"""Blob lifecycle — pure, so it is unit-testable without Home Assistant.

The file system is not part of the configuration store's transaction, so who
may write or delete a plan or an attachment, and when, is a correctness
question rather than housekeeping. It lives here, apart from the WebSocket and
HTTP plumbing, precisely because it is the part that has to be reasoned about
and tested.
"""
from __future__ import annotations

import logging
import os
import time
from pathlib import Path
from typing import Any

from .const import PLAN_ORPHAN_TTL_S, SCHEDULED_GRACE_S
from .validation import MAX_FILENAME, PLAN_EXTENSIONS, sanitize_filename

_LOGGER = logging.getLogger(__name__)

# Streaming uploads land here first. The prefix is a dot so the name can never
# collide with an attachment (sanitize_filename strips leading dots) and is easy
# to sweep.
TMP_PREFIX = ".upload-"


def reserve_filename(directory: Path, name: str) -> str:
    """Atomically claim a free name inside `directory` and return it.

    Creates the file, empty, with `O_CREAT | O_EXCL`, so the name is *taken* the
    moment it is chosen. The previous version asked `exists()` and returned a
    string; two uploads racing between the check and the write agreed on the
    same name and one silently overwrote the other, both reporting success
    (HP-1460-01). The caller writes the real bytes over the placeholder — it
    owns the name by then — and must remove it if it never gets that far.

    The result is guaranteed to satisfy `sanitize_filename(result) == result`:
    the content view sanitises the name in the request too, so a name it would
    shorten or rewrite is a file that is written and then never served.
    """
    directory.mkdir(parents=True, exist_ok=True)
    # Split the extension off the RAW name: sanitize_filename() truncates to
    # MAX_FILENAME, so sanitising first would cut ".pdf" off a long name and the
    # attachment would be stored — and served — without its type.
    base = name.rsplit("/", 1)[-1].rsplit("\\", 1)[-1]
    stem, dot, suffix = base.rpartition(".")
    if not dot:
        stem, suffix = base, ""
    stem = sanitize_filename(stem)
    ext = f".{sanitize_filename(suffix)[:16]}" if suffix else ""
    i = 1
    while True:
        tag = "" if i == 1 else f"-{i}"
        # budget the stem so the WHOLE name fits, including the collision tag —
        # appending "-2" to an already maximal name produced a url the view
        # truncated back to something else, i.e. a permanent 404
        room = MAX_FILENAME - len(ext) - len(tag)
        candidate = (stem[:room] if room > 0 else "f") + tag + ext
        candidate = sanitize_filename(candidate)
        if candidate.startswith("."):  # a name that is only an extension
            candidate = "file" + candidate
        try:
            fd = os.open(directory / candidate, os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0o644)
        except FileExistsError:
            i += 1
            if i > 10000:  # pathological directory; do not spin forever
                raise
            continue
        os.close(fd)
        return candidate


def attachment_refs(cfg: dict[str, Any] | None) -> set[str]:
    """"<marker>/<file>" for every attachment a configuration references."""
    out: set[str] = set()
    for m in (cfg or {}).get("markers") or []:
        for pdf in m.get("pdfs") or []:
            url = pdf.get("url") if isinstance(pdf, dict) else None
            if not isinstance(url, str) or "/files/" not in url:
                continue
            rel = url.split("?", 1)[0].split("/files/", 1)[1]
            if rel.count("/") == 1:
                out.add(rel)
    return out


def sweep_upload_temps(files_dir: Path, now: float | None = None) -> int:
    """Remove abandoned streaming temporaries (HP-1460-02).

    The request itself deletes its own, but a hard kill — a restart mid-upload,
    an OOM — leaves one behind, and the attachment collector only walks marker
    folders, so it would never be seen. Age-gated for the same reason as the
    rest: a fresh one belongs to a request still in flight.
    """
    cutoff = (time.time() if now is None else now) - PLAN_ORPHAN_TTL_S
    removed = 0
    try:
        items = [p for p in files_dir.iterdir() if p.is_file()] if files_dir.is_dir() else []
    except OSError as err:
        _LOGGER.warning("House Plan: could not list %s: %s", files_dir, err)
        return 0
    for item in items:
        if not item.name.startswith(TMP_PREFIX):
            continue
        try:
            if item.stat().st_mtime >= cutoff:
                continue
            item.unlink()
            removed += 1
        except OSError:
            continue
    return removed


def collect_attachments(
    files_dir: Path,
    old_cfg: dict[str, Any] | None,
    new_cfg: dict[str, Any],
    now: float | None = None,
) -> int:
    """The same commit-scoped rule as `collect_plans`, for marker attachments.

    A file the old revision referenced and the new one does not was superseded
    by this commit and goes. Otherwise: files of a marker that still exists are
    left alone, a staging folder (`up_*`, only ever a dialog that was never
    saved) is collected after PLAN_ORPHAN_TTL_S, and anything else waits out
    SCHEDULED_GRACE_S. Never raises: it runs behind a durable write.
    """
    new_refs = attachment_refs(new_cfg)
    old_refs = attachment_refs(old_cfg)
    # Same distinction as for plans. A staging folder (`up_*`) is different: it
    # only ever holds an upload from a dialog that was never saved, so the short
    # rule is exactly right there even on the timer.
    live_markers = {str(m.get("id")) for m in (new_cfg or {}).get("markers") or []}
    now_s = time.time() if now is None else now
    staging_cutoff = now_s - PLAN_ORPHAN_TTL_S
    cutoff = now_s - SCHEDULED_GRACE_S
    removed = 0
    try:
        folders = sorted(p for p in files_dir.iterdir() if p.is_dir()) if files_dir.is_dir() else []
    except OSError as err:
        _LOGGER.warning("House Plan: could not list %s: %s", files_dir, err)
        return 0
    removed += sweep_upload_temps(files_dir, now)
    for folder in folders:
        if folder.name in live_markers:
            continue  # the marker is still there; its files are its own business
        # a staging folder only ever holds an upload from a dialog that was
        # never saved — unambiguous, so the short rule is right there
        limit = staging_cutoff if folder.name.startswith("up_") else cutoff
        try:
            items = sorted(p for p in folder.iterdir() if p.is_file())
        except OSError:
            continue
        for item in items:
            rel = f"{folder.name}/{item.name}"
            if rel in new_refs:
                continue
            if rel not in old_refs:  # not superseded: absence alone is weak evidence
                try:
                    if item.stat().st_mtime >= limit:
                        continue
                except OSError:
                    continue
            try:
                item.unlink()
                removed += 1
            except OSError as err:
                _LOGGER.warning("House Plan: could not remove the attachment %s: %s", item, err)
        try:
            next(folder.iterdir())
        except StopIteration:
            try:
                folder.rmdir()
            except OSError:
                pass
        except OSError:
            pass
    return removed


def plan_basename(url: Any) -> str:
    """File name a stored plan_url points at ('' when there is none)."""
    if not isinstance(url, str) or not url:
        return ""
    return url.split("?", 1)[0].rsplit("/", 1)[-1]


def plan_refs(cfg: dict[str, Any] | None) -> set[str]:
    """Plan file names a configuration references."""
    out: set[str] = set()
    for sp in (cfg or {}).get("spaces") or []:
        name = plan_basename(sp.get("plan_url"))
        if name:
            out.add(name)
    return out


def is_plan_file(name: str) -> bool:
    """Does this look like a plan we wrote: <space>.<ext> or <space>.<token>.<ext>?"""
    parts = name.split(".")
    return len(parts) in (2, 3) and parts[-1].lower() in PLAN_EXTENSIONS


def collect_plans(
    plans_dir: Path,
    old_cfg: dict[str, Any] | None,
    new_cfg: dict[str, Any],
    now: float | None = None,
) -> int:
    """Drop plan files the accepted configuration made obsolete (review R3-1).

    Called inside the config write lock, right after the new revision is
    stored, so it decides from the two configurations that actually bracket the
    commit instead of trusting a client to say what may be deleted. The earlier
    design — a `plan/cleanup` command carrying `keep` — could not be ordered
    against another client's commit: a delayed call removed the file that
    client had just saved, leaving the accepted configuration pointing at
    nothing, which is the damage copy-on-write was introduced to prevent.

    Two rules, both conservative:
      * a file the OLD configuration referenced and the new one does not was
        authoritative and has been superseded — remove it;
      * any other unreferenced plan file is a rejected or abandoned upload, and
        is removed only once PLAN_ORPHAN_TTL_S has passed: a fresh one may
        belong to a transaction that has not committed yet.

    Never raises: the configuration is already stored by the time this runs, so
    a file-system problem must not turn a durable commit into a failed call.
    """
    new_refs = plan_refs(new_cfg)
    old_refs = plan_refs(old_cfg)
    # A commit knows what it superseded. The timer only knows what nothing
    # points at *right now*, and for a plan that is a reversible state: the
    # editor detaches the image when a space switches to "draw" and says the
    # file stays on disk. So the scheduled pass keeps anything belonging to a
    # space that still exists, and waits a month for the rest.
    live_spaces = {str(sp.get("id")) for sp in (new_cfg or {}).get("spaces") or []}
    cutoff = (time.time() if now is None else now) - SCHEDULED_GRACE_S
    removed = 0
    try:
        items = sorted(plans_dir.iterdir()) if plans_dir.is_dir() else []
    except OSError as err:
        # The directory can vanish or turn unreadable between the check and the
        # walk. This is housekeeping running behind a commit that is already
        # durable, so it reports "nothing collected" instead of failing (R4-1).
        _LOGGER.warning("House Plan: could not list %s: %s", plans_dir, err)
        return 0
    for item in items:
        if not item.is_file() or item.name in new_refs or not is_plan_file(item.name):
            continue
        superseded = item.name in old_refs
        if not superseded:
            if item.name.split(".")[0] in live_spaces:
                continue  # detached, not abandoned — the space is still there
            try:
                if item.stat().st_mtime >= cutoff:
                    continue
            except OSError:
                continue
        try:
            item.unlink()
            removed += 1
        except OSError as err:
            _LOGGER.warning("House Plan: could not remove the old plan %s: %s", item, err)
    return removed