def put(self, username, reponame):
# Create a new revision of the resource specified by `key`.
fmt = self.request.headers.get("Content-Type", "application/n-triples")
key = self.get_query_argument("key", None)
if username != self.current_user.name:
raise HTTPError(403)
if not key:
raise HTTPError(400)
datestr = self.get_query_argument("datetime", None)
ts = datestr and date(datestr, QSDATEFMT) or now()
try:
repo = (Repo.select(Repo.id).join(
User).where((User.name == username)
& (Repo.name == reponame)).naive().get())
except Repo.DoesNotExist:
raise HTTPError(404)
sha = shasum(key.encode("utf-8"))
chain = list(
CSet.select(CSet.time, CSet.type, CSet.len).where(
(CSet.repo == repo) & (CSet.hkey == sha) & (CSet.time >= SQL(
"COALESCE((SELECT time FROM cset "
"WHERE repo_id = %s "
"AND hkey_id = %s "
"AND type != %s "
"ORDER BY time DESC "
"LIMIT 1), 0)", repo.id, sha, CSet.DELTA))).order_by(
CSet.time).naive())
if len(chain) > 0 and not ts > chain[-1].time:
# Appended timestamps must be monotonically increasing!
raise HTTPError(400)
if len(chain) == 0:
# Mapping for `key` likely does not exist:
# Store the SHA-to-KEY mapping in HMap,
# looking out for possible collisions.
try:
HMap.create(sha=sha, val=key)
except IntegrityError:
val = HMap.select(HMap.val).where(HMap.sha == sha).scalar()
if val != key:
raise HTTPError(500)
# Parse and normalize into a set of N-Quad lines
stmts = parse(self.request.body, fmt)
snapc = compress(join(stmts, "\n"))
if len(chain) == 0 or chain[0].type == CSet.DELETE:
# Provide dummy value for `patch` which is never stored.
# If we get here, we always store a snapshot later on!
patch = ""
else:
# Reconstruct the previous state of the resource
prev = set()
blobs = (Blob.select(Blob.data).where(
(Blob.repo == repo) & (Blob.hkey == sha)
& (Blob.time << map(lambda e: e.time, chain))).order_by(
Blob.time).naive())
for i, blob in enumerate(blobs.iterator()):
data = decompress(blob.data)
if i == 0:
# Base snapshot for the delta chain
prev.update(data.splitlines())
else:
for line in data.splitlines():
mode, stmt = line[0], line[2:]
if mode == "A":
prev.add(stmt)
else:
prev.discard(stmt)
if stmts == prev:
# No changes, nothing to be done. Bail out.
return self.finish()
patch = compress(
join(
map(lambda s: "D " + s, prev - stmts) +
map(lambda s: "A " + s, stmts - prev), "\n"))
# Calculate the accumulated size of the delta chain including
# the (potential) patch from the previous to the pushed state.
acclen = reduce(lambda s, e: s + e.len, chain[1:], 0) + len(patch)
blen = len(chain) > 0 and chain[0].len or 0 # base length
if (len(chain) == 0 or chain[0].type == CSet.DELETE
or len(snapc) <= len(patch) or SNAPF * blen <= acclen):
# Store the current state as a new snapshot
Blob.create(repo=repo, hkey=sha, time=ts, data=snapc)
CSet.create(repo=repo,
hkey=sha,
time=ts,
type=CSet.SNAPSHOT,
len=len(snapc))
else:
# Store a directed delta between the previous and current state
Blob.create(repo=repo, hkey=sha, time=ts, data=patch)
CSet.create(repo=repo,
hkey=sha,
time=ts,
type=CSet.DELTA,
len=len(patch))
def get(self, username, reponame):
timemap = self.get_query_argument("timemap", "false") == "true"
index = self.get_query_argument("index", "false") == "true"
key = self.get_query_argument("key", None)
if (index and timemap) or (index and key) or (timemap and not key):
raise HTTPError(400)
if self.get_query_argument("datetime", None):
datestr = self.get_query_argument("datetime")
ts = date(datestr, QSDATEFMT)
elif "Accept-Datetime" in self.request.headers:
datestr = self.request.headers.get("Accept-Datetime")
ts = date(datestr, RFC1123DATEFMT)
else:
ts = now()
try:
repo = (Repo.select(Repo.id).join(
User).where((User.name == username)
& (Repo.name == reponame)).naive().get())
except Repo.DoesNotExist:
raise HTTPError(404)
if key and not timemap:
# Recreate the resource for the given key in its latest state -
# if no `datetime` was provided - or in the state it was in at
# the time indicated by the passed `datetime` argument.
self.set_header("Content-Type", "application/n-quads")
self.set_header("Vary", "accept-datetime")
sha = shasum(key.encode("utf-8"))
# Fetch all relevant changes from the last "non-delta" onwards,
# ordered by time. The returned delta-chain consists of either:
# a snapshot followed by 0 or more deltas, or
# a single delete.
chain = list(
CSet.select(CSet.time, CSet.type).where((CSet.repo == repo) & (
CSet.hkey == sha) & (CSet.time <= ts) & (CSet.time >= SQL(
"COALESCE((SELECT time FROM cset "
"WHERE repo_id = %s "
"AND hkey_id = %s "
"AND time <= %s "
"AND type != %s "
"ORDER BY time DESC "
"LIMIT 1), 0)", repo.id, sha, ts, CSet.DELTA))).
order_by(CSet.time).naive())
if len(chain) == 0:
# A resource does not exist for the given key.
raise HTTPError(404)
timegate_url = (self.request.protocol + "://" + self.request.host +
self.request.path)
timemap_url = (self.request.protocol + "://" + self.request.host +
self.request.uri + "&timemap=true")
self.set_header(
"Link", '<%s>; rel="original"'
', <%s>; rel="timegate"'
', <%s>; rel="timemap"' % (key, timegate_url, timemap_url))
self.set_header("Memento-Datetime",
chain[-1].time.strftime(RFC1123DATEFMT))
if chain[0].type == CSet.DELETE:
# The last change was a delete. Return a 404 response with
# appropriate "Link" and "Memento-Datetime" headers.
raise HTTPError(404)
# Load the data required in order to restore the resource state.
blobs = (Blob.select(Blob.data).where(
(Blob.repo == repo) & (Blob.hkey == sha)
& (Blob.time << map(lambda e: e.time, chain))).order_by(
Blob.time).naive())
if len(chain) == 1:
# Special case, where we can simply return
# the blob data of the snapshot.
snap = blobs.first().data
return self.finish(decompress(snap))
stmts = set()
for i, blob in enumerate(blobs.iterator()):
data = decompress(blob.data)
if i == 0:
# Base snapshot for the delta chain
stmts.update(data.splitlines())
else:
for line in data.splitlines():
mode, stmt = line[0], line[2:]
if mode == "A":
stmts.add(stmt)
else:
stmts.discard(stmt)
self.write(join(stmts, "\n"))
elif key and timemap:
# Generate a timemap containing historic change information
# for the requested key. The timemap is in the default link-format
# or as JSON (http://mementoweb.org/guide/timemap-json/).
sha = shasum(key.encode("utf-8"))
csets = (CSet.select(
CSet.time).where((CSet.repo == repo)
& (CSet.hkey == sha)).order_by(
CSet.time.desc()).naive())
# TODO: Paginate?
csit = csets.iterator()
try:
first = csit.next()
except StopIteration:
# Resource for given key does not exist.
raise HTTPError(404)
req = self.request
base = req.protocol + "://" + req.host + req.path
accept = self.request.headers.get("Accept", "")
if "application/json" in accept or "*/*" in accept:
self.set_header("Content-Type", "application/json")
self.write('{"original_uri": ' + json_encode(key))
self.write(', "mementos": {"list":[')
m = ('{{"datetime": "{0}", "uri": "' + base + '?key=' +
url_escape(key) + '&datetime={1}"}}')
self.write(
m.format(first.time.isoformat(),
first.time.strftime(QSDATEFMT)))
for cs in csit:
self.write(', ' + m.format(cs.time.isoformat(),
cs.time.strftime(QSDATEFMT)))
self.write(']}')
self.write('}')
else:
m = (',\n'
'<' + base + '?key=' + url_escape(key) + '&datetime={0}>'
'; rel="memento"'
'; datetime="{1}"'
'; type="application/n-quads"')
self.set_header("Content-Type", "application/link-format")
self.write('<' + key + '>; rel="original"')
self.write(
m.format(first.time.strftime(QSDATEFMT),
first.time.strftime(RFC1123DATEFMT)))
for cs in csit:
self.write(
m.format(cs.time.strftime(QSDATEFMT),
cs.time.strftime(RFC1123DATEFMT)))
elif index:
# Generate an index of all URIs contained in the dataset at the
# provided point in time or in its current state.
self.set_header("Vary", "accept-datetime")
self.set_header("Content-Type", "text/plain")
page = int(self.get_query_argument("page", "1"))
# Subquery for selecting max. time per hkey group
mx = (CSet.select(
CSet.hkey,
fn.Max(CSet.time).alias("maxtime")).where(
(CSet.repo == repo) & (CSet.time <= ts)).group_by(
CSet.hkey).order_by(CSet.hkey).paginate(
page, INDEX_PAGE_SIZE).alias("mx"))
# Query for all the relevant csets (those with max. time values)
cs = (CSet.select(CSet.hkey, CSet.time).join(
mx,
on=((CSet.hkey == mx.c.hkey_id) & (CSet.time == mx.c.maxtime)
)).where((CSet.repo == repo)
& (CSet.type != CSet.DELETE)).alias("cs"))
# Join with the hmap table to retrieve the plain key values
hm = (HMap.select(HMap.val).join(
cs, on=(HMap.sha == cs.c.hkey_id)).naive())
for h in hm.iterator():
self.write(h.val + "\n")
else:
raise HTTPError(400)
