[#1] Add '-f' flag to overwrite local cache

Sometimes multiple environments have blockchains with
the same magic number. In this case, user should not
reuse cached chain, because cache contains magic number
to identify different chains. With new '-f' flag user
will be able to repopulate cache with new data for the
chain with the same magic number.

Signed-off-by: Alex Vanin <a.vanin@yadro.com>

explorer.go

@@ -57,7 +57,7 @@ func explorer(c *cli.Context) (err error) {
 	}
 
 	endpoint := c.String(endpointFlagKey)
-	blockchain, err := chain.Open(ctx, cacheDir, endpoint)
+	blockchain, err := chain.Open(ctx, cacheDir, endpoint, false)
 	if err != nil {
 		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
 	}

flags.go

@@ -21,6 +21,7 @@ const (
 	workersFlagKey            = "workers"
 	disableProgressBarFlagKey = "disable-progress-bar"
 	stutterThresholdFlagKey   = "threshold"
+	forceCacheRewriteKey      = "force"
 )
 
 var (
@@ -78,6 +79,12 @@ var (
 		Usage:   "duration limit between block timestamps",
 		Value:   20 * time.Second,
 	}
+
+	forceCacheRewriteFlag = &cli.BoolFlag{
+		Name:    forceCacheRewriteKey,
+		Aliases: []string{"f"},
+		Usage:   "force blockchain cache rewrite",
+	}
 )
 
 func parseNotifications(notifications []string, cli *rpcclient.Client) (map[string]*util.Uint160, error) {

internal/chain/chain.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/binary"
 	"fmt"
+	"os"
 	"path"
 	"strconv"
 
@@ -27,7 +28,7 @@ var (
 	logsBucket   = []byte("logs")
 )
 
-func Open(ctx context.Context, dir, endpoint string) (*Chain, error) {
+func Open(ctx context.Context, dir, endpoint string, rewrite bool) (*Chain, error) {
 	cli, err := rpcclient.New(ctx, endpoint, rpcclient.Options{})
 	if err != nil {
 		return nil, fmt.Errorf("rpc connection: %w", err)
@@ -44,6 +45,9 @@ func Open(ctx context.Context, dir, endpoint string) (*Chain, error) {
 	}
 
 	dbPath := path.Join(dir, strconv.Itoa(int(v.Protocol.Network))+".db")
+	if rewrite {
+		_ = os.Remove(dbPath) // ignore error if file does not exist, etc.
+	}
 
 	db, err := bbolt.Open(dbPath, 0600, nil)
 	if err != nil {

main.go

@@ -35,6 +35,7 @@ func main() {
 					cacheFlag,
 					workersFlag,
 					disableProgressBarFlag,
+					forceCacheRewriteFlag,
 				},
 			},
 			{
@@ -84,7 +85,7 @@ func monza(c *cli.Context) (err error) {
 		}
 	}
 
-	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey))
+	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey), c.Bool(forceCacheRewriteKey))
 	if err != nil {
 		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
 	}

stutter.go

@@ -25,7 +25,7 @@ func stutter(c *cli.Context) (err error) {
 		}
 	}
 
-	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey))
+	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey), false)
 	if err != nil {
 		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
 	}