<template>
  <div
    class="d-flex flex-fill justify-content-center align-items-center diagram-container"
  >
    <div v-if="!longtermWaterlevels.length">
      <translate>No data available.</translate>
    </div>
  </div>
</template>

<style lang="sass" scoped>
.diagram-container
  /deep/
    .hide
      opacity: 0
    .line
      clip-path: url(#clip)
      stroke-width: 2
      fill: none
      &.mean
        stroke: steelblue
      &.median
        stroke: black
      &.q25
        stroke: orange
      &.q75
        stroke: purple
    .area
      clip-path: url(#clip)
      stroke: none
      fill: lightsteelblue

    .hdc-line,
    .ldc-line,
    .mw-line
      stroke-width: 1
      fill: none
      clip-path: url(#clip)
    .hdc-line
      stroke: red
    .ldc-line
      stroke: green
    .mw-line
      stroke: grey
    .ref-waterlevel-label
      font-size: 11px
      fill: #999
    .now-line
      stroke: #999
      stroke-width: 1
      stroke-dasharray: 5, 5
      clip-path: url(#clip)
    .now-line-label
      font-size: 11px
      fill: #999

    .tick
      line
        stroke-dasharray: 5
        stroke: #ccc

    .zoom
      cursor: move
      fill: none
      pointer-events: all
    .brush
      .selection
        stroke: none
        fill-opacity: 0.2
      .handle
        stroke: rgba($color-info, 0.5)
        fill: rgba($color-info, 0.5)
</style>

<script>
/* This is Free Software under GNU Affero General Public License v >= 3.0
 * without warranty, see README.md and license for details.
 *
 * SPDX-License-Identifier: AGPL-3.0-or-later
 * License-Filename: LICENSES/AGPL-3.0.txt
 *
 * Copyright (C) 2018 by via donau
 *   – Österreichische Wasserstraßen-Gesellschaft mbH
 * Software engineering by Intevation GmbH
 *
 * Author(s):
 * Markus Kottländer <markus.kottlaender@intevation.de>
 */

import { mapState, mapGetters } from "vuex";
import * as d3 from "d3";
import debounce from "debounce";
import { startOfYear, endOfYear } from "date-fns";

export default {
  data() {
    return {
      svg: null,
      diagram: null,
      navigation: null,
      dimensions: null,
      extent: null,
      scale: null,
      axes: null
    };
  },
  computed: {
    ...mapState("gauges", ["longtermWaterlevels", "yearWaterlevels"]),
    ...mapGetters("gauges", ["selectedGauge"])
  },
  methods: {
    drawDiagram() {
      // remove old diagram
      d3.select(".diagram-container svg").remove();
      if (!this.selectedGauge || !this.longtermWaterlevels.length) return;

      // PREPARE HELPERS

      // HDC/LDC/MW for the selected gauge
      const refWaterLevels = JSON.parse(
        this.selectedGauge.properties.reference_water_levels
      );

      // dimensions (widths, heights, margins)
      this.dimensions = this.getDimensions();

      // get min/max values for date and waterlevel axis
      this.extent = this.getExtent(refWaterLevels);

      // scaling helpers
      this.scale = this.getScale();

      // creating the axes based on the scales
      this.axes = this.getAxes();

      // DRAW DIAGRAM/NAVIGATION AREAS

      // create svg
      this.svg = d3
        .select(".diagram-container")
        .append("svg")
        .attr("width", "100%")
        .attr("height", "100%");

      // create container for main diagram
      this.diagram = this.svg
        .append("g")
        .attr("class", "main")
        .attr(
          "transform",
          `translate(${this.dimensions.mainMargin.left}, ${
            this.dimensions.mainMargin.top
          })`
        );

      // create container for navigation diagram
      this.navigation = this.svg
        .append("g")
        .attr("class", "nav")
        .attr(
          "transform",
          `translate(${this.dimensions.navMargin.left}, ${
            this.dimensions.navMargin.top
          })`
        );

      // define visible area, everything outside this area will be hidden
      this.svg
        .append("defs")
        .append("clipPath")
        .attr("id", "clip")
        .append("rect")
        .attr("width", this.dimensions.width)
        .attr("height", this.dimensions.mainHeight);

      // DRAW DIAGRAM PARTS

      // Each drawSomething function (with the exception of drawRefLines)
      // returns a fuction to update the respective chart/area/etc. These
      // updater functions are used by the zoom feature to rescale all elements.
      const updaters = [];

      // draw
      this.drawRefLines(refWaterLevels); // static, doesn't need an updater
      updaters.push(this.drawAxes());
      updaters.push(this.drawNowLines());
      updaters.push(this.drawWaterlevelMinMaxAreaChart());
      updaters.push(this.drawWaterlevelLineChart("median"));
      updaters.push(this.drawWaterlevelLineChart("q25"));
      updaters.push(this.drawWaterlevelLineChart("q75"));
      updaters.push(this.drawWaterlevelLineChart("mean", this.yearWaterlevels));

      // INTERACTIONS

      // create rectanlge on the main chart area to capture mouse events
      const eventRect = this.svg
        .append("rect")
        .attr("class", "zoom")
        .attr("width", this.dimensions.width)
        .attr("height", this.dimensions.mainHeight)
        .attr(
          "transform",
          `translate(${this.dimensions.mainMargin.left}, ${
            this.dimensions.mainMargin.top
          })`
        );

      this.createZoom(updaters, eventRect);
    },
    getDimensions() {
      // dimensions and margins
      const svgWidth = document.querySelector(".diagram-container").clientWidth;
      const svgHeight = document.querySelector(".diagram-container")
        .clientHeight;
      const mainMargin = { top: 20, right: 20, bottom: 110, left: 80 };
      const navMargin = {
        top: svgHeight - mainMargin.top - 65,
        right: 20,
        bottom: 30,
        left: 80
      };
      const width = +svgWidth - mainMargin.left - mainMargin.right;
      const mainHeight = +svgHeight - mainMargin.top - mainMargin.bottom;
      const navHeight = +svgHeight - navMargin.top - navMargin.bottom;

      return { width, mainHeight, navHeight, mainMargin, navMargin };
    },
    getExtent(refWaterLevels) {
      const waterlevelsRelevantForExtent = [];
      this.longtermWaterlevels.forEach(wl => {
        waterlevelsRelevantForExtent.push(wl.min, wl.max);
      });
      waterlevelsRelevantForExtent.push(
        refWaterLevels.HDC + (refWaterLevels.HDC - refWaterLevels.LDC) / 8,
        Math.max(
          refWaterLevels.LDC - (refWaterLevels.HDC - refWaterLevels.LDC) / 4,
          0
        )
      );
      return {
        // set min/max values for the date axis
        date: [startOfYear(new Date()), endOfYear(new Date())],
        // set min/max values for the waterlevel axis
        // including HDC (+ 1/8 HDC-LDC) and LDC (- 1/4 HDC-LDC)
        waterlevel: d3.extent(waterlevelsRelevantForExtent)
      };
    },
    getScale() {
      // scaling helpers to convert real world values into pixels
      const x = d3.scaleTime().range([0, this.dimensions.width]);
      const y = d3.scaleLinear().range([this.dimensions.mainHeight, 0]);
      const x2 = d3.scaleTime().range([0, this.dimensions.width]);
      const y2 = d3.scaleLinear().range([this.dimensions.navHeight, 0]);

      // setting the min and max values for the diagram axes
      x.domain(d3.extent(this.extent.date));
      y.domain(this.extent.waterlevel);
      x2.domain(x.domain());
      y2.domain(y.domain());

      return { x, y, x2, y2 };
    },
    getAxes() {
      return {
        x: d3
          .axisTop(this.scale.x)
          .tickSizeInner(this.dimensions.mainHeight)
          .tickSizeOuter(0)
          .tickFormat(date => {
            // make the x-axis label formats dynamic, based on zoom
            // but never display year numbers since they don't make any sense in
            // this diagram
            return (d3.timeSecond(date) < date
              ? d3.timeFormat(".%L")
              : d3.timeMinute(date) < date
              ? d3.timeFormat(":%S")
              : d3.timeHour(date) < date
              ? d3.timeFormat("%I:%M")
              : d3.timeDay(date) < date
              ? d3.timeFormat("%I %p")
              : d3.timeMonth(date) < date
              ? d3.timeWeek(date) < date
                ? d3.timeFormat("%a %d")
                : d3.timeFormat("%b %d")
              : d3.timeFormat("%B"))(date);
          }),
        y: d3
          .axisRight(this.scale.y)
          .tickSizeInner(this.dimensions.width)
          .tickSizeOuter(0),
        x2: d3.axisBottom(this.scale.x2)
      };
    },
    drawNowLines() {
      const nowLine = d3
        .line()
        .x(d => this.scale.x(d.x))
        .y(d => this.scale.y(d.y));

      const nowLabel = selection => {
        selection.attr(
          "transform",
          `translate(${this.scale.x(new Date())}, ${this.scale.y(
            this.extent.waterlevel[1] - 16
          )})`
        );
      };

      // draw in main
      this.diagram
        .append("path")
        .datum([
          { x: new Date(), y: this.extent.waterlevel[0] },
          { x: new Date(), y: this.extent.waterlevel[1] - 20 }
        ])
        .attr("class", "now-line")
        .attr("d", nowLine);
      this.diagram // label
        .append("text")
        .text(this.$gettext("Now"))
        .attr("class", "now-line-label")
        .attr("text-anchor", "middle")
        .call(nowLabel);

      // draw in nav
      this.navigation
        .append("path")
        .datum([
          { x: new Date(), y: this.extent.waterlevel[0] },
          { x: new Date(), y: this.extent.waterlevel[1] - 20 }
        ])
        .attr("class", "now-line")
        .attr(
          "d",
          d3
            .line()
            .x(d => this.scale.x2(d.x))
            .y(d => this.scale.y2(d.y))
        );

      return () => {
        this.diagram.select(".now-line").attr("d", nowLine);
        this.diagram.select(".now-line-label").call(nowLabel);
      };
    },
    drawAxes() {
      this.diagram
        .append("g")
        .attr("class", "axis--x")
        .attr("transform", `translate(0, ${this.dimensions.mainHeight})`)
        .call(this.axes.x)
        .selectAll(".tick text")
        .attr("y", 15);
      this.diagram // label
        .append("text")
        .text(this.$gettext("Waterlevel [cm]"))
        .attr("text-anchor", "middle")
        .attr(
          "transform",
          `translate(-45, ${this.dimensions.mainHeight / 2}) rotate(-90)`
        );
      this.diagram
        .append("g")
        .call(this.axes.y)
        .selectAll(".tick text")
        .attr("x", -25);

      this.navigation
        .append("g")
        .attr("class", "axis axis--x")
        .attr("transform", `translate(0, ${this.dimensions.navHeight})`)
        .call(this.axes.x2);

      return () => {
        this.diagram
          .select(".axis--x")
          .call(this.axes.x)
          .selectAll(".tick text")
          .attr("y", 15);
      };
    },
    drawWaterlevelMinMaxAreaChart() {
      const areaChart = isNav =>
        d3
          .area()
          .x(d => this.scale[isNav ? "x2" : "x"](d.date))
          .y0(d => this.scale[isNav ? "y2" : "y"](d.min))
          .y1(d => this.scale[isNav ? "y2" : "y"](d.max));

      this.diagram
        .append("path")
        .datum(this.longtermWaterlevels)
        .attr("class", "area")
        .attr("d", areaChart());

      this.navigation
        .append("path")
        .datum(this.longtermWaterlevels)
        .attr("class", "area")
        .attr("d", areaChart(true));

      return () => {
        this.diagram.select(".area").attr("d", areaChart());
      };
    },
    drawWaterlevelLineChart(type, data) {
      const lineChart = type =>
        d3
          .line()
          .x(d => this.scale.x(d.date))
          .y(d => this.scale.y(d[type]))
          .curve(d3.curveLinear);
      this.diagram
        .append("path")
        .attr("class", "line " + type)
        .datum(data || this.longtermWaterlevels)
        .attr("d", lineChart(type));

      return () => {
        this.diagram.select(".line." + type).attr("d", lineChart(type));
      };
    },
    drawRefLines(refWaterLevels) {
      const refWaterlevelLine = d3
        .line()
        .x(d => this.scale.x(d.x))
        .y(d => this.scale.y(d.y));

      // HDC
      this.diagram
        .append("path")
        .datum([
          { x: 0, y: refWaterLevels.HDC },
          { x: this.extent.date[1], y: refWaterLevels.HDC }
        ])
        .attr("class", "hdc-line")
        .attr("d", refWaterlevelLine);
      this.diagram // label
        .append("text")
        .text(`HDC (${refWaterLevels.HDC})`)
        .attr("class", "ref-waterlevel-label")
        .attr("x", 5)
        .attr("y", this.scale.y(refWaterLevels.HDC) - 3);
      // LDC
      this.diagram
        .append("path")
        .datum([
          { x: 0, y: refWaterLevels.LDC },
          { x: this.extent.date[1], y: refWaterLevels.LDC }
        ])
        .attr("class", "ldc-line")
        .attr("d", refWaterlevelLine);
      this.diagram // label
        .append("text")
        .text(`LDC (${refWaterLevels.LDC})`)
        .attr("class", "ref-waterlevel-label")
        .attr("x", 5)
        .attr("y", this.scale.y(refWaterLevels.LDC) - 3);
      // MW
      this.diagram
        .append("path")
        .datum([
          { x: 0, y: refWaterLevels.MW },
          { x: this.extent.date[1], y: refWaterLevels.MW }
        ])
        .attr("class", "mw-line")
        .attr("d", refWaterlevelLine);
      this.diagram // label
        .append("text")
        .text(`MW (${refWaterLevels.MW})`)
        .attr("class", "ref-waterlevel-label")
        .attr("x", 5)
        .attr("y", this.scale.y(refWaterLevels.MW) - 3);
    },
    createZoom(updaters, eventRect) {
      const brush = d3
        .brushX()
        .handleSize(4)
        .extent([[0, 0], [this.dimensions.width, this.dimensions.navHeight]]);

      const zoom = d3
        .zoom()
        .scaleExtent([1, Infinity])
        .translateExtent([
          [0, 0],
          [this.dimensions.width, this.dimensions.mainHeight]
        ])
        .extent([[0, 0], [this.dimensions.width, this.dimensions.mainHeight]]);

      brush.on("brush end", () => {
        if (d3.event.sourceEvent && d3.event.sourceEvent.type === "zoom")
          return; // ignore brush-by-zoom
        let s = d3.event.selection || this.scale.x2.range();
        this.scale.x.domain(s.map(this.scale.x2.invert, this.scale.x2));
        updaters.forEach(u => u && u());
        this.svg
          .select(".zoom")
          .call(
            zoom.transform,
            d3.zoomIdentity
              .scale(this.dimensions.width / (s[1] - s[0]))
              .translate(-s[0], 0)
          );
      });

      zoom.on("zoom", () => {
        if (d3.event.sourceEvent && d3.event.sourceEvent.type === "brush")
          return; // ignore zoom-by-brush
        let t = d3.event.transform;
        this.scale.x.domain(t.rescaleX(this.scale.x2).domain());
        updaters.forEach(u => u && u());
        this.navigation
          .select(".brush")
          .call(brush.move, this.scale.x.range().map(t.invertX, t));
      });
      zoom.on("start", () => {
        this.svg.select(".chart-dot").style("opacity", 0);
        this.svg.select(".chart-tooltip").style("opacity", 0);
      });

      this.navigation
        .append("g")
        .attr("class", "brush")
        .call(brush)
        .call(brush.move, this.scale.x.range());

      eventRect.call(zoom);
    },
    isNext(seconds) {
      // helper to check whether points in the chart are "next to each other"
      // for that they need to be exactly the specified amount of seconds apart.
      return (prev, current) => current.date - prev.date === seconds * 1000;
    }
  },
  created() {
    window.addEventListener("resize", debounce(this.drawDiagram), 100);
  },
  mounted() {
    this.drawDiagram();
  },
  updated() {
    this.drawDiagram();
  }
};
</script>