"""
Platform Adapter Registry

Allows platform adapters (built-in and plugin) to self-register so the gateway
can discover and instantiate them without hardcoded if/elif chains.

Built-in adapters continue to use the existing if/elif in _create_adapter()
for now.  Plugin adapters register here via PluginContext.register_platform()
and are looked up first -- if nothing is found the gateway falls through to
the legacy code path.

Usage (plugin side):

    from gateway.platform_registry import platform_registry, PlatformEntry

    platform_registry.register(PlatformEntry(
        name="irc",
        label="IRC",
        adapter_factory=lambda cfg: IRCAdapter(cfg),
        check_fn=check_requirements,
        validate_config=lambda cfg: bool(cfg.extra.get("server")),
        required_env=["IRC_SERVER"],
        install_hint="pip install irc",
    ))

Usage (gateway side):

    adapter = platform_registry.create_adapter("irc", platform_config)
"""

import logging
from dataclasses import dataclass, field
from typing import Any, Callable, Optional

logger = logging.getLogger(__name__)


@dataclass
class PlatformEntry:
    """Metadata and factory for a single platform adapter."""

    # Identifier used in config.yaml (e.g. "irc", "viber").
    name: str

    # Human-readable label (e.g. "IRC", "Viber").
    label: str

    # Factory callable: receives a PlatformConfig, returns an adapter instance.
    # Using a factory instead of a bare class lets plugins do custom init
    # (e.g. passing extra kwargs, wrapping in try/except).
    adapter_factory: Callable[[Any], Any]

    # Returns True when the platform's dependencies are available.
    check_fn: Callable[[], bool]

    # Optional: given a PlatformConfig, is it properly configured?
    # If None, the registry skips config validation and lets the adapter
    # fail at connect() time with a descriptive error.
    validate_config: Optional[Callable[[Any], bool]] = None

    # Optional: given a PlatformConfig, is the platform connected/enabled?
    # Used by ``GatewayConfig.get_connected_platforms()`` and setup UI status.
    # If None, falls back to ``validate_config`` or ``check_fn``.
    is_connected: Optional[Callable[[Any], bool]] = None

    # Env vars this platform needs (for ``hermes setup`` display).
    required_env: list = field(default_factory=list)

    # Hint shown when check_fn returns False.
    install_hint: str = ""

    # Optional setup function for interactive configuration.
    # Signature: () -> None (prompts user, saves env vars).
    # If None, falls back to _setup_standard_platform (needs token_var + vars)
    # or a generic "set these env vars" display.
    setup_fn: Optional[Callable[[], None]] = None

    # "builtin" or "plugin"
    source: str = "plugin"

    # Name of the plugin manifest that registered this entry (empty for
    # built-ins).  Used by ``hermes gateway setup`` to auto-enable the
    # owning plugin when the user configures its platform.
    plugin_name: str = ""

    # ── Auth env var names (for _is_user_authorized integration) ──
    # E.g. "IRC_ALLOWED_USERS" — checked for comma-separated user IDs.
    allowed_users_env: str = ""
    # E.g. "IRC_ALLOW_ALL_USERS" — if truthy, all users authorized.
    allow_all_env: str = ""

    # ── Message limits ──
    # Max message length for smart-chunking.  0 = no limit.
    max_message_length: int = 0

    # ── Privacy ──
    # If True, session descriptions redact PII (phone numbers, etc.)
    pii_safe: bool = False

    # ── Display ──
    # Emoji for CLI/gateway display (e.g. "💬")
    emoji: str = "🔌"

    # Whether this platform should appear in _UPDATE_ALLOWED_PLATFORMS
    # (allows /update command from this platform).
    allow_update_command: bool = True

    # ── LLM guidance ──
    # Platform hint injected into the system prompt (e.g. "You are on IRC.
    # Do not use markdown.").  Empty string = no hint.
    platform_hint: str = ""


class PlatformRegistry:
    """Central registry of platform adapters.

    Thread-safe for reads (dict lookups are atomic under GIL).
    Writes happen at startup during sequential discovery.
    """

    def __init__(self) -> None:
        self._entries: dict[str, PlatformEntry] = {}

    def register(self, entry: PlatformEntry) -> None:
        """Register a platform adapter entry.

        If an entry with the same name exists, it is replaced (last writer
        wins -- this lets plugins override built-in adapters if desired).
        """
        if entry.name in self._entries:
            prev = self._entries[entry.name]
            logger.info(
                "Platform '%s' re-registered (was %s, now %s)",
                entry.name,
                prev.source,
                entry.source,
            )
        self._entries[entry.name] = entry
        logger.debug("Registered platform adapter: %s (%s)", entry.name, entry.source)

    def unregister(self, name: str) -> bool:
        """Remove a platform entry.  Returns True if it existed."""
        return self._entries.pop(name, None) is not None

    def get(self, name: str) -> Optional[PlatformEntry]:
        """Look up a platform entry by name."""
        return self._entries.get(name)

    def all_entries(self) -> list[PlatformEntry]:
        """Return all registered platform entries."""
        return list(self._entries.values())

    def plugin_entries(self) -> list[PlatformEntry]:
        """Return only plugin-registered platform entries."""
        return [e for e in self._entries.values() if e.source == "plugin"]

    def is_registered(self, name: str) -> bool:
        return name in self._entries

    def create_adapter(self, name: str, config: Any) -> Optional[Any]:
        """Create an adapter instance for the given platform name.

        Returns None if:
        - No entry registered for *name*
        - check_fn() returns False (missing deps)
        - validate_config() returns False (misconfigured)
        - The factory raises an exception
        """
        entry = self._entries.get(name)
        if entry is None:
            return None

        if not entry.check_fn():
            hint = f" ({entry.install_hint})" if entry.install_hint else ""
            logger.warning(
                "Platform '%s' requirements not met%s",
                entry.label,
                hint,
            )
            return None

        if entry.validate_config is not None:
            try:
                if not entry.validate_config(config):
                    logger.warning(
                        "Platform '%s' config validation failed",
                        entry.label,
                    )
                    return None
            except Exception as e:
                logger.warning(
                    "Platform '%s' config validation error: %s",
                    entry.label,
                    e,
                )
                return None

        try:
            adapter = entry.adapter_factory(config)
            return adapter
        except Exception as e:
            logger.error(
                "Failed to create adapter for platform '%s': %s",
                entry.label,
                e,
                exc_info=True,
            )
            return None


# Module-level singleton
platform_registry = PlatformRegistry()
