src/coord/axisTickLabelBuilder.ts

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

import * as zrUtil from 'zrender/src/core/util';
import * as textContain from 'zrender/src/contain/text';
import {makeInner} from '../util/model';
import {
    makeLabelFormatter,
    getOptionCategoryInterval,
    shouldShowAllLabels
} from './axisHelper';
import Axis from './Axis';
import Model from '../model/Model';
import { AxisBaseOption } from './axisCommonTypes';
import OrdinalScale from '../scale/Ordinal';
import { AxisBaseModel } from './AxisBaseModel';
import type Axis2D from './cartesian/Axis2D';

type CacheKey = string | number;

type InnerTickLabelCache<T> = {
    key: CacheKey
    value: T
}[];

interface InnerLabelCachedVal {
    labels: MakeLabelsResultObj[]
    labelCategoryInterval?: number
}
interface InnerTickCachedVal {
    ticks: number[]
    tickCategoryInterval?: number
}

type InnerStore = {
    labels: InnerTickLabelCache<InnerLabelCachedVal>
    ticks: InnerTickLabelCache<InnerTickCachedVal>
    autoInterval: number
    lastAutoInterval: number
    lastTickCount: number
    axisExtent0: number
    axisExtent1: number
};

const inner = makeInner<InnerStore, any>();

export function createAxisLabels(axis: Axis): {
    labels: {
        level?: number,
        formattedLabel: string,
        rawLabel: string,
        tickValue: number
    }[],
    labelCategoryInterval?: number
} {
    // Only ordinal scale support tick interval
    return axis.type === 'category'
        ? makeCategoryLabels(axis)
        : makeRealNumberLabels(axis);
}

/**
 * @param {module:echats/coord/Axis} axis
 * @param {module:echarts/model/Model} tickModel For example, can be axisTick, splitLine, splitArea.
 * @return {Object} {
 *     ticks: Array.<number>
 *     tickCategoryInterval: number
 * }
 */
export function createAxisTicks(axis: Axis, tickModel: AxisBaseModel): {
    ticks: number[],
    tickCategoryInterval?: number
} {
    // Only ordinal scale support tick interval
    return axis.type === 'category'
        ? makeCategoryTicks(axis, tickModel)
        : {ticks: zrUtil.map(axis.scale.getTicks(), tick => tick.value) };
}

function makeCategoryLabels(axis: Axis) {
    const labelModel = axis.getLabelModel();
    const result = makeCategoryLabelsActually(axis, labelModel);

    return (!labelModel.get('show') || axis.scale.isBlank())
        ? {labels: [], labelCategoryInterval: result.labelCategoryInterval}
        : result;
}

function makeCategoryLabelsActually(axis: Axis, labelModel: Model<AxisBaseOption['axisLabel']>) {
    const labelsCache = getListCache(axis, 'labels');
    const optionLabelInterval = getOptionCategoryInterval(labelModel);
    const result = listCacheGet(labelsCache, optionLabelInterval as CacheKey);

    if (result) {
        return result;
    }

    let labels;
    let numericLabelInterval;

    if (zrUtil.isFunction(optionLabelInterval)) {
        labels = makeLabelsByCustomizedCategoryInterval(axis, optionLabelInterval);
    }
    else {
        numericLabelInterval = optionLabelInterval === 'auto'
            ? makeAutoCategoryInterval(axis) : optionLabelInterval;
        labels = makeLabelsByNumericCategoryInterval(axis, numericLabelInterval);
    }

    // Cache to avoid calling interval function repeatedly.
    return listCacheSet(labelsCache, optionLabelInterval as CacheKey, {
        labels: labels, labelCategoryInterval: numericLabelInterval
    });
}

function makeCategoryTicks(axis: Axis, tickModel: AxisBaseModel) {
    const ticksCache = getListCache(axis, 'ticks');
    const optionTickInterval = getOptionCategoryInterval(tickModel);
    const result = listCacheGet(ticksCache, optionTickInterval as CacheKey);

    if (result) {
        return result;
    }

    let ticks: number[];
    let tickCategoryInterval;

    // Optimize for the case that large category data and no label displayed,
    // we should not return all ticks.
    if (!tickModel.get('show') || axis.scale.isBlank()) {
        ticks = [];
    }

    if (zrUtil.isFunction(optionTickInterval)) {
        ticks = makeLabelsByCustomizedCategoryInterval(axis, optionTickInterval, true);
    }
    // Always use label interval by default despite label show. Consider this
    // scenario, Use multiple grid with the xAxis sync, and only one xAxis shows
    // labels. `splitLine` and `axisTick` should be consistent in this case.
    else if (optionTickInterval === 'auto') {
        const labelsResult = makeCategoryLabelsActually(axis, axis.getLabelModel());
        tickCategoryInterval = labelsResult.labelCategoryInterval;
        ticks = zrUtil.map(labelsResult.labels, function (labelItem) {
            return labelItem.tickValue;
        });
    }
    else {
        tickCategoryInterval = optionTickInterval;
        ticks = makeLabelsByNumericCategoryInterval(axis, tickCategoryInterval, true);
    }

    // Cache to avoid calling interval function repeatedly.
    return listCacheSet(ticksCache, optionTickInterval as CacheKey, {
        ticks: ticks, tickCategoryInterval: tickCategoryInterval
    });
}

function makeRealNumberLabels(axis: Axis) {
    const ticks = axis.scale.getTicks();
    const labelFormatter = makeLabelFormatter(axis);
    return {
        labels: zrUtil.map(ticks, function (tick, idx) {
            return {
                level: tick.level,
                formattedLabel: labelFormatter(tick, idx),
                rawLabel: axis.scale.getLabel(tick),
                tickValue: tick.value
            };
        })
    };
}

// Large category data calculation is performance sensitive, and ticks and label
// probably will be fetched multiple times. So we cache the result.
// axis is created each time during a ec process, so we do not need to clear cache.
function getListCache(axis: Axis, prop: 'ticks'): InnerStore['ticks'];
function getListCache(axis: Axis, prop: 'labels'): InnerStore['labels'];
function getListCache(axis: Axis, prop: 'ticks' | 'labels') {
    // Because key can be a function, and cache size always is small, we use array cache.
    return inner(axis)[prop] || (inner(axis)[prop] = []);
}

function listCacheGet<T>(cache: InnerTickLabelCache<T>, key: CacheKey): T {
    for (let i = 0; i < cache.length; i++) {
        if (cache[i].key === key) {
            return cache[i].value;
        }
    }
}

function listCacheSet<T>(cache: InnerTickLabelCache<T>, key: CacheKey, value: T): T {
    cache.push({key: key, value: value});
    return value;
}

function makeAutoCategoryInterval(axis: Axis) {
    const result = inner(axis).autoInterval;
    return result != null
        ? result
        : (inner(axis).autoInterval = axis.calculateCategoryInterval());
}

/**
 * Calculate interval for category axis ticks and labels.
 * To get precise result, at least one of `getRotate` and `isHorizontal`
 * should be implemented in axis.
 */
export function calculateCategoryInterval(axis: Axis) {
    const params = fetchAutoCategoryIntervalCalculationParams(axis);
    const labelFormatter = makeLabelFormatter(axis);
    const rotation = (params.axisRotate - params.labelRotate) / 180 * Math.PI;

    const ordinalScale = axis.scale as OrdinalScale;
    const ordinalExtent = ordinalScale.getExtent();
    // Providing this method is for optimization:
    // avoid generating a long array by `getTicks`
    // in large category data case.
    const tickCount = ordinalScale.count();

    if (ordinalExtent[1] - ordinalExtent[0] < 1) {
        return 0;
    }

    let step = 1;
    // Simple optimization. Empirical value: tick count should less than 40.
    if (tickCount > 40) {
        step = Math.max(1, Math.floor(tickCount / 40));
    }
    let tickValue = ordinalExtent[0];
    const unitSpan = axis.dataToCoord(tickValue + 1) - axis.dataToCoord(tickValue);
    const unitW = Math.abs(unitSpan * Math.cos(rotation));
    const unitH = Math.abs(unitSpan * Math.sin(rotation));

    let maxW = 0;
    let maxH = 0;

    // Caution: Performance sensitive for large category data.
    // Consider dataZoom, we should make appropriate step to avoid O(n) loop.
    for (; tickValue <= ordinalExtent[1]; tickValue += step) {
        let width = 0;
        let height = 0;

        // Not precise, do not consider align and vertical align
        // and each distance from axis line yet.
        const rect = textContain.getBoundingRect(
            labelFormatter({ value: tickValue }), params.font, 'center', 'top'
        );
        // Magic number
        width = rect.width * 1.3;
        height = rect.height * 1.3;

        // Min size, void long loop.
        maxW = Math.max(maxW, width, 7);
        maxH = Math.max(maxH, height, 7);
    }

    let dw = maxW / unitW;
    let dh = maxH / unitH;
    // 0/0 is NaN, 1/0 is Infinity.
    isNaN(dw) && (dw = Infinity);
    isNaN(dh) && (dh = Infinity);
    let interval = Math.max(0, Math.floor(Math.min(dw, dh)));

    const cache = inner(axis.model);
    const axisExtent = axis.getExtent();
    const lastAutoInterval = cache.lastAutoInterval;
    const lastTickCount = cache.lastTickCount;

    // Use cache to keep interval stable while moving zoom window,
    // otherwise the calculated interval might jitter when the zoom
    // window size is close to the interval-changing size.
    // For example, if all of the axis labels are `a, b, c, d, e, f, g`.
    // The jitter will cause that sometimes the displayed labels are
    // `a, d, g` (interval: 2) sometimes `a, c, e`(interval: 1).
    if (lastAutoInterval != null
        && lastTickCount != null
        && Math.abs(lastAutoInterval - interval) <= 1
        && Math.abs(lastTickCount - tickCount) <= 1
        // Always choose the bigger one, otherwise the critical
        // point is not the same when zooming in or zooming out.
        && lastAutoInterval > interval
        // If the axis change is caused by chart resize, the cache should not
        // be used. Otherwise some hidden labels might not be shown again.
        && cache.axisExtent0 === axisExtent[0]
        && cache.axisExtent1 === axisExtent[1]
    ) {
        interval = lastAutoInterval;
    }
    // Only update cache if cache not used, otherwise the
    // changing of interval is too insensitive.
    else {
        cache.lastTickCount = tickCount;
        cache.lastAutoInterval = interval;
        cache.axisExtent0 = axisExtent[0];
        cache.axisExtent1 = axisExtent[1];
    }

    return interval;
}

function fetchAutoCategoryIntervalCalculationParams(axis: Axis) {
    const labelModel = axis.getLabelModel();
    return {
        axisRotate: axis.getRotate
            ? axis.getRotate()
            : ((axis as Axis2D).isHorizontal && !(axis as Axis2D).isHorizontal())
            ? 90
            : 0,
        labelRotate: labelModel.get('rotate') || 0,
        font: labelModel.getFont()
    };
}

interface MakeLabelsResultObj {
    formattedLabel: string
    rawLabel: string
    tickValue: number
}

function makeLabelsByNumericCategoryInterval(axis: Axis, categoryInterval: number): MakeLabelsResultObj[];
/* eslint-disable-next-line */
function makeLabelsByNumericCategoryInterval(axis: Axis, categoryInterval: number, onlyTick: false): MakeLabelsResultObj[];
function makeLabelsByNumericCategoryInterval(axis: Axis, categoryInterval: number, onlyTick: true): number[];
function makeLabelsByNumericCategoryInterval(axis: Axis, categoryInterval: number, onlyTick?: boolean) {
    const labelFormatter = makeLabelFormatter(axis);
    const ordinalScale = axis.scale as OrdinalScale;
    const ordinalExtent = ordinalScale.getExtent();
    const labelModel = axis.getLabelModel();
    const result: (MakeLabelsResultObj | number)[] = [];

    // TODO: axisType: ordinalTime, pick the tick from each month/day/year/...

    const step = Math.max((categoryInterval || 0) + 1, 1);
    let startTick = ordinalExtent[0];
    const tickCount = ordinalScale.count();

    // Calculate start tick based on zero if possible to keep label consistent
    // while zooming and moving while interval > 0. Otherwise the selection
    // of displayable ticks and symbols probably keep changing.
    // 3 is empirical value.
    if (startTick !== 0 && step > 1 && tickCount / step > 2) {
        startTick = Math.round(Math.ceil(startTick / step) * step);
    }

    // (1) Only add min max label here but leave overlap checking
    // to render stage, which also ensure the returned list
    // suitable for splitLine and splitArea rendering.
    // (2) Scales except category always contain min max label so
    // do not need to perform this process.
    const showAllLabel = shouldShowAllLabels(axis);
    const includeMinLabel = labelModel.get('showMinLabel') || showAllLabel;
    const includeMaxLabel = labelModel.get('showMaxLabel') || showAllLabel;

    if (includeMinLabel && startTick !== ordinalExtent[0]) {
        addItem(ordinalExtent[0]);
    }

    // Optimize: avoid generating large array by `ordinalScale.getTicks()`.
    let tickValue = startTick;
    for (; tickValue <= ordinalExtent[1]; tickValue += step) {
        addItem(tickValue);
    }

    if (includeMaxLabel && tickValue - step !== ordinalExtent[1]) {
        addItem(ordinalExtent[1]);
    }

    function addItem(tickValue: number) {
        const tickObj = { value: tickValue };
        result.push(onlyTick
            ? tickValue
            : {
                formattedLabel: labelFormatter(tickObj),
                rawLabel: ordinalScale.getLabel(tickObj),
                tickValue: tickValue
            }
        );
    }

    return result;
}

type CategoryIntervalCb = (tickVal: number, rawLabel: string) => boolean;

// When interval is function, the result `false` means ignore the tick.
// It is time consuming for large category data.
/* eslint-disable-next-line */
function makeLabelsByCustomizedCategoryInterval(axis: Axis, categoryInterval: CategoryIntervalCb): MakeLabelsResultObj[];
/* eslint-disable-next-line */
function makeLabelsByCustomizedCategoryInterval(axis: Axis, categoryInterval: CategoryIntervalCb, onlyTick: false): MakeLabelsResultObj[];
/* eslint-disable-next-line */
function makeLabelsByCustomizedCategoryInterval(axis: Axis, categoryInterval: CategoryIntervalCb, onlyTick: true): number[];
function makeLabelsByCustomizedCategoryInterval(axis: Axis, categoryInterval: CategoryIntervalCb, onlyTick?: boolean) {
    const ordinalScale = axis.scale;
    const labelFormatter = makeLabelFormatter(axis);
    const result: (MakeLabelsResultObj | number)[] = [];

    zrUtil.each(ordinalScale.getTicks(), function (tick) {
        const rawLabel = ordinalScale.getLabel(tick);
        const tickValue = tick.value;
        if (categoryInterval(tick.value, rawLabel)) {
            result.push(
                onlyTick
                ? tickValue
                : {
                    formattedLabel: labelFormatter(tick),
                    rawLabel: rawLabel,
                    tickValue: tickValue
                }
            );
        }
    });

    return result;
}