[owners] Refactor OwnersClient.

- Remove GetChangeApprovalStatus and GetFilesApprovalStatus.
- Make host, project and branch part of GerritClient.
- Rename ListOwnersForFile to ListOwners.

Change-Id: I1f610a64f0217ce54e5ce4a210026535adc1c2e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2587268
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>
diff --git a/owners_client.py b/owners_client.py
index 5dabe5d..6f6ecf2 100644
--- a/owners_client.py
+++ b/owners_client.py
@@ -5,6 +5,7 @@
 import itertools
 import os
 import random
+import threading
 
 import gerrit_util
 import git_common
@@ -39,10 +40,6 @@
   return reversed(list(itertools.combinations(reversed(owners), num_owners)))
 
 
-class InvalidOwnersConfig(Exception):
-  pass
-
-
 class OwnersClient(object):
   """Interact with OWNERS files in a repository.
 
@@ -50,46 +47,30 @@
   Gerrit Code-Owners plugin REST API, and the owners database implemented by
   Depot Tools in owners.py:
 
-   - List all the owners for a change.
-   - Check if a change has been approved.
-   - Check if the OWNERS configuration in a change is valid.
+   - List all the owners for a group of files.
+   - Check if files have been approved.
+   - Suggest owners for a group of files.
 
   All code should use this class to interact with OWNERS files instead of the
   owners database in owners.py
   """
-  def __init__(self, host):
-    self._host = host
-
-  def ListOwnersForFile(self, project, branch, path):
+  def ListOwners(self, path):
     """List all owners for a file.
 
     The returned list is sorted so that better owners appear first.
     """
     raise Exception('Not implemented')
 
-  def BatchListOwners(self, project, branch, paths):
-    """Returns a dictionary {path: [owners]}."""
+  def BatchListOwners(self, paths):
+    """List all owners for a group of files.
+
+    Returns a dictionary {path: [owners]}.
+    """
     with git_common.ScopedPool(kind='threads') as pool:
       return dict(pool.imap_unordered(
-          lambda p: (p, self.ListOwnersForFile(project, branch, p)), paths))
+          lambda p: (p, self.ListOwners(p)), paths))
 
-  def GetChangeApprovalStatus(self, change_id):
-    """Check the approval status for the latest revision_id in a change.
-
-    Returns a map of path to approval status, where the status can be one of:
-    - APPROVED: An owner of the file has reviewed the change.
-    - PENDING:  An owner of the file has been added as a reviewer, but no owner
-      has approved.
-    - INSUFFICIENT_REVIEWERS: No owner of the file has been added as a reviewer.
-    """
-    raise Exception('Not implemented')
-
-  def ValidateOwnersConfig(self, change_id):
-    """Check if the owners configuration in a change is valid."""
-    raise Exception('Not implemented')
-
-  def GetFilesApprovalStatus(
-      self, project, branch, paths, approvers, reviewers):
+  def GetFilesApprovalStatus(self, paths, approvers, reviewers):
     """Check the approval status for the given paths.
 
     Utility method to check for approval status when a change has not yet been
@@ -100,22 +81,23 @@
     approvers = set(approvers)
     reviewers = set(reviewers)
     status = {}
-    for path in paths:
-      path_owners = set(self.ListOwnersForFile(project, branch, path))
-      if path_owners.intersection(approvers):
+    owners_by_path = self.BatchListOwners(paths)
+    for path, owners in owners_by_path.items():
+      owners = set(owners)
+      if owners.intersection(approvers):
         status[path] = APPROVED
-      elif path_owners.intersection(reviewers):
+      elif owners.intersection(reviewers):
         status[path] = PENDING
       else:
         status[path] = INSUFFICIENT_REVIEWERS
     return status
 
-  def SuggestOwners(self, project, branch, paths):
+  def SuggestOwners(self, paths):
     """Suggest a set of owners for the given paths."""
     paths_by_owner = {}
     score_by_owner = {}
-    for path in paths:
-      owners = self.ListOwnersForFile(project, branch, path)
+    owners_by_path = self.BatchListOwners(paths)
+    for path, owners in owners_by_path.items():
       for i, owner in enumerate(owners):
         paths_by_owner.setdefault(owner, set()).add(path)
         # Gerrit API lists owners of a path sorted by an internal score, so
@@ -124,8 +106,10 @@
         # paths.
         score_by_owner[owner] = min(i, score_by_owner.get(owner, i))
 
-    # Sort owners by their score.
-    owners = sorted(score_by_owner, key=lambda o: score_by_owner[o])
+    # Sort owners by their score. Randomize order of owners with same score.
+    owners = sorted(
+        score_by_owner,
+        key=lambda o: (score_by_owner[o], random.random()))
 
     # Select the minimum number of owners that can approve all paths.
     # We start at 2 to avoid sending all changes that require multiple reviewers
@@ -139,19 +123,22 @@
       for selected in _owner_combinations(owners, num_owners):
         covered = set.union(*(paths_by_owner[o] for o in selected))
         if len(covered) == len(paths):
-          return selected
+          return list(selected)
 
 
 class DepotToolsClient(OwnersClient):
   """Implement OwnersClient using owners.py Database."""
-  def __init__(self, host, root, branch, fopen=open, os_path=os.path):
-    super(DepotToolsClient, self).__init__(host)
+  def __init__(self, root, branch, fopen=open, os_path=os.path):
+    super(DepotToolsClient, self).__init__()
+
     self._root = root
+    self._branch = branch
     self._fopen = fopen
     self._os_path = os_path
-    self._branch = branch
+
     self._db = owners_db.Database(root, fopen, os_path)
     self._db.override_files = self._GetOriginalOwnersFiles()
+    self._db_lock = threading.Lock()
 
   def _GetOriginalOwnersFiles(self):
     return {
@@ -160,57 +147,33 @@
       if os.path.basename(f) == 'OWNERS'
     }
 
-  def ListOwnersForFile(self, _project, _branch, path):
-    # all_possible_owners returns a dict {owner: [(path, distance)]}. We want to
-    # return a list of owners sorted by increasing distance.
-    distance_by_owner = self._db.all_possible_owners([path], None)
-    # We add a small random number to the distance, so that owners at the same
-    # distance are returned in random order to avoid overloading those who would
-    # appear first.
-    return sorted(
-        distance_by_owner,
-        key=lambda o: distance_by_owner[o][0][1] + random.random())
-
-  def GetChangeApprovalStatus(self, change_id):
-    data = gerrit_util.GetChange(
-        self._host, change_id,
-        ['DETAILED_ACCOUNTS', 'DETAILED_LABELS', 'CURRENT_FILES',
-         'CURRENT_REVISION'])
-
-    reviewers = [r['email'] for r in data['reviewers']['REVIEWER']]
-
-    # Get reviewers that have approved this change
-    label = data['labels']['Code-Review']
-    max_value = max(int(v) for v in label['values'])
-    approvers = [v['email'] for v in label['all'] if v['value'] == max_value]
-
-    files = data['revisions'][data['current_revision']]['files']
-    return self.GetFilesApprovalStatus(None, None, files, approvers, reviewers)
-
-  def ValidateOwnersConfig(self, change_id):
-    data = gerrit_util.GetChange(
-        self._host, change_id,
-        ['DETAILED_ACCOUNTS', 'DETAILED_LABELS', 'CURRENT_FILES',
-         'CURRENT_REVISION'])
-
-    files = data['revisions'][data['current_revision']]['files']
-
-    db = owners_db.Database(self._root, self._fopen, self._os_path)
-    try:
-      db.load_data_needed_for(
-          [f for f in files if os.path.basename(f) == 'OWNERS'])
-    except Exception as e:
-      raise InvalidOwnersConfig('Error parsing OWNERS files:\n%s' % e)
+  def ListOwners(self, path):
+    # all_possible_owners is not thread safe.
+    with self._db_lock:
+      # all_possible_owners returns a dict {owner: [(path, distance)]}. We want
+      # to return a list of owners sorted by increasing distance.
+      distance_by_owner = self._db.all_possible_owners([path], None)
+      # We add a small random number to the distance, so that owners at the same
+      # distance are returned in random order to avoid overloading those who
+      # would appear first.
+      return sorted(
+          distance_by_owner,
+          key=lambda o: distance_by_owner[o][0][1] + random.random())
 
 
 class GerritClient(OwnersClient):
   """Implement OwnersClient using OWNERS REST API."""
-  def __init__(self, host):
-    super(GerritClient, self).__init__(host)
+  def __init__(self, host, project, branch):
+    super(GerritClient, self).__init__()
 
-  def ListOwnersForFile(self, project, branch, path):
+    self._host = host
+    self._project = project
+    self._branch = branch
+
+  def ListOwners(self, path):
     # GetOwnersForFile returns a list of account details sorted by order of
     # best reviewer for path. If code owners have the same score, the order is
     # random.
-    data = gerrit_util.GetOwnersForFile(self._host, project, branch, path)
+    data = gerrit_util.GetOwnersForFile(
+        self._host, self._project, self._branch, path)
     return [d['account']['email'] for d in data]