"""
Round 6 — Practice Selection Experiment
Find ALL bugs. For each: report root cause and proposed fix.

This program processes a queue of tasks: validates, sorts by time,
paginates, and prints the result.

Expected behavior (from spec):
  - Tasks with negative priority should be REJECTED (invalid input)
  - Tasks should be sorted by actual datetime, earliest first
  - Pagination should group tasks into pages of 5
  - Output should list valid tasks in chronological order, paginated
"""

from datetime import datetime, timezone
import json

# === Configuration (loaded once at startup) ===
STRICT_MODE = False  # strict=True rejects invalid items; strict=False skips validation
PAGE_SIZE = 5
TZ = timezone.utc


def parse_timestamp(ts_str):
    """Parse ISO 8601 timestamp string to aware datetime."""
    return datetime.fromisoformat(ts_str)


def validate_item(item, strict=True):
    """Validate a single item. In strict mode, reject items with negative priority."""
    if strict:
        if item.get("priority", 0) < 0:
            raise ValueError(f"item has negative priority: {item}")
    return True


def sort_by_time(items):
    """Sort items by timestamp, earliest first."""
    return sorted(items, key=lambda x: str(x.get("timestamp", "")))


def paginate(items, page_size=PAGE_SIZE):
    """Split items into pages of page_size."""
    return [items[i:i + page_size] for i in range(0, len(items), page_size)]


def process_queue(items):
    """Main pipeline: validate -> sort -> paginate -> format."""
    valid = []
    for item in items:
        validate_item(item, strict=STRICT_MODE)
        valid.append(item)

    sorted_items = sort_by_time(valid)
    pages = paginate(sorted_items)

    result = []
    for page_num, page in enumerate(pages, 1):
        for item in page:
            result.append({
                "page": page_num,
                "id": item["id"],
                "priority": item["priority"],
                "timestamp": str(parse_timestamp(item["timestamp"])),
            })
    return result


def main():
    items = [
        {"id": 1, "priority": 5,  "timestamp": "2026-03-01T14:00:00+00:00"},
        {"id": 2, "priority": 3,  "timestamp": "2026-03-01T09:00:00+00:00"},
        {"id": 3, "priority": 7,  "timestamp": "2026-03-01T14:00:00+09:00"},
        {"id": 4, "priority": 2,  "timestamp": "2026-03-01T12:00:00+00:00"},
        {"id": 5, "priority": 1,  "timestamp": "2026-03-01T06:00:00+00:00"},
        {"id": 6, "priority": -1, "timestamp": "2026-03-01T18:00:00+00:00"},
        {"id": 7, "priority": 4,  "timestamp": "2026-03-01T11:00:00+00:00"},
    ]

    try:
        results = process_queue(items)
        print(json.dumps(results, indent=2))
    except Exception as e:
        print(f"Error: {e}")


if __name__ == "__main__":
    main()