"""Builders for stage, resource-snapshot, and dataset manifests.

Every stage output carries ``input_manifest_sha256``, ``code_commit``,
``config_sha256``, and ``created_at`` so that an artifact can be traced to the
exact code, config, and upstream inputs that produced it (``docs/02_DATA_PIPELINE.md``
section 1). Image paths are stored relative to the manifest so outputs reproduce
across mounts.
"""

from __future__ import annotations

from collections.abc import Iterable
from dataclasses import dataclass
from pathlib import Path
from typing import Any

from .atomic_io import atomic_write_json, count_jsonl, read_jsonl
from .hashing import join_manifest_sha256, sha256_file, sha256_text

# Reserved provenance keys present on every stage manifest.
STAGE_PROVENANCE_KEYS = (
    "input_manifest_sha256",
    "code_commit",
    "config_sha256",
    "created_at",
)


def stage_manifest(
    *,
    stage: str,
    input_manifest_sha256: str | None,
    code_commit: str,
    config_sha256: str,
    created_at: str,
    renderer_version: str | None = None,
    answer_normalizer_version: str | None = None,
    extra: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Build a stage manifest record with required provenance fields.

    ``created_at`` must be supplied by the caller (RFC 3339, UTC preferred) so
    that the pipeline stays deterministic and never relies on wall-clock time
    inside a reproducible stage.
    """
    record: dict[str, Any] = {
        "stage": stage,
        "input_manifest_sha256": input_manifest_sha256,
        "code_commit": code_commit,
        "config_sha256": config_sha256,
        "created_at": created_at,
    }
    if renderer_version is not None:
        record["renderer_version"] = renderer_version
    if answer_normalizer_version is not None:
        record["answer_normalizer_version"] = answer_normalizer_version
    if extra:
        for key, value in extra.items():
            if key in STAGE_PROVENANCE_KEYS:
                raise ValueError(f"extra manifest key collides with reserved key {key!r}")
            record[key] = value
    return record


def input_manifest_hash_from_paths(paths: Iterable[str | Path]) -> str:
    """Hash an ordered set of input artifact files by their per-file SHA-256."""
    return join_manifest_sha256(sha256_file(path) for path in paths)


def input_manifest_hash_from_jsonl(path: str | Path) -> str:
    """Fold every row's ``sha256``/``base_id`` field of a JSONL file into one hash."""
    digests: list[str] = []
    for row in read_jsonl(path):
        digest = row.get("sha256") or row.get("base_id") or row.get("group_id")
        if digest is None:
            raise ValueError(f"row in {path} has no sha256/base_id/group_id field")
        digests.append(str(digest))
    return join_manifest_sha256(digests)


@dataclass(frozen=True)
class FileEntry:
    relative_path: str
    size: int
    sha256: str


def snapshot_file_tree(root: str | Path) -> list[FileEntry]:
    """Return ``{relative_path, size, sha256}`` for every regular file under ``root``.

    Symlinks are resolved to their target's content. Entries are sorted by
    relative path so the snapshot is deterministic.
    """
    root_path = Path(root)
    entries: list[FileEntry] = []
    if not root_path.exists():
        return entries
    for path in sorted(root_path.rglob("*")):
        if not path.is_file():
            continue
        if path.is_symlink():
            target = path.resolve()
            if not target.is_file():
                continue
        relative = path.relative_to(root_path).as_posix()
        entries.append(
            FileEntry(
                relative_path=relative,
                size=path.stat().st_size,
                sha256=sha256_file(path),
            )
        )
    return entries


def resource_snapshot_row(
    *,
    logical_name: str,
    repo_id: str,
    requested_revision: str,
    resolved_commit: str,
    local_path: str,
    downloaded_at: str,
    file_count: int,
    total_bytes: int,
    manifest_sha256: str,
    kind: str = "model",
) -> dict[str, Any]:
    """Build one ``resource_snapshot.jsonl`` row (``docs/01_RESOURCE_CATALOG.md`` §7)."""
    if resolved_commit != requested_revision:
        raise ValueError(
            f"resolved commit {resolved_commit} != requested {requested_revision} "
            f"for {logical_name}; this is a preflight failure"
        )
    return {
        "logical_name": logical_name,
        "kind": kind,
        "repo_id": repo_id,
        "requested_revision": requested_revision,
        "resolved_commit": resolved_commit,
        "local_path": local_path,
        "downloaded_at": downloaded_at,
        "file_count": file_count,
        "total_bytes": total_bytes,
        "manifest_sha256": manifest_sha256,
    }


def file_tree_manifest_sha256(entries: Iterable[FileEntry]) -> str:
    """SHA-256 of the canonical ``relative_path\0size\0sha256`` list (sorted)."""
    payload = "".join(
        f"{e.relative_path}\0{e.size}\0{e.sha256}\n"
        for e in sorted(entries, key=lambda e: e.relative_path)
    )
    return sha256_text(payload)


def artifact_manifest_sha256(path: str | Path) -> str:
    """Hash one file by bytes or one directory by its deterministic file tree."""

    source = Path(path)
    if source.is_file():
        return sha256_file(source)
    if source.is_dir():
        return file_tree_manifest_sha256(snapshot_file_tree(source))
    raise FileNotFoundError(f"artifact does not exist: {source}")


def build_dataset_manifest(
    *,
    dataset_name: str,
    items_path: str | Path,
    extra: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Build a ``<dataset_name>.manifest.json`` summarizing a normalized JSONL file."""
    items_path = Path(items_path)
    record: dict[str, Any] = {
        "dataset_name": dataset_name,
        "items_path": items_path.name,
        "row_count": count_jsonl(items_path),
        "items_sha256": sha256_file(items_path),
    }
    if extra:
        record.update(extra)
    return record


def write_dataset_manifest(
    *,
    output_path: str | Path,
    dataset_name: str,
    items_path: str | Path,
    extra: dict[str, Any] | None = None,
) -> dict[str, Any]:
    """Build and atomically write a dataset manifest, returning the record."""
    record = build_dataset_manifest(dataset_name=dataset_name, items_path=items_path, extra=extra)
    atomic_write_json(output_path, record)
    return record