from __future__ import annotations
import enum
import json
import uuid
from datetime import datetime, timezone
from sqlalchemy import (
    Boolean, CheckConstraint, DateTime, Float, ForeignKey, Index, Integer, String, Text,
)
from sqlalchemy.orm import Mapped, mapped_column
from .base import Base


class MonitorType(str, enum.Enum):
    """The kinds of synthetic/uptime check a Monitor can run."""
    icmp = "icmp"   # ICMP echo via the system ping binary
    tcp = "tcp"     # TCP connect to target:port
    dns = "dns"     # DNS A/AAAA resolution, optional expected-IP assertion
    http = "http"   # HTTP(S) request — status / content / TLS expiry


# Whitelist for the CHECK constraint. `type` is a plain String + CHECK rather
# than a native Postgres enum so a new monitor type ships as a same-change
# DROP/ADD CONSTRAINT (family rule 36) instead of the heavier ALTER TYPE ADD
# VALUE a native enum would force.
MONITOR_TYPE_VALUES = tuple(t.value for t in MonitorType)
_TYPE_CHECK = "type IN ('icmp', 'tcp', 'dns', 'http')"


class Monitor(Base):
    """A single configured uptime/synthetic check of any type.

    Unifies what used to be host-coupled ping/DNS facets (columns on `hosts`)
    and the standalone HTTP plugin monitor. `host_id` is OPTIONAL: set when the
    check belongs to a registered Host (then it surfaces on the host hub), or
    NULL for a free-standing custom destination. Type-specific settings live in
    `config_json` so adding a new type never widens this table.
    """
    __tablename__ = "monitors"

    id: Mapped[str] = mapped_column(
        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
    )
    name: Mapped[str] = mapped_column(String(128), nullable=False)
    type: Mapped[str] = mapped_column(String(16), nullable=False)
    # Address (icmp/tcp/dns) or URL (http) — free-form, not tied to a Host row.
    target: Mapped[str] = mapped_column(String(2048), nullable=False)
    host_id: Mapped[str | None] = mapped_column(
        String(36), ForeignKey("hosts.id", ondelete="CASCADE"), nullable=True, index=True
    )
    # Type-specific config as a JSON object. Keys by type:
    #   icmp -> {}
    #   tcp  -> {"port": int}
    #   dns  -> {"expected_ip": str | None}
    #   http -> {"method", "expected_status", "content_match", "headers",
    #            "timeout_seconds", "follow_redirects", "verify_ssl"}
    config_json: Mapped[str] = mapped_column(Text, nullable=False, default="{}")
    enabled: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
    # 0 = use the global monitors.poll_interval_seconds setting.
    check_interval_seconds: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    # Updated after each check so the scheduler can compute next-run efficiently.
    last_checked_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False,
        default=lambda: datetime.now(timezone.utc),
    )

    __table_args__ = (
        CheckConstraint(_TYPE_CHECK, name="ck_monitors_type"),
    )

    @property
    def config(self) -> dict:
        try:
            return json.loads(self.config_json or "{}")
        except (ValueError, TypeError):
            return {}

    def set_config(self, cfg: dict) -> None:
        self.config_json = json.dumps(cfg or {})


class MonitorResult(Base):
    """One check result for a Monitor, across all types.

    Superset of the old per-type result columns: response_ms is universal,
    while status_code/content_matched/tls_expires_at (http) and resolved_ip
    (dns) are populated only for the types that produce them.
    """
    __tablename__ = "monitor_results"

    id: Mapped[str] = mapped_column(
        String(36), primary_key=True, default=lambda: str(uuid.uuid4())
    )
    monitor_id: Mapped[str] = mapped_column(
        String(36), ForeignKey("monitors.id", ondelete="CASCADE"),
        nullable=False, index=True,
    )
    checked_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False,
        default=lambda: datetime.now(timezone.utc), index=True,
    )
    is_up: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    response_ms: Mapped[float | None] = mapped_column(Float, nullable=True)
    status_code: Mapped[int | None] = mapped_column(Integer, nullable=True)        # http
    resolved_ip: Mapped[str | None] = mapped_column(String(255), nullable=True)    # dns
    content_matched: Mapped[bool | None] = mapped_column(Boolean, nullable=True)   # http
    tls_expires_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True                                     # http
    )
    error_msg: Mapped[str | None] = mapped_column(String(512), nullable=True)

    __table_args__ = (
        # The status/heartbeat queries page the latest N per monitor by time.
        Index("ix_monitor_results_monitor_checked", "monitor_id", "checked_at"),
    )