"""PXE imaging progress tracking.

Imaging clients POST coarse-grained status updates to /imaging/status as
they progress through WIM apply -> drivers -> first boot -> PPKG -> per-PC
shopfloor setup. Each session is keyed by the BIOS serial number (stable
across the WinPE -> Windows transition; survives a target hostname change).

Storage is one JSON file per serial under IMAGING_DIR. Atomic write via
tempfile + rename. Reads merge the new payload into existing state so
clients can post partial updates (just the current_stage + log_tail tick).
"""
from __future__ import annotations

import json
import os
import re
import tempfile
from datetime import datetime, timezone
from typing import Optional

import config

# How many recent log lines to keep per session.
LOG_TAIL_MAX = 50
# Sessions older than this are considered stale and dropped from the dashboard
# "active" list. Still readable individually.
ACTIVE_WINDOW_HOURS = 6

# Filenames are derived from serial; sanitize to avoid path traversal /
# weird filesystem characters. Anything outside [A-Za-z0-9._-] becomes _.
_SAFE_SERIAL = re.compile(r"[^A-Za-z0-9._-]")


def _ensure_dir():
    os.makedirs(config.IMAGING_DIR, exist_ok=True)


def _path_for(serial: str) -> str:
    safe = _SAFE_SERIAL.sub("_", serial.strip()) or "unknown"
    return os.path.join(config.IMAGING_DIR, f"{safe}.json")


def _now_iso() -> str:
    return datetime.now().astimezone().isoformat(timespec="seconds")


def update_session(payload: dict) -> dict:
    """Merge `payload` into the JSON file for payload['serial'].

    payload must include 'serial'. All other fields are optional; whatever is
    present overwrites the existing field. log_tail is appended to (capped).
    Returns the resulting full state.
    """
    serial = (payload.get("serial") or "").strip()
    if not serial:
        raise ValueError("payload missing 'serial'")

    _ensure_dir()
    path = _path_for(serial)

    state: dict = {}
    if os.path.isfile(path):
        try:
            with open(path, "r") as f:
                state = json.load(f)
        except (json.JSONDecodeError, OSError):
            state = {}

    if not state:
        state = {
            "serial": serial,
            "started_at": _now_iso(),
            "log_tail": [],
        }

    # Append any new log lines (preserve old; cap to LOG_TAIL_MAX).
    new_lines = payload.pop("log_lines", None)
    if new_lines:
        if isinstance(new_lines, str):
            new_lines = [new_lines]
        tail = list(state.get("log_tail", []))
        tail.extend(new_lines)
        state["log_tail"] = tail[-LOG_TAIL_MAX:]

    for key, value in payload.items():
        if value is None or value == "":
            continue
        state[key] = value

    state["last_updated"] = _now_iso()
    if "status" not in state:
        state["status"] = "in_progress"

    fd, tmp = tempfile.mkstemp(dir=config.IMAGING_DIR, prefix=".tmp-", suffix=".json")
    try:
        with os.fdopen(fd, "w") as f:
            json.dump(state, f, indent=2)
        os.replace(tmp, path)
    except Exception:
        try:
            os.unlink(tmp)
        except OSError:
            pass
        raise
    return state


def list_sessions() -> list[dict]:
    """Return all sessions sorted by last_updated desc."""
    _ensure_dir()
    out: list[dict] = []
    for name in os.listdir(config.IMAGING_DIR):
        if not name.endswith(".json") or name.startswith(".tmp-"):
            continue
        path = os.path.join(config.IMAGING_DIR, name)
        try:
            with open(path, "r") as f:
                out.append(json.load(f))
        except (json.JSONDecodeError, OSError):
            continue
    out.sort(key=lambda s: s.get("last_updated", ""), reverse=True)
    return out


def get_session(serial: str) -> Optional[dict]:
    path = _path_for(serial)
    if not os.path.isfile(path):
        return None
    try:
        with open(path, "r") as f:
            return json.load(f)
    except (json.JSONDecodeError, OSError):
        return None


def delete_session(serial: str) -> bool:
    path = _path_for(serial)
    if not os.path.isfile(path):
        return False
    try:
        os.unlink(path)
        return True
    except OSError:
        return False