weather/internal/web/handler.go

package web

import (
	"encoding/json"
	"fmt"
	"go/weather/internal/storage"
	"go/weather/pkg/headers"
	"go/weather/pkg/logger"
	"io"
	"net/http"
	"time"

	"github.com/gorilla/mux"
	"go.elastic.co/apm"
	"go.elastic.co/apm/module/apmzap"
	"go.uber.org/zap"
)

const (
	welcomeMessage = "Welcome to the weather API"
)

// WeatherHandler object grouping all handler for http web server
type WeatherHandler struct {
	baseRouter *mux.Router
	subRouters map[string]*mux.Router
	wlogger    *logger.WeatherLogger
	storage    *storage.S3Storage
}

func NewWeatherHandler(logger *logger.WeatherLogger, s3 *storage.S3Storage, baseRouter *mux.Router) *WeatherHandler {
	wh := WeatherHandler{
		baseRouter: baseRouter,
		subRouters: make(map[string]*mux.Router, 1),
		wlogger:    logger,
		storage:    s3,
	}
	return &wh
}

//getOrCreateSubRouterByName return a router by name or create if it doesn't exist yet
func (wh *WeatherHandler) GetOrCreateSubRouterByName(name, prefix string) *mux.Router {
	if api := wh.subRouters[name]; api == nil {
		wh.subRouters[name] = wh.baseRouter.PathPrefix(prefix).Subrouter()
	}
	return wh.subRouters[name]
}

//RegisterBase base endpoint
func (wh *WeatherHandler) RegisterBase() {
	wh.baseRouter.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
		rw.Write([]byte(welcomeMessage))
	})
}

//RegisterApi health endpoint
func (wh *WeatherHandler) RegisterApi(version string) {
	api := wh.GetOrCreateSubRouterByName(apiRouterName, apiPrefix)

	api.HandleFunc("/health", func(rw http.ResponseWriter, r *http.Request) {
		rw.Header().Add(headers.ContentType, "application/json")
		json.NewEncoder(rw).Encode(map[string]interface{}{
			"ok":      true,
			"version": version,
		})
	})

	api.HandleFunc("/all", func(rw http.ResponseWriter, r *http.Request) {
		span, ctx := apm.StartSpan(r.Context(), "s3GetAllWeather", "custom")
		defer span.End()

		// application/stream+json
		// application/x-ndjson
		// text/event-stream
		rw.Header().Set(headers.ContentType, "text/plain")
		rw.Header().Set(headers.CacheControl, "no-cache")
		rw.Header().Set(headers.Connection, "keep-alive")

		// List all objects from a bucket-name with a matching prefix.
		wh.ResponseStream(rw, r, wh.storage.GetAll(ctx), func(enc *json.Encoder, obj storage.Streamable) {
			if o, ok := obj.(storage.WeatherFile); ok {
				fmt.Printf("name : %s\n", o.Name)
			}

			err := enc.Encode(obj)
			if err != nil {
				wh.wlogger.Sugar().Errorf("All encoding error %v\n", obj)
			}
		})
	})

	api.HandleFunc("/at/{atDate}", func(rw http.ResponseWriter, r *http.Request) {
		span, ctx := apm.StartSpan(r.Context(), "s3GetWeatherInfo", "custom")
		defer span.End()

		vars := mux.Vars(r)
		atDate, err := time.Parse(time.RFC3339, vars["atDate"])
		if err != nil {
			wh.wlogger.Error(fmt.Sprintf("AtDate parse invalid format %s", vars["atDate"]), zap.Error(err))
			rw.WriteHeader(http.StatusBadRequest)
		} else {
			wh.wlogger.Debug("AtDate GetObject", append(
				apmzap.TraceContext(ctx),
				zap.String("name", fmt.Sprintf("%s.json", atDate.Format(time.RFC3339))),
			)...)

			reader := wh.storage.GetAtDate(ctx, atDate)
			if reader == nil {
				rw.WriteHeader(http.StatusInternalServerError)
			}
			defer reader.Close()

			rw.Header().Add(headers.ContentType, "application/json")
			nb, err := io.Copy(rw, reader)
			if err != nil {
				wh.wlogger.Error("AtDate write response failed", zap.Error(err))
				rw.WriteHeader(http.StatusInternalServerError)
			} else {
				wh.wlogger.Debugf("AtDate write %d", []interface{}{nb}, apmzap.TraceContext(ctx)...)
			}
		}
	})
}

func (wh *WeatherHandler) ResponseStream(
	w http.ResponseWriter, r *http.Request, stream <-chan storage.Streamable, f func(enc *json.Encoder, obj storage.Streamable),
) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		wh.wlogger.Debug("Flusher cast error")
		http.NotFound(w, r)
		return
	}

	w.Header().Set(headers.TransferEncoding, "chunked")
	w.WriteHeader(http.StatusOK)
	flusher.Flush()

	enc := json.NewEncoder(w)

	cn := r.Context()
	for object := range stream {
		select {
		case <-cn.Done():
			wh.wlogger.Debug("Client stopped listening", zap.Error(cn.Err()))
			return
		default:
			f(enc, object)
			flusher.Flush()
		}
	}
}