Add different data providers and improve docs

This adds support for switching between in-memory, local filesystem, s3
or sqlite.

stores/aws/documents.go

@@ -0,0 +1,71 @@
+package aws
+
+import (
+	"bytes"
+	"context"
+	"excalidraw-complete/core"
+	"fmt"
+	"io/ioutil"
+	"log"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/oklog/ulid/v2"
+)
+
+type documentStore struct {
+	s3Client *s3.Client
+	bucket   string // Name of the S3 bucket
+}
+
+func NewDocumentStore(bucketName string) core.DocumentStore {
+	cfg, err := config.LoadDefaultConfig(context.TODO())
+	if err != nil {
+		log.Fatalf("unable to load SDK config, %v", err)
+	}
+
+	s3Client := s3.NewFromConfig(cfg)
+
+	return &documentStore{
+		s3Client: s3Client,
+		bucket:   bucketName,
+	}
+}
+
+func (s *documentStore) FindID(ctx context.Context, id string) (*core.Document, error) {
+	resp, err := s.s3Client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(id),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to get document with id %s: %v", id, err)
+	}
+	defer resp.Body.Close()
+
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read document data: %v", err)
+	}
+
+	document := core.Document{
+		Data: *bytes.NewBuffer(data),
+	}
+
+	return &document, nil
+}
+
+func (s *documentStore) Create(ctx context.Context, document *core.Document) (string, error) {
+	id := ulid.Make().String()
+
+	_, err := s.s3Client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(id),
+		Body:   bytes.NewReader(document.Data.Bytes()),
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to upload document: %v", err)
+	}
+
+	return id, nil
+}