Rename forestrie mmrblobs to massifs (#178)

* Rename forestrie mmrblobs to massifs

re: AB#9461

---------

Co-authored-by: jgough <[email protected]>

massifs/bloblast.go

@@ -0,0 +1,168 @@
+package massifs
+
+import (
+	"context"
+	"errors"
+
+	azStorageBlob "github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
+	"github.com/datatrails/go-datatrails-common/azblob"
+)
+
+var (
+	ErrBlobNotFound = errors.New("the blob was not found")
+)
+
+// LastPrefixedBlob returns the details of last blob found under the prefix path
+// And the total number of blobs under the path.
+func LastPrefixedBlob(
+	ctx context.Context, store logBlobReader, blobPrefixPath string,
+	opts ...azblob.Option,
+) (LogBlobContext, uint64, error) {
+
+	bc := LogBlobContext{}
+
+	var foundCount uint64
+
+	opts = append([]azblob.Option{azblob.WithListPrefix(blobPrefixPath)}, opts...)
+
+	var marker azblob.ListMarker
+	for {
+		r, err := store.List(ctx, append(opts, azblob.WithListMarker(marker))...)
+		if err != nil {
+			return bc, foundCount, err
+		}
+		if len(r.Items) == 0 {
+			return bc, foundCount, nil
+		}
+
+		foundCount += uint64(len(r.Items))
+
+		// we want the _last_ listed, so we just keep over-writing
+		i := r.Items[len(r.Items)-1]
+		bc.ETag = *i.Properties.Etag
+		bc.LastModified = *i.Properties.LastModified
+		if i.Properties.ContentLength != nil {
+			bc.ContentLength = *i.Properties.ContentLength
+		}
+		bc.BlobPath = *i.Name
+		marker = r.Marker
+		if marker == nil || *marker == "" {
+			bc.Tags = listResponseTags(i.BlobTags)
+			break
+		}
+	}
+
+	return bc, foundCount, nil
+}
+
+// FirstPrefixedBlob returns the first blob found under the prefix path
+func FirstPrefixedBlob(
+	ctx context.Context, store logBlobReader, blobPrefixPath string,
+	opts ...azblob.Option,
+) (LogBlobContext, error) {
+
+	bc := LogBlobContext{}
+
+	opts = append([]azblob.Option{
+		azblob.WithListPrefix(blobPrefixPath),
+		azblob.WithListMaxResults(1),
+	}, opts...)
+
+	r, err := store.List(ctx, opts...)
+	if err != nil {
+		return bc, err
+	}
+	if len(r.Items) == 0 {
+		return bc, ErrBlobNotFound
+	}
+
+	i := r.Items[0]
+	bc.ETag = *i.Properties.Etag
+	bc.LastModified = *i.Properties.LastModified
+	if i.Properties.ContentLength != nil {
+		bc.ContentLength = *i.Properties.ContentLength
+	}
+	bc.BlobPath = *i.Name
+	bc.Tags = listResponseTags(r.Items[0].BlobTags)
+
+	return bc, nil
+}
+
+// PrefixedBlobLastN returns contexts for the last n blobs under the provided prefix.
+//
+// The number of items in the returned tail is always min(massifCount, n)
+// Un filled items are zero valued.
+func PrefixedBlobLastN(
+	ctx context.Context,
+	store logBlobReader,
+	blobPrefixPath string,
+	n int,
+	opts ...azblob.Option,
+) ([]LogBlobContext, uint64, error) {
+
+	opts = append([]azblob.Option{azblob.WithListPrefix(blobPrefixPath)}, opts...)
+
+	tail := make([]LogBlobContext, n)
+
+	var foundCount uint64
+
+	var marker azblob.ListMarker
+	for {
+		r, err := store.List(ctx, append(opts, azblob.WithListMarker(marker))...)
+		if err != nil {
+			return tail, foundCount, err
+		}
+		if len(r.Items) == 0 {
+			return tail, foundCount, nil
+		}
+
+		foundCount += uint64(len(r.Items))
+
+		// The stale items are those from the previous round that can be
+		// replaced by the current. Typically, len(r.Items) will be greater than
+		// n and so it will be n. Note that stale is > 0 here due to the len 0
+		// check above.
+		stale := min(len(r.Items), n)
+
+		// copy the items *after* the stale items to the front.
+		if stale != n {
+			copy(tail, tail[n-stale-1:])
+		}
+
+		for i := 0; i < stale; i++ {
+
+			// stale is also the count of items we are taking from items.
+
+			it := r.Items[len(r.Items)-stale+i]
+			tail[n-stale+i].ETag = *it.Properties.Etag
+			tail[n-stale+i].LastModified = *it.Properties.LastModified
+			if it.Properties.ContentLength != nil {
+				tail[n-stale+i].ContentLength = *it.Properties.ContentLength
+			}
+			tail[n-stale+i].BlobPath = *it.Name
+			tail[n-stale+i].Tags = listResponseTags(it.BlobTags)
+		}
+
+		marker = r.Marker
+		if marker == nil || *marker == "" {
+			break
+		}
+	}
+
+	// Note massifIndex will be zero, the id of the first massif blob
+	return tail, foundCount, nil
+}
+
+func listResponseTags(blobTags *azStorageBlob.BlobTags) map[string]string {
+	if blobTags == nil {
+		return nil
+	}
+	tags := map[string]string{}
+	for _, tag := range blobTags.BlobTagSet {
+		if tag.Key == nil || tag.Value == nil {
+			continue
+		}
+		tags[*tag.Key] = *tag.Value
+	}
+	return tags
+}