package blockdag

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

	"github.com/daglabs/btcd/dagconfig"
	"github.com/daglabs/btcd/database"
	_ "github.com/daglabs/btcd/database/ffldb"
	"github.com/daglabs/btcd/txscript"
	"github.com/daglabs/btcd/wire"
)

const (
	// testDbType is the database backend type to use for the tests.
	testDbType = "ffldb"

	// testDbRoot is the root directory used to create all test databases.
	testDbRoot = "testdbs"

	// blockDataNet is the expected network in the test block data.
	blockDataNet = wire.MainNet
)

// isSupportedDbType returns whether or not the passed database type is
// currently supported.
func isSupportedDbType(dbType string) bool {
	supportedDrivers := database.SupportedDrivers()
	for _, driver := range supportedDrivers {
		if dbType == driver {
			return true
		}
	}

	return false
}

// filesExists returns whether or not the named file or directory exists.
func fileExists(name string) bool {
	if _, err := os.Stat(name); err != nil {
		if os.IsNotExist(err) {
			return false
		}
	}
	return true
}

// DAGSetup is used to create a new db and chain instance with the genesis
// block already inserted.  In addition to the new chain instance, it returns
// a teardown function the caller should invoke when done testing to clean up.
func DAGSetup(dbName string, params *dagconfig.Params) (*BlockDAG, func(), error) {
	if !isSupportedDbType(testDbType) {
		return nil, nil, fmt.Errorf("unsupported db type %v", testDbType)
	}

	// Handle memory database specially since it doesn't need the disk
	// specific handling.
	var db database.DB
	var teardown func()
	// Create the root directory for test databases.
	if !fileExists(testDbRoot) {
		if err := os.MkdirAll(testDbRoot, 0700); err != nil {
			err := fmt.Errorf("unable to create test db "+
				"root: %v", err)
			return nil, nil, err
		}
	}

	// Create a new database to store the accepted blocks into.
	dbPath := filepath.Join(testDbRoot, dbName)
	_ = os.RemoveAll(dbPath)
	ndb, err := database.Create(testDbType, dbPath, blockDataNet)
	if err != nil {
		return nil, nil, fmt.Errorf("error creating db: %v", err)
	}
	db = ndb

	// Setup a teardown function for cleaning up.  This function is
	// returned to the caller to be invoked when it is done testing.
	teardown = func() {
		db.Close()
		os.RemoveAll(dbPath)
		os.RemoveAll(testDbRoot)
	}

	// Copy the chain params to ensure any modifications the tests do to
	// the chain parameters do not affect the global instance.
	paramsCopy := *params

	// Create the DAG instance.
	dag, err := New(&Config{
		DB:          db,
		DAGParams:   &paramsCopy,
		Checkpoints: nil,
		TimeSource:  NewMedianTime(),
		SigCache:    txscript.NewSigCache(1000),
	})
	if err != nil {
		teardown()
		err := fmt.Errorf("failed to create dag instance: %v", err)
		return nil, nil, err
	}
	return dag, teardown, nil
}