from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
from typing import TYPE_CHECKING

from tht.config import ConfigError

if TYPE_CHECKING:
    from tht.config import Config


@dataclass(frozen=True)
class ResolvedPaths:
    workspace: Path
    sessions: Path
    artifacts: Path
    indexes: Path
    corpus: Path


def _resolve_root(path: Path, workspace: Path, name: str) -> Path:
    if path.is_absolute():
        # Existing deployments commonly point at an external workspace checkout. Keep
        # those paths working while `tht doctor` identifies them for migration.
        return path

    resolved = (workspace / path).resolve()
    if not resolved.is_relative_to(workspace):
        raise ConfigError(f"paths.{name} resolves outside workspace root")
    return resolved


def resolve_workspace_paths(
    config_path: Path, cfg: Config, data_root: Path
) -> ResolvedPaths:
    """Resolve portable paths under ``<data_root>/workspaces/<config stem>``.

    Relative roots are sandboxed to the logical workspace. Absolute roots are a
    compatibility bridge for existing installations and are never rewritten.
    """
    canonical_data_root = data_root.resolve()
    workspaces_root = canonical_data_root / "workspaces"
    workspace = (workspaces_root / config_path.stem).resolve()
    if not workspace.is_relative_to(workspaces_root):
        raise ConfigError("workspace resolves outside workspaces root")
    roots = cfg.roots
    return ResolvedPaths(
        workspace=workspace,
        sessions=_resolve_root(roots.sessions, workspace, "sessions"),
        artifacts=_resolve_root(roots.artifacts, workspace, "artifacts"),
        indexes=_resolve_root(roots.indexes, workspace, "indexes"),
        corpus=_resolve_root(Path("corpus"), workspace, "corpus"),
    )