package modules

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strconv"

	"github.com/filecoin-project/dagstore"
	"go.uber.org/fx"
	"golang.org/x/xerrors"

	"github.com/filecoin-project/go-fil-markets/retrievalmarket"

	mdagstore "github.com/filecoin-project/lotus/markets/dagstore"
	"github.com/filecoin-project/lotus/node/config"
	"github.com/filecoin-project/lotus/node/modules/dtypes"
	"github.com/filecoin-project/lotus/node/repo"
)

const (
	EnvDAGStoreCopyConcurrency = "LOTUS_DAGSTORE_COPY_CONCURRENCY"
	DefaultDAGStoreDir         = "dagstore"
)

// NewMinerAPI creates a new MinerAPI adaptor for the dagstore mounts.
func NewMinerAPI(lc fx.Lifecycle, r repo.LockedRepo, pieceStore dtypes.ProviderPieceStore, rpn retrievalmarket.RetrievalProviderNode) (mdagstore.MinerAPI, error) {
	cfg, err := extractDAGStoreConfig(r)
	if err != nil {
		return nil, err
	}

	// caps the amount of concurrent calls to the storage, so that we don't
	// spam it during heavy processes like bulk migration.
	if v, ok := os.LookupEnv("LOTUS_DAGSTORE_MOUNT_CONCURRENCY"); ok {
		concurrency, err := strconv.Atoi(v)
		if err == nil {
			cfg.MaxConcurrencyStorageCalls = concurrency
		}
	}

	mountApi := mdagstore.NewMinerAPI(pieceStore, rpn, cfg.MaxConcurrencyStorageCalls)
	ready := make(chan error, 1)
	pieceStore.OnReady(func(err error) {
		ready <- err
	})
	lc.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			if err := <-ready; err != nil {
				return fmt.Errorf("aborting dagstore start; piecestore failed to start: %s", err)
			}
			return mountApi.Start(ctx)
		},
		OnStop: func(context.Context) error {
			return nil
		},
	})

	return mountApi, nil
}

// DAGStore constructs a DAG store using the supplied minerAPI, and the
// user configuration. It returns both the DAGStore and the Wrapper suitable for
// passing to markets.
func DAGStore(lc fx.Lifecycle, r repo.LockedRepo, minerAPI mdagstore.MinerAPI) (*dagstore.DAGStore, *mdagstore.Wrapper, error) {
	cfg, err := extractDAGStoreConfig(r)
	if err != nil {
		return nil, nil, err
	}

	// fall back to default root directory if not explicitly set in the config.
	if cfg.RootDir == "" {
		cfg.RootDir = filepath.Join(r.Path(), DefaultDAGStoreDir)
	}

	v, ok := os.LookupEnv(EnvDAGStoreCopyConcurrency)
	if ok {
		concurrency, err := strconv.Atoi(v)
		if err == nil {
			cfg.MaxConcurrentReadyFetches = concurrency
		}
	}

	dagst, w, err := mdagstore.NewDAGStore(cfg, minerAPI)
	if err != nil {
		return nil, nil, xerrors.Errorf("failed to create DAG store: %w", err)
	}

	lc.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			return w.Start(ctx)
		},
		OnStop: func(context.Context) error {
			return w.Close()
		},
	})

	return dagst, w, nil
}

func extractDAGStoreConfig(r repo.LockedRepo) (config.DAGStoreConfig, error) {
	cfg, err := r.Config()
	if err != nil {
		return config.DAGStoreConfig{}, xerrors.Errorf("could not load config: %w", err)
	}
	mcfg, ok := cfg.(*config.StorageMiner)
	if !ok {
		return config.DAGStoreConfig{}, xerrors.Errorf("config not expected type; expected config.StorageMiner, got: %T", cfg)
	}
	return mcfg.DAGStore, nil
}