From e087b1f7f45bd0becb07e91968e695226707e2cb Mon Sep 17 00:00:00 2001
From: Yuxin Wang <yuxinwang.dev@gmail.com>
Date: Wed, 26 Sep 2018 22:20:22 -0400
Subject: [PATCH] Implement download method.

---
 p2pfs/core/peer.py | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/p2pfs/core/peer.py b/p2pfs/core/peer.py
index c0d29a8..429f16c 100644
--- a/p2pfs/core/peer.py
+++ b/p2pfs/core/peer.py
@@ -5,6 +5,8 @@ import logging
 import os.path
 import threading
 from queue import Queue
+import math
+import pybase64
 logger = logging.getLogger(__name__)
 
 
@@ -88,8 +90,42 @@ class Peer(MessageServer):
         })
         # wait until reply is ready
         fileinfo, chunkinfo = self._download_results[file].get()
+        totalchunknum = math.ceil(fileinfo['size'] / (512 * 1024))
         logger.debug('{}: {} ==> {}'.format(file, fileinfo, chunkinfo))
 
+        # TODO: refactor this block, make it prettier
+        for chunknum in range(totalchunknum):
+            for peer_id, possessed_chunks in chunkinfo.items():
+                # first one is a range
+                smallest, largest = possessed_chunks[0]
+                if smallest <= chunknum <= largest or chunknum in possessed_chunks:
+                    # find the client based on peer id
+                    peer = None
+                    for client, client_id in self._peers.items():
+                        if client_id == peer_id:
+                            peer = client
+                    # TODO: handle this later
+                    assert peer is not None
+                    # write the message to ask the chunk
+                    self._write_message(peer, {
+                        'type': MessageType.PEER_REQUEST_CHUNK,
+                        'filename': file,
+                        'chunknum': chunknum
+                    })
+                    break
+
+        with open(destination, 'wb') as dest_file:
+            dest_file.write(b'0' * fileinfo['size'])
+            dest_file.flush()
+            self._file_map[file] = destination
+            for i in range(totalchunknum):
+                number, raw_data = self._download_results[file].get()
+                dest_file.seek(number * (512 * 1024), 0)
+                dest_file.write(pybase64.b64decode(raw_data.encode('utf-8'), validate=True))
+                dest_file.flush()
+                progress(i + 1, totalchunknum)
+                logger.debug('Got {}\'s chunk # {}'.format(file, number))
+
         with self._download_lock:
             del self._download_results[file]
 
@@ -132,6 +168,25 @@ class Peer(MessageServer):
             self._file_list_result.put(message['file_list'])
         elif message['type'] == MessageType.REPLY_FILE_LOCATION:
             self._download_results[message['filename']].put((message['fileinfo'], message['chunkinfo']))
+        elif message['type'] == MessageType.PEER_REQUEST_CHUNK:
+            assert message['filename'] in self._file_map, 'File {} requested does not exist'.format(message['filename'])
+            local_file = self._file_map[message['filename']]
+            with open(local_file, 'rb') as f:
+                f.seek(message['chunknum'] * (512 * 1024), 0)
+                raw_data = f.read(512 * 1024)
+            self._write_message(client, {
+                'type': MessageType.PEER_REPLY_CHUNK,
+                'filename': message['filename'],
+                'chunknum': message['chunknum'],
+                'data': pybase64.b64encode(raw_data).decode('utf-8')
+            })
+            self._write_message(self._server_sock, {
+                'type': MessageType.REQUEST_CHUNK_REGISTER,
+                'filename': message['filename'],
+                'chunknum': message['chunknum']
+            })
+        elif message['type'] == MessageType.PEER_REPLY_CHUNK:
+            self._download_results[message['filename']].put((message['chunknum'], message['data']))
         else:
             logger.error('Undefined message with type {}, full message: {}'.format(message['type'], message))