from __future__ import annotations
from typing import Any, Dict
import os
from pathlib import Path
try:
    import wandb
except Exception:  # pragma: no cover
    wandb = None
from .distributed import is_main_process


def _read_text(path: Path) -> str | None:
    try:
        if path.exists():
            text = path.read_text().strip()
            return text or None
    except Exception:
        pass
    return None


def _write_text(path: Path, text: str) -> None:
    try:
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_text(text.strip() + "\n")
    except Exception:
        # W&B should never crash training just because the local ID file could not be written.
        pass


def _env_int(name: str, default: int) -> int:
    try:
        return int(os.environ.get(name, default))
    except Exception:
        return default


def init_wandb(cfg: Dict[str, Any], run_name: str | None = None):
    """Initialize W&B on rank 0 only and never crash training if W&B is slow/down.

    Resume behavior:
    - If wandb.id or WANDB_RUN_ID is provided, use it.
    - Otherwise, if <output_dir>/wandb_run_id.txt exists, reuse that ID.
    - If a run ID is used, default resume mode is "allow" unless overridden by
      wandb.resume or WANDB_RESUME.

    Reliability behavior:
    - WANDB_INIT_TIMEOUT controls wandb.init timeout seconds (default 300).
    - WANDB_SERVICE_WAIT controls W&B service startup wait seconds (default 300).
    - If wandb.init raises any exception, training continues with W&B disabled.
    """
    wb_cfg = cfg.get("wandb", {})
    if not wb_cfg.get("enabled", False) or not is_main_process() or wandb is None:
        return None

    mode = os.environ.get("WANDB_MODE", wb_cfg.get("mode", "online"))
    entity = wb_cfg.get("entity") or os.environ.get("WANDB_ENTITY") or None
    project = os.environ.get("WANDB_PROJECT", wb_cfg.get("project", "SACFlow-FM"))

    out_dir = Path(cfg.get("output_dir", "."))
    run_id_file = out_dir / "wandb_run_id.txt"

    run_id = (
        wb_cfg.get("id")
        or os.environ.get("WANDB_RUN_ID")
        or _read_text(run_id_file)
    )

    resume_mode = wb_cfg.get("resume") or os.environ.get("WANDB_RESUME")
    if run_id and resume_mode is None:
        resume_mode = "allow"

    init_timeout = _env_int("WANDB_INIT_TIMEOUT", int(wb_cfg.get("init_timeout", 300)))
    service_wait = _env_int("WANDB_SERVICE_WAIT", int(wb_cfg.get("service_wait", 300)))

    # Keep W&B files away from home/cache quotas if an output directory exists.
    os.environ.setdefault("WANDB_DIR", str(out_dir / "wandb"))
    os.environ.setdefault("WANDB_CACHE_DIR", str(out_dir / "wandb_cache"))
    os.environ.setdefault("WANDB_CONFIG_DIR", str(out_dir / "wandb_config"))

    try:
        settings = wandb.Settings(init_timeout=init_timeout, _service_wait=service_wait)
        run = wandb.init(
            project=project,
            entity=entity,
            mode=mode,
            name=run_name,
            id=run_id,
            resume=resume_mode,
            tags=wb_cfg.get("tags", []),
            config=cfg,
            settings=settings,
        )
    except Exception as e:  # pragma: no cover - depends on external W&B service/network
        print(
            f"[W&B WARNING] wandb.init failed ({type(e).__name__}: {e}). "
            "Continuing training with W&B disabled for this run. "
            "To avoid this, use WANDB_MODE=offline or increase WANDB_INIT_TIMEOUT.",
            flush=True,
        )
        return None

    # Persist the generated or reused run ID so future --resume auto attaches to
    # the same W&B run from this output directory.
    if getattr(run, "id", None):
        _write_text(run_id_file, run.id)

    return run


def wandb_log(run, data: Dict[str, Any], step: int | None = None):
    if run is not None:
        try:
            run.log(data, step=step)
        except Exception as e:
            print(f"[W&B WARNING] wandb.log failed: {e}", flush=True)


def wandb_finish(run):
    if run is not None:
        try:
            run.finish()
        except Exception as e:
            print(f"[W&B WARNING] wandb.finish failed: {e}", flush=True)