"""Shared data loading, file integrity and subprocess helpers."""
import hashlib
import csv
import json
from pathlib import Path
import subprocess

ROOT = Path(__file__).resolve().parents[1]


def sha256(path):
    digest = hashlib.sha256()
    with Path(path).open("rb") as stream:
        for chunk in iter(lambda: stream.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def contained(root, relative):
    path = Path(relative)
    if path.is_absolute() or ".." in path.parts or not path.parts:
        raise ValueError(f"Unsafe relative path: {relative}")
    resolved = (Path(root) / path).resolve()
    if not resolved.is_relative_to(Path(root).resolve()):
        raise ValueError(f"Path escapes root: {relative}")
    return resolved


def resolve_instance_id(instance_id):
    # Check input paths before looking up aliases, including unknown identifiers.
    contained(ROOT / "instances", instance_id)
    mapping_path = ROOT / "data/instance-id-map.tsv"
    if mapping_path.is_file():
        with mapping_path.open() as stream:
            rows = list(csv.DictReader(stream, delimiter="\t"))
        aliases = {}
        for row in rows:
            canonical = row["instance_id"]
            for alias in (row["original_instance_id"], canonical):
                if alias in aliases and aliases[alias] != canonical:
                    raise ValueError("Ambiguous instance ID mapping")
                aliases[alias] = canonical
        if instance_id not in aliases:
            raise ValueError(f"Unknown instance ID: {instance_id}")
        return aliases[instance_id]
    return instance_id


def load_task(instance_id):
    canonical = resolve_instance_id(instance_id)
    path = contained(ROOT / "instances", canonical) / "task.json"
    task = json.loads(path.read_text())
    if task["instance_id"] != canonical:
        raise ValueError("Task ID does not match directory")
    return task


def run(*args, cwd=None, capture=False):
    return subprocess.run(args, cwd=cwd, check=True, text=True,
                          stdout=subprocess.PIPE if capture else None).stdout