"""Stage 3 (Mistral) — turn Mistral OCR's block stream into per-section chunks.

The counterpart of `normalize.py`, for the Mistral OCR backend. With
`include_blocks=True` Mistral returns a per-page list of typed blocks
(`title` / `text` / `equation` / `table` / `caption` / `list` / `image` /
`header` / `footer`), each with a bbox and its content — a structure ~1:1 with
MinerU's `content_list.json`. So this is a close port of `normalize.py`, and it
REUSES that module's `_heading` logic verbatim so section boundaries are decided
identically on both backends.

Two things it does that `normalize.py` does not have to:

  - **Strip markdown markup from text.** Mistral renders content as markdown, so
    a text line arrives as `*Production* yang **digunakan** ...`. Those `*`/`#`
    are markup Mistral added, NOT characters in the source PDF — and the
    extraction span-check locates LLM-quoted spans LITERALLY inside `text`, so
    leaving them in makes a quote of "Production" fail to match. Stripping markup
    is the same move `render.py` makes for LaTeX/HTML; it is NOT reflowing.
    Whitespace and line breaks are still left exactly as they are.

  - **Correlate image descriptions across the response.** A block of type
    `image` carries only `![img-N](...)` + an `image_id`; the model-written
    description lives at the page level in `pages[].images[].image_annotation`
    (produced by `bbox_annotation`). They are matched by id here.

⚠️ Text is NEVER tidied beyond markup stripping — no rejoining lines, no
whitespace normalisation. See contracts.py for why.
"""

from __future__ import annotations

import hashlib
import re
from collections.abc import Iterator
from functools import lru_cache
from pathlib import Path
from typing import Any

from .contracts import Chunk
from .normalize import MAX_CHUNK_CHARS, _heading  # identical section-boundary logic
from .render import render_latex, render_table

# Fingerprint of the code that decides chunk CONTENT on this backend — same
# mechanism and reasoning as normalize.normaliser_version (see there). Covers
# this module and render.py; contracts.py is deliberately excluded (its shape is
# versioned by schema_version).
_CONTENT_MODULES = ("normalize_mistral.py", "render.py")


@lru_cache(maxsize=1)
def normaliser_version() -> str:
    here = Path(__file__).parent
    h = hashlib.sha256()
    for name in _CONTENT_MODULES:
        h.update((here / name).read_bytes())
    return h.hexdigest()[:12]


# Page furniture, dropped on purpose — matches normalize._DISCARDED. `header`
# is handled separately (it becomes chapter context). `signature` is Mistral's
# label for the cover-page "Disusun/Disetujui" stamps, whose content is empty in
# the source anyway.
_DISCARDED = {"page_number", "footer"}

_LEADING_HASHES = re.compile(r"^\s*(#{1,6})\s*")
_MD_IMAGE = re.compile(r"!\[[^\]]*\]\([^)]*\)")
_MD_LINK = re.compile(r"\[([^\]]*)\]\([^)]*\)")
_MD_BOLD = re.compile(r"\*\*(.+?)\*\*", re.S)
_MD_ITALIC = re.compile(r"\*(.+?)\*", re.S)
# Inline math inside prose: "... nilai $x_i$ ...". Rendered to readable text for
# the same reason render.render_table renders math inside table cells.
_INLINE_MATH = re.compile(r"\$([^$]{1,400})\$")


def _strip_markdown(text: str, vocabulary: frozenset[str] | None = None) -> str:
    """Remove markup Mistral ADDED, keep the document's own characters.

    Deliberately conservative: only paired `*`/`**` emphasis, heading `#`,
    backticks, image and link syntax, and inline `$…$`. Underscores are left
    untouched — they appear in real variable names (`INPR_Hours`) far more often
    than as emphasis, and stripping them would damage content. Whitespace and
    newlines are preserved: this is markup removal, not reflow.
    """
    text = _MD_IMAGE.sub("", text)                                    # images: drop
    text = _MD_LINK.sub(r"\1", text)                                  # links: keep label
    text = _INLINE_MATH.sub(lambda m: " " + render_latex(m.group(1), vocabulary) + " ", text)
    text = _LEADING_HASHES.sub("", text)
    text = _MD_BOLD.sub(r"\1", text)
    text = _MD_ITALIC.sub(r"\1", text)
    return text.replace("`", "")


def _clean_heading(raw: str) -> tuple[str, int | None]:
    """A `title` block's markdown → (plain heading text, level from '#' depth)."""
    m = _LEADING_HASHES.match(raw)
    level = len(m.group(1)) if m else None
    text = _LEADING_HASHES.sub("", raw)
    text = _MD_BOLD.sub(r"\1", text)
    text = _MD_ITALIC.sub(r"\1", text)
    return text.strip(), level


def _bbox(block: dict[str, Any]) -> list[int] | None:
    keys = ("top_left_x", "top_left_y", "bottom_right_x", "bottom_right_y")
    if all(k in block and block[k] is not None for k in keys):
        return [int(block[k]) for k in keys]
    return None


def _blocks_with_pages(response: dict[str, Any]) -> Iterator[tuple[int, dict[str, Any]]]:
    """Flatten pages[].blocks into (page_idx, block), page order preserved."""
    for page in response.get("pages", []):
        pidx = int(page.get("index", 0))
        for block in page.get("blocks") or []:
            yield pidx, block


def _image_descriptions(response: dict[str, Any]) -> dict[str, str]:
    """image_id -> description, from the page-level annotations (bbox_annotation).

    Empty when the OCR call did not request annotations; description then stays
    None, exactly as it does on MinerU's `pipeline` backend.
    """
    out: dict[str, str] = {}
    for page in response.get("pages", []):
        for im in page.get("images") or []:
            ann = im.get("image_annotation")
            iid = im.get("id")
            if iid and ann:
                out[iid] = ann if isinstance(ann, str) else str(ann)
    return out


def _chunk_by_page(
    blocks: list[tuple[int, dict[str, Any]]],
    descriptions: dict[str, str],
    chapter_per_page: dict[int, str],
    doc_id: str,
) -> list[Chunk]:
    """Page granularity: all prose on a page → one chunk; tables/images their own.

    Recall-only. A page chunk has no single heading, so `heading_path` /
    `section_no` stay empty and the extraction outline degrades — section
    granularity (the default) is the real path.
    """
    def chapters(page: int) -> list[str]:
        return [chapter_per_page[page]] if page in chapter_per_page else []

    chunks: list[Chunk] = []
    by_page: dict[int, list[tuple[int, dict[str, Any]]]] = {}
    for i, (pidx, block) in enumerate(blocks):
        by_page.setdefault(pidx, []).append((i, block))

    for pidx in sorted(by_page):
        pieces: list[str] = []
        latex: list[str] = []
        src: list[int] = []
        has_formula = False
        prose_bbox: list[int] | None = None

        for i, block in by_page[pidx]:
            kind = block.get("type")
            if kind in _DISCARDED or kind == "header":
                continue

            if kind == "table":
                c = Chunk(
                    chunk_id=f"{doc_id}::{len(chunks):04d}", doc_id=doc_id,
                    kind="table", text=render_table(block.get("content") or ""),
                    page_idx=pidx, page_idxs=[pidx], chapters=chapters(pidx),
                    is_tabular=True, table_html=block.get("content") or None,
                    source_items=[i], bbox=_bbox(block),
                )
                if c.text or c.images:
                    chunks.append(c)
                continue

            if kind == "image":
                iid = block.get("image_id")
                chunks.append(Chunk(
                    chunk_id=f"{doc_id}::{len(chunks):04d}", doc_id=doc_id,
                    kind="image", text="", page_idx=pidx, page_idxs=[pidx],
                    chapters=chapters(pidx),
                    generated_description=descriptions.get(iid) if iid else None,
                    source_items=[i], bbox=_bbox(block),
                    images=[iid] if iid else [],
                ))
                continue

            if kind == "equation":
                raw = (block.get("content") or "").strip().strip("$").strip()
                has_formula = True
                src.append(i)
                if raw:
                    latex.append(raw)
                    rendered = render_latex(raw)
                    if rendered:
                        pieces.append(rendered)
                continue

            # text / title / list / caption / signature -> prose. A numbered
            # heading is NOT a boundary in page mode; it stays as prose text.
            text = _strip_markdown(block.get("content") or "").rstrip()
            if not text.strip():
                continue
            if prose_bbox is None:
                prose_bbox = _bbox(block)
            src.append(i)
            pieces.append(text)

        if pieces:
            chunks.append(Chunk(
                chunk_id=f"{doc_id}::{len(chunks):04d}", doc_id=doc_id,
                kind="equation" if has_formula else "text",
                text="\n\n".join(pieces).strip(),
                page_idx=pidx, page_idxs=[pidx], chapters=chapters(pidx),
                has_formula=has_formula, latex=latex, source_items=src,
                bbox=prose_bbox,
            ))
    return chunks


def normalise_mistral(
    response: dict[str, Any], doc_id: str, granularity: str = "section"
) -> list[Chunk]:
    """Mistral OCR response (include_blocks=True) → chunks.

    `granularity` decides how prose is grouped, and only that:

      - "section" (default): a numbered heading opens a new chunk, mirroring
        normalize.py. This is the default because the extraction half derives
        the document `outline` from `heading_path` and drives `source_wording`
        from `heading` — page grouping leaves both EMPTY (a page chunk has no
        single heading), which silently degrades a locked product behaviour.
      - "page": all prose on a page becomes ONE chunk. Higher raw term recall
        (bigger context per NER window) but no per-chunk heading, so only fit
        for a recall-only measurement, never for the real pipeline.

    The section/page recall gap (0.878 vs 0.951 on the BUMA fixture) is the NER
    filter's, not content: every gold term is present in the text either way, and
    closing it is the extraction side's lever (span-filter overlap resolution).

    In BOTH modes tables and images are their OWN chunks, so `table_html` stays
    one-table-per-chunk regardless. Switching modes is a one-word change and
    never touches the extraction half — the artifact shape is identical.

    No `page_vocabulary` parameter: Mistral does not spell formulas out one
    character at a time, so the word-boundary recovery that MinerU needs has
    nothing to do here.
    """
    if granularity not in {"page", "section"}:
        raise ValueError(f"granularity must be 'page' or 'section', got {granularity!r}")

    blocks = list(_blocks_with_pages(response))
    if not blocks:
        raise ValueError(
            "no blocks in Mistral response — call ocr.process with include_blocks=True"
        )
    descriptions = _image_descriptions(response)

    # Chapter context per page, from the running header (type 'header').
    chapter_per_page: dict[int, str] = {}
    for pidx, b in blocks:
        if b.get("type") == "header":
            txt = _strip_markdown(b.get("content") or "").strip()
            if txt:
                chapter_per_page.setdefault(pidx, txt)

    # --- page mode: recall-only; a page chunk has no single heading ---
    if granularity == "page":
        return _chunk_by_page(blocks, descriptions, chapter_per_page, doc_id)

    # --- section mode (default): a numbered heading opens a new chunk (mirrors normalize.py) ---
    chunks: list[Chunk] = []
    running: Chunk | None = None
    pieces: list[str] = []
    stack: list[tuple[int, str]] = []

    def push_heading(level: int, text: str) -> None:
        while stack and stack[-1][0] >= level:
            stack.pop()
        stack.append((level, text))

    def close() -> None:
        nonlocal running, pieces
        if running is not None:
            running.text = "\n\n".join(pieces).strip()
            if running.text or running.images:
                running.page_idxs = sorted(set(running.page_idxs))
                chunks.append(running)
        running, pieces = None, []

    def open_chunk(
        kind: str, page: int, section_no: str | None = None, heading: str | None = None
    ) -> Chunk:
        return Chunk(
            chunk_id=f"{doc_id}::{len(chunks):04d}",
            doc_id=doc_id, kind=kind, text="",
            page_idx=page, page_idxs=[page],
            section_no=section_no, heading=heading,
            chapters=[chapter_per_page[page]] if page in chapter_per_page else [],
            heading_path=[t for _, t in stack],
        )

    for i, (page, block) in enumerate(blocks):
        kind = block.get("type")
        if kind in _DISCARDED or kind == "header":
            continue

        if kind == "table":
            close()
            c = open_chunk("table", page)
            c.text = render_table(block.get("content") or "")
            c.is_tabular = True
            c.table_html = block.get("content") or None
            c.source_items = [i]
            c.bbox = _bbox(block)
            if c.text or c.images:
                chunks.append(c)
            continue

        if kind == "image":
            close()
            c = open_chunk("image", page)
            iid = block.get("image_id")
            c.generated_description = descriptions.get(iid) if iid else None
            c.source_items = [i]
            c.bbox = _bbox(block)
            if iid:
                c.images = [iid]
            # text stays "" — a printed caption arrives as its own `caption`
            # block; the model description is kept OUT of text on purpose.
            chunks.append(c)
            continue

        if kind == "equation":
            latex = (block.get("content") or "").strip().strip("$").strip()
            if running is None:
                running = open_chunk("text", page)
            running.has_formula = True
            running.source_items.append(i)
            running.page_idxs.append(page)
            if latex:
                running.latex.append(latex)              # raw, for the formula branch
                rendered = render_latex(latex)
                if rendered:
                    pieces.append(rendered)              # prose, so NER can find it
            continue

        raw = block.get("content") or ""

        # `list` and `caption` are ALWAYS content, never a section boundary: a
        # bullet or a caption can look like a numbered heading, and letting one
        # open a section would split a list from the paragraph introducing it
        # (see normalize.py's list note).
        if kind in {"list", "caption"}:
            text = _strip_markdown(raw).rstrip()
            if text.strip():
                if running is None:
                    running = open_chunk("text", page)
                    running.bbox = _bbox(block)
                running.source_items.append(i)
                running.page_idxs.append(page)
                pieces.append(text)
            continue

        # `text` / `title` / `signature`: a NUMBERED line may open a section.
        # normalize._heading is applied to BOTH text and title items on MinerU —
        # here too, because Mistral labels many numbered headings as `text`, not
        # `title`. Checking only `title` left whole sections unopened and every
        # equation piled into one chunk. A title's level comes from its `#`
        # depth; a text line's from numbering depth (fallback inside _heading).
        if kind == "title":
            htext, level = _clean_heading(raw)
        else:
            htext, level = _strip_markdown(raw).strip(), None
        number, heading, hlevel = _heading(
            {"type": "title", "text": htext, "text_level": level}
        )
        if heading is not None:
            if any(htext == t for _, t in stack):        # reprinted breadcrumb
                if running is not None:
                    running.page_idxs.append(page)
                continue
            close()
            push_heading(hlevel or 1, heading)
            running = open_chunk("text", page, section_no=number, heading=heading)
            running.source_items = [i]
            running.bbox = _bbox(block)
            # heading line NOT copied into text — lives in `heading`. See
            # normalize.py for the measured reason (mention_count inflation).
            continue

        text = _strip_markdown(raw).rstrip()
        if not text.strip():
            continue

        if running is None:
            running = open_chunk("text", page)
            running.bbox = _bbox(block)
        running.source_items.append(i)
        running.page_idxs.append(page)
        chapter = chapter_per_page.get(page)
        if chapter and chapter not in running.chapters:
            running.chapters.append(chapter)
        pieces.append(text)                              # verbatim (markup only removed)

        if sum(len(x) for x in pieces) >= MAX_CHUNK_CHARS:
            continued_from = running
            close()
            running = open_chunk("text", page,
                                 section_no=continued_from.section_no,
                                 heading=continued_from.heading)

    close()
    return chunks