scripts: backfill record_type on legacy events imported with hardcoded "Waveform"

Pre-v0.16.1 (commit aac1c8e), every event ingested through
read_blastware_file got record_type="Waveform" regardless of actual
type because the field was hardcoded.  New ingests derive correctly
from the AB0T filename scheme (H/W/M/E/C).  Existing rows still hold
the wrong value.

This script walks the events table, derives the correct record_type
from each row's blastware_filename, and bulk-updates rows that differ.
Idempotent + dry-run by default.

Usage:
  python -m scripts.backfill_record_type --db bridges/captures/seismo_relay.db
  python -m scripts.backfill_record_type --db bridges/captures/seismo_relay.db --apply

Terra-view's event-detail modal already derives the record_type
client-side from the filename for display, so operators see the
correct type in the UI even before this backfill runs.  This script
brings the DB column in line with what the UI is already showing —
matters for reporting and any downstream consumer that reads the
column directly.

scripts/backfill_record_type.py

@@ -0,0 +1,150 @@
+"""
+scripts/backfill_record_type.py — fix `record_type` on legacy event
+rows whose value was hardcoded to "Waveform" regardless of actual type.
+
+Why this is needed
+──────────────────
+Pre-v0.16.1 the BW file importer (`event_file_io.read_blastware_file`)
+hardcoded `ev.record_type = "Waveform"` for every imported event.  Fixed
+in commit aac1c8e — new ingests now derive the type from the Blastware
+filename's extension last character (H=Histogram, W=Waveform, M=Manual,
+E=Event, C=Combo) per the V10.72+ MiniMate Plus AB0T filename scheme.
+
+Effect on a server that imported events under the old code: every
+events row has `record_type = "Waveform"`, even for histograms,
+manuals, etc.  Visible in terra-view's event-detail modal under the
+"Record Type" field.  Terra-view also has a client-side workaround
+that derives the type from the filename for display purposes, so
+operators see the correct type in the UI even before this backfill.
+This script makes the DB column match what the UI is already showing,
+which matters for reporting and any downstream consumer that reads
+events.record_type directly.
+
+This script
+───────────
+Walks the `events` table and updates each row's `record_type` to the
+derived value from its `blastware_filename`.  Old S338 firmware files
+(3-char extensions ending in `0`) and any unrecognized suffix get
+left at the existing value (defaults to "Waveform").
+
+Idempotent: re-running after a successful backfill finds zero rows
+needing updates and exits cleanly (it always re-derives but only
+writes when the value would change).
+
+Usage
+─────
+  # Dry-run (default): print what would change, don't touch the DB
+  python -m scripts.backfill_record_type --db bridges/captures/seismo_relay.db
+
+  # Apply the backfill
+  python -m scripts.backfill_record_type --db bridges/captures/seismo_relay.db --apply
+"""
+
+from __future__ import annotations
+
+import argparse
+import sqlite3
+import sys
+from collections import Counter
+from pathlib import Path
+
+
+# Must stay in sync with minimateplus.event_file_io._RECORD_TYPE_BY_EXT_SUFFIX.
+_TYPE_FROM_SUFFIX = {
+    "H": "Histogram",
+    "W": "Waveform",
+    "M": "Manual",
+    "E": "Event",
+    "C": "Combo",
+}
+
+
+def derive_record_type(filename: str | None, default: str = "Waveform") -> str:
+    """Mirror of minimateplus.event_file_io.derive_record_type_from_filename.
+
+    Vendored here so this script runs without needing the seismo-relay
+    package on the Python path (useful on prod where you might be
+    running it via `docker exec` against a container's DB volume).
+    """
+    if not filename:
+        return default
+    name = Path(filename).name
+    if "." not in name:
+        return default
+    ext = name.rsplit(".", 1)[1]
+    if not ext:
+        return default
+    return _TYPE_FROM_SUFFIX.get(ext[-1].upper(), default)
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description=__doc__)
+    ap.add_argument("--db", required=True, help="Path to seismo_relay.db")
+    ap.add_argument("--apply", action="store_true",
+                    help="Actually write changes (default is dry-run).")
+    ap.add_argument("--default", default="Waveform",
+                    help="Fallback record_type when filename doesn't encode one. "
+                         "Default: Waveform (matches the pre-fix bug's behavior).")
+    args = ap.parse_args()
+
+    db_path = Path(args.db)
+    if not db_path.exists():
+        print(f"ERROR: database not found at {db_path}", file=sys.stderr)
+        return 1
+
+    conn = sqlite3.connect(str(db_path))
+    conn.row_factory = sqlite3.Row
+    cur = conn.cursor()
+
+    cur.execute("""
+        SELECT id, blastware_filename, record_type
+        FROM events
+        WHERE blastware_filename IS NOT NULL
+          AND blastware_filename != ''
+    """)
+    rows = cur.fetchall()
+    total = len(rows)
+    print(f"Scanning {total:,} event rows…")
+    print()
+
+    # Tally proposed changes.
+    transitions: Counter[tuple[str, str]] = Counter()
+    update_ids: list[tuple[str, str]] = []
+    unrecognized = 0
+
+    for row in rows:
+        derived = derive_record_type(row["blastware_filename"], default=args.default)
+        current = row["record_type"] or ""
+        if derived == current:
+            continue
+        transitions[(current, derived)] += 1
+        update_ids.append((row["id"], derived))
+
+    if not update_ids:
+        print("Nothing to update — all rows already match.")
+        conn.close()
+        return 0
+
+    print(f"{len(update_ids):,} row(s) need updating:")
+    for (old, new), count in sorted(transitions.items(), key=lambda x: -x[1]):
+        print(f"  {count:>6,}  {old!r:14s} → {new!r}")
+    print()
+
+    if not args.apply:
+        print("(dry-run — re-run with --apply to write changes)")
+        conn.close()
+        return 0
+
+    print("Applying changes…")
+    cur.executemany(
+        "UPDATE events SET record_type = ? WHERE id = ?",
+        [(new, eid) for eid, new in update_ids],
+    )
+    conn.commit()
+    print(f"Done. Updated {cur.rowcount:,} row(s).")
+    conn.close()
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())