"""Load the JSON Schema contracts and validate canon logs / origin seeds.

Schemas are the single source of truth in /docs/schemas. This module is the
api's half of the contract (charter §11): every canon log the client posts is
validated here before it could ever reach a prompt.
"""

import json
import os
from functools import lru_cache
from pathlib import Path

from jsonschema import Draft202012Validator


def _schema_dir() -> Path:
    """Locate the schema directory.

    Honours CANON_SCHEMA_DIR, else walks up from this file looking for
    docs/schemas (local checkout) or schemas (bundled into the Docker image).
    """
    env = os.environ.get("CANON_SCHEMA_DIR")
    if env:
        return Path(env)
    here = Path(__file__).resolve()
    for parent in here.parents:
        for candidate in (parent / "docs" / "schemas", parent / "schemas"):
            if candidate.is_dir():
                return candidate
    raise RuntimeError("schema directory not found")


@lru_cache(maxsize=None)
def _validator(schema_name: str) -> Draft202012Validator:
    with open(_schema_dir() / schema_name) as f:
        return Draft202012Validator(json.load(f))


def validation_errors(doc: dict, schema_name: str) -> list[str]:
    validator = _validator(schema_name)
    # Stringify path segments before sorting: a path can mix str property names
    # and int array indices, which are not orderable against each other.
    return [e.message for e in sorted(validator.iter_errors(doc), key=lambda e: [str(p) for p in e.path])]


def validate_origin(doc: dict) -> list[str]:
    return validation_errors(doc, "origin.schema.json")


def validate_canon_log(doc: dict) -> list[str]:
    return validation_errors(doc, "canon-log.schema.json")