// Package caseapi ist die HTTP-Bindung fuer das Akte/Vorgang-Objektmodell
// (VOR-01). Nutzeridentitaet kommt uebergangsweise aus X-User-Id, wie
// bereits bei approvalapi (APR-01) etabliert.
package caseapi

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

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

type Server struct {
	svc *caseobj.Service
}

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

func (s *Server) RegisterRoutes(mux *http.ServeMux) {
	mux.HandleFunc("POST /cases", s.requireUser(s.handleCreate))
	mux.HandleFunc("GET /cases/{id}", s.requireUser(s.handleGet))
	mux.HandleFunc("POST /cases/{id}/transition", s.requireUser(s.handleTransition))
}

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)
	}
}

type createRequest struct {
	CaseNumber  string              `json:"case_number"`
	Responsible string              `json:"responsible"`
	References  []caseobj.Reference `json:"references"`
}

func (s *Server) handleCreate(w http.ResponseWriter, r *http.Request, userID string) {
	var req createRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "ungueltiger anfrage-koerper")
		return
	}
	c, err := s.svc.Create(r.Context(), req.CaseNumber, req.Responsible, userID, req.References)
	switch {
	case err == nil:
		writeJSON(w, http.StatusCreated, c)
	case errors.Is(err, caseobj.ErrDuplicateCaseNumber):
		writeError(w, http.StatusConflict, "aktenzeichen bereits vergeben")
	default:
		writeError(w, http.StatusInternalServerError, "akte konnte nicht angelegt werden")
	}
}

func (s *Server) handleGet(w http.ResponseWriter, r *http.Request, _ string) {
	id := r.PathValue("id")
	c, err := s.svc.Get(r.Context(), id)
	switch {
	case err == nil:
		writeJSON(w, http.StatusOK, c)
	case errors.Is(err, caseobj.ErrNotFound):
		writeError(w, http.StatusNotFound, "akte nicht gefunden")
	default:
		writeError(w, http.StatusInternalServerError, "akte konnte nicht gelesen werden")
	}
}

type transitionRequest struct {
	To     string `json:"to"`
	Reason string `json:"reason"`
}

func (s *Server) handleTransition(w http.ResponseWriter, r *http.Request, userID string) {
	id := r.PathValue("id")
	var req transitionRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "ungueltiger anfrage-koerper")
		return
	}
	err := s.svc.Transition(r.Context(), id, req.To, userID, req.Reason)
	switch {
	case err == nil:
		c, getErr := s.svc.Get(r.Context(), id)
		if getErr != nil {
			writeError(w, http.StatusInternalServerError, "status geaendert, lesen fehlgeschlagen")
			return
		}
		writeJSON(w, http.StatusOK, c)
	case errors.Is(err, caseobj.ErrNotFound):
		writeError(w, http.StatusNotFound, "akte nicht gefunden")
	default:
		writeError(w, http.StatusUnprocessableEntity, "statuswechsel nicht zulaessig")
	}
}

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})
}