package main

import (
	"fmt"
	_ "github.com/go-sql-driver/mysql"
	"github.com/gorilla/mux"
	"log"
	"net/http"
)

const DEBUG = true

func main() {
	err := setup()
	defer teardown()
	if err == nil {
		startServer()
	}
}

func setup() error {
	err := InitDb()
	if err != nil {
		return err
	}
	return nil
}

func teardown() {
	CloseDb()
}

func startServer() {
	port := "8001"
	r := mux.NewRouter()
	r.HandleFunc("/", showCharts).Methods("GET")
	r.HandleFunc("/data/", sendData).Methods("GET")
	r.HandleFunc("/", saveSnapshot).Methods("POST")
	http.Handle("/", r)
	fmt.Printf("Listening on port %s...\n", port)
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

func showCharts(w http.ResponseWriter, r *http.Request) {
	http.ServeFile(w, r, "charts.html")
}

func sendData(w http.ResponseWriter, r *http.Request) {
	records, err := getSnapshotRecordsFromDb(50)
	if err != nil {
		sendInternalError(fmt.Errorf("couldn't read rows from the database: %w", err), w, r)
		return
	}
	json, err := createJsonFromSnapshotRecords(records)
	if err != nil {
		sendInternalError(fmt.Errorf("couldn't create a json from the records: %w", err), w, r)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_, err = fmt.Fprintf(w, string(json))
	if err != nil {
		sendInternalError(err, w, r)
		return
	}
}

func saveSnapshot(w http.ResponseWriter, r *http.Request) {
	snapshotSub, err := createSnapshotSubFromJsonBodyStream(r.Body)
	if err != nil {
		sendInternalError(fmt.Errorf("couldn't create snapshot from JSON: %w", err), w, r)
	}
	err = writeSnapshotToDb(snapshotSub)
	if err != nil {
		sendInternalError(fmt.Errorf("couldn't submit snapshot into the database: %w", err), w, r)
	}
}

func sendInternalError(err error, w http.ResponseWriter, r *http.Request) {
	errorMessage := "Internal Server Error!"
	if DEBUG {
		errorMessage += fmt.Sprintf(" Happened during %s request for pattern '%s': %s",
			r.Method,
			r.URL,
			err.Error())
	}
	fmt.Println(errorMessage)
	http.Error(w, errorMessage, 500)
}