/**
 * The five health conditions, compactly, at the top of the page that explains
 * failures. Healthy conditions stay quiet; a degraded one is highlighted and
 * offers the way out.
 *
 * A degraded condition whose explanation is on this page narrows this page
 * rather than navigating away: the filter link sets `component` and drops every
 * other filter. A time window, a severity or a `state=resolved` left from an
 * earlier investigation would each hide the very episode the reader was sent to
 * read, and a link that lands on "no events" states something false.
 *
 * The load contract is the one the deleted Overview status section carried: a
 * visible loading state before the first reading, and a refetch failure that
 * says so — the conditions on screen become the last reading that arrived, never
 * a claim about the current state, until a poll succeeds again.
 */

import { useQuery } from "@tanstack/react-query";
import { Link } from "@tanstack/react-router";
import * as stylex from "@stylexjs/stylex";
import InlineError from "@/lib/InlineError";
import { healthQuery } from "@/lib/queries";
import { styles as shared } from "@/ui/styles";
import { colors } from "@/ui/tokens.stylex";
import { healthFacts, type FactLink, type FactTone, type HealthFact } from "./healthFacts";

const DARK = "@media (prefers-color-scheme: dark)";

const styles = stylex.create({
	list: {
		marginTop: "0.75rem",
		display: "grid",
		gap: "0.5rem",
		// Five is prime, so every count between one and five leaves a short last
		// row; three columns made it 3 then 2, which reads as a layout that ran out
		// of room rather than one that chose. So the strip goes from one column
		// straight to two and then to a single row of five, and is never ragged.
		gridTemplateColumns: {
			default: "minmax(0, 1fr)",
			"@media (min-width: 640px)": "repeat(2, minmax(0, 1fr))",
			"@media (min-width: 1100px)": "repeat(5, minmax(0, 1fr))",
		},
		listStyleType: "none",
		padding: 0,
	},
	fact: {
		display: "flex",
		flexWrap: "wrap",
		alignItems: "baseline",
		gap: "0.375rem",
		borderRadius: "0.25rem",
		borderWidth: 1,
		borderStyle: "solid",
		paddingInline: "0.625rem",
		paddingBlock: "0.5rem",
		fontSize: "0.875rem",
		lineHeight: "1.25rem",
	},
	/** Quiet: a healthy condition is the normal state and gets no emphasis. */
	quiet: {
		borderColor: colors.border,
		backgroundColor: "transparent",
	},
	highlighted: {
		borderColor: colors.borderStrong,
		backgroundColor: colors.surfaceRaised,
	},
	label: {
		color: colors.textSecondary,
	},
	value: {
		fontWeight: 500,
	},
	detail: {
		flexBasis: "100%",
		fontSize: "0.75rem",
		lineHeight: "1rem",
		color: colors.textMuted,
	},
	link: {
		fontSize: "0.875rem",
		lineHeight: "1.25rem",
		color: colors.primaryOnSurface,
		textDecorationLine: "none",
	},
	ok: {
		color: { default: "oklch(43.2% 0.095 166.913)", [DARK]: "oklch(84.5% 0.143 164.978)" },
	},
	notice: {
		color: { default: "oklch(47.3% 0.137 46.201)", [DARK]: "oklch(87.9% 0.169 91.605)" },
	},
	warn: {
		color: { default: "oklch(47.3% 0.137 46.201)", [DARK]: "oklch(87.9% 0.169 91.605)" },
	},
	danger: {
		color: colors.dangerText,
	},
	message: {
		marginTop: "0.5rem",
		fontSize: "0.875rem",
		lineHeight: "1.25rem",
		color: colors.textMuted,
	},
});

const TONES = { ok: styles.ok, notice: styles.notice, warn: styles.warn, danger: styles.danger } as const;

/** Text and icon carry the state; the colour only agrees with them. */
const ICONS: Record<FactTone, string> = { ok: "●", notice: "‖", warn: "!", danger: "✕" };

function FactLinkAnchor({ link }: { link: FactLink }) {
	if (link.kind === "filter") {
		return (
			<Link
				to="/diagnostics"
				// Sets the component and clears every filter that could hide what it
				// points at: a time window from an older investigation, and a severity
				// or state — `resolved` above all — that would exclude the very episode
				// explaining the condition this link came from.
				search={() => ({ component: link.component })}
				{...stylex.props(styles.link, shared.focusRing)}
			>
				{link.label}
			</Link>
		);
	}
	// The tab belongs to the destination, not to the fact: a source that stopped
	// loading is read on Protection's Sources tab, an upstream on Resolution's.
	if (link.to === "/configuration/protection") {
		return (
			<Link
				to="/configuration/protection"
				search={{ tab: "sources" }}
				{...stylex.props(styles.link, shared.focusRing)}
			>
				{link.label}
			</Link>
		);
	}
	return (
		<Link
			to="/configuration/resolution"
			search={{ tab: "upstreams" }}
			{...stylex.props(styles.link, shared.focusRing)}
		>
			{link.label}
		</Link>
	);
}

function Fact({ fact }: { fact: HealthFact }) {
	return (
		<li {...stylex.props(styles.fact, fact.tone === "ok" ? styles.quiet : styles.highlighted)}>
			<span aria-hidden="true" {...stylex.props(TONES[fact.tone])}>
				{ICONS[fact.tone]}
			</span>
			<span {...stylex.props(styles.label)}>{fact.label}</span>
			<span {...stylex.props(styles.value, TONES[fact.tone])}>{fact.value}</span>
			{fact.link !== undefined && <FactLinkAnchor link={fact.link} />}
			{fact.detail !== undefined && <span {...stylex.props(styles.detail)}>{fact.detail}</span>}
		</li>
	);
}

export default function HealthStrip() {
	const health = useQuery(healthQuery());

	if (health.data === undefined) {
		return health.isError ? (
			<InlineError error={health.error} onRetry={() => void health.refetch()} />
		) : (
			<p role="status" {...stylex.props(styles.message, shared.pulse)}>
				Loading status…
			</p>
		);
	}

	return (
		<>
			<ul aria-label="Current status" {...stylex.props(styles.list)}>
				{healthFacts(health.data).map((fact) => (
					<Fact key={fact.key} fact={fact} />
				))}
			</ul>
			{health.isError && (
				<>
					<p role="status" {...stylex.props(styles.message)}>
						This is the last reading that arrived. The current state is unknown.
					</p>
					<InlineError error={health.error} onRetry={() => void health.refetch()} />
				</>
			)}
		</>
	);
}