"""Loaders for evidence record files (JSON Lines).

The sample datasets under ``data/samples/`` use one JSON object per
line with the shape::

    {
      "evidence_id": "ev-cal-001",          # optional; derived if absent
      "kind": "calendar.event",
      "source": "ical:personal",
      "observed_at": "2024-09-02T09:45:00Z",
      "attributes": { ... }
    }

This mirrors the evidence payloads the milestone-3 import adapters emit
onto the operation log, so the same records can be fed either through
the adapters or directly through ``mnema-derive ingest``.
"""

from __future__ import annotations

import hashlib
import json
from pathlib import Path
from typing import Any, Iterable, List, Mapping

from mnema.core.canonical import canonical_json
from mnema.derive.model import Evidence


def evidence_from_record(record: Mapping[str, Any]) -> Evidence:
    for required in ("kind", "source", "observed_at"):
        if required not in record:
            raise ValueError("evidence record missing required field %r" % required)
    evidence_id = record.get("evidence_id")
    if not evidence_id:
        evidence_id = "ev_" + hashlib.sha256(
            canonical_json(
                {
                    "kind": record["kind"],
                    "source": record["source"],
                    "observed_at": record["observed_at"],
                    "attributes": record.get("attributes", {}),
                }
            )
        ).hexdigest()[:24]
    return Evidence(
        evidence_id=evidence_id,
        kind=record["kind"],
        source=record["source"],
        observed_at=record["observed_at"],
        attributes=dict(record.get("attributes", {})),
    )


def load_evidence_jsonl(path: Path) -> List[Evidence]:
    records: List[Evidence] = []
    with open(path, "r", encoding="utf-8") as handle:
        for line_number, line in enumerate(handle, start=1):
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            try:
                record = json.loads(line)
            except json.JSONDecodeError as exc:
                raise ValueError(
                    "%s:%d: invalid JSON: %s" % (path, line_number, exc)
                ) from exc
            records.append(evidence_from_record(record))
    return records


def load_evidence_files(paths: Iterable[Path]) -> List[Evidence]:
    """Load several files and return all evidence sorted by observation
    time (stable on evidence id), so ingestion order is deterministic."""
    all_records: List[Evidence] = []
    for path in paths:
        all_records.extend(load_evidence_jsonl(Path(path)))
    all_records.sort(key=lambda ev: (ev.observed_at, ev.evidence_id))
    return all_records