Implement basic layout of FAT-107

107/DataStoreBuilder.js

@@ -0,0 +1,134 @@
+const fctUtil = require('factom/src/util');
+
+class DataStoreBuilder {
+    constructor(buffer) {
+
+        //set up defaults
+        this._namespace = [];
+
+        this._buffer = buffer;
+        this._size = buffer.length;
+
+        //calculate the hash of the buffer for the 1st external ID
+        this._bufferHash = fctUtil.sha256d(buffer);
+    }
+
+    compression(format) {
+
+        //must be one of "zlib" or "gzip"
+
+        //compress the buffer
+        this._buffer = compress(this._buffer);
+
+        //construct the compression object, including the length of the compressed buffer
+        this._compression = {
+            format,
+            size: this._buffer.length
+        }
+    }
+
+    namespace(name, encoding) {
+        //validate encoding string if it is present
+
+        this._namespace.push({name, encoding});
+    }
+
+    metadata(metadata) {
+        this._metadata = metadata;
+    }
+
+    build() {
+        //validate for buffer missing? (what does spec say?)
+
+        return new DataStore(this);
+    }
+}
+
+const {Entry, Chain} = require('factom');
+
+class DataStore {
+    constructor(builder) {
+        if (!builder instanceof DataStoreBuilder) throw new TypeError('Constructor argument must be of type DataStoreBuilder');
+
+        //pull in vars from builder to build chain first entry
+
+        //calculate the Data Store Chain ID
+
+        let firstEntry = Entry.builder()
+            .extId(Buffer.from('data-store'))
+            .extId(Buffer.from(fctUtil.sha256d(builder._buffer)));
+
+        //handle namespaces in extids
+        builder._namespace.forEach(function (ns) {
+            firstEntry.extId(ns.name, ns.encoding);
+        });
+
+        firstEntry = firstEntry.build();
+
+        const chainId = new Chain(firstEntry).chainIdHex;
+
+        //Build up Data Block Entries
+        const dataBlockEntries = [];
+
+        //create a buffer out of the ordered data block entryhashes for the next step
+        let hashBuffer = Buffer.from('');
+
+        while (builder._buffer.length > 0) {
+            const dbe = Entry.builder()
+                .chainId(chainId)
+                .content(builder._buffer.slice(0, 10240))
+                .build();
+
+            dataBlockEntries.push(dbe);
+            hashBuffer = Buffer.concat(hashBuffer, Buffer.from(dbe.hashHex()));
+
+            if (builder._buffer.length > 10240) builder._buffer = builder._buffer.slice(10240);
+            else builder._buffer = buffer.from('');
+        }
+
+        //create Data Block Index Entries
+        const dataBlockIndexEntries = [];
+
+        while (hashBuffer.length > 0) {
+            let hashes;
+
+            if (hashBuffer.length > 10240) hashes = hashBuffer.slice(0, 10240);
+            else hashes = hashBuffer;
+
+            //construct the index entry
+            const dbie = Entry.builder()
+                .chainId(chainId)
+                .content(hashes)
+                .build();
+
+            dataBlockIndexEntries.push(dbie);
+
+            //go back one index entry if possible and set its extid to our entryhash to form the linked list
+            if (dataBlockIndexEntries.length > 1) {
+
+                dataBlockIndexEntries[dataBlockIndexEntries.length - 1] = Entry.builder(dataBlockIndexEntries[dataBlockIndexEntries.length - 1])
+                    .extId(dbie.hashHex())
+                    .build();
+            }
+
+            //slice down the buffer if there are remaining elements that were not covered
+            if (hashBuffer.length > 10240) hashBuffer = hashBuffer.slice(10240);
+            else hashBuffer = Buffer.from(''); //we are done otherwise
+        }
+
+        //Build up Data Store first chain entry object
+
+        const firstEntryContent = {
+            'data-store': '1.0',
+            'size': builder._size,
+            'dbi-start': dataBlockIndexEntries[0].hashHex()
+        };
+
+        firstEntry = Entry.builder(firstEntry)
+            .content(firstEntryContent)
+            .build();
+
+
+
+    }
+}