From 7ef46efb82c69561cd630e342cadd833b3a9b63e Mon Sep 17 00:00:00 2001
From: Nathan McRae <nathanm@electroimpact.com>
Date: Sat, 6 Jul 2024 12:12:01 -0700
Subject: [PATCH] Add log

---
 libwyag.py | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)

diff --git a/libwyag.py b/libwyag.py
index 29395eb..6ea702f 100644
--- a/libwyag.py
+++ b/libwyag.py
@@ -327,3 +327,133 @@ def object_hash(fd, fmt, repo=None):
         case _         : raise Exception(f"Unknown type {fmt}")
 
     return object_write(obj, repo)
+
+def kvlm_parse(raw, start=0, dct=None):
+    if not dct:
+        dct = collections.OrderedDict()
+        # You CANNOT declare the argument as dct=OrderedDict() or all
+        # call to the functions will endlessly grow the same dict.
+
+    # This function is recursive: it reads a key/value pair, then call
+    # itself back with the new position. So we first need to know
+    # where we are: at a keyword, or already in the messageQ
+
+    # We search for the next space and the next newline.
+    spc = raw.find(b' ', start)
+    nl = raw.find(b'\n', start)
+
+    # If space appears before newline, we have a keyword. Otherwise,
+    # it's the final message, which we just read to the end of the file.
+
+    # Base case
+    # =========
+    #
+    # If newline appears first (or there's no space at all), we asume
+    # a blank line. A blank line means the remainder of the data is the
+    # message. We store it in the dictionary, with None as the key, and
+    # return.
+    if (spc < 0) or (nl < spc):
+        assert nl == start
+        dct[None] = raw[start+1:]
+        return dct
+
+    # Recursive case
+    # ==============
+    #
+    # We read a key-value pair and recurse for the next.
+    key = raw[start:spc]
+
+    # Find the end of the value. Continuation lines begin with a
+    # space, so we loop until we find a "\n" not followed by a space.
+    end = start
+    while True:
+        end = raw.find(b'\n', end+1)
+        if raw[end+1] != ord(' '): break
+
+    value = raw[spc+1:end].replace(b'\n ', b'\n')
+
+    # Don't overwrite existing data contents
+    if key in dct:
+        if type(dct[key]) == list:
+            dct[key].append(value)
+        else:
+            dct[key] = [ dct[key], value ]
+    else:
+        dct[key] = value
+
+    return kvlm_parse(raw, start=end+1, dct=dct)
+
+def kvlm_serialize(kvlm):
+    ret = b''
+
+    # Output fiels
+    for k in kvlm.keys():
+        # Skip the message itself
+        if k == None: continue
+        val = kvlm[k]
+        # Normalize to a list
+        if type(val) != list:
+            val = [ val ]
+
+        for v in val:
+            ret += k + b' ' + (v.replace(b'\n', b'\n ')) + b'\n'
+
+    ret += b'\n' + kvlm[None] + b'\n'
+
+    return ret
+
+class GitCommit(GitObject):
+    fmt = b'commit'
+
+    def deserialize(self, data):
+        self.kvlm = kvlm_parse(data)
+
+    def serialize(self):
+        return kvlm_serialize(self.kvlm)
+
+    def init(self):
+        self.kvlm = dict()
+
+argsp = argsubparsers.add_parser("log", help="Display history of a given commit.")
+argsp.add_argument("commit",
+                   default="HEAD",
+                   nargs="?",
+                   help="Commit to start at.")
+
+def cmd_log(args):
+    repo = repo_find()
+
+    print("digraph wyaglog{")
+    print("  node[shape=rect]")
+    log_graphviz(repo, object_find(repo, args.commit), set())
+    print("}")
+
+def log_graphviz(repo, sha, seen):
+    if sha in seen:
+        return
+    seen.add(sha)
+
+    commit = object_read(repo, sha)
+    short_hash = sha[0:8]
+    message = commit.kvlm[None].decode("utf8").strip()
+    message = message.replace("\\", "\\\\")
+    message = message.replace("\"", "\\\"")
+
+    if "\n" in message: # keep only the first line
+        message = message[:message.index("\n")]
+    print(f"  c_{sha} [label=\"{sha[0:7]}: {message}\"]")
+    assert commit.fmt==b'commit'
+
+    if not b'parent' in commit.kvlm.keys():
+        # Base case: the initial commit.
+        return
+
+    parents = commit.kvlm[b'parent']
+
+    if type(parents) != list:
+        parents = [ parents ]
+
+    for p in parents:
+        p = p.decode("ascii")
+        print (f"  c_{sha} -> c_{p}")
+        log_graphviz(repo, p, seen)