"""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 in the JSON (dashboard tile
# quick view). The full unbounded log is appended to a sidecar .log file
# next to the .json so the detail page can show everything.
LOG_TAIL_MAX = 50
# Cap how many stage transitions we record per session (bounds JSON size on
# pathological loops; 30 covers more than any real run uses).
STAGE_HISTORY_MAX = 30
# Detail page caps how many bytes of the sidecar .log it sends to the
# browser, to avoid blowing up the response for a runaway log.
DETAIL_LOG_MAX_BYTES = 1024 * 1024  # 1 MB
# 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 _log_path_for(serial: str) -> str:
    safe = _SAFE_SERIAL.sub("_", serial.strip()) or "unknown"
    return os.path.join(config.IMAGING_DIR, f"{safe}.log")


def _append_full_log(serial: str, lines):
    """Best-effort append to the per-serial sidecar log file. Each line is
    timestamped. Failures are swallowed (status-tracking is not the
    authoritative log source; the .log is a convenience for the detail
    page)."""
    if not lines:
        return
    if isinstance(lines, str):
        lines = [lines]
    try:
        _ensure_dir()
        with open(_log_path_for(serial), "a") as f:
            ts = _now_iso()
            for line in lines:
                f.write(f"{ts}  {line}\n")
    except OSError:
        pass


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 = {}

    # Reimage detection: if the new payload's stage_index <= 2 (WinPE startnet
    # = 2, Run-ShopfloorSetup start = 1) AND that's lower than the cached
    # stage_index, treat as a fresh imaging run on the same bay. Clear
    # log_tail + reset started_at; preserve serial; remember the previous
    # run's last_updated for audit. Without this, a reimage leaves stale
    # "succeeded" / high-idx state visible until the new run progresses
    # past idx 2.
    #
    # Threshold of 2 covers the first signal of a new run: the WinPE-phase
    # status push from startnet.cmd at idx=2 (fires within seconds of PXE
    # menu choice). Previously the threshold was 1, which meant the reset
    # only triggered once Run-ShopfloorSetup ran post-PPKG, ~10-20 minutes
    # into a new run.
    if state:
        try:
            old_idx = int(state.get("stage_index") or 0)
            new_idx = int(payload.get("stage_index") or 0)
        except (TypeError, ValueError):
            old_idx, new_idx = 0, 0
        rewind = new_idx > 0 and new_idx < old_idx and new_idx <= 1
        prev_done = state.get("status") in ("succeeded", "failed")
        if rewind or (prev_done and new_idx > 0 and new_idx <= 1):
            state = {"serial": serial, "previous_run_at": state.get("last_updated"), "log_tail": []}

    if not state:
        state = {
            "serial": serial,
            "started_at": _now_iso(),
            "log_tail": [],
        }
    elif "started_at" not in state:
        # Fresh state after a rewind - mint a new started_at.
        state["started_at"] = _now_iso()

    # Append any new log lines: capped tail in the JSON for the dashboard
    # quick view, and unbounded append to the sidecar .log for the detail
    # page.
    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:]
        _append_full_log(serial, new_lines)

    # Stage history: record a transition row whenever stage_index increases
    # or status changes. Bounded to STAGE_HISTORY_MAX so a bouncing client
    # can't blow up the JSON. The dashboard tile only needs current state;
    # the detail page renders the timeline from this list.
    history = list(state.get("stage_history", []))
    try:
        new_idx = int(payload.get("stage_index") or 0)
    except (TypeError, ValueError):
        new_idx = 0
    try:
        old_idx = int(state.get("stage_index") or 0)
    except (TypeError, ValueError):
        old_idx = 0
    new_status = payload.get("status") or state.get("status") or "in_progress"
    old_status = state.get("status") or ""
    stage_changed = new_idx > old_idx
    status_changed = new_status != old_status and new_status in ("succeeded", "failed")
    if stage_changed or status_changed or not history:
        history.append({
            "ts": _now_iso(),
            "stage_index": new_idx or old_idx,
            "current_stage": payload.get("current_stage") or state.get("current_stage", ""),
            "status": new_status,
        })
        state["stage_history"] = history[-STAGE_HISTORY_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(include_inferred: bool = True) -> list[dict]:
    """Return all sessions sorted by last_updated desc.

    When include_inferred is True (default for the dashboard), also pull
    server-side log-tail evidence and append synthesized sessions for any
    bay that has touched DHCP/TFTP/boot.wim but not yet pushed status.
    Real client-pushed sessions always win for the same MAC.
    """
    _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
    if include_inferred:
        from services import imaging_log_tail
        out = imaging_log_tail.merge_with_client_sessions(out)
    else:
        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 read_full_log(serial: str, max_bytes: int = DETAIL_LOG_MAX_BYTES) -> tuple[str, bool]:
    """Return (text, truncated). Reads the trailing max_bytes of the sidecar
    .log. `truncated` is True when the file was larger than max_bytes and
    the leading slice was dropped."""
    path = _log_path_for(serial)
    try:
        size = os.path.getsize(path)
    except OSError:
        return ("", False)
    truncated = size > max_bytes
    start = max(0, size - max_bytes)
    try:
        with open(path, "rb") as f:
            f.seek(start)
            data = f.read()
    except OSError:
        return ("", False)
    text = data.decode("utf-8", errors="replace")
    if truncated:
        nl = text.find("\n")
        if nl >= 0:
            text = text[nl + 1:]
    return (text, truncated)


def delete_session(serial: str) -> bool:
    path = _path_for(serial)
    if not os.path.isfile(path):
        return False
    try:
        os.unlink(path)
    except OSError:
        return False
    # Best-effort sidecar cleanup.
    try:
        os.unlink(_log_path_for(serial))
    except OSError:
        pass
    return True


def delete_all_sessions() -> int:
    """Wipe every per-bay JSON + sidecar .log in IMAGING_DIR. Returns count
    of JSON files removed."""
    _ensure_dir()
    removed = 0
    for fn in os.listdir(config.IMAGING_DIR):
        if fn.endswith(".json") or fn.endswith(".log"):
            try:
                os.unlink(os.path.join(config.IMAGING_DIR, fn))
            except OSError:
                continue
            if fn.endswith(".json"):
                removed += 1
    return removed