DEV: patchbot: let the page fetch the shared review state

This adds the read side of the review syncing to the generated page: a
"Get updates" button at the top right retrieves the shared state from
update.cgi (reached by a bare relative URL, so it must be in a cgi-bin
directory next to the page) and applies it. Nothing is fetched
automatically, not even at load time: it's up to the user to explicitly
click to resynchronize, and without it (or with the server down) the
page keeps behaving fully standalone as today.

Three states exist per line to make this work. The original state is
the verdict the bot chose, captured at load time and constant. The
reference state is the last known shared state, on top of which the
user's edits sit; it starts equal to the original. The local state is
the DOM itself (the checked radios). Applying a fetched overlay
recomputes every line's reference as "the server's entry if any,
otherwise the bot's verdict", so a removed override properly falls back
to the original; the reference always advances but the displayed state
only moves where the user had no local edit: local edits win, and
re-applying the same overlay twice changes nothing.

The received commit ids are resolved exactly first, then by symmetric
prefix (one id being a prefix of the other, for mixed-length ids), first
line wins. The shared notes land in a dedicated container below the AI
explanation, rendered via innerText (no HTML injection) and replaced
wholesale so the operation stays idempotent; entries for commits absent
from the page are simply ignored.

The whole exchange was tested with the real generated page's scripts
running against a stubbed DOM covering load capture, prefix resolution,
adopt-vs-keep on both changed and disappeared entries, idempotent
re-application, and silent degradation on fetch failure.

diff --git a/dev/patchbot/scripts/post-ai.sh b/dev/patchbot/scripts/post-ai.sh
index 0db78aae906976a6212d9dbdedec420135459862..0a7427cdeed39815442890c5ae911dcf92236718 100755 (executable)
--- a/dev/patchbot/scripts/post-ai.sh
+++ b/dev/patchbot/scripts/post-ai.sh
@@ -141,10 +141,17 @@ input.y[type="radio"]:checked {
   border: 2px solid black;
   background-color: $BT_Y;
 }
+
+/* shared reviewers' notes, shown below the AI explanation */
+div.notes {
+  font-style: italic;
+  margin-top: 2px;
+}
 </style>
 
 <script type="text/javascript"><!--
 
+var cgi_url = "cgi-bin/update.cgi";
 var nb_patches = 0;
 var cid = [];
 var bkp = [];
@@ -154,6 +161,143 @@ var bkp = [];
 // which case no syncing is possible and the page works standalone.
 var branch = '$VERSION';
 
+// Three states exist per line. The original state (orig[]) is the verdict
+// the bot chose, captured at load time and constant. The reference state
+// (ref_state[]/ref_notes[]) is the last known shared state, i.e. what the
+// server last told us, on top of which the user's edits sit; it starts
+// equal to the original and is only advanced by "Get updates" and by a
+// successful save. The local state is the DOM itself (the checked radios),
+// there is no separate copy. Nothing is fetched automatically: the user
+// explicitly clicks "Get updates" to retrieve the shared state.
+var orig = [];
+var ref_state = [];
+var ref_notes = [];
+var cidmap = {};
+
+// returns the letter of the checked verdict radio of line <i>, or ""
+function cur_state(i) {
+  if (document.getElementById("bt_" + i + "_n").checked) return "n";
+  if (document.getElementById("bt_" + i + "_u").checked) return "u";
+  if (document.getElementById("bt_" + i + "_w").checked) return "w";
+  if (document.getElementById("bt_" + i + "_y").checked) return "y";
+  return "";
+}
+
+// checks the verdict radio <s> of line <i> (authoritative set, idempotent)
+function set_state(i, s) {
+  var el = document.getElementById("bt_" + i + "_" + s);
+  if (el)
+    el.checked = true;
+}
+
+// Returns the verdict letter emitted in the page for line <i>, i.e. the
+// bot's verdict. It relies on defaultChecked, which reflects the "checked"
+// attribute present in the HTML and not the radio's current state: across
+// a reload, the browser restores the radios to the user's last local
+// state, so looking at cur_state() at load time would wrongly capture the
+// user's own edits as being the original state.
+function gen_state(i) {
+  if (document.getElementById("bt_" + i + "_n").defaultChecked) return "n";
+  if (document.getElementById("bt_" + i + "_u").defaultChecked) return "u";
+  if (document.getElementById("bt_" + i + "_w").defaultChecked) return "w";
+  if (document.getElementById("bt_" + i + "_y").defaultChecked) return "y";
+  return "";
+}
+
+// captures the bot's verdicts once the table is fully loaded: they preset
+// both the original and the reference states. After a reload, the radios
+// (and thus the local state) may differ from the bot's verdicts since the
+// browser restores them: this is desired, such differences are unsaved
+// local edits and must remain detected as such.
+function init_ref() {
+  var i;
+
+  for (i = 1; i < nb_patches; i++) {
+    orig[i] = gen_state(i);
+    ref_state[i] = orig[i];
+    ref_notes[i] = "";
+    cidmap[cid[i]] = i;
+  }
+}
+
+function sync_msg(m) {
+  var el = document.getElementById("sync_msg");
+  if (el)
+    el.innerText = m;
+}
+
+// renders the reference notes of line <i> by replacing the whole container
+// (never appending), so that re-applying the same notes is idempotent.
+function show_notes(i) {
+  var el = document.getElementById("notes_" + i);
+  if (el)
+    el.innerText = ref_notes[i] ? "Notes: " + ref_notes[i] : "";
+}
+
+// resolves a commit id received from the server to a line number: exact
+// match first (the normal case), then symmetric-prefix (one id is a prefix
+// of the other, which only happens with mixed-length ids), first line wins.
+// Returns 0 when unknown (eg: a commit which is not on this page).
+function find_line(ocid) {
+  var i;
+
+  if (cidmap[ocid])
+    return cidmap[ocid];
+  for (i = 1; i < nb_patches; i++)
+    if (cid[i].startsWith(ocid) || ocid.startsWith(cid[i]))
+      return i;
+  return 0;
+}
+
+// Applies a freshly fetched overlay (the complete list of shared entries).
+// The new reference of every line is recomputed as "the server's entry if
+// any, otherwise the bot's original verdict", so that an entry removed on
+// the server properly falls back to the original. The reference always
+// advances, but the displayed state only moves where the user had no local
+// edit: local edits win and will overwrite the shared state at save time.
+function apply_ref(list) {
+  var over_state = [], over_notes = [], claimed = [];
+  var i, j, e, newref, newnotes;
+
+  for (j = 0; j < list.length; j++) {
+    e = list[j];
+    i = find_line(String(e.cid));
+    if (!i || claimed[i])
+      continue;
+    claimed[i] = 1;
+    if (e.state)
+      over_state[i] = String(e.state);
+    if (e.notes)
+      over_notes[i] = String(e.notes);
+  }
+
+  for (i = 1; i < nb_patches; i++) {
+    newref = over_state[i] ? over_state[i] : orig[i];
+    if (newref != ref_state[i] && ref_state[i] == cur_state(i))
+      set_state(i, newref);
+    ref_state[i] = newref;
+
+    newnotes = over_notes[i] ? over_notes[i] : "";
+    if (newnotes != ref_notes[i]) {
+      ref_notes[i] = newnotes;
+      show_notes(i);
+    }
+  }
+  updt_table(0);
+  updt_output();
+}
+
+// "Get updates" button: fetches the current shared state from the server
+function fetch_ref() {
+  if (!branch)
+    return;
+  sync_msg("fetching...");
+  fetch(cgi_url + "?branch=" + branch)
+    .then(function(r) { if (!r.ok) throw 0; return r.json(); })
+    .then(function(list) { apply_ref(list); sync_msg("reference updated"); })
+    .catch(function() { sync_msg("fetch failed (server unreachable?)"); });
+}
+
 // first line to review
 var review = 0;
 
@@ -308,6 +452,15 @@ function init_review() {
 EOF
 
 echo "<BODY>"
+
+# the syncing UI is only emitted when the branch is known; the page reaches
+# update.cgi with a bare relative URL so it must sit in the same directory.
+if [ -n "$VERSION" ]; then
+       echo -n "<div style='float: right; text-align: right;'>"
+       echo -n "<button onclick='fetch_ref();' title='Retrieve the latest shared review state'>Get updates</button>"
+       echo "<br/><small id='sync_msg'></small></div>"
+fi
+
 echo -n "<table cellpadding=3 cellspacing=5 style='font-size: 150%;'><tr><th align=left>Backported</th>"
 echo -n "<td style='background-color:$BG_N'><a href='#' onclick='show_only(1,1,0,0,0);'> N: <span id='cnt_bn'>0</span> </a></td>"
 echo -n "<td style='background-color:$BG_U'><a href='#' onclick='show_only(1,0,1,0,0);'> U: <span id='cnt_bu'>0</span> </a></td>"
@@ -430,7 +583,10 @@ for patch in "${PATCHES[@]}"; do
         echo -n "<input type='radio' onclick='updt($seq_num,\"w\");' id='bt_${seq_num}_w' class='w' name='$cid' value='w' title='wait in -next' $([ "$verdict" != wait ]   || echo -n checked) />"
         echo -n "<input type='radio' onclick='updt($seq_num,\"y\");' id='bt_${seq_num}_y' class='y' name='$cid' value='y' title='Pick' $(         [ "$verdict" != yes ]    || echo -n checked) />"
         echo -n "</TD>"
-        echo -n "<TD>$resp</TD>"
+
+        # the div is the dedicated container for the shared reviewers' notes,
+        # filled by full replacement (never appended to) by the JS
+        echo -n "<TD>$resp<div class='notes' id='notes_$seq_num'></div></TD>"
         echo "</TR>"
         echo
         ((seq_num++))
@@ -451,5 +607,5 @@ echo "<P/>"
 echo "<H3>Output:</H3>"
 echo "<textarea cols=120 rows=10 id='output'></textarea>"
 echo "<P/>"
-echo "<script type='text/javascript'>nb_patches=$seq_num; review=$review; init_review(); updt_table(0); updt_output();</script>"
+echo "<script type='text/javascript'>nb_patches=$seq_num; review=$review; init_review(); init_ref(); updt_table(0); updt_output();</script>"
 echo "</BODY></HTML>"