"""Persistent copy flags shared by page splitting, margin review and the GUI."""
from pathlib import Path

from copienator import CliError, EvaluationWorkspace, atomic_update_json, read_json


def _path(workspace: EvaluationWorkspace) -> Path:
    return workspace.metadata_dir / "copy_errors.json"


def _validate(value) -> dict[str, str]:
    if not isinstance(value, dict) or any(
        not isinstance(name, str) or not isinstance(reason, str)
        or "/" in name or "\\" in name or Path(name).suffix.casefold() != ".pdf"
        for name, reason in value.items()
    ):
        raise CliError("Invalid copy_errors.json: expected PDF filenames and error descriptions")
    return value


def copy_errors(workspace: EvaluationWorkspace) -> dict[str, str]:
    return _validate(read_json(_path(workspace), default={}))


def mark_copy_error(workspace: EvaluationWorkspace, pdf: Path, reason: str) -> None:
    def update(errors):
        _validate(errors)[pdf.name] = reason
    atomic_update_json(_path(workspace), update, default_factory=dict)


def clear_copy_error(workspace: EvaluationWorkspace, pdf: Path) -> None:
    if not _path(workspace).exists():
        return
    def update(errors):
        _validate(errors).pop(pdf.name, None)
    atomic_update_json(_path(workspace), update, default_factory=dict)


def marked_copy_paths(workspace: EvaluationWorkspace, *, originals: bool = False) -> list[Path]:
    directories = ([workspace.original_copies_dir, workspace.copies_dir, workspace.root]
                   if originals else [workspace.copies_dir])
    result = []
    for name in sorted(copy_errors(workspace), key=str.casefold):
        path = next((directory / name for directory in directories if (directory / name).is_file()), None)
        if path is None:
            raise CliError(f"Marked copy not found: {name}")
        result.append(path)
    return result