvalapi

import (
	"encoding/json"
	"errors"
	"net/http"

	"gitea.perlbach24.de/scripte/nexarch/workflow/internal/approval"
)

type Server struct {
	svc *approval.Service
}

func NewServer(svc *approval.Service) *Server {
	return &Server{svc: svc}
}

func (s *Server) RegisterRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /approvals", s.requireUser(s.handleList))
	mux.HandleFunc("POST /approvals/{id}/decide", s.requireUser(s.handleDecide))
}

func (s *Server) requireUser(next func(w http.ResponseWriter, r *http.Request, userID string)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		userID := r.Header.Get("X-User-Id")
		if userID == "" {
			writeError(w, http.StatusUnauthorized, "X-User-Id fehlt")
			return
		}
		next(w, r, userID)
	}
}

func (s *Server) handleList(w http.ResponseWriter, r *http.Request, userID string) {
	tasks, err := s.svc.OpenForAssignee(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "aufgaben konnten nicht gelesen werden")
		return
	}
	writeJSON(w, http.StatusOK, tasks)
}

type decideRequest struct {
	Decision string `json:"decision"`
	Reason   string `json:"reason"`
}

func (s *Server) handleDecide(w http.ResponseWriter, r *http.Request, userID string) {
	id := r.PathValue("id")
	var req decideRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "ungueltiger anfrage-koerper")
		return
	}
	task, err := s.svc.Decide(r.Context(), id, userID, approval.Decision(req.Decision), req.Reason)
	switch {
	case err == nil:
		writeJSON(w, http.StatusOK, task)
	case errors.Is(err, approval.ErrNotFound):
		writeError(w, http.StatusNotFound, "aufgabe nicht gefunden")
	case errors.Is(err, approval.ErrForbidden):
		writeError(w, http.StatusForbidden, "nicht zustaendig fuer diese aufgabe")
	case errors.Is(err, approval.ErrAlreadyDecided):
		writeError(w, http.StatusConflict, "aufgabe wurde bereits entschieden")
	default:
		writeError(w, http.StatusInternalServerError, "entscheidung konnte nicht verarbeitet werden")
	}
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]string{"error": message})
}