"""Optional historical report migration; production only reads existing journals."""

import hashlib
import json
import shutil
from pathlib import Path
from tools.rag.common import DATA_DIR
from tools.runtime.report_files import CORE_JSON, run_id


def migration_plan(data_dir: Path = DATA_DIR) -> list[dict]:
    moves = []
    for path in sorted(data_dir.iterdir()):
        if not path.is_file() or path.name.startswith(".") or path.name in CORE_JSON:
            continue
        if path.suffix == ".json":
            target = data_dir / "reports/archive/legacy" / path.name
        elif path.suffix == ".log":
            target = data_dir / "logs/archive/legacy" / path.name
        else:
            continue
        moves.append(
            {
                "source": str(path.absolute()),
                "destination": str(target.absolute()),
                "sha256": hashlib.sha256(path.read_bytes()).hexdigest(),
            }
        )
    return moves


def retention_plan(data_dir: Path = DATA_DIR, *, keep: int = 5) -> list[dict]:
    if keep < 1:
        raise ValueError("Keep at least one verification")
    completed = []
    for path in (data_dir / "reports/verification").glob("*.json"):
        try:
            data = json.loads(path.read_text())
            if isinstance(data, dict) and type(data.get("passed")) is bool:
                completed.append(path)
        except (ValueError, OSError):
            continue
    moves = []
    for path in sorted(completed, key=lambda p: (p.stat().st_mtime_ns, p.name), reverse=True)[
        keep:
    ]:
        target = data_dir / "reports/archive/verification" / path.name
        moves.append(
            {
                "source": str(path.absolute()),
                "destination": str(target.absolute()),
                "sha256": hashlib.sha256(path.read_bytes()).hexdigest(),
            }
        )
        log = data_dir / "logs/verification" / path.with_suffix(".pytest.log").name
        if log.exists():
            target = data_dir / "logs/archive/verification" / log.name
            moves.append(
                {
                    "source": str(log.absolute()),
                    "destination": str(target.absolute()),
                    "sha256": hashlib.sha256(log.read_bytes()).hexdigest(),
                }
            )
    return moves


def apply_moves(moves: list[dict], *, data_dir: Path = DATA_DIR) -> Path:
    # Validate the entire plan before moving anything. Never replace existing files.
    for move in moves:
        source, destination = Path(move["source"]), Path(move["destination"])
        if (
            destination.exists()
            or hashlib.sha256(source.read_bytes()).hexdigest() != move["sha256"]
        ):
            raise RuntimeError("Report migration conflict; no files moved")
    journal = data_dir / "reports/migrations" / (run_id() + ".json")
    journal.parent.mkdir(parents=True, exist_ok=True)
    record = {
        "method": "Move without rewriting content or deleting historical evidence",
        "moves": [],
    }

    def write_journal():
        temporary = journal.with_suffix(".tmp")
        temporary.write_text(json.dumps(record, indent=2) + "\n")
        temporary.replace(journal)

    write_journal()
    for move in moves:
        destination = Path(move["destination"])
        destination.parent.mkdir(parents=True, exist_ok=True)
        shutil.move(move["source"], destination)
        record["moves"].append(move)
        write_journal()
    return journal