from __future__ import annotations

import os
import re
import tempfile
from pathlib import Path
from typing import Any

import rrdtool

SAFE_ID = re.compile(r"^[A-Za-z0-9-]+$")


class RRDStore:
    def __init__(self, data_dir: str, step: int):
        self.root = Path(data_dir)
        self.root.mkdir(parents=True, exist_ok=True)
        self.step = step
        self.heartbeat = max(step * 3, 120)

    def update(self, snapshot: dict[str, list[dict[str, Any]]]) -> None:
        for group in snapshot["groups"]:
            path = self.path("group", group["id"])
            self._ensure_group(path)
            rrdtool.update(str(path), "N:%s:%s:%s:%s:%s" % (
                group["available"], group["on"], group["off"], group["unavailable"], group["brightness"]
            ))
        for sensor in snapshot["sensors"]:
            path = self.path("sensor", sensor["id"])
            self._ensure_sensor(path)
            value = "U" if sensor["value"] is None else sensor["value"]
            rrdtool.update(str(path), f"N:{value}:{int(sensor['available'])}")

    def path(self, kind: str, item_id: str) -> Path:
        if kind not in {"group", "sensor"} or not SAFE_ID.fullmatch(item_id):
            raise ValueError("Invalid RRD identifier")
        return self.root / f"{kind}-{item_id}.rrd"

    def _archives(self) -> list[str]:
        five_minutes = max(1, round(300 / self.step))
        one_hour = max(1, round(3600 / self.step))
        return [
            f"RRA:AVERAGE:0.5:1:{max(1, round(7 * 86400 / self.step))}",
            f"RRA:AVERAGE:0.5:{five_minutes}:{90 * 288}",
            f"RRA:AVERAGE:0.5:{one_hour}:{2 * 365 * 24}",
        ]

    def _ensure_group(self, path: Path) -> None:
        if not path.exists():
            rrdtool.create(
                str(path), "--step", str(self.step),
                f"DS:available:GAUGE:{self.heartbeat}:0:U", f"DS:on:GAUGE:{self.heartbeat}:0:U",
                f"DS:off:GAUGE:{self.heartbeat}:0:U", f"DS:unavailable:GAUGE:{self.heartbeat}:0:U",
                f"DS:brightness:GAUGE:{self.heartbeat}:0:100", *self._archives(),
            )

    def _ensure_sensor(self, path: Path) -> None:
        if not path.exists():
            rrdtool.create(
                str(path), "--step", str(self.step), f"DS:value:GAUGE:{self.heartbeat}:U:U",
                f"DS:available:GAUGE:{self.heartbeat}:0:1", *self._archives(),
            )

    def graph(self, kind: str, item: dict[str, Any], period: str) -> bytes:
        start = {"6h": "-6h", "24h": "-24h", "7d": "-7d", "30d": "-30d"}.get(period, "-24h")
        path = self.path(kind, item["id"])
        if not path.exists():
            raise FileNotFoundError(path)
        handle, output = tempfile.mkstemp(suffix=".png")
        os.close(handle)
        try:
            args = [
                output, "--start", start, "--end", "now", "--width", "900", "--height", "260",
                "--font", "DEFAULT:0:DejaVu Sans", "--color", "BACK#111827", "--color", "CANVAS#111827",
                "--color", "FONT#d1d5db", "--color", "GRID#374151", "--color", "MGRID#4b5563",
                "--border", "0", "--slope-mode",
            ]
            escaped = str(path).replace(":", "\\:")
            if kind == "group":
                args += [
                    "--vertical-label", "% of lights / intensity", "--lower-limit", "0", "--upper-limit", "100", "--rigid",
                    f"DEF:u={escaped}:unavailable:AVERAGE", f"DEF:o={escaped}:off:AVERAGE",
                    f"DEF:n={escaped}:on:AVERAGE", f"DEF:b={escaped}:brightness:AVERAGE",
                    "CDEF:t=u,o,+,n,+", "CDEF:up=t,0,EQ,0,u,t,/,100,*,IF",
                    "CDEF:op=t,0,EQ,0,o,t,/,100,*,IF", "CDEF:np=t,0,EQ,0,n,t,/,100,*,IF",
                    "AREA:up#8b0000:Unavailable", "AREA:op#4b5563:Off:STACK", "AREA:np#facc15:On:STACK",
                    "LINE2:b#22c55e:Average intensity",
                ]
            else:
                label = "Temperature (°C)" if item["type"] == "temperature" else "Illuminance (lux)"
                args += ["--vertical-label", label, f"DEF:v={escaped}:value:AVERAGE", "LINE2:v#38bdf8:Value"]
            rrdtool.graph(*args)
            return Path(output).read_bytes()
        finally:
            Path(output).unlink(missing_ok=True)