package async

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

	"predictor-refactored/internal/api/httpjson"
	"predictor-refactored/internal/api/v2"
)

// Handler implements the /api/v1/predictions{,/{id}} endpoints.
type Handler struct {
	mgr *Manager
}

// NewHandler wires a handler.
func NewHandler(mgr *Manager) *Handler { return &Handler{mgr: mgr} }

// Register installs the async routes on mux.
func (h *Handler) Register(mux *http.ServeMux) {
	mux.HandleFunc("POST /api/v1/predictions", h.create)
	mux.HandleFunc("GET /api/v1/predictions/{id}", h.get)
	mux.HandleFunc("DELETE /api/v1/predictions/{id}", h.cancel)
}

func (h *Handler) create(w http.ResponseWriter, r *http.Request) {
	var req v2.PredictionRequest
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	if err := dec.Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid body: "+err.Error())
		return
	}
	info, accepted := h.mgr.Enqueue(req)
	if !accepted {
		writeJSON(w, http.StatusServiceUnavailable, info)
		return
	}
	w.Header().Set("Location", "/api/v1/predictions/"+info.ID)
	writeJSON(w, http.StatusAccepted, info)
}

func (h *Handler) get(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	info, ok := h.mgr.Get(id)
	if !ok {
		writeError(w, http.StatusNotFound, "prediction job not found")
		return
	}
	writeJSON(w, http.StatusOK, info)
}

func (h *Handler) cancel(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if !h.mgr.Cancel(id) {
		writeError(w, http.StatusConflict, "job not found or already terminal")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

var writeJSON = httpjson.Write
var writeError = httpjson.Error