from __future__ import annotations

from pathlib import Path

from .types import TaskSpec


def discover_tasks(base_tasks: Path, *, task_glob: str, task_ids: set[str] | None) -> list[TaskSpec]:
    tasks_root = base_tasks / "tasks"
    if not tasks_root.is_dir():
        raise FileNotFoundError(f"tasks directory not found: {tasks_root}")

    script_root = find_script_root(base_tasks)
    specs: list[TaskSpec] = []
    for task_dir in sorted(path for path in tasks_root.glob(task_glob) if path.is_dir()):
        task_id = task_dir.name
        if task_ids is not None and task_id not in task_ids:
            continue

        env_builder_path = task_dir / "env_builder.py"
        if not env_builder_path.is_file():
            continue

        prompt_path = find_prompt_path(tasks_root, task_dir, task_id)
        verifier_path = find_verifier_path(script_root, task_id) if script_root is not None else None
        specs.append(
            TaskSpec(
                task_id=task_id,
                task_dir=task_dir,
                prompt_path=prompt_path,
                env_builder_path=env_builder_path,
                verifier_path=verifier_path,
            )
        )

    if task_ids is not None:
        found_ids = {spec.task_id for spec in specs}
        missing_ids = sorted(task_ids - found_ids)
        if missing_ids:
            raise FileNotFoundError(f"requested task ids not found or missing env_builder.py: {missing_ids}")
    if not specs:
        raise FileNotFoundError(f"no task directories matched {task_glob!r} under {tasks_root}")
    return specs


def find_script_root(base_tasks: Path) -> Path | None:
    for dirname in ("scrips", "scripts"):
        candidate = base_tasks / dirname
        if candidate.is_dir():
            return candidate
    return None


def find_prompt_path(tasks_root: Path, task_dir: Path, task_id: str) -> Path:
    candidates = (
        tasks_root / "prompts" / f"{task_id}.md",
        task_dir / "prompt.md",
        task_dir / "task.md",
    )
    for candidate in candidates:
        if candidate.is_file():
            return candidate
    raise FileNotFoundError(
        f"prompt file not found for {task_id}; tried: "
        + ", ".join(str(path) for path in candidates)
    )


def find_verifier_path(script_root: Path, task_id: str) -> Path | None:
    candidates = (
        script_root / task_id / "verify_workplace.py",
        script_root / f"{task_id}.py",
        script_root / "verify_workplace.py",
    )
    for candidate in candidates:
        if candidate.is_file():
            return candidate
    return None