mlbstats/cmd/subscribe.go

/*
Copyright © 2024,2025 filifa

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package cmd

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"time"

	"github.com/evanphx/json-patch/v5"
	"github.com/gorilla/websocket"
	"github.com/spf13/cobra"
	"scm.dairydemon.net/filifa/mlbstats/api"
)

var gamePk int32

func extractPatches(resp []byte) ([]jsonpatch.Patch, error) {
	var patches []jsonpatch.Patch

	var objs []map[string]jsonpatch.Patch
	err := json.Unmarshal(resp, &objs)
	if err != nil {
		return patches, err
	}

	for _, obj := range objs {
		patch := obj["diff"]
		patches = append(patches, patch)
	}

	return patches, nil
}

func patch(body []byte, client *api.APIClient) ([]byte, error) {
	var v any
	err := json.Unmarshal(body, &v)
	if err != nil {
		return body, err
	}

	vobj := v.(map[string]any)
	metaData := vobj["metaData"].(map[string]any)
	timestamp := metaData["timeStamp"]

	req := client.GameAPI.LiveGameDiffPatchV1(context.Background(), gamePk)
	req = req.StartTimecode(timestamp)

	resp, err := req.Execute()
	if err != nil {
		return body, err
	}

	diffPatch, err := io.ReadAll(resp.Body)
	if err != nil {
		return body, err
	}

	patches, err := extractPatches(diffPatch)
	if err != nil {
		return body, err
	}

	for _, patch := range patches {
		body, err = patch.Apply(body)
		if err != nil {
			return body, err
		}
	}

	return body, nil
}

func newWebsocket(gamePk int32) (*gamedayWebsocket, <-chan error, error) {
	ws, err := newGamedayWebsocket(gamePk)
	if err != nil {
		return nil, nil, err
	}

	ch := make(chan error)
	go ws.keepAlive(10*time.Second, ch)

	return ws, ch, nil
}

func handleUnexpectedClose(body []byte, client *api.APIClient) (*gamedayWebsocket, error) {
	ws, _, err := newWebsocket(gamePk)
	if err != nil {
		return nil, err
	}

	req := client.GameAPI.LiveGameV1(context.Background(), gamePk)
	resp, err := req.Execute()
	if err != nil {
		return ws, err
	}

	body, err = io.ReadAll(resp.Body)
	return ws, err
}

func updateFeed(body []byte, ws *gamedayWebsocket, client *api.APIClient) ([]byte, error) {
	var p push
	err := ws.ReadJSON(&p)
	if websocket.IsUnexpectedCloseError(err, GameFinalCode, GameUnavailableCode) {
		log.Println(err)

		newWs, err := handleUnexpectedClose(body, client)
		if err != nil {
			return body, err
		}

		*ws = *newWs
		return body, nil
	} else if err != nil {
		return body, err
	}

	body, err = patch(body, client)
	if err != nil {
		req := client.GameAPI.LiveGameV1(context.Background(), gamePk)
		resp, err := req.Execute()
		if err != nil {
			return body, err
		}

		body, err = io.ReadAll(resp.Body)
		if err != nil {
			return body, err
		}
	}

	return body, nil
}

func subscribe(cmd *cobra.Command, args []string) {
	ws, _, err := newWebsocket(gamePk)
	if err != nil {
		log.Fatal(err)
	}
	defer ws.Close()

	req := statsAPIClient.GameAPI.LiveGameV1(context.Background(), gamePk)

	resp, err := req.Execute()
	if err != nil {
		log.Fatal(err)
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
	}

	for {
		fmt.Println(string(body))

		body, err = updateFeed(body, ws, statsAPIClient)
		if err != nil {
			log.Fatal(err)
		}
	}
}

// subscribeCmd represents the subscribe command
var subscribeCmd = &cobra.Command{
	Use:   "subscribe -g [gamePk]",
	Short: "Output live game data",
	Long: `Output live game data.

Establish a websocket connection with ws.statsapi.mlb.com and output JSON with
live updates of a game.`,
	Args: cobra.NoArgs,
	Run:  subscribe,
}

func init() {
	rootCmd.AddCommand(subscribeCmd)

	// Here you will define your flags and configuration settings.

	// Cobra supports Persistent Flags which will work for this command
	// and all subcommands, e.g.:
	// subscribeCmd.PersistentFlags().String("foo", "", "A help for foo")

	// Cobra supports local flags which will only run when this command
	// is called directly, e.g.:
	subscribeCmd.Flags().Int32VarP(&gamePk, "gamePk", "g", 0, "game PK")
	subscribeCmd.MarkFlagRequired("gamePk")
}