"""Standard-library helpers for immutable droid-mind training data."""

import hashlib
import json
from pathlib import Path
from typing import TypedDict


class Example(TypedDict):
    user: str
    emotion: str
    reply: str


def sha256_file(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as source:
        for chunk in iter(lambda: source.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def load_emotion_ids(path: Path) -> list[str]:
    payload = json.loads(path.read_text())
    if not isinstance(payload, list):
        raise ValueError(f"{path}: expected a JSON list")
    ids = [item.get("id") for item in payload if isinstance(item, dict)]
    if not ids or any(not isinstance(emotion, str) or not emotion for emotion in ids):
        raise ValueError(f"{path}: every emotion must have a non-empty id")
    if len(ids) != len(set(ids)):
        raise ValueError(f"{path}: emotion ids must be unique")
    return ids


def load_examples(
    path: Path,
    emotion_ids: set[str],
    max_rows: int | None = None,
) -> list[Example]:
    if max_rows is not None and max_rows < 1:
        raise ValueError("max_rows must be positive")

    examples: list[Example] = []
    with path.open() as source:
        for line_number, line in enumerate(source, 1):
            if not line.strip():
                continue
            try:
                row = json.loads(line)
            except json.JSONDecodeError as error:
                raise ValueError(f"{path}:{line_number}: invalid JSON: {error}") from error
            if not isinstance(row, dict):
                raise ValueError(f"{path}:{line_number}: expected a JSON object")
            values: dict[str, str] = {}
            for field in ("user", "emotion", "reply"):
                value = row.get(field)
                if not isinstance(value, str) or not value.strip():
                    raise ValueError(
                        f"{path}:{line_number}: {field} must be a non-empty string"
                    )
                values[field] = value
            if values["emotion"] not in emotion_ids:
                raise ValueError(
                    f"{path}:{line_number}: unknown emotion {values['emotion']!r}"
                )
            examples.append(
                {
                    "user": values["user"],
                    "emotion": values["emotion"],
                    "reply": values["reply"],
                }
            )
            if max_rows is not None and len(examples) == max_rows:
                break

    if not examples:
        raise ValueError(f"{path}: no examples")
    return examples