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// ┃ ██████ ██████ ██████       █      █      █      █      █ █▄  ▀███ █       ┃
// ┃ ▄▄▄▄▄█ █▄▄▄▄▄ ▄▄▄▄▄█  ▀▀▀▀▀█▀▀▀▀▀ █ ▀▀▀▀▀█ ████████▌▐███ ███▄  ▀█ █ ▀▀▀▀▀ ┃
// ┃ █▀▀▀▀▀ █▀▀▀▀▀ █▀██▀▀ ▄▄▄▄▄ █ ▄▄▄▄▄█ ▄▄▄▄▄█ ████████▌▐███ █████▄   █ ▄▄▄▄▄ ┃
// ┃ █      ██████ █  ▀█▄       █ ██████      █      ███▌▐███ ███████▄ █       ┃
// ┣━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┫
// ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
// ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
// ┃ This file is part of the Perspective library, distributed under the terms ┃
// ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛

import { AbstractChart } from "../chart-base";
import type { ColumnDataMap } from "../../data/view-reader";
import { NodeStore, NULL_NODE } from "./node-store";
import { LazyTooltip } from "../../interaction/lazy-tooltip";

/**
 * Sentinel fallback for the Size slot when the user hasn't picked one:
 * use the first non-metadata column in the incoming view. Tree charts
 * still need *some* numeric-ish column to size geometry.
 */
export function firstNonMetadataColumn(columns: ColumnDataMap): string {
    for (const k of columns.keys()) {
        if (!k.startsWith("__")) {
            return k;
        }
    }

    return "";
}

/**
 * Shared state for hierarchical charts (treemap, sunburst). Holds the
 * tree store + streaming-insert scaffolding + per-row tooltip data
 * buffers. Concrete chart classes extend this and add their own
 * layout / render / interact state.
 *
 * Fields are `public` so the `tree-data.ts` helpers and per-chart
 * layout modules can read/write them without friction.
 */
export abstract class TreeChartBase extends AbstractChart {
    //  Shared column-slot resolution
    _sizeName = "";
    _colorName = "";

    /**
     * Color-slot semantics.
     * - `"empty"`: no Color slot → single palette[0], legend suppressed.
     * - `"numeric"`: Color column is float / integer / date / datetime →
     *   continuous gradient via `colorValueToT`.
     * - `"series"`: Color column is any other type → discrete series
     *   palette keyed by the composite of group_by level values.
     */
    _colorMode: "empty" | "numeric" | "series" = "empty";

    //  Tree storage (SOA + linked-list children)
    _nodeStore: NodeStore = new NodeStore();
    _rootId: number = NULL_NODE;
    _currentRootId: number = NULL_NODE;
    _breadcrumbIds: number[] = [];

    /**
     * Per-parent `Map<childName, childId>` for O(1) find-or-create
     * during streaming tree insertion. Rebuilt on each dataset reset.
     */
    _childLookup: Map<number, Map<string, number>> = new Map();

    //  Streaming-insert row counter
    // Source-view row offset tracked across chunks so `leafRowIdx` on
    // each leaf points back to the correct view row for lazy tooltip
    // fetches via `AbstractChart._lazyRows`.
    _rowCount = 0;

    //  Color extents / categorical key table
    _colorMin = Infinity;
    _colorMax = -Infinity;
    _uniqueColorLabels: Map<string, number> = new Map();

    //  Visible-node cache (populated per frame by layout/collect) ──────
    _visibleNodeIds: Int32Array | null = null;
    _visibleNodeCount = 0;

    /**
     * Lazy-tooltip cache. `lines` is `null` until the async row fetch
     * resolves; the controller's serial dance drops stale results so
     * rapid mouse motion doesn't paint out-of-date text. The render
     * path consults `hoveredTarget` to verify cached lines belong to
     * the currently hovered node before painting.
     */
    _lazyTooltip = new LazyTooltip<number>();
}