from __future__ import annotations

from dataclasses import dataclass, field
from typing import Literal, Optional

AnchorKind = Literal["slide", "page", "heading"]


@dataclass(frozen=True)
class Anchor:
    """Exact, immutable pointer back to where text came from."""
    file: str            # e.g. "heap-sort.pptx"
    kind: AnchorKind     # "slide" | "page" | "heading"
    locator: str         # slide/page number as str, or heading text
    label: str           # human-readable, e.g. 'heap-sort.pptx — slide 12 ("Heap Sort")'
    is_notes: bool = False  # True for PPTX speaker-notes blocks


@dataclass
class ParsedBlock:
    """One structural unit (a slide, a page, a heading-section) as plain text."""
    text: str
    anchor: Anchor
    title: Optional[str] = None
    has_text: bool = True   # False => no extractable text (flag for OCR in Phase 2)


@dataclass
class Chunk:
    """A retrievable unit; inherits its block's anchor."""
    id: str
    file: str
    anchor: Anchor
    title: Optional[str]
    text: str
    concepts: list[str] = field(default_factory=list)