package forecastapi

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

	"github.com/itworx/pulse/internal/auth"
	"github.com/itworx/pulse/internal/forecast"
	"github.com/itworx/pulse/internal/problem"
)

type Handler struct {
	Provider forecast.Provider
}

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet || r.URL.Path != "/api/v1/forecasts" {
		http.NotFound(w, r)
		return
	}
	if _, ok := auth.PrincipalFromContext(r.Context()); !ok {
		problem.Write(w, r, http.StatusUnauthorized, "UNAUTHORIZED", "Authentication required", "Authentication is required to read forecasts.", nil)
		return
	}
	if err := r.Context().Err(); err != nil {
		return
	}
	snapshot, err := h.snapshot(r)
	if err != nil {
		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
			return
		}
		problem.Write(w, r, http.StatusServiceUnavailable, "FORECASTS_UNAVAILABLE", "Forecastgegevens niet beschikbaar", "De capaciteitsvoorspellingen konden niet worden gelezen.", nil)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "private, max-age=15")
	_ = json.NewEncoder(w).Encode(snapshot)
}

func (h Handler) snapshot(r *http.Request) (forecast.Snapshot, error) {
	if h.Provider == nil {
		return forecast.UnknownSnapshot(time.Now().UTC(), "source_unavailable"), nil
	}
	return h.Provider.Snapshot(r.Context())
}