"""Cut an OKF bundle to one contract-conformant payload for one question.

This is the **pre-pass** `docs/consumption-contract.md` SS 1 names: the
deterministic program that reads the bundle, ranks its concepts, cuts them to a
bounded set, and emits one payload. It decides nothing about the question being
asked -- the skill does the judgement, this does the reading, the ranking and
the cut (SS 2.1).

**What it deliberately does not do, and the failure each refusal prevents:**

- **It calls no model.** A model in the run path makes the same question at the
  same ref return different bytes, which is the whole property a declared cut
  buys over an emergent one.
- **It opens no socket.** The repository requires an explicit per-run opt-in for
  network access; this command takes no such flag, so it can never reach one.
- **It enumerates no directory.** SS 9.2 forbids that unless the named profile
  says the index is derived, and measured 2026-09-07, `entries_match_directory`
  is `True` for `STRICT_V1` alone -- for none of the profiles a segmented v0.2
  bundle could have been built under. So the walk follows the INDEX TREE. That
  costs nothing: measured on the 629-concept K2 bundle, the index walk reaches
  exactly the set `rglob` finds.
- **It imports nothing outside the standard library and this repository.** The
  package pins exactly one runtime dependency and a packaging test enforces it.

It lives outside `src/`, so it never enters a wheel and no consumer's install
surface changes because it exists -- the reason `tools/okf_contract_check.py`
states for its own location. The entry point is `build_payload(...)`, with the
CLI a thin `main()`, so lifting it into `src/` the day a consumer asks for a
wheel-installed command is a move rather than a rewrite.
"""

from __future__ import annotations

import hashlib
import sys
from collections.abc import Mapping
from dataclasses import dataclass
from pathlib import Path
from typing import Literal

sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))

from llm_ingestion_okf.inbox import (  # noqa: E402
    ADJUDICATION_ADJUDICATED,
    ADJUDICATION_PROPOSED,
    ADJUDICATION_STATES,
)
from llm_ingestion_okf.materialize import parse_frontmatter  # noqa: E402
from llm_ingestion_okf.profiles import SEGMENTED_OKF_V0_2, BundleProfile  # noqa: E402

#: The profile whose index policy reads a faceted, per-directory index -- the
#: shape both the in-repo golden bundle and the K2 corpus carry. Named as this
#: instrument's default rather than hard-coded at each call site: a caller with
#: a differently-shaped bundle passes its own.
DEFAULT_PROFILE = SEGMENTED_OKF_V0_2

#: The algorithm the `ref` names, spelled in the value itself. SS 3.3 requires
#: "a commit or equivalent content identity" and names no algorithm; a bundle
#: that is not a git checkout has no commit, so the identity is computed. Naming
#: the algorithm inline is what lets a consumer reproduce it without a document.
REF_ALGORITHM = "sha256-tree"

#: The one concept suffix this instrument reads, taken from the profile so a
#: second literal cannot drift from it.
CONCEPT_SUFFIX = DEFAULT_PROFILE.paths.concept_suffix


def _walk_index_tree(
    bundle_root: Path, *, profile: BundleProfile
) -> tuple[tuple[str, ...], tuple[str, ...]]:
    """Every index file and every concept id the index tree reaches.

    One walk, two results, because the alternative is two walks that can
    disagree -- and a ref computed over a different set than the one that was
    read is an identity for something nobody consumed.
    """
    index_name = profile.index.name
    suffix = profile.paths.concept_suffix
    indexes: set[str] = set()
    concepts: set[str] = set()
    pending: list[str] = [index_name]
    while pending:
        relative = pending.pop()
        if relative in indexes:
            continue
        indexes.add(relative)
        index_file = bundle_root / relative
        if not index_file.is_file():
            continue
        parent = _parent_dir(relative)
        for line in index_file.read_text(encoding="utf-8").splitlines():
            entry = profile.index.parse_entry(line)
            # `None` is curated prose, not a defect: the index is the one file
            # where this library writes beside somebody else's text.
            if entry is None:
                continue
            target = _join(parent, entry.target)
            if target is None:
                continue
            if target.rsplit("/", 1)[-1] == index_name:
                pending.append(target)
            elif target.endswith(suffix):
                concepts.add(target[: -len(suffix)])
    return _byte_sorted(indexes), _byte_sorted(concepts)


def _byte_sorted(values: set[str]) -> tuple[str, ...]:
    """Sorted by the UTF-8 encoding, never by the locale.

    A locale-dependent order makes byte-identical output a claim about the
    machine rather than about the bundle.
    """
    return tuple(sorted(values, key=lambda value: value.encode("utf-8")))


def enumerate_concepts(
    bundle_root: Path, *, profile: BundleProfile = DEFAULT_PROFILE
) -> tuple[str, ...]:
    """Every concept id in the bundle, reached through the index tree.

    Ids are bundle-relative POSIX paths with the profile's concept suffix
    removed -- slash-preserving, so two same-named concepts in different
    documents stay two concepts.

    **Not `rglob`.** SS 9.2 forbids the consumer path from enumerating a
    directory unless the named profile says the index is derived. The index is
    safe to rely on here because Door B recomputes it as a projection over the
    whole bundle each round, which is what makes a rebuild from scratch equal an
    incremental update byte for byte.
    """
    _, concepts = _walk_index_tree(bundle_root, profile=profile)
    return concepts


def _parent_dir(relative: str) -> str:
    """The directory part of a bundle-relative POSIX path, or `""` at the root.

    Spelled here rather than as `PurePosixPath(...).parent` so the root case is
    `""` and not `"."` -- joining `"."` would put a `./` segment into every id
    at depth one, and two ids differing only by that segment are two ids for one
    concept.
    """
    head, sep, _ = relative.rpartition("/")
    return head if sep else ""


def _join(parent: str, target: str) -> str | None:
    """A relative index target resolved against the index's own directory.

    Returns `None` for a target that climbs above the bundle root or is
    absolute. A target escaping the root is refused rather than clamped: a
    clamped path names a real file the bundle never pointed at.
    """
    if target.startswith("/"):
        return None
    parts: list[str] = parent.split("/") if parent else []
    for segment in target.split("/"):
        if segment in ("", "."):
            continue
        if segment == "..":
            if not parts:
                return None
            parts.pop()
            continue
        parts.append(segment)
    return "/".join(parts) if parts else None


def bundle_ref(bundle_root: Path, *, profile: BundleProfile = DEFAULT_PROFILE) -> str:
    """A content identity for the bundle: `sha256-tree:<hex>`.

    The digest is taken over the LF-joined, byte-sorted lines
    `<posix-relative-path>\t<sha256 of the file bytes>` across every file the
    INDEX TREE reaches -- the indexes themselves and the concepts they name.

    **Reachable, not `rglob`, and the cost is stated rather than hidden.** A
    file in the directory that no index names is outside this identity. It is
    also outside what the pre-pass may read (SS 9.2), so an identity covering it
    would be an assertion about bytes this command is forbidden to look at. The
    property that matters holds: every byte that can reach a payload is inside
    the ref, so the ref moves whenever a delivered excerpt could.

    **Path and bytes, never mtime or size.** A digest over metadata would move
    on a copy and hold still on an edit that preserved length, which is the
    opposite of what an identity is for.
    """
    indexes, concepts = _walk_index_tree(bundle_root, profile=profile)
    suffix = profile.paths.concept_suffix
    lines: list[bytes] = []
    for relative in (*indexes, *(f"{concept}{suffix}" for concept in concepts)):
        path = bundle_root / relative
        if not path.is_file():
            continue
        digest = hashlib.sha256(path.read_bytes()).hexdigest()
        lines.append(f"{relative}\t{digest}".encode())
    joined = b"\n".join(sorted(lines))
    return f"{REF_ALGORITHM}:{hashlib.sha256(joined).hexdigest()}"


class ConsumeError(Exception):
    """A refusal this instrument can name.

    Carries a `code` for the same reason `okf_contract_check.Finding` does: one
    "invalid" verdict over a dozen defects is a diagnostic no caller can act on.
    """

    def __init__(self, message: str, *, code: str) -> None:
        super().__init__(message)
        self.code = code


#: The three states a CONSUMER must distinguish (SS 6.1), against the two the
#: WIRE carries (`inbox.ADJUDICATION_STATES`). The difference is the whole
#: point: `unknown` is not a value a producer writes, it is what the absence of
#: the key means, and it is written explicitly here so a reader never has to
#: infer it from a missing member.
CONSUMER_ADJUDICATION_STATES = (*ADJUDICATION_STATES, "unknown")

AdjudicationState = Literal["proposed", "adjudicated", "unknown"]


@dataclass(frozen=True)
class Concept:
    """One concept read off disk, with every state written rather than implied."""

    path: Path
    concept_id: str
    bundle_id: str
    #: `True` when `bundle_id` came from the root index rather than the concept.
    #: Recorded rather than silently defaulted: SS 3.1 makes identity the
    #: `(bundle_id, concept_id)` tuple, so where the first half came from is
    #: part of what the payload is asserting.
    bundle_id_inherited: bool
    sha256: str
    okf_type: str
    title: str
    source_file: str
    adjudication: AdjudicationState
    #: `False` when the key was absent. `adjudication == "unknown"` already says
    #: so, but a separate flag keeps the two facts from being one inference.
    adjudication_present: bool
    frontmatter: Mapping[str, str]
    body: str


def read_concept(path: Path, *, bundle_root: Path, root_bundle_id: str) -> Concept:
    """One concept file as a record. Reads; derives nothing about the question.

    `sha256` is the digest of the CONCEPT FILE (SS 3.2), never the
    `source_sha256` frontmatter key -- that one digests the source document the
    concept was extracted from, and conflating them would make the payload's
    content identity point at a PDF nobody in the chain reads. Both exist on
    every K2 concept, which is what makes the confusion available.
    """
    frontmatter = parse_frontmatter(path)
    relative = path.relative_to(bundle_root).as_posix()
    #: The slash-preserving id: the bundle-relative path minus the suffix. This
    #: instrument's own choice, consistent with the RULE at `importer.py:244`
    #: and `inbox.py:1101-1102` -- but deliberately NOT `importer.import_slug`,
    #: which one line further down flattens the id to a single hyphenated
    #: segment. A flattened id fails a document-prefix match in a way that looks
    #: like a ranking miss rather than an id-format bug.
    concept_id = relative[: -len(CONCEPT_SUFFIX)] if relative.endswith(CONCEPT_SUFFIX) else relative
    raw = frontmatter.get("adjudication")
    if raw is None:
        adjudication: AdjudicationState = "unknown"
    elif raw == ADJUDICATION_PROPOSED:
        adjudication = "proposed"
    elif raw == ADJUDICATION_ADJUDICATED:
        adjudication = "adjudicated"
    else:
        raise ConsumeError(
            f"{relative} carries adjudication={raw!r}, outside the wire set "
            f"{ADJUDICATION_STATES}; refusing to map it to 'unknown', which "
            "would report 'we cannot tell whether it was judged' where the "
            "truth is that the bundle said something this consumer does not "
            "understand",
            code="adjudication_unknown_value",
        )
    declared = frontmatter.get("bundle_id")
    return Concept(
        path=path,
        concept_id=concept_id,
        bundle_id=declared if declared else root_bundle_id,
        bundle_id_inherited=not declared,
        sha256=hashlib.sha256(path.read_bytes()).hexdigest(),
        okf_type=frontmatter.get("type", ""),
        title=frontmatter.get("title", ""),
        source_file=frontmatter.get("source_file", ""),
        adjudication=adjudication,
        adjudication_present=raw is not None,
        frontmatter=frontmatter,
        body=_body(path),
    )


def _body(path: Path) -> str:
    """The text after the frontmatter block, or the whole file when there is none."""
    text = path.read_text(encoding="utf-8")
    lines = text.splitlines()
    if not lines or lines[0].strip() != "---":
        return text
    for offset, line in enumerate(lines[1:], start=2):
        if line.strip() == "---":
            return "\n".join(lines[offset:])
    return text


#: SS 6.2, from SPEC SS 5.3, lowest to highest. Imported from the checker's own
#: constant would be circular (the checker is a separate tool); spelled here and
#: held to the checker's set by the anti-drift test.
TrustTier = Literal["unverified", "machine-confirmed", "human-reviewed"]

#: The prefix that makes an actor a person. A PREFIX, never a substring: an
#: actor id `bot/human:2` contains the literal and is a machine, and promoting
#: it would be fabricated provenance produced by a matching bug.
HUMAN_ACTOR_PREFIX = "human:"


def trust_tier(verified_raw: str | None) -> TrustTier | None:
    """The tier `verified` implies, or `None` when the value cannot be read.

    Three inputs, three different facts, and collapsing any two is the defect:

    - `None` -- the key is ABSENT. SS 6.2: no `verified` key means
      `unverified`, and SS 6.3 forbids rejecting a concept for it.
    - `""` -- the key is PRESENT and this library cannot read it. Measured
      2026-09-07: the line-oriented `parse_frontmatter` returns `''` for a
      block-form value and the full string for a flow one, so the two are
      distinguishable. Returning `None` here is not a tier; the caller withholds
      the concept under a named rule. Emitting `unverified` instead would assert
      a fact nobody measured, which is exactly what SS 6.4 forbids.
    - a flow value -- decoded, and the tier follows the actors.
    """
    if verified_raw is None:
        return "unverified"
    if not verified_raw.strip():
        return None
    entries = _parse_flow_mappings(verified_raw)
    if entries is None:
        return None
    actors: list[str] = []
    for entry in entries:
        actor = entry.get("by")
        if not actor:
            raise ConsumeError(
                f"a `verified` entry names no `by` actor ({verified_raw!r}); "
                "refusing to tier it, because the tier IS a claim about who "
                "checked and there is nobody to name",
                code="verified_actorless",
            )
        actors.append(actor)
    if not actors:
        return None
    if any(actor.startswith(HUMAN_ACTOR_PREFIX) for actor in actors):
        return "human-reviewed"
    return "machine-confirmed"


def _parse_flow_mappings(value: str) -> list[dict[str, str]] | None:
    """A YAML flow sequence of flow mappings, or `None` when it is not one.

    Modelled on `structure._parse_flow_list` -- flow form only, because this
    library's standing rule is that a value it can write is a value it can read
    back. Not reused: that one splits on every comma, and `{ by: x, at: y }`
    carries a comma INSIDE a mapping, so it would return four fragments where
    there are two pairs.
    """
    stripped = value.strip()
    if not (stripped.startswith("[") and stripped.endswith("]")):
        return None
    body = stripped[1:-1].strip()
    if not body:
        return []
    mappings: list[dict[str, str]] = []
    for chunk in _split_top_level(body, "{", "}"):
        item = chunk.strip()
        if not (item.startswith("{") and item.endswith("}")):
            return None
        pairs: dict[str, str] = {}
        for field in item[1:-1].split(","):
            key, separator, raw = field.partition(":")
            if separator:
                pairs[key.strip()] = raw.strip()
        mappings.append(pairs)
    return mappings


def _split_top_level(body: str, opener: str, closer: str) -> list[str]:
    """Split on commas that are not inside a `{...}`."""
    parts: list[str] = []
    depth = 0
    current: list[str] = []
    for character in body:
        if character == opener:
            depth += 1
        elif character == closer:
            depth -= 1
        if character == "," and depth == 0:
            parts.append("".join(current))
            current = []
            continue
        current.append(character)
    parts.append("".join(current))
    return [part for part in parts if part.strip()]