"""Context budget estimation and compaction."""
from typing import Optional


def estimate_tokens(text: str) -> int:
    """Rough token count estimation (chars / 4)."""
    if not text:
        return 0
    return max(1, len(text) // 4)


def estimate_ratio(estimated_tokens: int, max_context_tokens: int) -> float:
    """Return ratio of used tokens to max context."""
    if max_context_tokens <= 0:
        return 0.0
    return estimated_tokens / max_context_tokens


def should_warn(ratio: float, threshold: float = 0.8) -> bool:
    """Check if a warning should be issued based on usage ratio."""
    return ratio >= threshold


def should_hard_compact(ratio: float, threshold: float = 0.9) -> bool:
    """Check if forced compaction is needed."""
    return ratio >= threshold


def compact_text(text: str, max_lines: int = 80) -> str:
    """Compress text by keeping head and tail lines, inserting a compaction marker."""
    lines = text.splitlines()
    if len(lines) <= max_lines:
        return text
    head = lines[:max_lines // 2]
    tail = lines[-max_lines // 2:]
    return "\n".join(head + ["", "... [compacted] ...", ""] + tail)