"""Desktop-application resolver over an `AppDef` (parsed from an MCP manifest's `app:` block).

`locate` stats every declared location in order (fixed paths, PATH, uninstall entries, the flatpak,
snap and Applications directories) and lists directories for a `*` path segment; the first present
one wins. `inspect` reads the version source in-process.
`probe` re-reads the vendor's runtime file on every call; the bearer token in it never
leaves this module.
"""

from __future__ import annotations

import glob
import json
import os
import plistlib
import re
import sys
import time
from dataclasses import dataclass
from typing import Any, Callable, Iterator, Literal
from urllib.parse import urlsplit

from hermes_platform.resolver import known_dirs
from hermes_platform.resolver.base import Effort, Inspection, Probe
from hermes_platform.resolver.core import (
    Candidate,
    CheckState,
    Kind,
    LookupContext,
    Observation,
    Resolution,
    locate_command,
)

PresenceKind = Literal["executable", "bundle"]
VersionKind = Literal["pe_resource", "plist", "uninstall_registry", "none"]
LivenessKind = Literal["server_json", "none"]

_LOOPBACK_HOSTS = frozenset({"127.0.0.1", "localhost", "::1", "[::1]"})


@dataclass(frozen=True)
class AppLocation:
    """One place to look. `kind` is `path` or a key of `LOCATION_KINDS`. `value` is the path, or the
    value of that kind's `key`. `file` is joined onto an uninstall entry's `InstallLocation`."""

    kind: str
    value: str
    file: str = ""


@dataclass(frozen=True)
class AppDef:
    """One application on one OS. Paths use `%VAR%` and `~`; expansion happens at lookup."""

    app_id: str
    os_family: str
    presence: PresenceKind
    locations: tuple[AppLocation, ...]
    version_kind: VersionKind = "none"
    version_arg: str = ""
    liveness_kind: LivenessKind = "none"
    liveness_path: str = ""
    liveness_pid_key: str = "pid"
    liveness_url_key: str = "http"
    liveness_token_key: str = "token"
    endpoint_path: str = "/mcp"


def _expand(path: str) -> str:
    return os.path.expandvars(os.path.expanduser(path))


@dataclass(frozen=True)
class Endpoint:
    url: str
    token: str = ""

    def __repr__(self) -> str:
        return f"Endpoint(url={self.url!r}, token=<redacted>)"


@dataclass(frozen=True)
class AppResolver:
    definition: AppDef

    @property
    def name(self) -> str:
        return self.definition.app_id

    # ---- locate: stat only -------------------------------------------------------------

    def locate(self, ctx: LookupContext | None = None) -> Resolution:
        d = self.definition
        found = [hit for loc in d.locations for hit in _locator(loc.kind)(d, loc, ctx)]
        kind: Kind = next((k for c, k in found if c.present), "missing")
        return Resolution(kind, tuple(c for c, _ in found))

    # ---- inspect: bounded file reads and in-process OS APIs -----------------------------

    def inspect(self, res: Resolution, ctx: LookupContext | None = None) -> Inspection:
        if not res.found:
            return Inspection(Observation.not_checked(), Observation.not_checked())
        return Inspection(version=self._version(res.command[0]), signer=Observation.not_checked())

    def _version(self, path: str) -> Observation[str]:
        kind = self.definition.version_kind
        try:
            if kind == "none":
                return Observation.not_checked()
            if kind == "plist":
                return _plist_version(path)
            if kind == "pe_resource":
                return _pe_version(path)
            if kind == "uninstall_registry":
                return _uninstall_registry_version(self.definition.version_arg)
        except Exception as exc:  # a vendor's plist/PE/registry entry is untrusted input; never abort the caller
            return Observation(CheckState.ERROR, detail=exc.__class__.__name__)
        return Observation(CheckState.UNAVAILABLE, detail=f"unknown version kind {kind}")

    # ---- probe: fresh, never cached ------------------------------------------------------

    def endpoint(self) -> Endpoint | None:
        """Read and validate the current runtime endpoint."""
        d = self.definition
        if d.liveness_kind != "server_json":
            return None
        session = _read_server_json(_expand(d.liveness_path), d)
        if session is None or _pid_alive(session.pid).value is not True:
            return None
        endpoint = _endpoint_observation(session.url, d.endpoint_path)
        if endpoint.state is not CheckState.PRESENT or not endpoint.value:
            return None
        return Endpoint(endpoint.value, session.token)

    def probe(self, res: Resolution, *, effort: Effort, deadline_s: float = 3.0) -> Probe:
        d = self.definition
        nc: Observation = Observation.not_checked()
        if d.liveness_kind != "server_json":
            return Probe(running=nc, answering=nc, endpoint=nc)
        session = _read_server_json(_expand(d.liveness_path), d)
        if session is None:
            absent = Observation(CheckState.ABSENT, False, "runtime file missing or unreadable")
            return Probe(running=absent, answering=nc, endpoint=Observation(CheckState.ABSENT))
        running = _pid_alive(session.pid)
        endpoint_obs = _endpoint_observation(session.url, d.endpoint_path)
        if effort is Effort.LOCAL or running.value is not True or endpoint_obs.state is not CheckState.PRESENT:
            return Probe(running=running, answering=nc, endpoint=endpoint_obs)
        answering = _mcp_initialize(session, endpoint_obs.value or "", deadline_s)
        return Probe(running=running, answering=answering, endpoint=endpoint_obs)


# ---- locations: each yields (candidate, resolution kind) in probe order -----------------

_Hit = tuple[Candidate, Kind]
_Locator = Callable[[AppDef, AppLocation, LookupContext | None], list[_Hit]]


def _present(presence: PresenceKind, path: str) -> bool:
    if presence == "bundle":
        return os.path.isdir(path) and os.path.isfile(os.path.join(path, "Contents", "Info.plist"))
    return os.path.isfile(path)


def _hit(d: AppDef, source: str, path: str) -> _Hit:
    present = os.path.isabs(path) and _present(d.presence, path)
    return Candidate(path, source, present), "known_path"


def _version_order(path: str) -> list:
    return [(1, int(part)) if part.isdigit() else (0, part) for part in re.split(r"(\d+)", path)]


def _path_hits(d: AppDef, loc: AppLocation, ctx: LookupContext | None) -> list[_Hit]:
    target, source = _expand(loc.value), f"app:{d.app_id}"
    not_found: list[_Hit] = [(Candidate(target, source, False), "known_path")]
    if not os.path.isabs(target) or "%" in target or "$" in target:
        return not_found
    if "*" not in target:
        return [_hit(d, source, target)]
    # A `*` segment stands for a versioned folder (`Blender 5.2`); the highest version is tried first.
    pattern = "*".join(glob.escape(part) for part in target.split("*"))
    matches = sorted(glob.glob(pattern), key=_version_order, reverse=True)
    return [_hit(d, source, match) for match in matches] or not_found


def _command_hits(d: AppDef, loc: AppLocation, ctx: LookupContext | None) -> list[_Hit]:
    res = locate_command(loc.value, ctx)
    return [(Candidate(c.value, f"app:{d.app_id}:{loc.kind}", c.present), "path_executable") for c in res.candidates]


def _uninstall_hits(d: AppDef, loc: AppLocation, ctx: LookupContext | None) -> list[_Hit]:
    if sys.platform != "win32":
        return []
    # A UNC InstallLocation is skipped so a presence check never touches the network.
    return [_hit(d, f"app:{d.app_id}:{loc.kind}", os.path.join(entry["InstallLocation"], loc.file))
            for entry in _uninstall_entries(loc.value)
            if entry.get("InstallLocation") and not entry["InstallLocation"].startswith(("\\\\", "//"))]


def _in_dirs(dirs: Callable[[], tuple[str, ...]]) -> _Locator:
    def hits(d: AppDef, loc: AppLocation, ctx: LookupContext | None) -> list[_Hit]:
        return [_hit(d, f"app:{d.app_id}:{loc.kind}", os.path.join(_expand(root), loc.value)) for root in dirs()]
    return hits


@dataclass(frozen=True)
class LocationSpec:
    """A location kind a declaration names in a mapping. `only_on` is the one OS family it is valid
    under (None: any), `key` names the mapping field holding what to find, `yields` is the presence
    it finds, and `needs_file` says the mapping also carries a relative `file`."""

    only_on: str | None
    key: str
    yields: PresenceKind
    locate: _Locator
    needs_file: bool = False


LOCATION_KINDS: dict[str, LocationSpec] = {
    "command": LocationSpec(None, "name", "executable", _command_hits),
    "uninstall_registry": LocationSpec("win32", "display_name_prefix", "executable", _uninstall_hits, needs_file=True),
    "app_bundle": LocationSpec("darwin", "name", "bundle", _in_dirs(known_dirs.mac_application_dirs)),
    "flatpak": LocationSpec("linux", "app_id", "executable", _in_dirs(known_dirs.flatpak_export_dirs)),
    "snap": LocationSpec("linux", "name", "executable", _in_dirs(known_dirs.snap_bin_dirs)),
}


def _locator(kind: str) -> _Locator:
    """A plain string location is a `path`; every other kind comes from `LOCATION_KINDS`."""
    return _path_hits if kind == "path" else LOCATION_KINDS[kind].locate


# ---- version sources -------------------------------------------------------------------


def _plist_version(bundle: str) -> Observation[str]:
    with open(os.path.join(bundle, "Contents", "Info.plist"), "rb") as fh:  # windows-footgun: ok — binary mode
        info = plistlib.load(fh)
    value = info.get("CFBundleShortVersionString") or info.get("CFBundleVersion")
    if not value:
        return Observation(CheckState.UNAVAILABLE, detail="no version key in Info.plist")
    return Observation(CheckState.PRESENT, str(value))


def _pe_version(path: str) -> Observation[str]:
    if sys.platform != "win32":
        return Observation(CheckState.UNAVAILABLE, detail="pe_resource needs Windows")
    import ctypes
    from ctypes import wintypes

    ver = ctypes.windll.version  # type: ignore[attr-defined]
    ver.GetFileVersionInfoSizeW.argtypes = [wintypes.LPCWSTR, ctypes.POINTER(wintypes.DWORD)]
    ver.GetFileVersionInfoSizeW.restype = wintypes.DWORD
    size = ver.GetFileVersionInfoSizeW(path, None)
    if not size:
        return Observation(CheckState.UNAVAILABLE, detail="no version resource")
    buf = ctypes.create_string_buffer(size)
    ver.GetFileVersionInfoW.argtypes = [wintypes.LPCWSTR, wintypes.DWORD, wintypes.DWORD, ctypes.c_void_p]
    ver.GetFileVersionInfoW.restype = wintypes.BOOL
    if not ver.GetFileVersionInfoW(path, 0, size, buf):
        return Observation(CheckState.ERROR, detail="GetFileVersionInfoW failed")
    ptr = ctypes.c_void_p()
    length = wintypes.UINT()
    ver.VerQueryValueW.argtypes = [ctypes.c_void_p, wintypes.LPCWSTR, ctypes.POINTER(ctypes.c_void_p), ctypes.POINTER(wintypes.UINT)]
    ver.VerQueryValueW.restype = wintypes.BOOL
    if not ver.VerQueryValueW(buf, "\\", ctypes.byref(ptr), ctypes.byref(length)) or not ptr.value:
        return Observation(CheckState.UNAVAILABLE, detail="no fixed file info")
    # VS_FIXEDFILEINFO: dwFileVersionMS at offset 8, dwFileVersionLS at offset 12.
    ms = ctypes.cast(ptr.value + 8, ctypes.POINTER(wintypes.DWORD)).contents.value
    ls = ctypes.cast(ptr.value + 12, ctypes.POINTER(wintypes.DWORD)).contents.value
    return Observation(CheckState.PRESENT, f"{ms >> 16}.{ms & 0xFFFF}.{ls >> 16}.{ls & 0xFFFF}")


def _uninstall_values(entry: Any) -> dict[str, str]:
    """The uninstall entry's values that exist; any of them may be missing."""
    import winreg

    values: dict[str, str] = {}
    for value_name in ("DisplayName", "DisplayVersion", "InstallLocation"):
        try:
            values[value_name] = str(winreg.QueryValueEx(entry, value_name)[0])
        except OSError:
            continue
    return values


def _uninstall_entry(key: Any, index: int) -> dict[str, str]:
    """One child entry's values; an entry can vanish between EnumKey and OpenKey, which reads as no values."""
    import winreg

    try:
        with winreg.OpenKey(key, winreg.EnumKey(key, index)) as entry:
            return _uninstall_values(entry)
    except OSError:
        return {}


def _uninstall_entries(display_name_prefix: str) -> Iterator[dict[str, str]]:
    """Each uninstall entry whose `DisplayName` starts with the prefix, machine-wide before per-user."""
    import winreg

    roots = (
        (winreg.HKEY_LOCAL_MACHINE, r"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall"),
        (winreg.HKEY_LOCAL_MACHINE, r"SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall"),
        (winreg.HKEY_CURRENT_USER, r"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall"),
    )
    for hive, root in roots:
        try:
            with winreg.OpenKey(hive, root) as key:
                count = winreg.QueryInfoKey(key)[0]
                for i in range(count):
                    values = _uninstall_entry(key, i)
                    if values.get("DisplayName", "").startswith(display_name_prefix):
                        yield values
        except OSError:
            continue


def _uninstall_registry_version(display_name_prefix: str) -> Observation[str]:
    if sys.platform != "win32":
        return Observation(CheckState.UNAVAILABLE, detail="uninstall_registry needs Windows")
    entry = next(_uninstall_entries(display_name_prefix), None)
    if entry is None:
        return Observation(CheckState.ABSENT, detail="no uninstall entry")
    if "DisplayVersion" not in entry:
        return Observation(CheckState.UNAVAILABLE, detail="entry has no DisplayVersion")
    return Observation(CheckState.PRESENT, entry["DisplayVersion"])


# ---- liveness: the token stays inside this section -------------------------------------


@dataclass(frozen=True)
class _Session:
    pid: int | None
    url: str
    token: str

    def __repr__(self) -> str:
        return f"_Session(pid={self.pid}, url={self.url!r}, token=<redacted>)"


def _read_server_json(path: str, d: AppDef) -> _Session | None:
    try:
        with open(path, encoding="utf-8") as fh:
            data = json.load(fh)
    except (OSError, ValueError):
        return None
    if not isinstance(data, dict):
        return None
    pid = data.get(d.liveness_pid_key)
    url = data.get(d.liveness_url_key)
    token = data.get(d.liveness_token_key)
    return _Session(
        pid=pid if isinstance(pid, int) else None,
        url=url if isinstance(url, str) else "",
        token=token if isinstance(token, str) else "",
    )


def _pid_alive(pid: int | None) -> Observation[bool]:
    if pid is None or pid <= 0:
        return Observation(CheckState.UNAVAILABLE, detail="no pid in runtime file")
    if sys.platform == "win32":
        import ctypes
        from ctypes import wintypes

        k32 = ctypes.windll.kernel32  # type: ignore[attr-defined]
        k32.OpenProcess.argtypes = [wintypes.DWORD, wintypes.BOOL, wintypes.DWORD]
        k32.OpenProcess.restype = wintypes.HANDLE
        handle = k32.OpenProcess(0x1000, False, pid)  # PROCESS_QUERY_LIMITED_INFORMATION
        if not handle:
            return Observation(CheckState.ABSENT, False)
        k32.CloseHandle.argtypes = [wintypes.HANDLE]
        k32.CloseHandle(handle)
        return Observation(CheckState.PRESENT, True)
    try:
        os.kill(pid, 0)  # windows-footgun: ok — POSIX only, the win32 branch returned above
    except ProcessLookupError:
        return Observation(CheckState.ABSENT, False)
    except PermissionError:
        return Observation(CheckState.PRESENT, True)
    return Observation(CheckState.PRESENT, True)


def _endpoint_observation(raw_url: str, fixed_path: str) -> Observation[str]:
    """Accept only a loopback http URL with a numeric port and no userinfo; the path is ours."""
    if not raw_url:
        return Observation(CheckState.UNAVAILABLE, detail="no url in runtime file")
    try:
        parts = urlsplit(raw_url)
        hostname, port, username, password = parts.hostname, parts.port, parts.username, parts.password
    except ValueError:
        return Observation(CheckState.UNAVAILABLE, detail="malformed endpoint")
    if parts.scheme != "http" or username or password:
        return Observation(CheckState.UNAVAILABLE, detail="endpoint must be plain http without userinfo")
    if hostname not in _LOOPBACK_HOSTS:
        return Observation(CheckState.UNAVAILABLE, detail="endpoint must be loopback")
    if port is None or not (1 <= port <= 65535):
        return Observation(CheckState.UNAVAILABLE, detail="endpoint needs a numeric port")
    return Observation(CheckState.PRESENT, f"http://{hostname}:{port}{fixed_path}")


def _mcp_initialize(session: _Session, endpoint: str, deadline_s: float) -> Observation[bool]:
    """One MCP `initialize` POST under one absolute deadline covering connect, headers, and body."""
    import http.client

    parts = urlsplit(endpoint)
    body = json.dumps({
        "jsonrpc": "2.0", "id": 1, "method": "initialize",
        "params": {"protocolVersion": "2025-06-18", "capabilities": {},
                   "clientInfo": {"name": "hermes", "version": "probe"}},
    }).encode()
    headers = {"Content-Type": "application/json", "Accept": "application/json, text/event-stream"}
    if session.token:
        headers["Authorization"] = f"Bearer {session.token}"
    deadline = time.monotonic() + max(0.1, deadline_s)

    def remaining() -> float:
        left = deadline - time.monotonic()
        if left <= 0:
            raise TimeoutError
        return left

    conn = http.client.HTTPConnection(parts.hostname or "127.0.0.1", parts.port or 80, timeout=remaining())
    try:
        conn.request("POST", parts.path or "/", body=body, headers=headers)
        conn.sock.settimeout(remaining())
        status = conn.getresponse().status
    except TimeoutError:
        return Observation(CheckState.ABSENT, False, f"no answer within {deadline_s:g} s")
    except (OSError, http.client.HTTPException):
        return Observation(CheckState.ABSENT, False, "connection refused or timed out")
    finally:
        conn.close()
    if status in (200, 401, 403):
        return Observation(CheckState.PRESENT, True, f"http {status}")
    return Observation(CheckState.ABSENT, False, f"http {status}")