Add export to file (#58)

* Initial addition of a game exporter

* Fix snake state bug, remove test logs, fix final output line being empty

* Ignore test JSONL file

* Added explanation for design decision on the you key in SnakeResponse

* Adjust gitignore to be more generic

* Retain consistency in usage of pointer

* Re-word explanation to refer to requests instead of responses

* Remove unnecessary nil check

* Check error returned by WriteString

* Change file permissions for output file

* Initialise gameexporter regardless of whether output is requested

* Print error and exit if export to file fails

* Added another comment explaining reasoning around export checks

* Fixed broken test due to changed return type

.gitignore

@@ -5,3 +5,7 @@
 
 # General
 .DS_Store
+
+# Build and Output 
+/battlesnake
+*.jsonl

cli/commands/output.go

@@ -0,0 +1,86 @@
+package commands
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/BattlesnakeOfficial/rules/client"
+)
+
+type GameExporter struct {
+	game          client.Game
+	snakeRequests []client.SnakeRequest
+	winner        SnakeState
+	isDraw        bool
+}
+
+type result struct {
+	WinnerID   string `json:"winnerId"`
+	WinnerName string `json:"winnerName"`
+	IsDraw     bool   `json:"isDraw"`
+}
+
+func (ge *GameExporter) FlushToFile(filepath string, format string) error {
+	var formattedOutput []string
+	var formattingErr error
+
+	// TODO: Support more formats
+	if format == "JSONL" {
+		formattedOutput, formattingErr = ge.ConvertToJSON()
+	} else {
+		log.Fatalf("Invalid output format passed: %s", format)
+	}
+
+	if formattingErr != nil {
+		return formattingErr
+	}
+
+	f, err := os.OpenFile(filepath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	for _, line := range formattedOutput {
+		_, err := f.WriteString(fmt.Sprintf("%s\n", line))
+		if err != nil {
+			return err
+		}
+	}
+
+	log.Printf("Written %d lines of output to file: %s\n", len(formattedOutput), filepath)
+
+	return nil
+}
+
+func (ge *GameExporter) ConvertToJSON() ([]string, error) {
+	output := make([]string, 0)
+	serialisedGame, err := json.Marshal(ge.game)
+	if err != nil {
+		return output, err
+	}
+	output = append(output, string(serialisedGame))
+	for _, board := range ge.snakeRequests {
+		serialisedBoard, err := json.Marshal(board)
+		if err != nil {
+			return output, err
+		}
+		output = append(output, string(serialisedBoard))
+	}
+	serialisedResult, err := json.Marshal(result{
+		WinnerID:   ge.winner.ID,
+		WinnerName: ge.winner.Name,
+		IsDraw:     ge.isDraw,
+	})
+	if err != nil {
+		return output, err
+	}
+	output = append(output, string(serialisedResult))
+	return output, nil
+}
+
+func (ge *GameExporter) AddSnakeRequest(snakeRequest client.SnakeRequest) {
+	ge.snakeRequests = append(ge.snakeRequests, snakeRequest)
+}

cli/commands/play.go

@@ -9,6 +9,7 @@ import (
 	"math/rand"
 	"net/http"
 	"net/url"
+	"os"
 	"path"
 	"strconv"
 	"sync"
@@ -48,6 +49,7 @@ var ViewMap bool
 var Seed int64
 var TurnDelay int32
 var DebugRequests bool
+var Output string
 
 var FoodSpawnChance int32
 var MinimumFood int32
@@ -76,6 +78,7 @@ func init() {
 	playCmd.Flags().Int64VarP(&Seed, "seed", "r", time.Now().UTC().UnixNano(), "Random Seed")
 	playCmd.Flags().Int32VarP(&TurnDelay, "delay", "d", 0, "Turn Delay in Milliseconds")
 	playCmd.Flags().BoolVar(&DebugRequests, "debug-requests", false, "Log body of all requests sent")
+	playCmd.Flags().StringVarP(&Output, "output", "o", "", "File path to output game state to. Existing files will be overwritten")
 
 	playCmd.Flags().Int32Var(&FoodSpawnChance, "foodSpawnChance", 15, "Percentage chance of spawning a new food every round")
 	playCmd.Flags().Int32Var(&MinimumFood, "minimumFood", 1, "Minimum food to keep on the board every turn")
@@ -95,6 +98,14 @@ var run = func(cmd *cobra.Command, args []string) {
 
 	ruleset := getRuleset(Seed, snakeStates)
 	state := initializeBoardFromArgs(ruleset, snakeStates)
+	exportGame := Output != ""
+
+	gameExporter := GameExporter{
+		game:          createClientGame(ruleset),
+		snakeRequests: make([]client.SnakeRequest, 0),
+		winner:        SnakeState{},
+		isDraw:        false,
+	}
 
 	for v := false; !v; v, _ = ruleset.IsGameOver(state) {
 		Turn++
@@ -109,25 +120,54 @@ var run = func(cmd *cobra.Command, args []string) {
 		if TurnDelay > 0 {
 			time.Sleep(time.Duration(TurnDelay) * time.Millisecond)
 		}
+
+		if exportGame {
+			// The output file was designed in a way so that (nearly) every entry is equivalent to a valid API request.
+			// This is meant to help unlock further development of tools such as replaying a saved game by simply copying each line and sending it as a POST request.
+			// There was a design choice to be made here: the difference between SnakeRequest and BoardState is the `you` key.
+			// We could choose to either store the SnakeRequest of each snake OR to omit the `you` key OR fill the `you` key with one of the snakes
+			// In all cases the API request is technically non-compliant with how the actual API request should be.
+			// The third option (filling the `you` key with an arbitrary snake) is the closest to the actual API request that would need the least manipulation to
+			// be adjusted to look like an API call for a specific snake in the game.
+			snakeState := snakeStates[state.Snakes[0].ID]
+			snakeRequest := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+			gameExporter.AddSnakeRequest(snakeRequest)
+		}
 	}
 
+	isDraw := true
 	if GameType == "solo" {
 		log.Printf("[DONE]: Game completed after %v turns.", Turn)
+		if exportGame {
+			// These checks for exportGame are present to avoid vacuuming up RAM when an export is not requred.
+			gameExporter.winner = snakeStates[state.Snakes[0].ID]
+		}
 	} else {
-		var winner string
+		var winner SnakeState
-		isDraw := true
 		for _, snake := range state.Snakes {
+			snakeState := snakeStates[snake.ID]
 			if snake.EliminatedCause == rules.NotEliminated {
 				isDraw = false
-				winner = snakeStates[snake.ID].Name
+				winner = snakeState
 			}
-			sendEndRequest(ruleset, state, snakeStates[snake.ID], snakeStates)
+			sendEndRequest(ruleset, state, snakeState, snakeStates)
 		}
 
 		if isDraw {
 			log.Printf("[DONE]: Game completed after %v turns. It was a draw.", Turn)
 		} else {
-			log.Printf("[DONE]: Game completed after %v turns. %v is the winner.", Turn, winner)
+			log.Printf("[DONE]: Game completed after %v turns. %v is the winner.", Turn, winner.Name)
+		}
+		if exportGame {
+			gameExporter.winner = winner
+		}
+	}
+
+	if exportGame {
+		err := gameExporter.FlushToFile(Output, "JSONL")
+		if err != nil {
+			log.Printf("[WARN]: Unable to export game. Reason: %v\n", err.Error())
+			os.Exit(1)
 		}
 	}
 }
@@ -204,7 +244,8 @@ func initializeBoardFromArgs(ruleset rules.Ruleset, snakeStates map[string]Snake
 	}
 
 	for _, snakeState := range snakeStates {
-		requestBody := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+		snakeRequest := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+		requestBody := serialiseSnakeRequest(snakeRequest)
 		u, _ := url.ParseRequestURI(snakeState.URL)
 		u.Path = path.Join(u.Path, "start")
 		if DebugRequests {
@@ -267,7 +308,8 @@ func createNextBoardState(ruleset rules.Ruleset, state *rules.BoardState, snakeS
 }
 
 func getMoveForSnake(ruleset rules.Ruleset, state *rules.BoardState, snakeState SnakeState, snakeStates map[string]SnakeState) rules.SnakeMove {
-	requestBody := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+	snakeRequest := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+	requestBody := serialiseSnakeRequest(snakeRequest)
 	u, _ := url.ParseRequestURI(snakeState.URL)
 	u.Path = path.Join(u.Path, "move")
 	if DebugRequests {
@@ -297,7 +339,8 @@ func getMoveForSnake(ruleset rules.Ruleset, state *rules.BoardState, snakeState
 }
 
 func sendEndRequest(ruleset rules.Ruleset, state *rules.BoardState, snakeState SnakeState, snakeStates map[string]SnakeState) {
-	requestBody := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+	snakeRequest := getIndividualBoardStateForSnake(state, snakeState, snakeStates, ruleset)
+	requestBody := serialiseSnakeRequest(snakeRequest)
 	u, _ := url.ParseRequestURI(snakeState.URL)
 	u.Path = path.Join(u.Path, "end")
 	if DebugRequests {
@@ -309,7 +352,7 @@ func sendEndRequest(ruleset rules.Ruleset, state *rules.BoardState, snakeState S
 	}
 }
 
-func getIndividualBoardStateForSnake(state *rules.BoardState, snakeState SnakeState, snakeStates map[string]SnakeState, ruleset rules.Ruleset) []byte {
+func getIndividualBoardStateForSnake(state *rules.BoardState, snakeState SnakeState, snakeStates map[string]SnakeState, ruleset rules.Ruleset) client.SnakeRequest {
 	var youSnake rules.Snake
 	for _, snk := range state.Snakes {
 		if snakeState.ID == snk.ID {
@@ -318,7 +361,25 @@ func getIndividualBoardStateForSnake(state *rules.BoardState, snakeState SnakeSt
 		}
 	}
 	request := client.SnakeRequest{
-		Game: client.Game{ID: GameId, Timeout: Timeout, Ruleset: client.Ruleset{
+		Game:  createClientGame(ruleset),
+		Turn:  Turn,
+		Board: convertStateToBoard(state, snakeStates),
+		You:   convertRulesSnake(youSnake, snakeStates[youSnake.ID]),
+	}
+	return request
+}
+
+func serialiseSnakeRequest(snakeRequest client.SnakeRequest) []byte {
+	requestJSON, err := json.Marshal(snakeRequest)
+	if err != nil {
+		log.Panic("[PANIC]: Error Marshalling JSON from State")
+		panic(err)
+	}
+	return requestJSON
+}
+
+func createClientGame(ruleset rules.Ruleset) client.Game {
+	return client.Game{ID: GameId, Timeout: Timeout, Ruleset: client.Ruleset{
 		Name:    ruleset.Name(),
 		Version: "cli", // TODO: Use GitHub Release Version
 		Settings: client.RulesetSettings{
@@ -335,23 +396,7 @@ func getIndividualBoardStateForSnake(state *rules.BoardState, snakeState SnakeSt
 				SharedLength:        true,
 			},
 		},
-		}},
+	}}
-		Turn: Turn,
-		Board: client.Board{
-			Height:  state.Height,
-			Width:   state.Width,
-			Food:    client.CoordFromPointArray(state.Food),
-			Hazards: client.CoordFromPointArray(state.Hazards),
-			Snakes:  convertRulesSnakes(state.Snakes, snakeStates),
-		},
-		You: convertRulesSnake(youSnake, snakeStates[youSnake.ID]),
-	}
-	requestJSON, err := json.Marshal(request)
-	if err != nil {
-		log.Panic("[PANIC]: Error Marshalling JSON from State")
-		panic(err)
-	}
-	return requestJSON
 }
 
 func convertRulesSnake(snake rules.Snake, snakeState SnakeState) client.Snake {
@@ -383,6 +428,16 @@ func convertRulesSnakes(snakes []rules.Snake, snakeStates map[string]SnakeState)
 	return a
 }
 
+func convertStateToBoard(state *rules.BoardState, snakeStates map[string]SnakeState) client.Board {
+	return client.Board{
+		Height:  state.Height,
+		Width:   state.Width,
+		Food:    client.CoordFromPointArray(state.Food),
+		Hazards: client.CoordFromPointArray(state.Hazards),
+		Snakes:  convertRulesSnakes(state.Snakes, snakeStates),
+	}
+}
+
 func buildSnakesFromOptions() map[string]SnakeState {
 	bodyChars := []rune{'■', '⌀', '●', '⍟', '◘', '☺', '□', '☻'}
 	var numSnakes int

cli/commands/play_test.go

@@ -35,7 +35,8 @@ func TestGetIndividualBoardStateForSnake(t *testing.T) {
 		s1State.ID: s1State,
 		s2State.ID: s2State,
 	}
-	requestBody := getIndividualBoardStateForSnake(state, s1State, snakeStates, &rules.StandardRuleset{})
+	snakeRequest := getIndividualBoardStateForSnake(state, s1State, snakeStates, &rules.StandardRuleset{})
+	requestBody := serialiseSnakeRequest(snakeRequest)
 
 	test.RequireJSONMatchesFixture(t, "testdata/snake_request_body.json", string(requestBody))
 }