/**
 * Client activity over the same window as the query-volume chart: one stacked
 * series per named client, plus everything outside the top eight as "Other".
 *
 * The x-axis is derived from this response's own `since` and `bucket_seconds`,
 * which the API aligns with the timeseries buckets, so the two charts stack
 * directly above one another and a spike in one is at the same horizontal
 * position in the other. Colour goes by rank (`seriesColors.ts`): the busiest
 * client wears the first palette hue, and the legend names every band.
 */

import * as stylex from "@stylexjs/stylex";
import { Group } from "@visx/group";
import { BarStack } from "@visx/shape";
import { formatCount, formatTime } from "@/lib/format";
import type { OverviewClientSeries } from "@/lib/types";
import { styles as shared } from "@/ui/styles";
import { clientLabel, useClientNames, type ClientNames } from "@/features/clients/clientNames";
import {
	CHART_HEIGHT,
	ChartFrame,
	ChartLegend,
	ChartRoot,
	ChartTooltip,
	EmptyChart,
	HitBands,
	STACK_BLEED,
	StackSegment,
	bandScale,
	labelTickValues,
	plotArea,
	slotCenter,
	useActiveIndex,
	useMeasuredWidth,
	valueScale,
	valueTicks,
	type TooltipContent,
} from "./chartKit";
import { OTHER_KEY, clientKey, clientSeriesColor, seriesColor } from "./seriesColors";

/** How many named clients a bucket's tooltip lists before the aggregate and the total. */
const TOOLTIP_CLIENTS = 4;

interface Series {
	key: string;
	label: string;
	color: string;
	buckets: number[];
}

/**
 * "Other" last, so it sits at the top of every column rather than under a client.
 * It is always a series, even at zero across the window (ui-visual-redesign.md:
 * eight named clients plus Other): a reader comparing two scopes sees the same
 * legend in both, and a zero says the named clients were the whole story.
 */
function seriesOf(data: ClientChartData, names: ClientNames): Series[] {
	const named = data.clients.map((client, rank) => ({
		key: clientKey(client.client),
		// The name if the client is registered under one, the address otherwise —
		// the same precedence and the same lookup the query tables use.
		label: clientLabel(client.client, names)?.text ?? client.client,
		color: clientSeriesColor(rank),
		buckets: client.buckets,
	}));
	return [...named, { key: OTHER_KEY, label: "Other", color: seriesColor(OTHER_KEY), buckets: data.other }];
}

/**
 * The slice of the Overview body this chart draws. Declared here rather than
 * taken whole, so what the chart reads is stated where it is read.
 */
export interface ClientChartData {
	since: number;
	bucket_seconds: number;
	clients: OverviewClientSeries[];
	other: number[];
}

/** One column: the timestamp plus one entry per series, keyed by the series key. */
type Column = { ts: number } & Record<string, number>;

export default function ClientChart({ data }: { data: ClientChartData }) {
	const [containerRef, width] = useMeasuredWidth();
	// A hover survives a re-render only while it still names the same bucket at
	// the same place: a poll that rolls the window, or a resize, retires it.
	const hovered = useActiveIndex(`${data.since}:${data.bucket_seconds}:${data.other.length}:${width}`);
	const names = useClientNames();

	const series = seriesOf(data, names);
	const bucketCount = data.other.length;
	const columns: Column[] = Array.from({ length: bucketCount }, (_, i) => {
		const column: Column = { ts: data.since + i * data.bucket_seconds };
		for (const one of series) column[one.key] = one.buckets[i] ?? 0;
		return column;
	});

	if (bucketCount === 0 || columns.every((column) => series.every((one) => column[one.key] === 0))) {
		return <EmptyChart containerRef={containerRef} />;
	}

	const timestamps = columns.map((column) => column.ts);
	const totals = columns.map((column) => series.reduce((sum, one) => sum + column[one.key], 0));
	const plot = plotArea(width, Math.max(...totals));
	const xScale = bandScale(timestamps, plot);
	// Every series here is a disjoint part of the whole rather than a highlighted
	// subset of a separately reported total, so the tallest column's own sum is
	// the scale.
	const yScale = valueScale(Math.max(...totals), [plot.bottom, plot.y]);
	const yTicks = valueTicks(yScale);
	const colorOf = new Map(series.map((one) => [one.key, one.color]));
	const centers = timestamps.map((ts) => slotCenter(xScale, ts, plot));

	/**
	 * The bucket's busiest clients, then Other, then the total — eight named
	 * rows would be a table, and the reader pointing at a spike wants to know
	 * who made it. Other is always there, at zero when the named clients were
	 * the whole bucket, so the rows read the same from bucket to bucket.
	 */
	function tooltipOf(index: number): TooltipContent {
		const column = columns[index];
		const named = series
			.filter((one) => one.key !== OTHER_KEY && column[one.key] > 0)
			.sort((a, b) => column[b.key] - column[a.key])
			.slice(0, TOOLTIP_CLIENTS);
		const other = series.find((one) => one.key === OTHER_KEY);
		const rows = [...named, ...(other !== undefined ? [other] : [])].map((one) => ({
			key: one.key,
			label: one.label,
			color: one.color,
			value: formatCount(column[one.key]),
		}));
		return {
			title: formatTime(column.ts),
			rows: [...rows, { key: "total", label: "All clients", value: formatCount(totals[index]) }],
		};
	}

	return (
		<ChartRoot containerRef={containerRef}>
			<svg
				role="img"
				aria-label={`Client activity over time, ${formatCount(bucketCount)} buckets, ${formatCount(series.length)} series`}
				width="100%"
				height={CHART_HEIGHT}
				viewBox={`0 0 ${width} ${CHART_HEIGHT}`}
				onMouseLeave={hovered.clear}
			>
				<ChartFrame
					plot={plot}
					yScale={yScale}
					yTicks={yTicks}
					xScale={xScale}
					xTickValues={labelTickValues(timestamps, plot.width)}
					bucketSeconds={data.bucket_seconds}
				/>
				<BarStack<Column, string>
					data={columns}
					keys={series.map((one) => one.key)}
					x={(column) => column.ts}
					xScale={xScale}
					yScale={yScale}
					color={(key) => colorOf.get(key) ?? seriesColor(key)}
				>
					{(stacks) =>
						columns.map((column, index) => (
							<Group
								key={column.ts}
								opacity={hovered.index === null || hovered.index === index ? 1 : 0.55}
							>
								{stacks.map((stack) => {
									const bar = stack.bars[index];
									const restsOnAnother = bar.y + bar.height < plot.bottom - STACK_BLEED;
									return (
										<StackSegment
											key={stack.key}
											x={bar.x}
											y={bar.y}
											width={bar.width}
											height={bar.height}
											fill={bar.color}
											bleed={restsOnAnother ? STACK_BLEED : 0}
										/>
									);
								})}
							</Group>
						))
					}
				</BarStack>
				<HitBands plot={plot} centers={centers} onEnter={hovered.show} />
			</svg>
			{hovered.index !== null && (
				<ChartTooltip index={hovered.index} content={tooltipOf(hovered.index)} left={centers[hovered.index]} />
			)}
			<ChartLegend entries={series} />
			<div {...stylex.props(shared.srOnly)}>
				<table>
					<caption>Queries per client per time bucket</caption>
					<thead>
						<tr>
							<th scope="col">Time</th>
							{series.map((one) => (
								<th key={one.key} scope="col">
									{one.label}
								</th>
							))}
						</tr>
					</thead>
					<tbody>
						{columns.map((column) => (
							<tr key={column.ts}>
								<th scope="row">{formatTime(column.ts)}</th>
								{series.map((one) => (
									<td key={one.key}>{formatCount(column[one.key])}</td>
								))}
							</tr>
						))}
					</tbody>
				</table>
			</div>
		</ChartRoot>
	);
}