/**
 * The compact status block at the sidebar's foot (milestone 39): whether
 * filtering is in force, how fast queries are arriving, and how long the
 * process has been up. Three readings the operator glances at from any page,
 * each from data the shell already holds — no request of its own.
 *
 * Queries/min derives from the Overview body the page in front of the reader
 * is drawing, so it appears only while that page is open and its window has
 * landed; on every other page the row is absent rather than stale.
 */

import { useEffect, useState } from "react";
import { useQuery } from "@tanstack/react-query";
import { useMatch } from "@tanstack/react-router";
import * as stylex from "@stylexjs/stylex";
import { formatDuration, formatRate } from "@/lib/format";
import { overviewQuery, versionQuery } from "@/lib/queries";
import { useProtection } from "@/features/pause/protection";
import { DEFAULT_PERIOD } from "@/features/overview/period";
import { styles as shared } from "@/ui/styles";
import { colors, metrics } from "@/ui/tokens.stylex";

const styles = stylex.create({
	block: {
		display: "flex",
		flexDirection: "column",
		gap: "0.4375rem",
		marginInline: "1rem",
		marginBottom: "0.75rem",
		borderRadius: metrics.radius,
		borderWidth: 1,
		borderStyle: "solid",
		borderColor: colors.border,
		backgroundColor: colors.surface,
		paddingInline: "0.75rem",
		paddingBlock: "0.875rem",
		fontSize: "0.75rem",
		lineHeight: "1rem",
		color: colors.textMuted,
	},
	line: {
		display: "flex",
		alignItems: "center",
		justifyContent: "space-between",
		gap: "0.625rem",
		margin: 0,
	},
	key: {
		display: "inline-flex",
		alignItems: "center",
		gap: "0.4375rem",
	},
	value: {
		fontWeight: 550,
		color: colors.text,
	},
	dot: {
		flexShrink: 0,
		width: "7px",
		height: "7px",
		borderRadius: "999px",
	},
	dotActive: { backgroundColor: colors.chartGreen },
	dotPaused: { backgroundColor: colors.warnBorderStrong },
	dotUnavailable: { backgroundColor: colors.chartRed },
	dotUnknown: { backgroundColor: colors.borderStrong },
	/** The narrow header's rendering: the dot and the state alone, inline. */
	inline: {
		display: "inline-flex",
		alignItems: "center",
		gap: "0.4375rem",
		fontSize: "0.75rem",
		lineHeight: "1rem",
		color: colors.textSecondary,
	},
});

const PROTECTION_TEXT = {
	active: "Active",
	paused: "Paused",
	unavailable: "Unavailable",
	unknown: "Unknown",
} as const;

const DOT_STYLE = {
	active: styles.dotActive,
	paused: styles.dotPaused,
	unavailable: styles.dotUnavailable,
	unknown: styles.dotUnknown,
} as const;

/** The dot and the word, for the narrow header where there is room for nothing more. */
export function ProtectionDot() {
	const { state } = useProtection();
	return (
		<span {...stylex.props(styles.inline)}>
			<span aria-hidden="true" {...stylex.props(styles.dot, DOT_STYLE[state])} />
			<span>Protection {PROTECTION_TEXT[state].toLowerCase()}</span>
		</span>
	);
}

/**
 * Uptime as of now, not as of the fetch: the version answer is a minute old at
 * most, so the seconds it reported are aged by the time since it landed. A
 * restart shows within that minute. Ticks every second, because the first
 * minute reads in seconds.
 */
function useUptimeSeconds(): number | null {
	const version = useQuery(versionQuery());
	const [now, setNow] = useState(() => Date.now());
	useEffect(() => {
		const timer = setInterval(() => setNow(Date.now()), 1000);
		return () => clearInterval(timer);
	}, []);
	if (version.data === undefined) return null;
	return version.data.uptime_seconds + Math.max(0, now - version.dataUpdatedAt) / 1000;
}

function useQueriesPerMinute(): number | null {
	const match = useMatch({ from: "/shell/overview", shouldThrow: false });
	const period = match?.search.period ?? DEFAULT_PERIOD;
	// Reads the body the page fetched; never fetches one of its own. A failed
	// refetch leaves the last body in the cache, and the page is then showing
	// its error, not that body: the row goes with it.
	const overview = useQuery({ ...overviewQuery(period, match?.search.client), enabled: false });
	if (match === undefined || overview.isError || overview.data === undefined) return null;
	if (overview.data.period !== period) return null;
	const minutes = (overview.data.until - overview.data.since) / 60;
	return minutes > 0 ? overview.data.totals.queries / minutes : null;
}

export default function SidebarStatus() {
	const { state } = useProtection();
	const rate = useQueriesPerMinute();
	const uptime = useUptimeSeconds();
	return (
		<dl aria-label="Status" {...stylex.props(styles.block)}>
			<div {...stylex.props(styles.line)}>
				<dt {...stylex.props(styles.key)}>
					<span aria-hidden="true" {...stylex.props(styles.dot, DOT_STYLE[state])} />
					Protection
				</dt>
				<dd {...stylex.props(styles.value)}>{PROTECTION_TEXT[state]}</dd>
			</div>
			{rate !== null && (
				<div {...stylex.props(styles.line)}>
					<dt>Queries/min</dt>
					<dd {...stylex.props(styles.value, shared.tabularNums)}>{formatRate(rate)}</dd>
				</div>
			)}
			<div {...stylex.props(styles.line)}>
				<dt>Uptime</dt>
				<dd {...stylex.props(styles.value, shared.tabularNums)}>
					{uptime === null ? "—" : formatDuration(uptime)}
				</dd>
			</div>
		</dl>
	);
}