import { EventPhase } from "../core/InteractEvent.js";
import * as modifiers from "../modifiers/base.js";
import * as utils from "../utils/index.js";
import raf from "../utils/raf.js";
EventPhase.Resume = 'resume';
EventPhase.InertiaStart = 'inertiastart';

function install(scope) {
  const {
    defaults
  } = scope;
  scope.usePlugin(modifiers.default);
  defaults.perAction.inertia = {
    enabled: false,
    resistance: 10,
    // the lambda in exponential decay
    minSpeed: 100,
    // target speed must be above this for inertia to start
    endSpeed: 10,
    // the speed at which inertia is slow enough to stop
    allowResume: true,
    // allow resuming an action in inertia phase
    smoothEndDuration: 300 // animate to snap/restrict endOnly if there's no inertia

  };
}

function resume({
  interaction,
  event,
  pointer,
  eventTarget
}, scope) {
  const state = interaction.inertia; // Check if the down event hits the current inertia target

  if (state.active) {
    let element = eventTarget; // climb up the DOM tree from the event target

    while (utils.is.element(element)) {
      // if interaction element is the current inertia target element
      if (element === interaction.element) {
        // stop inertia
        raf.cancel(state.timeout);
        state.active = false;
        interaction.simulation = null; // update pointers to the down event's coordinates

        interaction.updatePointer(pointer, event, eventTarget, true);
        utils.pointer.setCoords(interaction.coords.cur, interaction.pointers.map(p => p.pointer), interaction._now()); // fire appropriate signals

        const signalArg = {
          interaction,
          phase: EventPhase.Resume
        };
        scope.fire('interactions:action-resume', signalArg); // fire a reume event

        const resumeEvent = new scope.InteractEvent(interaction, event, interaction.prepared.name, EventPhase.Resume, interaction.element);

        interaction._fireEvent(resumeEvent);

        utils.pointer.copyCoords(interaction.coords.prev, interaction.coords.cur);
        break;
      }

      element = utils.dom.parentNode(element);
    }
  }
}

function release({
  interaction,
  event,
  noPreEnd
}, scope) {
  const state = interaction.inertia;

  if (!interaction.interacting() || interaction.simulation && interaction.simulation.active || noPreEnd) {
    return null;
  }

  const options = getOptions(interaction);

  const now = interaction._now();

  const {
    client: velocityClient
  } = interaction.coords.velocity;
  const pointerSpeed = utils.hypot(velocityClient.x, velocityClient.y);
  let smoothEnd = false;
  let modifierResult; // check if inertia should be started

  const inertiaPossible = options && options.enabled && interaction.prepared.name !== 'gesture' && event !== state.startEvent;
  const inertia = inertiaPossible && now - interaction.coords.cur.timeStamp < 50 && pointerSpeed > options.minSpeed && pointerSpeed > options.endSpeed;
  const modifierArg = {
    interaction,
    interactable: interaction.interactable,
    element: interaction.element,
    rect: interaction.rect,
    edges: interaction.edges,
    pageCoords: interaction.coords.cur.page,
    states: inertiaPossible && interaction.modifiers.states.map(modifierState => utils.extend({}, modifierState)),
    preEnd: true,
    prevCoords: null,
    prevRect: null,
    requireEndOnly: null,
    phase: EventPhase.InertiaStart
  }; // smoothEnd

  if (inertiaPossible && !inertia) {
    modifierArg.prevCoords = interaction.modifiers.result.coords;
    modifierArg.prevRect = interaction.modifiers.result.rect;
    modifierArg.requireEndOnly = false;
    modifierResult = modifiers.setAll(modifierArg);
    smoothEnd = modifierResult.changed;
  }

  if (!(inertia || smoothEnd)) {
    return null;
  }

  utils.pointer.copyCoords(state.upCoords, interaction.coords.cur);
  modifiers.setCoords(modifierArg);
  interaction.pointers[0].pointer = state.startEvent = new scope.InteractEvent(interaction, event, // FIXME add proper typing Action.name
  interaction.prepared.name, EventPhase.InertiaStart, interaction.element);
  modifiers.restoreCoords(modifierArg);
  state.t0 = now;
  state.active = true;
  state.allowResume = options.allowResume;
  interaction.simulation = state;
  interaction.interactable.fire(state.startEvent);

  if (inertia) {
    state.vx0 = interaction.coords.velocity.client.x;
    state.vy0 = interaction.coords.velocity.client.y;
    state.v0 = pointerSpeed;
    calcInertia(interaction, state);
    utils.extend(modifierArg.pageCoords, interaction.coords.cur.page);
    modifierArg.pageCoords.x += state.xe;
    modifierArg.pageCoords.y += state.ye;
    modifierArg.prevCoords = null;
    modifierArg.prevRect = null;
    modifierArg.requireEndOnly = true;
    modifierResult = modifiers.setAll(modifierArg);
    state.modifiedXe += modifierResult.delta.x;
    state.modifiedYe += modifierResult.delta.y;
    state.timeout = raf.request(() => inertiaTick(interaction));
  } else {
    state.smoothEnd = true;
    state.xe = modifierResult.delta.x;
    state.ye = modifierResult.delta.y;
    state.sx = state.sy = 0;
    state.timeout = raf.request(() => smothEndTick(interaction));
  }

  return false;
}

function stop({
  interaction
}) {
  const state = interaction.inertia;

  if (state.active) {
    raf.cancel(state.timeout);
    state.active = false;
    interaction.simulation = null;
  }
}

function calcInertia(interaction, state) {
  const options = getOptions(interaction);
  const lambda = options.resistance;
  const inertiaDur = -Math.log(options.endSpeed / state.v0) / lambda;
  state.x0 = interaction.prevEvent.page.x;
  state.y0 = interaction.prevEvent.page.y;
  state.t0 = state.startEvent.timeStamp / 1000;
  state.sx = state.sy = 0;
  state.modifiedXe = state.xe = (state.vx0 - inertiaDur) / lambda;
  state.modifiedYe = state.ye = (state.vy0 - inertiaDur) / lambda;
  state.te = inertiaDur;
  state.lambda_v0 = lambda / state.v0;
  state.one_ve_v0 = 1 - options.endSpeed / state.v0;
}

function inertiaTick(interaction) {
  updateInertiaCoords(interaction);
  utils.pointer.setCoordDeltas(interaction.coords.delta, interaction.coords.prev, interaction.coords.cur);
  utils.pointer.setCoordVelocity(interaction.coords.velocity, interaction.coords.delta);
  const state = interaction.inertia;
  const options = getOptions(interaction);
  const lambda = options.resistance;
  const t = interaction._now() / 1000 - state.t0;

  if (t < state.te) {
    const progress = 1 - (Math.exp(-lambda * t) - state.lambda_v0) / state.one_ve_v0;

    if (state.modifiedXe === state.xe && state.modifiedYe === state.ye) {
      state.sx = state.xe * progress;
      state.sy = state.ye * progress;
    } else {
      const quadPoint = utils.getQuadraticCurvePoint(0, 0, state.xe, state.ye, state.modifiedXe, state.modifiedYe, progress);
      state.sx = quadPoint.x;
      state.sy = quadPoint.y;
    }

    interaction.move({
      event: state.startEvent
    });
    state.timeout = raf.request(() => inertiaTick(interaction));
  } else {
    state.sx = state.modifiedXe;
    state.sy = state.modifiedYe;
    interaction.move({
      event: state.startEvent
    });
    interaction.end(state.startEvent);
    state.active = false;
    interaction.simulation = null;
  }

  utils.pointer.copyCoords(interaction.coords.prev, interaction.coords.cur);
}

function smothEndTick(interaction) {
  updateInertiaCoords(interaction);
  const state = interaction.inertia;
  const t = interaction._now() - state.t0;
  const {
    smoothEndDuration: duration
  } = getOptions(interaction);

  if (t < duration) {
    state.sx = utils.easeOutQuad(t, 0, state.xe, duration);
    state.sy = utils.easeOutQuad(t, 0, state.ye, duration);
    interaction.move({
      event: state.startEvent
    });
    state.timeout = raf.request(() => smothEndTick(interaction));
  } else {
    state.sx = state.xe;
    state.sy = state.ye;
    interaction.move({
      event: state.startEvent
    });
    interaction.end(state.startEvent);
    state.smoothEnd = state.active = false;
    interaction.simulation = null;
  }
}

function updateInertiaCoords(interaction) {
  const state = interaction.inertia; // return if inertia isn't running

  if (!state.active) {
    return;
  }

  const pageUp = state.upCoords.page;
  const clientUp = state.upCoords.client;
  utils.pointer.setCoords(interaction.coords.cur, [{
    pageX: pageUp.x + state.sx,
    pageY: pageUp.y + state.sy,
    clientX: clientUp.x + state.sx,
    clientY: clientUp.y + state.sy
  }], interaction._now());
}

function getOptions({
  interactable,
  prepared
}) {
  return interactable && interactable.options && prepared.name && interactable.options[prepared.name].inertia;
}

const inertia = {
  id: 'inertia',
  install,
  listeners: {
    'interactions:new': ({
      interaction
    }) => {
      interaction.inertia = {
        active: false,
        smoothEnd: false,
        allowResume: false,
        upCoords: {},
        timeout: null
      };
    },
    'interactions:before-action-end': release,
    'interactions:down': resume,
    'interactions:stop': stop
  },
  before: ['modifiers/base'],
  calcInertia,
  inertiaTick,
  smothEndTick,
  updateInertiaCoords
};
export default inertia;
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