package app

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"log/slog"
	"time"

	"galaxy/postgres"
	"galaxy/redisconn"

	"galaxy/gamemaster/internal/adapters/postgres/migrations"
	"galaxy/gamemaster/internal/api/internalhttp"
	"galaxy/gamemaster/internal/config"
	"galaxy/gamemaster/internal/telemetry"

	"github.com/redis/go-redis/v9"
)

// Runtime owns the runnable Game Master process plus the cleanup
// functions that release runtime resources after shutdown.
type Runtime struct {
	cfg config.Config

	app *App

	wiring *wiring

	internalServer *internalhttp.Server

	cleanupFns []func() error
}

// NewRuntime constructs the runnable Game Master process from cfg.
//
// The runtime opens one shared `*redis.Client`, one `*sql.DB`, and one
// OpenTelemetry runtime; all are released in reverse construction order
// on shutdown. Embedded goose migrations apply synchronously after the
// PostgreSQL pool is opened and pinged, before any listener is constructed.
func NewRuntime(ctx context.Context, cfg config.Config, logger *slog.Logger) (*Runtime, error) {
	if ctx == nil {
		return nil, errors.New("new gamemaster runtime: nil context")
	}
	if err := cfg.Validate(); err != nil {
		return nil, fmt.Errorf("new gamemaster runtime: %w", err)
	}
	if logger == nil {
		logger = slog.Default()
	}

	runtime := &Runtime{
		cfg: cfg,
	}

	cleanupOnError := func(err error) (*Runtime, error) {
		if cleanupErr := runtime.Close(); cleanupErr != nil {
			return nil, fmt.Errorf("%w; cleanup: %w", err, cleanupErr)
		}

		return nil, err
	}

	telemetryRuntime, err := telemetry.NewProcess(ctx, telemetry.ProcessConfig{
		ServiceName:          cfg.Telemetry.ServiceName,
		TracesExporter:       cfg.Telemetry.TracesExporter,
		MetricsExporter:      cfg.Telemetry.MetricsExporter,
		TracesProtocol:       cfg.Telemetry.TracesProtocol,
		MetricsProtocol:      cfg.Telemetry.MetricsProtocol,
		StdoutTracesEnabled:  cfg.Telemetry.StdoutTracesEnabled,
		StdoutMetricsEnabled: cfg.Telemetry.StdoutMetricsEnabled,
	}, logger)
	if err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: telemetry: %w", err))
	}
	runtime.cleanupFns = append(runtime.cleanupFns, func() error {
		shutdownCtx, cancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
		defer cancel()
		return telemetryRuntime.Shutdown(shutdownCtx)
	})

	redisClient := newRedisClient(cfg.Redis)
	if err := instrumentRedisClient(redisClient, telemetryRuntime); err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: %w", err))
	}
	runtime.cleanupFns = append(runtime.cleanupFns, func() error {
		err := redisClient.Close()
		if errors.Is(err, redis.ErrClosed) {
			return nil
		}
		return err
	})
	if err := pingRedis(ctx, cfg.Redis, redisClient); err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: %w", err))
	}

	pgPool, err := postgres.OpenPrimary(ctx, cfg.Postgres.Conn,
		postgres.WithTracerProvider(telemetryRuntime.TracerProvider()),
		postgres.WithMeterProvider(telemetryRuntime.MeterProvider()),
	)
	if err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: open postgres: %w", err))
	}
	runtime.cleanupFns = append(runtime.cleanupFns, pgPool.Close)
	unregisterPGStats, err := postgres.InstrumentDBStats(pgPool,
		postgres.WithMeterProvider(telemetryRuntime.MeterProvider()),
	)
	if err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: instrument postgres: %w", err))
	}
	runtime.cleanupFns = append(runtime.cleanupFns, func() error {
		return unregisterPGStats()
	})
	if err := postgres.Ping(ctx, pgPool, cfg.Postgres.Conn.OperationTimeout); err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: ping postgres: %w", err))
	}
	if err := postgres.RunMigrations(ctx, pgPool, migrations.FS(), "."); err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: run postgres migrations: %w", err))
	}

	wiring, err := newWiring(cfg, redisClient, pgPool, time.Now, logger, telemetryRuntime)
	if err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: wiring: %w", err))
	}
	runtime.wiring = wiring
	runtime.cleanupFns = append(runtime.cleanupFns, wiring.close)

	probe := newReadinessProbe(pgPool, redisClient, cfg)

	internalServer, err := internalhttp.NewServer(internalhttp.Config{
		Addr:              cfg.InternalHTTP.Addr,
		ReadHeaderTimeout: cfg.InternalHTTP.ReadHeaderTimeout,
		ReadTimeout:       cfg.InternalHTTP.ReadTimeout,
		WriteTimeout:      cfg.InternalHTTP.WriteTimeout,
		IdleTimeout:       cfg.InternalHTTP.IdleTimeout,
	}, internalhttp.Dependencies{
		Logger:                logger,
		Telemetry:             telemetryRuntime,
		Readiness:             probe,
		RuntimeRecords:        wiring.runtimeRecords,
		RegisterRuntime:       wiring.registerRuntimeSvc,
		ForceNextTurn:         wiring.forceNextTurnSvc,
		StopRuntime:           wiring.stopRuntimeSvc,
		PatchRuntime:          wiring.patchRuntimeSvc,
		BanishRace:            wiring.banishRaceSvc,
		InvalidateMemberships: wiring.membershipCache,
		GameLiveness:          wiring.livenessSvc,
		EngineVersions:        wiring.engineVersionSvc,
		CommandExecute:        wiring.commandExecuteSvc,
		PutOrders:             wiring.orderPutSvc,
		GetReport:             wiring.reportGetSvc,
	})
	if err != nil {
		return cleanupOnError(fmt.Errorf("new gamemaster runtime: internal HTTP server: %w", err))
	}
	runtime.internalServer = internalServer

	runtime.app = New(cfg,
		internalServer,
		wiring.schedulerTicker,
		wiring.healthEventsConsumer,
	)

	return runtime, nil
}

// InternalServer returns the internal HTTP server owned by runtime. It is
// primarily exposed for tests; production code should not depend on it.
func (runtime *Runtime) InternalServer() *internalhttp.Server {
	if runtime == nil {
		return nil
	}

	return runtime.internalServer
}

// Run serves the internal HTTP listener until ctx is canceled or one
// component fails.
func (runtime *Runtime) Run(ctx context.Context) error {
	if ctx == nil {
		return errors.New("run gamemaster runtime: nil context")
	}
	if runtime == nil {
		return errors.New("run gamemaster runtime: nil runtime")
	}
	if runtime.app == nil {
		return errors.New("run gamemaster runtime: nil app")
	}

	return runtime.app.Run(ctx)
}

// Close releases every runtime dependency in reverse construction order.
// Close is safe to call multiple times.
func (runtime *Runtime) Close() error {
	if runtime == nil {
		return nil
	}

	var joined error
	for index := len(runtime.cleanupFns) - 1; index >= 0; index-- {
		if err := runtime.cleanupFns[index](); err != nil {
			joined = errors.Join(joined, err)
		}
	}
	runtime.cleanupFns = nil

	return joined
}

// readinessProbe pings every steady-state dependency the listener
// guards: PostgreSQL primary and Redis master.
type readinessProbe struct {
	pgPool      *sql.DB
	redisClient *redis.Client

	postgresTimeout time.Duration
	redisTimeout    time.Duration
}

func newReadinessProbe(pgPool *sql.DB, redisClient *redis.Client, cfg config.Config) *readinessProbe {
	return &readinessProbe{
		pgPool:          pgPool,
		redisClient:     redisClient,
		postgresTimeout: cfg.Postgres.Conn.OperationTimeout,
		redisTimeout:    cfg.Redis.Conn.OperationTimeout,
	}
}

// Check pings PostgreSQL and Redis. The first failing dependency aborts
// the check so callers see a single, actionable error.
func (probe *readinessProbe) Check(ctx context.Context) error {
	if err := postgres.Ping(ctx, probe.pgPool, probe.postgresTimeout); err != nil {
		return err
	}
	return redisconn.Ping(ctx, probe.redisClient, probe.redisTimeout)
}