#!/usr/bin/env python3
"""Diff two openfut_snapshot_*.json files from snapshot_lineup_tables.lua.

Usage: diff_snapshots.py before.json after.json

Reports, per table, which rows changed and which fields differed —
this is how the real DB write behind FLE's "Freeze Lineup" GUI feature
gets discovered (see docs/foundational-xi-injection-test.md).
"""
import json
import sys


def row_key(row):
    for candidate in ("playerid", "player_id", "id", "rowid"):
        if candidate in row:
            return row[candidate]
    return json.dumps(row, sort_keys=True)


def diff_table(name, before, after):
    before_rows = {row_key(r): r for r in before.get("rows", [])}
    after_rows = {row_key(r): r for r in after.get("rows", [])}

    changes = []
    for key, after_row in after_rows.items():
        before_row = before_rows.get(key)
        if before_row is None:
            changes.append({"row": key, "type": "added", "row_data": after_row})
            continue
        field_diffs = {}
        for field in set(before_row) | set(after_row):
            bval = before_row.get(field)
            aval = after_row.get(field)
            if bval != aval:
                field_diffs[field] = {"before": bval, "after": aval}
        if field_diffs:
            changes.append({"row": key, "type": "modified", "fields": field_diffs})

    for key in before_rows:
        if key not in after_rows:
            changes.append({"row": key, "type": "removed"})

    if changes:
        print(f"\n=== {name}: {len(changes)} changed row(s) ===")
        for c in changes:
            print(json.dumps(c, indent=2))


def main():
    if len(sys.argv) != 3:
        print(__doc__)
        sys.exit(1)

    with open(sys.argv[1]) as f:
        before = json.load(f)
    with open(sys.argv[2]) as f:
        after = json.load(f)

    table_names = set(before.get("tables", {})) | set(after.get("tables", {}))
    any_changes = False
    for name in sorted(table_names):
        b = before.get("tables", {}).get(name, {"rows": []})
        a = after.get("tables", {}).get(name, {"rows": []})
        before_len = len(b.get("rows", []))
        after_len = len(a.get("rows", []))
        if before_len != after_len:
            print(f"{name}: row count changed {before_len} -> {after_len}")
            any_changes = True
        diff_table(name, b, a)

    if not any_changes:
        print("(row-count-only check found no differences; per-field diffs above are authoritative)")


if __name__ == "__main__":
    main()